Search Results

Search found 8224 results on 329 pages for 'sometimes'.

Page 256/329 | < Previous Page | 252 253 254 255 256 257 258 259 260 261 262 263  | Next Page >

• Is there any equivalence of `--depth immediates` in `git`?

  - by ???

  Currently, I'm try to setup git front-end to the Subversion repository. My Subversion repository is a single large repository which consists of several co-related projects: svn-root |-- project1 | |-- branches | |-- tags | `-- trunk |-- project2 | |-- branches | |-- tags | `-- trunk `-- project3 |-- branches |-- tags `-- trunk Because it's sometimes needs to move files between different projects, so I don't want to break the repository to separate ones. I'm going to use git-svn to setup a git front-end, but I don't see how to exactly mapping the svn to git structure. The two systems treat branches and tags very different and I doubt it is possible. To simplify the problem, I would just git svn clone the whole root directory and let branches/tags/trunk directories just sit there. But this will definitely result in too many files in branches and tags directories. In Subversion, it's easy to just set the depth of checkout to immediates, which will only checkout the branch/tag titles, without the directory contents. but I don't know if this can be done in git. The git-svn messed me up. I hope there's more elegant solution.

  Read the article

• How many VPS do I need for my website? [duplicate]

  - by michael

  This question already has an answer here: How do you do load testing and capacity planning for web sites? 3 answers I made a website which aims at simulating a trading market. There are a list of prices and corresponding volumes that people want to purchase. Users can purchase at any price any time. My website retrieves the prices and volumes from my database every 2 seconds (I have to update the user's browser frequently to allow them to see the current market). Users' database INSERT query can be sent any time if they purchase. I used ajax to post or get data from my database (sometimes nested ajax calls). So, every 2 seconds, each user will send or retrieve data by using more than 20 database queries (in order to show a users the current prices and volumes). Also, I may have 200 users at a time. I was not using VPS before, and I got banned because of using too much CPU resources on my host. Now, I've purchased VPS*2 from a hosting servers. I have: CPU Speed: 2000 Mhz Memory: 2048 MB Disk Space: 20000 MB Bandwidth: 2000 GB Connection: 40 Mb/s Dedicated IP's 2 IP's Is this enough for my 200 users? Also, which VPS OS is suitable for me? Thank you.

  Read the article

• How to display a JSON error message?

  - by Tiny Giant Studios

  I'm currently developing a tumblr theme and have built a jQuery JSON thingamabob that uses the Tumblr API to do the following: The user would click on the "post type" link (e.g. Video Posts), at which stage jQuery would use JSON to grab all the posts that's related to that type and then dynamically display them in a designated area. Now everything works absolutely peachy, except that with Tumblr being Tumblr and their servers taking a knock every now and then, the Tumblr API thingy is sometimes offline. Now I can't foresee when this function will be down, which is why I want to display some generic error message if JSON (for whatever reason) was unable to load the post. You'll see I've already written some code to show an error message when jQuery can't find any posts related to that post type BUT it doesn't cover any server errors. Note: I sometimes get this error: Failed to load resource: the server responded with a status of 503 (Service Temporarily Unavailable) It is for this 503 Error message that I need to write some code, but I'm slightly clueless :) Here's the jQuery JSON code: $('ul.right li').find('a').click(function() { var postType = this.className; var count = 0; byCategory(postType); return false; function byCategory(postType, callback) { $.getJSON('{URL}/api/read/json?type=' + postType + '&callback=?', function(data) { var article = []; $.each(data.posts, function(i, item) { // i = index // item = data for a particular post switch(item.type) { case 'photo': article[i] = '<div class="post_wrap"><div class="photo" style="padding-bottom:5px;">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/XSTldh6ds/photo_icon.png" alt="type_icon"/></a>' + '<a href="' + item.url + '" title="{Title}"><img src="' + item['photo-url-500'] + '"alt="image" /></a></div></div>'; count = 1; break; case 'video': article[i] = '<div class="post_wrap"><div class="video" style="padding-bottom:5px;">' + '<a href="' + item.url + '" title="{Title}" class="type_icon">' + '<img src="http://static.tumblr.com/ewjv7ap/nuSldhclv/video_icon.png" alt="type_icon"/></a>' + '<span style="margin: auto;">' + item['video-player'] + '</span>' + '</div></div>'; count = 1; break; case 'audio': if (use_IE == true) { article[i] = '<div class="post_wrap"><div class="regular">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/R50ldh5uj/audio_icon.png" alt="type_icon"/></a>' + '<h3><a href="' + item.url + '">' + item['id3-artist'] +' - ' + item['id3-title'] + '</a></h3>' + '</div></div>'; } else { article[i] = '<div class="post_wrap"><div class="regular">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/R50ldh5uj/audio_icon.png" alt="type_icon"/></a>' + '<h3><a href="' + item.url + '">' + item['id3-artist'] +' - ' + item['id3-title'] + '</a></h3><div class="player">' + item['audio-player'] + '</div>' + '</div></div>'; }; count = 1; break; case 'regular': article[i] = '<div class="post_wrap"><div class="regular">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/dwxldhck1/regular_icon.png" alt="type_icon"/></a><h3><a href="' + item.url + '">' + item['regular-title'] + '</a></h3><div class="description_container">' + item['regular-body'] + '</div></div></div>'; count = 1; break; case 'quote': article[i] = '<div class="post_wrap"><div class="quote">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/loEldhcpr/quote_icon.png" alt="type_icon"/></a><blockquote><h3><a href="' + item.url + '" title="{Title}">' + item['quote-text'] + '</a></h3></blockquote><cite>- ' + item['quote-source'] + '</cite></div></div>'; count = 1; break; case 'conversation': article[i] = '<div class="post_wrap"><div class="chat">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/MVuldhcth/conversation_icon.png" alt="type_icon"/></a><h3><a href="' + item.url + '">' + item['conversation-title'] + '</a></h3></div></div>'; count = 1; break; case 'link': article[i] = '<div class="post_wrap"><div class="link">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/EQGldhc30/link_icon.png" alt="type_icon"/></a><h3><a href="' + item['link-url'] + '" target="_blank">' + item['link-text'] + '</a></h3></div></div>'; count = 1; break; default: alert('No Entries Found.'); }; }) // end each if (!(count == 0)) { $('#content_right') .hide('fast') .html('<div class="first_div"><span class="left_corner"></span><span class="right_corner"></span><h2>Displaying ' + postType + ' Posts Only</h2></div>' + article.join('')) .slideDown('fast') } else { $('#content_right') .hide('fast') .html('<div class="first_div"><span class="left_corner"></span><span class="right_corner"></span><h2>Hmmm, currently there are no ' + postType + ' posts to display</h2></div>') .slideDown('fast') } // end getJSON }); // end byCategory } }); If you'd like to see the demo in action, check out Elegantem but do note that everything might work absolutely fine for you (or not), depending on Tumblr's temperament.

  Read the article

• ASP.NET exception gives irrelevant stack trace on YSOD, very challenging!

  - by pootow

  Here is the YSOD: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.] System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +428 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 ECommerce.PMethod.Sql.SqlConns.Open() +78 ECommerce.PMethod.Sql.SqlConns..ctor() +120 ECommerce.login.DatasInfo.Proc.UserCenter.IsLogin(String UserGUID, Int32 UserID) +49 ECommerce.login.Rules.Users.UserLogin.isLogin() +44 Config.isUserLogined() +5 Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +99 System.Web.UI.Control.LoadRecursive() +50 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627 [TypeInitializationException: The type initializer for 'ECommerce.ERP.DAL.DBConn' threw an exception.] ECommerce.ERP.DAL.DBConn.get_ConnString() +0 [ObjectDefinitionStoreException: Factory method 'System.String get_ConnString()' threw an Exception.] Spring.Objects.Factory.Support.SimpleInstantiationStrategy.Instantiate(RootObjectDefinition definition, String name, IObjectFactory factory, MethodInfo factoryMethod, Object[] arguments) +257 Spring.Objects.Factory.Support.ConstructorResolver.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +624 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +60 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +56 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +436 [ObjectCreationException: Error thrown by a dependency of object 'styleService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 56' : Initialization of object failed : Factory method 'System.String get_ConnString()' threw an Exception. while resolving 'constructor argument with name promotionservice' to 'promotionService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 31' while resolving 'constructor argument with name domainservice' to 'promotionDomainService' defined in 'assembly [ECommerce.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Domain.AppContext.xml] line 20' while resolving 'constructor argument with name promotionrepos' to 'promotionRepos' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34' while resolving 'constructor argument with name connstr' to 'ECommerce.ERP.DAL.DBConn#389F399' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34'] Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveReference(IObjectDefinition definition, String name, String argumentName, RuntimeObjectReference reference) +394 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolvePropertyValue(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +312 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveValueIfNecessary(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +17 Spring.Objects.Factory.Support.ConstructorResolver.ResolveConstructorArguments(String objectName, RootObjectDefinition definition, ObjectWrapper wrapper, ConstructorArgumentValues cargs, ConstructorArgumentValues resolvedValues) +993 Spring.Objects.Factory.Support.ConstructorResolver.AutowireConstructor(String objectName, RootObjectDefinition rod, ConstructorInfo[] chosenCtors, Object[] explicitArgs) +171 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.AutowireConstructor(String name, RootObjectDefinition definition, ConstructorInfo[] ctors, Object[] explicitArgs) +65 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +161 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +636 Spring.Objects.Factory.Support.AbstractObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +174 Spring.Objects.Factory.Support.WebObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +150 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObjectInternal(String name, Type requiredType, Object[] arguments, Boolean suppressConfigure) +990 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObject(String name) +10 Spring.Context.Support.AbstractApplicationContext.GetObject(String name) +20 ECommerce.Common.ServiceLocator.GetService() +334 ECommerce.Mvc.Controllers.StylesController..ctor() +72 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) +86 System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) +230 System.Activator.CreateInstance(Type type, Boolean nonPublic) +67 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +80 [InvalidOperationException: An error occurred when trying to create a controller of type 'ECommerce.Mvc.Controllers.StylesController'. Make sure that the controller has a parameterless public constructor.] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +190 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +68 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +118 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +46 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +63 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +13 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8677954 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082 Question is: the first stack trace is irrelevant to others, what happened? Any ideas? Let me make this more clear: a MVC page uses the spring part trying to load a lazy-init service which constructor wants a connection string through a static property like this: <object id="promotionRepos" type="ECommerce.Data.AdoNet.Promotions.PromotionRepos, ECommerce.Data.AdoNet" lazy-init="true"> <constructor-arg name="provider"> <null /> </constructor-arg> <constructor-arg name="connStr"> <object type="ECommerce.ERP.DAL.DBConn, ECommerce.ERP.DAL" factory-method="get_ConnString" /> </constructor-arg> <property name="RefreshInterval" value="00:00:10" /> </object> the timeout part is some what irrelevent to all others. see this in the first exception: Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 it's another page at all. And also, ECommerce.PMethod.Sql.SqlConns.Open() uses its own connection string, not the one loaded by spring, it's different module from diffrent team. And I am sure the connection string is correct. And, this ysod cames up randomly. Sometimes nothing is wrong, and sometimes, it appears. I thought there could be something wrong with my database or the network/firewall, I will check it later, but now I want understand this tricky stack trace.

  Read the article

• Authoritative sources about Database vs. Flatfile decision

  - by FastAl

  <tldr>looking for a reference to a book or other undeniably authoritative source that gives reasons when you should choose a database vs. when you should choose other storage methods. I have provided an un-authoritative list of reasons about 2/3 of the way down this post.</tldr> I have a situation at my company where a database is being used where it would be better to use another solution (in this case, an auto-generated piece of source code that contains a static lookup table, searched by binary sort). Normally, a database would be an OK solution even though the problem does not require a database, e.g, none of the elements of ACID are needed, as it is read-only data, updated about every 3-5 years (also requiring other sourcecode changes), and fits in memory, and can be keyed into via binary search (a tad faster than db, but speed is not an issue). The problem is that this code runs on our enterprise server, but is shared with several PC platforms (some disconnected, some use a central DB, etc.), and parts of it are managed by multiple programming units, parts by the DBAs, parts even by mathematicians in another department, etc. These hit their own platform’s version of their databases (containing their own copy of the static data). What happens is that every implementation, every little change, something different goes wrong. There are many other issues as well. I can’t even use a flatfile, because one mode of running on our enterprise server does not have permission to read files (only databases, and of course, its own literal storage, e.g., in-source table). Of course, other parts of the system use databases in proper, less obscure manners; there is no problem with those parts. So why don’t we just change it? I don’t have administrative ability to force a change. But I’m affected because sometimes I have to help fix the problems, but mostly because it causes outages and tons of extra IT time by other programmers and d*mmit that makes me mad! The reason neither management, nor the designers of the system, can see the problem is that they propose a solution that won’t work: increase communication; implement more safeguards and standards; etc. But every time, in a different part of the already-pared-down but still multi-step processes, a few different diligent, hard-working, top performing IT personnel make a unique subtle error that causes it to fail, sometimes after the last round of testing! And in general these are not single-person failures, but understandable miscommunications. And communication at our company is actually better than most. People just don't think that's the case because they haven't dug into the matter. However, I have it on very good word from somebody with extensive formal study of sociology and psychology that the relatively small amount of less-than-proper database usage in this gigantic cross-platform multi-source, multi-language project is bureaucratically un-maintainable. Impossible. No chance. At least with Human Beings in the loop, and it can’t be automated. In addition, the management and developers who could change this, though intelligent and capable, don’t understand the rigidity of this ‘how humans are’ issue, and are not convincible on the matter. The reason putting the static data in sourcecode will solve the problem is, although the solution is less sexy than a database, it would function with no technical drawbacks; and since the sharing of sourcecode already works very well, you basically erase any database-related effort from this section of the project, along with all the drawbacks of it that are causing problems. OK, that’s the background, for the curious. I won’t be able to convince management that this is an unfixable sociological problem, and that the real solution is coding around these limits of human nature, just as you would code around a bug in a 3rd party component that you can’t change. So what I have to do is exploit the unsuitableness of the database solution, and not do it using logic, but rather authority. I am aware of many reasons, and posts on this site giving reasons for one over the other; I’m not looking for lists of reasons like these (although you can add a comment if I've miss a doozy): WHY USE A DATABASE? instead of flatfile/other DB vs. file: if you need... Random Read / Transparent search optimization Advanced / varied / customizable Searching and sorting capabilities Transaction/rollback Locks, semaphores Concurrency control / Shared users Security 1-many/m-m is easier Easy modification Scalability Load Balancing Random updates / inserts / deletes Advanced query Administrative control of design, etc. SQL / learning curve Debugging / Logging Centralized / Live Backup capabilities Cached queries / dvlp & cache execution plans Interleaved update/read Referential integrity, avoid redundant/missing/corrupt/out-of-sync data Reporting (from on olap or oltp db) / turnkey generation tools [Disadvantages:] Important to get right the first time - professional design - but only b/c it's meant to last s/w & h/w cost Usu. over a network, speed issue (best vs. best design vs. local=even then a separate process req's marshalling/netwk layers/inter-p comm) indicies and query processing can stand in the way of simple processing (vs. flatfile) WHY USE FLATFILE: If you only need... Sequential Row processing only Limited usage append only (no reading, no master key/update) Only Update the record you're reading (fixed length recs only) Too big to fit into memory If Local disk / read-ahead network connection Portability / small system Email / cut & Paste / store as document by novice - simple format Low design learning curve but high cost later WHY USE IN-MEMORY/TABLE (tables, arrays, etc.): if you need... Processing a single db/ff record that was imported Known size of data Static data if hardcoding the table Narrow, unchanging use (e.g., one program or proc) -includes a class that will be shared, but encapsulates its data manipulation Extreme speed needed / high transaction frequency Random access - but search is dependent on implementation Following are some other posts about the topic: http://stackoverflow.com/questions/1499239/database-vs-flat-text-file-what-are-some-technical-reasons-for-choosing-one-over http://stackoverflow.com/questions/332825/are-flat-file-databases-any-good http://stackoverflow.com/questions/2356851/database-vs-flat-files http://stackoverflow.com/questions/514455/databases-vs-plain-text/514530 What I’d like to know is if anybody could recommend a hard, authoritative source containing these reasons. I’m looking for a paper book I can buy, or a reputable website with whitepapers about the issue (e.g., Microsoft, IBM), not counting the user-generated content on those sites. This will have a greater change to elicit a change that I’m looking for: less wasted programmer time, and more reliable programs. Thanks very much for your help. You win a prize for reading such a large post!

  Read the article

• How do I prove I should put a table of values in source code instead of a database table?

  - by FastAl

  <tldr>looking for a reference to a book or other undeniably authoritative source that gives reasons when you should choose a database vs. when you should choose other storage methods. I have provided an un-authoritative list of reasons about 2/3 of the way down this post.</tldr> I have a situation at my company where a database is being used where it would be better to use another solution (in this case, an auto-generated piece of source code that contains a static lookup table, searched by binary sort). Normally, a database would be an OK solution even though the problem does not require a database, e.g, none of the elements of ACID are needed, as it is read-only data, updated about every 3-5 years (also requiring other sourcecode changes), and fits in memory, and can be keyed into via binary search (a tad faster than db, but speed is not an issue). The problem is that this code runs on our enterprise server, but is shared with several PC platforms (some disconnected, some use a central DB, etc.), and parts of it are managed by multiple programming units, parts by the DBAs, parts even by mathematicians in another department, etc. These hit their own platform’s version of their databases (containing their own copy of the static data). What happens is that every implementation, every little change, something different goes wrong. There are many other issues as well. I can’t even use a flatfile, because one mode of running on our enterprise server does not have permission to read files (only databases, and of course, its own literal storage, e.g., in-source table). Of course, other parts of the system use databases in proper, less obscure manners; there is no problem with those parts. So why don’t we just change it? I don’t have administrative ability to force a change. But I’m affected because sometimes I have to help fix the problems, but mostly because it causes outages and tons of extra IT time by other programmers and d*mmit that makes me mad! The reason neither management, nor the designers of the system, can see the problem is that they propose a solution that won’t work: increase communication; implement more safeguards and standards; etc. But every time, in a different part of the already-pared-down but still multi-step processes, a few different diligent, hard-working, top performing IT personnel make a unique subtle error that causes it to fail, sometimes after the last round of testing! And in general these are not single-person failures, but understandable miscommunications. And communication at our company is actually better than most. People just don't think that's the case because they haven't dug into the matter. However, I have it on very good word from somebody with extensive formal study of sociology and psychology that the relatively small amount of less-than-proper database usage in this gigantic cross-platform multi-source, multi-language project is bureaucratically un-maintainable. Impossible. No chance. At least with Human Beings in the loop, and it can’t be automated. In addition, the management and developers who could change this, though intelligent and capable, don’t understand the rigidity of this ‘how humans are’ issue, and are not convincible on the matter. The reason putting the static data in sourcecode will solve the problem is, although the solution is less sexy than a database, it would function with no technical drawbacks; and since the sharing of sourcecode already works very well, you basically erase any database-related effort from this section of the project, along with all the drawbacks of it that are causing problems. OK, that’s the background, for the curious. I won’t be able to convince management that this is an unfixable sociological problem, and that the real solution is coding around these limits of human nature, just as you would code around a bug in a 3rd party component that you can’t change. So what I have to do is exploit the unsuitableness of the database solution, and not do it using logic, but rather authority. I am aware of many reasons, and posts on this site giving reasons for one over the other; I’m not looking for lists of reasons like these (although you can add a comment if I've miss a doozy): WHY USE A DATABASE? instead of flatfile/other DB vs. file: if you need... Random Read / Transparent search optimization Advanced / varied / customizable Searching and sorting capabilities Transaction/rollback Locks, semaphores Concurrency control / Shared users Security 1-many/m-m is easier Easy modification Scalability Load Balancing Random updates / inserts / deletes Advanced query Administrative control of design, etc. SQL / learning curve Debugging / Logging Centralized / Live Backup capabilities Cached queries / dvlp & cache execution plans Interleaved update/read Referential integrity, avoid redundant/missing/corrupt/out-of-sync data Reporting (from on olap or oltp db) / turnkey generation tools [Disadvantages:] Important to get right the first time - professional design - but only b/c it's meant to last s/w & h/w cost Usu. over a network, speed issue (best vs. best design vs. local=even then a separate process req's marshalling/netwk layers/inter-p comm) indicies and query processing can stand in the way of simple processing (vs. flatfile) WHY USE FLATFILE: If you only need... Sequential Row processing only Limited usage append only (no reading, no master key/update) Only Update the record you're reading (fixed length recs only) Too big to fit into memory If Local disk / read-ahead network connection Portability / small system Email / cut & Paste / store as document by novice - simple format Low design learning curve but high cost later WHY USE IN-MEMORY/TABLE (tables, arrays, etc.): if you need... Processing a single db/ff record that was imported Known size of data Static data if hardcoding the table Narrow, unchanging use (e.g., one program or proc) -includes a class that will be shared, but encapsulates its data manipulation Extreme speed needed / high transaction frequency Random access - but search is dependent on implementation Following are some other posts about the topic: http://stackoverflow.com/questions/1499239/database-vs-flat-text-file-what-are-some-technical-reasons-for-choosing-one-over http://stackoverflow.com/questions/332825/are-flat-file-databases-any-good http://stackoverflow.com/questions/2356851/database-vs-flat-files http://stackoverflow.com/questions/514455/databases-vs-plain-text/514530 What I’d like to know is if anybody could recommend a hard, authoritative source containing these reasons. I’m looking for a paper book I can buy, or a reputable website with whitepapers about the issue (e.g., Microsoft, IBM), not counting the user-generated content on those sites. This will have a greater change to elicit a change that I’m looking for: less wasted programmer time, and more reliable programs. Thanks very much for your help. You win a prize for reading such a large post!

  Read the article

• OpenCL: Strange buffer or image bahaviour with NVidia but not Amd

  - by Alex R.

  I have a big problem (on Linux): I create a buffer with defined data, then an OpenCL kernel takes this data and puts it into an image2d_t. When working on an AMD C50 (Fusion CPU/GPU) the program works as desired, but on my GeForce 9500 GT the given kernel computes the correct result very rarely. Sometimes the result is correct, but very often it is incorrect. Sometimes it depends on very strange changes like removing unused variable declarations or adding a newline. I realized that disabling the optimization will increase the probability to fail. I have the most actual display driver in both systems. Here is my reduced code: #include <CL/cl.h> #include <string> #include <iostream> #include <sstream> #include <cmath> void checkOpenCLErr(cl_int err, std::string name){ const char* errorString[] = { "CL_SUCCESS", "CL_DEVICE_NOT_FOUND", "CL_DEVICE_NOT_AVAILABLE", "CL_COMPILER_NOT_AVAILABLE", "CL_MEM_OBJECT_ALLOCATION_FAILURE", "CL_OUT_OF_RESOURCES", "CL_OUT_OF_HOST_MEMORY", "CL_PROFILING_INFO_NOT_AVAILABLE", "CL_MEM_COPY_OVERLAP", "CL_IMAGE_FORMAT_MISMATCH", "CL_IMAGE_FORMAT_NOT_SUPPORTED", "CL_BUILD_PROGRAM_FAILURE", "CL_MAP_FAILURE", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "CL_INVALID_VALUE", "CL_INVALID_DEVICE_TYPE", "CL_INVALID_PLATFORM", "CL_INVALID_DEVICE", "CL_INVALID_CONTEXT", "CL_INVALID_QUEUE_PROPERTIES", "CL_INVALID_COMMAND_QUEUE", "CL_INVALID_HOST_PTR", "CL_INVALID_MEM_OBJECT", "CL_INVALID_IMAGE_FORMAT_DESCRIPTOR", "CL_INVALID_IMAGE_SIZE", "CL_INVALID_SAMPLER", "CL_INVALID_BINARY", "CL_INVALID_BUILD_OPTIONS", "CL_INVALID_PROGRAM", "CL_INVALID_PROGRAM_EXECUTABLE", "CL_INVALID_KERNEL_NAME", "CL_INVALID_KERNEL_DEFINITION", "CL_INVALID_KERNEL", "CL_INVALID_ARG_INDEX", "CL_INVALID_ARG_VALUE", "CL_INVALID_ARG_SIZE", "CL_INVALID_KERNEL_ARGS", "CL_INVALID_WORK_DIMENSION", "CL_INVALID_WORK_GROUP_SIZE", "CL_INVALID_WORK_ITEM_SIZE", "CL_INVALID_GLOBAL_OFFSET", "CL_INVALID_EVENT_WAIT_LIST", "CL_INVALID_EVENT", "CL_INVALID_OPERATION", "CL_INVALID_GL_OBJECT", "CL_INVALID_BUFFER_SIZE", "CL_INVALID_MIP_LEVEL", "CL_INVALID_GLOBAL_WORK_SIZE", }; if (err != CL_SUCCESS) { std::stringstream str; str << errorString[-err] << " (" << err << ")"; throw std::string(name)+(str.str()); } } int main(){ try{ cl_context m_context; cl_platform_id* m_platforms; unsigned int m_numPlatforms; cl_command_queue m_queue; cl_device_id m_device; cl_int error = 0; // Used to handle error codes clGetPlatformIDs(0,NULL,&m_numPlatforms); m_platforms = new cl_platform_id[m_numPlatforms]; error = clGetPlatformIDs(m_numPlatforms,m_platforms,&m_numPlatforms); checkOpenCLErr(error, "getPlatformIDs"); // Device error = clGetDeviceIDs(m_platforms[0], CL_DEVICE_TYPE_GPU, 1, &m_device, NULL); checkOpenCLErr(error, "getDeviceIDs"); // Context cl_context_properties properties[] = { CL_CONTEXT_PLATFORM, (cl_context_properties)(m_platforms[0]), 0}; m_context = clCreateContextFromType(properties, CL_DEVICE_TYPE_GPU, NULL, NULL, NULL); // m_private->m_context = clCreateContext(properties, 1, &m_private->m_device, NULL, NULL, &error); checkOpenCLErr(error, "Create context"); // Command-queue m_queue = clCreateCommandQueue(m_context, m_device, 0, &error); checkOpenCLErr(error, "Create command queue"); //Build program and kernel const char* source = "#pragma OPENCL EXTENSION cl_khr_byte_addressable_store : enable\n" "\n" "__kernel void bufToImage(__global unsigned char* in, __write_only image2d_t out, const unsigned int offset_x, const unsigned int image_width , const unsigned int maxval ){\n" "\tint i = get_global_id(0);\n" "\tint j = get_global_id(1);\n" "\tint width = get_global_size(0);\n" "\tint height = get_global_size(1);\n" "\n" "\tint pos = j*image_width*3+(offset_x+i)*3;\n" "\tif( maxval < 256 ){\n" "\t\tfloat4 c = (float4)(in[pos],in[pos+1],in[pos+2],1.0f);\n" "\t\tc.x /= maxval;\n" "\t\tc.y /= maxval;\n" "\t\tc.z /= maxval;\n" "\t\twrite_imagef(out, (int2)(i,j), c);\n" "\t}else{\n" "\t\tfloat4 c = (float4)(255.0f*in[2*pos]+in[2*pos+1],255.0f*in[2*pos+2]+in[2*pos+3],255.0f*in[2*pos+4]+in[2*pos+5],1.0f);\n" "\t\tc.x /= maxval;\n" "\t\tc.y /= maxval;\n" "\t\tc.z /= maxval;\n" "\t\twrite_imagef(out, (int2)(i,j), c);\n" "\t}\n" "}\n" "\n" "__constant sampler_t imageSampler = CLK_NORMALIZED_COORDS_FALSE | CLK_ADDRESS_CLAMP_TO_EDGE | CLK_FILTER_NEAREST;\n" "\n" "__kernel void imageToBuf(__read_only image2d_t in, __global unsigned char* out, const unsigned int offset_x, const unsigned int image_width ){\n" "\tint i = get_global_id(0);\n" "\tint j = get_global_id(1);\n" "\tint pos = j*image_width*3+(offset_x+i)*3;\n" "\tfloat4 c = read_imagef(in, imageSampler, (int2)(i,j));\n" "\tif( c.x <= 1.0f && c.y <= 1.0f && c.z <= 1.0f ){\n" "\t\tout[pos] = c.x*255.0f;\n" "\t\tout[pos+1] = c.y*255.0f;\n" "\t\tout[pos+2] = c.z*255.0f;\n" "\t}else{\n" "\t\tout[pos] = 200.0f;\n" "\t\tout[pos+1] = 0.0f;\n" "\t\tout[pos+2] = 255.0f;\n" "\t}\n" "}\n"; cl_int err; cl_program prog = clCreateProgramWithSource(m_context,1,&source,NULL,&err); if( -err != CL_SUCCESS ) throw std::string("clCreateProgramWithSources"); err = clBuildProgram(prog,0,NULL,"-cl-opt-disable",NULL,NULL); if( -err != CL_SUCCESS ) throw std::string("clBuildProgram(fromSources)"); cl_kernel kernel = clCreateKernel(prog,"bufToImage",&err); checkOpenCLErr(err,"CreateKernel"); cl_uint imageWidth = 8; cl_uint imageHeight = 9; //Initialize datas cl_uint maxVal = 255; cl_uint offsetX = 0; int size = imageWidth*imageHeight*3; int resSize = imageWidth*imageHeight*4; cl_uchar* data = new cl_uchar[size]; cl_float* expectedData = new cl_float[resSize]; for( int i = 0,j=0; i < size; i++,j++ ){ data[i] = (cl_uchar)i; expectedData[j] = (cl_float)i/255.0f; if ( i%3 == 2 ){ j++; expectedData[j] = 1.0f; } } cl_mem inBuffer = clCreateBuffer(m_context,CL_MEM_READ_ONLY|CL_MEM_COPY_HOST_PTR,size*sizeof(cl_uchar),data,&err); checkOpenCLErr(err, "clCreateBuffer()"); clFinish(m_queue); cl_image_format imgFormat; imgFormat.image_channel_order = CL_RGBA; imgFormat.image_channel_data_type = CL_FLOAT; cl_mem outImg = clCreateImage2D( m_context, CL_MEM_READ_WRITE, &imgFormat, imageWidth, imageHeight, 0, NULL, &err ); checkOpenCLErr(err,"get2DImage()"); clFinish(m_queue); size_t kernelRegion[]={imageWidth,imageHeight}; size_t kernelWorkgroup[]={1,1}; //Fill kernel with data clSetKernelArg(kernel,0,sizeof(cl_mem),&inBuffer); clSetKernelArg(kernel,1,sizeof(cl_mem),&outImg); clSetKernelArg(kernel,2,sizeof(cl_uint),&offsetX); clSetKernelArg(kernel,3,sizeof(cl_uint),&imageWidth); clSetKernelArg(kernel,4,sizeof(cl_uint),&maxVal); //Run kernel err = clEnqueueNDRangeKernel(m_queue,kernel,2,NULL,kernelRegion,kernelWorkgroup,0,NULL,NULL); checkOpenCLErr(err,"RunKernel"); clFinish(m_queue); //Check resulting data for validty cl_float* computedData = new cl_float[resSize];; size_t region[]={imageWidth,imageHeight,1}; const size_t offset[] = {0,0,0}; err = clEnqueueReadImage(m_queue,outImg,CL_TRUE,offset,region,0,0,computedData,0,NULL,NULL); checkOpenCLErr(err, "readDataFromImage()"); clFinish(m_queue); for( int i = 0; i < resSize; i++ ){ if( fabs(expectedData[i]-computedData[i])>0.1 ){ std::cout << "Expected: \n"; for( int j = 0; j < resSize; j++ ){ std::cout << expectedData[j] << " "; } std::cout << "\nComputed: \n"; std::cout << "\n"; for( int j = 0; j < resSize; j++ ){ std::cout << computedData[j] << " "; } std::cout << "\n"; throw std::string("Error, computed and expected data are not the same!\n"); } } }catch(std::string& e){ std::cout << "\nCaught an exception: " << e << "\n"; return 1; } std::cout << "Works fine\n"; return 0; } I also uploaded the source code for you to make it easier to test it: http://www.file-upload.net/download-3513797/strangeOpenCLError.cpp.html Please can you tell me if I've done wrong anything? Is there any mistake in the code or is this a bug in my driver? Best reagards, Alex

  Read the article

• Service Discovery in WCF 4.0 &ndash; Part 1

  - by Shaun

  When designing a service oriented architecture (SOA) system, there will be a lot of services with many service contracts, endpoints and behaviors. Besides the client calling the service, in a large distributed system a service may invoke other services. In this case, one service might need to know the endpoints it invokes. This might not be a problem in a small system. But when you have more than 10 services this might be a problem. For example in my current product, there are around 10 services, such as the user authentication service, UI integration service, location service, license service, device monitor service, event monitor service, schedule job service, accounting service, player management service, etc..   Benefit of Discovery Service Since almost all my services need to invoke at least one other service. This would be a difficult task to make sure all services endpoints are configured correctly in every service. And furthermore, it would be a nightmare when a service changed its endpoint at runtime. Hence, we need a discovery service to remove the dependency (configuration dependency). A discovery service plays as a service dictionary which stores the relationship between the contracts and the endpoints for every service. By using the discovery service, when service X wants to invoke service Y, it just need to ask the discovery service where is service Y, then the discovery service will return all proper endpoints of service Y, then service X can use the endpoint to send the request to service Y. And when some services changed their endpoint address, all need to do is to update its records in the discovery service then all others will know its new endpoint. In WCF 4.0 Discovery it supports both managed proxy discovery mode and ad-hoc discovery mode. In ad-hoc mode there is no standalone discovery service. When a client wanted to invoke a service, it will broadcast an message (normally in UDP protocol) to the entire network with the service match criteria. All services which enabled the discovery behavior will receive this message and only those matched services will send their endpoint back to the client. The managed proxy discovery service works as I described above. In this post I will only cover the managed proxy mode, where there’s a discovery service. For more information about the ad-hoc mode please refer to the MSDN.   Service Announcement and Probe The main functionality of discovery service should be return the proper endpoint addresses back to the service who is looking for. In most cases the consume service (as a client) will send the contract which it wanted to request to the discovery service. And then the discovery service will find the endpoint and respond. Sometimes the contract and endpoint are not enough. It also contains versioning, extensions attributes. This post I will only cover the case includes contract and endpoint. When a client (or sometimes a service who need to invoke another service) need to connect to a target service, it will firstly request the discovery service through the “Probe” method with the criteria. Basically the criteria contains the contract type name of the target service. Then the discovery service will search its endpoint repository by the criteria. The repository might be a database, a distributed cache or a flat XML file. If it matches, the discovery service will grab the endpoint information (it’s called discovery endpoint metadata in WCF) and send back. And this is called “Probe”. Finally the client received the discovery endpoint metadata and will use the endpoint to connect to the target service. Besides the probe, discovery service should take the responsible to know there is a new service available when it goes online, as well as stopped when it goes offline. This feature is named “Announcement”. When a service started and stopped, it will announce to the discovery service. So the basic functionality of a discovery service should includes: 1, An endpoint which receive the service online message, and add the service endpoint information in the discovery repository. 2, An endpoint which receive the service offline message, and remove the service endpoint information from the discovery repository. 3, An endpoint which receive the client probe message, and return the matches service endpoints, and return the discovery endpoint metadata. WCF 4.0 discovery service just covers all these features in it's infrastructure classes.   Discovery Service in WCF 4.0 WCF 4.0 introduced a new assembly named System.ServiceModel.Discovery which has all necessary classes and interfaces to build a WS-Discovery compliant discovery service. It supports ad-hoc and managed proxy modes. For the case mentioned in this post, what we need to build is a standalone discovery service, which is the managed proxy discovery service mode. To build a managed discovery service in WCF 4.0 just create a new class inherits from the abstract class System.ServiceModel.Discovery.DiscoveryProxy. This class implemented and abstracted the procedures of service announcement and probe. And it exposes 8 abstract methods where we can implement our own endpoint register, unregister and find logic. These 8 methods are asynchronized, which means all invokes to the discovery service are asynchronously, for better service capability and performance. 1, OnBeginOnlineAnnouncement, OnEndOnlineAnnouncement: Invoked when a service sent the online announcement message. We need to add the endpoint information to the repository in this method. 2, OnBeginOfflineAnnouncement, OnEndOfflineAnnouncement: Invoked when a service sent the offline announcement message. We need to remove the endpoint information from the repository in this method. 3, OnBeginFind, OnEndFind: Invoked when a client sent the probe message that want to find the service endpoint information. We need to look for the proper endpoints by matching the client’s criteria through the repository in this method. 4, OnBeginResolve, OnEndResolve: Invoked then a client sent the resolve message. Different from the find method, when using resolve method the discovery service will return the exactly one service endpoint metadata to the client. In our example we will NOT implement this method.   Let’s create our own discovery service, inherit the base System.ServiceModel.Discovery.DiscoveryProxy. We also need to specify the service behavior in this class. Since the build-in discovery service host class only support the singleton mode, we must set its instance context mode to single. 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Text; 5: using System.ServiceModel.Discovery; 6: using System.ServiceModel; 7:  8: namespace Phare.Service 9: { 10: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] 11: public class ManagedProxyDiscoveryService : DiscoveryProxy 12: { 13: protected override IAsyncResult OnBeginFind(FindRequestContext findRequestContext, AsyncCallback callback, object state) 14: { 15: throw new NotImplementedException(); 16: } 17:  18: protected override IAsyncResult OnBeginOfflineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state) 19: { 20: throw new NotImplementedException(); 21: } 22:  23: protected override IAsyncResult OnBeginOnlineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state) 24: { 25: throw new NotImplementedException(); 26: } 27:  28: protected override IAsyncResult OnBeginResolve(ResolveCriteria resolveCriteria, AsyncCallback callback, object state) 29: { 30: throw new NotImplementedException(); 31: } 32:  33: protected override void OnEndFind(IAsyncResult result) 34: { 35: throw new NotImplementedException(); 36: } 37:  38: protected override void OnEndOfflineAnnouncement(IAsyncResult result) 39: { 40: throw new NotImplementedException(); 41: } 42:  43: protected override void OnEndOnlineAnnouncement(IAsyncResult result) 44: { 45: throw new NotImplementedException(); 46: } 47:  48: protected override EndpointDiscoveryMetadata OnEndResolve(IAsyncResult result) 49: { 50: throw new NotImplementedException(); 51: } 52: } 53: } Then let’s implement the online, offline and find methods one by one. WCF discovery service gives us full flexibility to implement the endpoint add, remove and find logic. For the demo purpose we will use an internal dictionary to store the services’ endpoint metadata. In the next post we will see how to serialize and store these information in database. Define a concurrent dictionary inside the service class since our it will be used in the multiple threads scenario. 1: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] 2: public class ManagedProxyDiscoveryService : DiscoveryProxy 3: { 4: private ConcurrentDictionary<EndpointAddress, EndpointDiscoveryMetadata> _services; 5:  6: public ManagedProxyDiscoveryService() 7: { 8: _services = new ConcurrentDictionary<EndpointAddress, EndpointDiscoveryMetadata>(); 9: } 10: } Then we can simply implement the logic of service online and offline. 1: protected override IAsyncResult OnBeginOnlineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state) 2: { 3: _services.AddOrUpdate(endpointDiscoveryMetadata.Address, endpointDiscoveryMetadata, (key, value) => endpointDiscoveryMetadata); 4: return new OnOnlineAnnouncementAsyncResult(callback, state); 5: } 6:  7: protected override void OnEndOnlineAnnouncement(IAsyncResult result) 8: { 9: OnOnlineAnnouncementAsyncResult.End(result); 10: } 11:  12: protected override IAsyncResult OnBeginOfflineAnnouncement(DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, object state) 13: { 14: EndpointDiscoveryMetadata endpoint = null; 15: _services.TryRemove(endpointDiscoveryMetadata.Address, out endpoint); 16: return new OnOfflineAnnouncementAsyncResult(callback, state); 17: } 18:  19: protected override void OnEndOfflineAnnouncement(IAsyncResult result) 20: { 21: OnOfflineAnnouncementAsyncResult.End(result); 22: } Regards the find method, the parameter FindRequestContext.Criteria has a method named IsMatch, which can be use for us to evaluate which service metadata is satisfied with the criteria. So the implementation of find method would be like this. 1: protected override IAsyncResult OnBeginFind(FindRequestContext findRequestContext, AsyncCallback callback, object state) 2: { 3: _services.Where(s => findRequestContext.Criteria.IsMatch(s.Value)) 4: .Select(s => s.Value) 5: .All(meta => 6: { 7: findRequestContext.AddMatchingEndpoint(meta); 8: return true; 9: }); 10: return new OnFindAsyncResult(callback, state); 11: } 12:  13: protected override void OnEndFind(IAsyncResult result) 14: { 15: OnFindAsyncResult.End(result); 16: } As you can see, we checked all endpoints metadata in repository by invoking the IsMatch method. Then add all proper endpoints metadata into the parameter. Finally since all these methods are asynchronized we need some AsyncResult classes as well. Below are the base class and the inherited classes used in previous methods. 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Text; 5: using System.Threading; 6:  7: namespace Phare.Service 8: { 9: abstract internal class AsyncResult : IAsyncResult 10: { 11: AsyncCallback callback; 12: bool completedSynchronously; 13: bool endCalled; 14: Exception exception; 15: bool isCompleted; 16: ManualResetEvent manualResetEvent; 17: object state; 18: object thisLock; 19:  20: protected AsyncResult(AsyncCallback callback, object state) 21: { 22: this.callback = callback; 23: this.state = state; 24: this.thisLock = new object(); 25: } 26:  27: public object AsyncState 28: { 29: get 30: { 31: return state; 32: } 33: } 34:  35: public WaitHandle AsyncWaitHandle 36: { 37: get 38: { 39: if (manualResetEvent != null) 40: { 41: return manualResetEvent; 42: } 43: lock (ThisLock) 44: { 45: if (manualResetEvent == null) 46: { 47: manualResetEvent = new ManualResetEvent(isCompleted); 48: } 49: } 50: return manualResetEvent; 51: } 52: } 53:  54: public bool CompletedSynchronously 55: { 56: get 57: { 58: return completedSynchronously; 59: } 60: } 61:  62: public bool IsCompleted 63: { 64: get 65: { 66: return isCompleted; 67: } 68: } 69:  70: object ThisLock 71: { 72: get 73: { 74: return this.thisLock; 75: } 76: } 77:  78: protected static TAsyncResult End<TAsyncResult>(IAsyncResult result) 79: where TAsyncResult : AsyncResult 80: { 81: if (result == null) 82: { 83: throw new ArgumentNullException("result"); 84: } 85:  86: TAsyncResult asyncResult = result as TAsyncResult; 87:  88: if (asyncResult == null) 89: { 90: throw new ArgumentException("Invalid async result.", "result"); 91: } 92:  93: if (asyncResult.endCalled) 94: { 95: throw new InvalidOperationException("Async object already ended."); 96: } 97:  98: asyncResult.endCalled = true; 99:  100: if (!asyncResult.isCompleted) 101: { 102: asyncResult.AsyncWaitHandle.WaitOne(); 103: } 104:  105: if (asyncResult.manualResetEvent != null) 106: { 107: asyncResult.manualResetEvent.Close(); 108: } 109:  110: if (asyncResult.exception != null) 111: { 112: throw asyncResult.exception; 113: } 114:  115: return asyncResult; 116: } 117:  118: protected void Complete(bool completedSynchronously) 119: { 120: if (isCompleted) 121: { 122: throw new InvalidOperationException("This async result is already completed."); 123: } 124:  125: this.completedSynchronously = completedSynchronously; 126:  127: if (completedSynchronously) 128: { 129: this.isCompleted = true; 130: } 131: else 132: { 133: lock (ThisLock) 134: { 135: this.isCompleted = true; 136: if (this.manualResetEvent != null) 137: { 138: this.manualResetEvent.Set(); 139: } 140: } 141: } 142:  143: if (callback != null) 144: { 145: callback(this); 146: } 147: } 148:  149: protected void Complete(bool completedSynchronously, Exception exception) 150: { 151: this.exception = exception; 152: Complete(completedSynchronously); 153: } 154: } 155: } 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; 4: using System.Text; 5: using System.ServiceModel.Discovery; 6: using Phare.Service; 7:  8: namespace Phare.Service 9: { 10: internal sealed class OnOnlineAnnouncementAsyncResult : AsyncResult 11: { 12: public OnOnlineAnnouncementAsyncResult(AsyncCallback callback, object state) 13: : base(callback, state) 14: { 15: this.Complete(true); 16: } 17:  18: public static void End(IAsyncResult result) 19: { 20: AsyncResult.End<OnOnlineAnnouncementAsyncResult>(result); 21: } 22:  23: } 24:  25: sealed class OnOfflineAnnouncementAsyncResult : AsyncResult 26: { 27: public OnOfflineAnnouncementAsyncResult(AsyncCallback callback, object state) 28: : base(callback, state) 29: { 30: this.Complete(true); 31: } 32:  33: public static void End(IAsyncResult result) 34: { 35: AsyncResult.End<OnOfflineAnnouncementAsyncResult>(result); 36: } 37: } 38:  39: sealed class OnFindAsyncResult : AsyncResult 40: { 41: public OnFindAsyncResult(AsyncCallback callback, object state) 42: : base(callback, state) 43: { 44: this.Complete(true); 45: } 46:  47: public static void End(IAsyncResult result) 48: { 49: AsyncResult.End<OnFindAsyncResult>(result); 50: } 51: } 52:  53: sealed class OnResolveAsyncResult : AsyncResult 54: { 55: EndpointDiscoveryMetadata matchingEndpoint; 56:  57: public OnResolveAsyncResult(EndpointDiscoveryMetadata matchingEndpoint, AsyncCallback callback, object state) 58: : base(callback, state) 59: { 60: this.matchingEndpoint = matchingEndpoint; 61: this.Complete(true); 62: } 63:  64: public static EndpointDiscoveryMetadata End(IAsyncResult result) 65: { 66: OnResolveAsyncResult thisPtr = AsyncResult.End<OnResolveAsyncResult>(result); 67: return thisPtr.matchingEndpoint; 68: } 69: } 70: } Now we have finished the discovery service. The next step is to host it. The discovery service is a standard WCF service. So we can use ServiceHost on a console application, windows service, or in IIS as usual. The following code is how to host the discovery service we had just created in a console application. 1: static void Main(string[] args) 2: { 3: using (var host = new ServiceHost(new ManagedProxyDiscoveryService())) 4: { 5: host.Opened += (sender, e) => 6: { 7: host.Description.Endpoints.All((ep) => 8: { 9: Console.WriteLine(ep.ListenUri); 10: return true; 11: }); 12: }; 13:  14: try 15: { 16: // retrieve the announcement, probe endpoint and binding from configuration 17: var announcementEndpointAddress = new EndpointAddress(ConfigurationManager.AppSettings["announcementEndpointAddress"]); 18: var probeEndpointAddress = new EndpointAddress(ConfigurationManager.AppSettings["probeEndpointAddress"]); 19: var binding = Activator.CreateInstance(Type.GetType(ConfigurationManager.AppSettings["bindingType"], true, true)) as Binding; 20: var announcementEndpoint = new AnnouncementEndpoint(binding, announcementEndpointAddress); 21: var probeEndpoint = new DiscoveryEndpoint(binding, probeEndpointAddress); 22: probeEndpoint.IsSystemEndpoint = false; 23: // append the service endpoint for announcement and probe 24: host.AddServiceEndpoint(announcementEndpoint); 25: host.AddServiceEndpoint(probeEndpoint); 26:  27: host.Open(); 28:  29: Console.WriteLine("Press any key to exit."); 30: Console.ReadKey(); 31: } 32: catch (Exception ex) 33: { 34: Console.WriteLine(ex.ToString()); 35: } 36: } 37:  38: Console.WriteLine("Done."); 39: Console.ReadKey(); 40: } What we need to notice is that, the discovery service needs two endpoints for announcement and probe. In this example I just retrieve them from the configuration file. I also specified the binding of these two endpoints in configuration file as well. 1: <?xml version="1.0"?> 2: <configuration> 3: <startup> 4: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/> 5: </startup> 6: <appSettings> 7: <add key="announcementEndpointAddress" value="net.tcp://localhost:10010/announcement"/> 8: <add key="probeEndpointAddress" value="net.tcp://localhost:10011/probe"/> 9: <add key="bindingType" value="System.ServiceModel.NetTcpBinding, System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> 10: </appSettings> 11: </configuration> And this is the console screen when I ran my discovery service. As you can see there are two endpoints listening for announcement message and probe message.   Discoverable Service and Client Next, let’s create a WCF service that is discoverable, which means it can be found by the discovery service. To do so, we need to let the service send the online announcement message to the discovery service, as well as offline message before it shutdown. Just create a simple service which can make the incoming string to upper. The service contract and implementation would be like this. 1: [ServiceContract] 2: public interface IStringService 3: { 4: [OperationContract] 5: string ToUpper(string content); 6: } 1: public class StringService : IStringService 2: { 3: public string ToUpper(string content) 4: { 5: return content.ToUpper(); 6: } 7: } Then host this service in the console application. In order to make the discovery service easy to be tested the service address will be changed each time it’s started. 1: static void Main(string[] args) 2: { 3: var baseAddress = new Uri(string.Format("net.tcp://localhost:11001/stringservice/{0}/", Guid.NewGuid().ToString())); 4:  5: using (var host = new ServiceHost(typeof(StringService), baseAddress)) 6: { 7: host.Opened += (sender, e) => 8: { 9: Console.WriteLine("Service opened at {0}", host.Description.Endpoints.First().ListenUri); 10: }; 11:  12: host.AddServiceEndpoint(typeof(IStringService), new NetTcpBinding(), string.Empty); 13:  14: host.Open(); 15:  16: Console.WriteLine("Press any key to exit."); 17: Console.ReadKey(); 18: } 19: } Currently this service is NOT discoverable. We need to add a special service behavior so that it could send the online and offline message to the discovery service announcement endpoint when the host is opened and closed. WCF 4.0 introduced a service behavior named ServiceDiscoveryBehavior. When we specified the announcement endpoint address and appended it to the service behaviors this service will be discoverable. 1: var announcementAddress = new EndpointAddress(ConfigurationManager.AppSettings["announcementEndpointAddress"]); 2: var announcementBinding = Activator.CreateInstance(Type.GetType(ConfigurationManager.AppSettings["bindingType"], true, true)) as Binding; 3: var announcementEndpoint = new AnnouncementEndpoint(announcementBinding, announcementAddress); 4: var discoveryBehavior = new ServiceDiscoveryBehavior(); 5: discoveryBehavior.AnnouncementEndpoints.Add(announcementEndpoint); 6: host.Description.Behaviors.Add(discoveryBehavior); The ServiceDiscoveryBehavior utilizes the service extension and channel dispatcher to implement the online and offline announcement logic. In short, it injected the channel open and close procedure and send the online and offline message to the announcement endpoint.   On client side, when we have the discovery service, a client can invoke a service without knowing its endpoint. WCF discovery assembly provides a class named DiscoveryClient, which can be used to find the proper service endpoint by passing the criteria. In the code below I initialized the DiscoveryClient, specified the discovery service probe endpoint address. Then I created the find criteria by specifying the service contract I wanted to use and invoke the Find method. This will send the probe message to the discovery service and it will find the endpoints back to me. The discovery service will return all endpoints that matches the find criteria, which means in the result of the find method there might be more than one endpoints. In this example I just returned the first matched one back. In the next post I will show how to extend our discovery service to make it work like a service load balancer. 1: static EndpointAddress FindServiceEndpoint() 2: { 3: var probeEndpointAddress = new EndpointAddress(ConfigurationManager.AppSettings["probeEndpointAddress"]); 4: var probeBinding = Activator.CreateInstance(Type.GetType(ConfigurationManager.AppSettings["bindingType"], true, true)) as Binding; 5: var discoveryEndpoint = new DiscoveryEndpoint(probeBinding, probeEndpointAddress); 6:  7: EndpointAddress address = null; 8: FindResponse result = null; 9: using (var discoveryClient = new DiscoveryClient(discoveryEndpoint)) 10: { 11: result = discoveryClient.Find(new FindCriteria(typeof(IStringService))); 12: } 13:  14: if (result != null && result.Endpoints.Any()) 15: { 16: var endpointMetadata = result.Endpoints.First(); 17: address = endpointMetadata.Address; 18: } 19: return address; 20: } Once we probed the discovery service we will receive the endpoint. So in the client code we can created the channel factory from the endpoint and binding, and invoke to the service. When creating the client side channel factory we need to make sure that the client side binding should be the same as the service side. WCF discovery service can be used to find the endpoint for a service contract, but the binding is NOT included. This is because the binding was not in the WS-Discovery specification. In the next post I will demonstrate how to add the binding information into the discovery service. At that moment the client don’t need to create the binding by itself. Instead it will use the binding received from the discovery service. 1: static void Main(string[] args) 2: { 3: Console.WriteLine("Say something..."); 4: var content = Console.ReadLine(); 5: while (!string.IsNullOrWhiteSpace(content)) 6: { 7: Console.WriteLine("Finding the service endpoint..."); 8: var address = FindServiceEndpoint(); 9: if (address == null) 10: { 11: Console.WriteLine("There is no endpoint matches the criteria."); 12: } 13: else 14: { 15: Console.WriteLine("Found the endpoint {0}", address.Uri); 16:  17: var factory = new ChannelFactory<IStringService>(new NetTcpBinding(), address); 18: factory.Opened += (sender, e) => 19: { 20: Console.WriteLine("Connecting to {0}.", factory.Endpoint.ListenUri); 21: }; 22: var proxy = factory.CreateChannel(); 23: using (proxy as IDisposable) 24: { 25: Console.WriteLine("ToUpper: {0} => {1}", content, proxy.ToUpper(content)); 26: } 27: } 28:  29: Console.WriteLine("Say something..."); 30: content = Console.ReadLine(); 31: } 32: } Similarly, the discovery service probe endpoint and binding were defined in the configuration file. 1: <?xml version="1.0"?> 2: <configuration> 3: <startup> 4: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/> 5: </startup> 6: <appSettings> 7: <add key="announcementEndpointAddress" value="net.tcp://localhost:10010/announcement"/> 8: <add key="probeEndpointAddress" value="net.tcp://localhost:10011/probe"/> 9: <add key="bindingType" value="System.ServiceModel.NetTcpBinding, System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> 10: </appSettings> 11: </configuration> OK, now let’s have a test. Firstly start the discovery service, and then start our discoverable service. When it started it will announced to the discovery service and registered its endpoint into the repository, which is the local dictionary. And then start the client and type something. As you can see the client asked the discovery service for the endpoint and then establish the connection to the discoverable service. And more interesting, do NOT close the client console but terminate the discoverable service but press the enter key. This will make the service send the offline message to the discovery service. Then start the discoverable service again. Since we made it use a different address each time it started, currently it should be hosted on another address. If we enter something in the client we could see that it asked the discovery service and retrieve the new endpoint, and connect the the service.   Summary In this post I discussed the benefit of using the discovery service and the procedures of service announcement and probe. I also demonstrated how to leverage the WCF Discovery feature in WCF 4.0 to build a simple managed discovery service. For test purpose, in this example I used the in memory dictionary as the discovery endpoint metadata repository. And when finding I also just return the first matched endpoint back. I also hard coded the bindings between the discoverable service and the client. In next post I will show you how to solve the problem mentioned above, as well as some additional feature for production usage. You can download the code here.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

  Read the article

• New features of C# 4.0

  This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for .NET Professionals 50 New Features of SQL Server 2008 IIS 7.0 New features Introduction It is now close to a year since Microsoft Visual C# 3.0 shipped as part of Visual Studio 2008. In the VS Managed Languages team we are hard at work on creating the next version of the language (with the unsurprising working title of C# 4.0), and this document is a first public description of the planned language features as we currently see them. Please be advised that all this is in early stages of production and is subject to change. Part of the reason for sharing our plans in public so early is precisely to get the kind of feedback that will cause us to improve the final product before it rolls out. Simultaneously with the publication of this whitepaper, a first public CTP (community technology preview) of Visual Studio 2010 is going out as a Virtual PC image for everyone to try. Please use it to play and experiment with the features, and let us know of any thoughts you have. We ask for your understanding and patience working with very early bits, where especially new or newly implemented features do not have the quality or stability of a final product. The aim of the CTP is not to give you a productive work environment but to give you the best possible impression of what we are working on for the next release. The CTP contains a number of walkthroughs, some of which highlight the new language features of C# 4.0. Those are excellent for getting a hands-on guided tour through the details of some common scenarios for the features. You may consider this whitepaper a companion document to these walkthroughs, complementing them with a focus on the overall language features and how they work, as opposed to the specifics of the concrete scenarios. C# 4.0 The major theme for C# 4.0 is dynamic programming. Increasingly, objects are “dynamic” in the sense that their structure and behavior is not captured by a static type, or at least not one that the compiler knows about when compiling your program. Some examples include a. objects from dynamic programming languages, such as Python or Ruby b. COM objects accessed through IDispatch c. ordinary .NET types accessed through reflection d. objects with changing structure, such as HTML DOM objects While C# remains a statically typed language, we aim to vastly improve the interaction with such objects. A secondary theme is co-evolution with Visual Basic. Going forward we will aim to maintain the individual character of each language, but at the same time important new features should be introduced in both languages at the same time. They should be differentiated more by style and feel than by feature set. The new features in C# 4.0 fall into four groups: Dynamic lookup Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime. Named and optional parameters Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position. COM specific interop features Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience. Variance It used to be that an IEnumerable<string> wasn’t an IEnumerable<object>. Now it is – C# embraces type safe “co-and contravariance” and common BCL types are updated to take advantage of that. Dynamic Lookup Dynamic lookup allows you a unified approach to invoking things dynamically. With dynamic lookup, when you have an object in your hand you do not need to worry about whether it comes from COM, IronPython, the HTML DOM or reflection; you just apply operations to it and leave it to the runtime to figure out what exactly those operations mean for that particular object. This affords you enormous flexibility, and can greatly simplify your code, but it does come with a significant drawback: Static typing is not maintained for these operations. A dynamic object is assumed at compile time to support any operation, and only at runtime will you get an error if it wasn’t so. Oftentimes this will be no loss, because the object wouldn’t have a static type anyway, in other cases it is a tradeoff between brevity and safety. In order to facilitate this tradeoff, it is a design goal of C# to allow you to opt in or opt out of dynamic behavior on every single call. The dynamic type C# 4.0 introduces a new static type called dynamic. When you have an object of type dynamic you can “do things to it” that are resolved only at runtime: dynamic d = GetDynamicObject(…); d.M(7); The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it. The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs: dynamic d = 7; // implicit conversion int i = d; // assignment conversion Dynamic operations Not only method calls, but also field and property accesses, indexer and operator calls and even delegate invocations can be dispatched dynamically: dynamic d = GetDynamicObject(…); d.M(7); // calling methods d.f = d.P; // getting and settings fields and properties d[“one”] = d[“two”]; // getting and setting thorugh indexers int i = d + 3; // calling operators string s = d(5,7); // invoking as a delegate The role of the C# compiler here is simply to package up the necessary information about “what is being done to d”, so that the runtime can pick it up and determine what the exact meaning of it is given an actual object d. Think of it as deferring part of the compiler’s job to runtime. The result of any dynamic operation is itself of type dynamic. Runtime lookup At runtime a dynamic operation is dispatched according to the nature of its target object d: COM objects If d is a COM object, the operation is dispatched dynamically through COM IDispatch. This allows calling to COM types that don’t have a Primary Interop Assembly (PIA), and relying on COM features that don’t have a counterpart in C#, such as indexed properties and default properties. Dynamic objects If d implements the interface IDynamicObject d itself is asked to perform the operation. Thus by implementing IDynamicObject a type can completely redefine the meaning of dynamic operations. This is used intensively by dynamic languages such as IronPython and IronRuby to implement their own dynamic object models. It will also be used by APIs, e.g. by the HTML DOM to allow direct access to the object’s properties using property syntax. Plain objects Otherwise d is a standard .NET object, and the operation will be dispatched using reflection on its type and a C# “runtime binder” which implements C#’s lookup and overload resolution semantics at runtime. This is essentially a part of the C# compiler running as a runtime component to “finish the work” on dynamic operations that was deferred by the static compiler. Example Assume the following code: dynamic d1 = new Foo(); dynamic d2 = new Bar(); string s; d1.M(s, d2, 3, null); Because the receiver of the call to M is dynamic, the C# compiler does not try to resolve the meaning of the call. Instead it stashes away information for the runtime about the call. This information (often referred to as the “payload”) is essentially equivalent to: “Perform an instance method call of M with the following arguments: 1. a string 2. a dynamic 3. a literal int 3 4. a literal object null” At runtime, assume that the actual type Foo of d1 is not a COM type and does not implement IDynamicObject. In this case the C# runtime binder picks up to finish the overload resolution job based on runtime type information, proceeding as follows: 1. Reflection is used to obtain the actual runtime types of the two objects, d1 and d2, that did not have a static type (or rather had the static type dynamic). The result is Foo for d1 and Bar for d2. 2. Method lookup and overload resolution is performed on the type Foo with the call M(string,Bar,3,null) using ordinary C# semantics. 3. If the method is found it is invoked; otherwise a runtime exception is thrown. Overload resolution with dynamic arguments Even if the receiver of a method call is of a static type, overload resolution can still happen at runtime. This can happen if one or more of the arguments have the type dynamic: Foo foo = new Foo(); dynamic d = new Bar(); var result = foo.M(d); The C# runtime binder will choose between the statically known overloads of M on Foo, based on the runtime type of d, namely Bar. The result is again of type dynamic. The Dynamic Language Runtime An important component in the underlying implementation of dynamic lookup is the Dynamic Language Runtime (DLR), which is a new API in .NET 4.0. The DLR provides most of the infrastructure behind not only C# dynamic lookup but also the implementation of several dynamic programming languages on .NET, such as IronPython and IronRuby. Through this common infrastructure a high degree of interoperability is ensured, but just as importantly the DLR provides excellent caching mechanisms which serve to greatly enhance the efficiency of runtime dispatch. To the user of dynamic lookup in C#, the DLR is invisible except for the improved efficiency. However, if you want to implement your own dynamically dispatched objects, the IDynamicObject interface allows you to interoperate with the DLR and plug in your own behavior. This is a rather advanced task, which requires you to understand a good deal more about the inner workings of the DLR. For API writers, however, it can definitely be worth the trouble in order to vastly improve the usability of e.g. a library representing an inherently dynamic domain. Open issues There are a few limitations and things that might work differently than you would expect. · The DLR allows objects to be created from objects that represent classes. However, the current implementation of C# doesn’t have syntax to support this. · Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload. · Anonymous functions (i.e. lambda expressions) cannot appear as arguments to a dynamic method call. The compiler cannot bind (i.e. “understand”) an anonymous function without knowing what type it is converted to. One consequence of these limitations is that you cannot easily use LINQ queries over dynamic objects: dynamic collection = …; var result = collection.Select(e => e + 5); If the Select method is an extension method, dynamic lookup will not find it. Even if it is an instance method, the above does not compile, because a lambda expression cannot be passed as an argument to a dynamic operation. There are no plans to address these limitations in C# 4.0. Named and Optional Arguments Named and optional parameters are really two distinct features, but are often useful together. Optional parameters allow you to omit arguments to member invocations, whereas named arguments is a way to provide an argument using the name of the corresponding parameter instead of relying on its position in the parameter list. Some APIs, most notably COM interfaces such as the Office automation APIs, are written specifically with named and optional parameters in mind. Up until now it has been very painful to call into these APIs from C#, with sometimes as many as thirty arguments having to be explicitly passed, most of which have reasonable default values and could be omitted. Even in APIs for .NET however you sometimes find yourself compelled to write many overloads of a method with different combinations of parameters, in order to provide maximum usability to the callers. Optional parameters are a useful alternative for these situations. Optional parameters A parameter is declared optional simply by providing a default value for it: public void M(int x, int y = 5, int z = 7); Here y and z are optional parameters and can be omitted in calls: M(1, 2, 3); // ordinary call of M M(1, 2); // omitting z – equivalent to M(1, 2, 7) M(1); // omitting both y and z – equivalent to M(1, 5, 7) Named and optional arguments C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write: M(1, z: 3); // passing z by name or M(x: 1, z: 3); // passing both x and z by name or even M(z: 3, x: 1); // reversing the order of arguments All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1. Optional and named arguments can be used not only with methods but also with indexers and constructors. Overload resolution Named and optional arguments affect overload resolution, but the changes are relatively simple: A signature is applicable if all its parameters are either optional or have exactly one corresponding argument (by name or position) in the call which is convertible to the parameter type. Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes. If two signatures are equally good, one that does not omit optional parameters is preferred. M(string s, int i = 1); M(object o); M(int i, string s = “Hello”); M(int i); M(5); Given these overloads, we can see the working of the rules above. M(string,int) is not applicable because 5 doesn’t convert to string. M(int,string) is applicable because its second parameter is optional, and so, obviously are M(object) and M(int). M(int,string) and M(int) are both better than M(object) because the conversion from 5 to int is better than the conversion from 5 to object. Finally M(int) is better than M(int,string) because no optional arguments are omitted. Thus the method that gets called is M(int). Features for COM interop Dynamic lookup as well as named and optional parameters greatly improve the experience of interoperating with COM APIs such as the Office Automation APIs. In order to remove even more of the speed bumps, a couple of small COM-specific features are also added to C# 4.0. Dynamic import Many COM methods accept and return variant types, which are represented in the PIAs as object. In the vast majority of cases, a programmer calling these methods already knows the static type of a returned object from context, but explicitly has to perform a cast on the returned value to make use of that knowledge. These casts are so common that they constitute a major nuisance. In order to facilitate a smoother experience, you can now choose to import these COM APIs in such a way that variants are instead represented using the type dynamic. In other words, from your point of view, COM signatures now have occurrences of dynamic instead of object in them. This means that you can easily access members directly off a returned object, or you can assign it to a strongly typed local variable without having to cast. To illustrate, you can now say excel.Cells[1, 1].Value = "Hello"; instead of ((Excel.Range)excel.Cells[1, 1]).Value2 = "Hello"; and Excel.Range range = excel.Cells[1, 1]; instead of Excel.Range range = (Excel.Range)excel.Cells[1, 1]; Compiling without PIAs Primary Interop Assemblies are large .NET assemblies generated from COM interfaces to facilitate strongly typed interoperability. They provide great support at design time, where your experience of the interop is as good as if the types where really defined in .NET. However, at runtime these large assemblies can easily bloat your program, and also cause versioning issues because they are distributed independently of your application. The no-PIA feature allows you to continue to use PIAs at design time without having them around at runtime. Instead, the C# compiler will bake the small part of the PIA that a program actually uses directly into its assembly. At runtime the PIA does not have to be loaded. Omitting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. Contrary to refs in C#, these are typically not meant to mutate a passed-in argument for the subsequent benefit of the caller, but are simply another way of passing value parameters. It therefore seems unreasonable that a C# programmer should have to create temporary variables for all such ref parameters and pass these by reference. Instead, specifically for COM methods, the C# compiler will allow you to pass arguments by value to such a method, and will automatically generate temporary variables to hold the passed-in values, subsequently discarding these when the call returns. In this way the caller sees value semantics, and will not experience any side effects, but the called method still gets a reference. Open issues A few COM interface features still are not surfaced in C#. Most notably these include indexed properties and default properties. As mentioned above these will be respected if you access COM dynamically, but statically typed C# code will still not recognize them. There are currently no plans to address these remaining speed bumps in C# 4.0. Variance An aspect of generics that often comes across as surprising is that the following is illegal: IList<string> strings = new List<string>(); IList<object> objects = strings; The second assignment is disallowed because strings does not have the same element type as objects. There is a perfectly good reason for this. If it were allowed you could write: objects[0] = 5; string s = strings[0]; Allowing an int to be inserted into a list of strings and subsequently extracted as a string. This would be a breach of type safety. However, there are certain interfaces where the above cannot occur, notably where there is no way to insert an object into the collection. Such an interface is IEnumerable<T>. If instead you say: IEnumerable<object> objects = strings; There is no way we can put the wrong kind of thing into strings through objects, because objects doesn’t have a method that takes an element in. Variance is about allowing assignments such as this in cases where it is safe. The result is that a lot of situations that were previously surprising now just work. Covariance In .NET 4.0 the IEnumerable<T> interface will be declared in the following way: public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IEnumerator { bool MoveNext(); T Current { get; } } The “out” in these declarations signifies that the T can only occur in output position in the interface – the compiler will complain otherwise. In return for this restriction, the interface becomes “covariant” in T, which means that an IEnumerable<A> is considered an IEnumerable<B> if A has a reference conversion to B. As a result, any sequence of strings is also e.g. a sequence of objects. This is useful e.g. in many LINQ methods. Using the declarations above: var result = strings.Union(objects); // succeeds with an IEnumerable<object> This would previously have been disallowed, and you would have had to to some cumbersome wrapping to get the two sequences to have the same element type. Contravariance Type parameters can also have an “in” modifier, restricting them to occur only in input positions. An example is IComparer<T>: public interface IComparer<in T> { public int Compare(T left, T right); } The somewhat baffling result is that an IComparer<object> can in fact be considered an IComparer<string>! It makes sense when you think about it: If a comparer can compare any two objects, it can certainly also compare two strings. This property is referred to as contravariance. A generic type can have both in and out modifiers on its type parameters, as is the case with the Func<…> delegate types: public delegate TResult Func<in TArg, out TResult>(TArg arg); Obviously the argument only ever comes in, and the result only ever comes out. Therefore a Func<object,string> can in fact be used as a Func<string,object>. Limitations Variant type parameters can only be declared on interfaces and delegate types, due to a restriction in the CLR. Variance only applies when there is a reference conversion between the type arguments. For instance, an IEnumerable<int> is not an IEnumerable<object> because the conversion from int to object is a boxing conversion, not a reference conversion. Also please note that the CTP does not contain the new versions of the .NET types mentioned above. In order to experiment with variance you have to declare your own variant interfaces and delegate types. COM Example Here is a larger Office automation example that shows many of the new C# features in action. using System; using System.Diagnostics; using System.Linq; using Excel = Microsoft.Office.Interop.Excel; using Word = Microsoft.Office.Interop.Word; class Program { static void Main(string[] args) { var excel = new Excel.Application(); excel.Visible = true; excel.Workbooks.Add(); // optional arguments omitted excel.Cells[1, 1].Value = "Process Name"; // no casts; Value dynamically excel.Cells[1, 2].Value = "Memory Usage"; // accessed var processes = Process.GetProcesses() .OrderByDescending(p =&gt; p.WorkingSet) .Take(10); int i = 2; foreach (var p in processes) { excel.Cells[i, 1].Value = p.ProcessName; // no casts excel.Cells[i, 2].Value = p.WorkingSet; // no casts i++; } Excel.Range range = excel.Cells[1, 1]; // no casts Excel.Chart chart = excel.ActiveWorkbook.Charts. Add(After: excel.ActiveSheet); // named and optional arguments chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); //named+optional chart.ChartStyle = 45; chart.CopyPicture(Excel.XlPictureAppearance.xlScreen, Excel.XlCopyPictureFormat.xlBitmap, Excel.XlPictureAppearance.xlScreen); var word = new Word.Application(); word.Visible = true; word.Documents.Add(); // optional arguments word.Selection.Paste(); } } The code is much more terse and readable than the C# 3.0 counterpart. Note especially how the Value property is accessed dynamically. This is actually an indexed property, i.e. a property that takes an argument; something which C# does not understand. However the argument is optional. Since the access is dynamic, it goes through the runtime COM binder which knows to substitute the default value and call the indexed property. Thus, dynamic COM allows you to avoid accesses to the puzzling Value2 property of Excel ranges. Relationship with Visual Basic A number of the features introduced to C# 4.0 already exist or will be introduced in some form or other in Visual Basic: · Late binding in VB is similar in many ways to dynamic lookup in C#, and can be expected to make more use of the DLR in the future, leading to further parity with C#. · Named and optional arguments have been part of Visual Basic for a long time, and the C# version of the feature is explicitly engineered with maximal VB interoperability in mind. · NoPIA and variance are both being introduced to VB and C# at the same time. VB in turn is adding a number of features that have hitherto been a mainstay of C#. As a result future versions of C# and VB will have much better feature parity, for the benefit of everyone. Resources All available resources concerning C# 4.0 can be accessed through the C# Dev Center. Specifically, this white paper and other resources can be found at the Code Gallery site. Enjoy! span.fullpost {display:none;}

  Read the article

• Apache segfault glibc segfault

  - by tester

  I keep getting (about every 5-6 hours) this segfault in apache: [Tue Jun 26 12:43:10 2012] [notice] child pid 26810 exit signal Aborted (6) *** glibc detected *** /usr/sbin/apache2: free(): invalid pointer: 0xb68c2628 *** ======= Backtrace: ========= /lib/i386-linux-gnu/libc.so.6(+0x6ff22)[0xb75aef22] /lib/i386-linux-gnu/libc.so.6(+0x70bc2)[0xb75afbc2] /lib/i386-linux-gnu/libc.so.6(cfree+0x6d)[0xb75b2cad] /usr/lib/apache2/modules/libphp5.so(destroy_zend_class+0x228)[0xb5d40518] /usr/lib/apache2/modules/libphp5.so(zend_hash_clean+0x77)[0xb5d58957] /usr/lib/php5/220100525+lfs/apc.so(apc_interned_strings_shutdown+0x32)[0xb64930b2] /usr/lib/apache2/modules/libphp5.so(+0x318ff0)[0xb5d56ff0] /usr/lib/apache2/modules/libphp5.so(zend_hash_graceful_reverse_destroy+0x27)[0xb5d58a67] /usr/lib/apache2/modules/libphp5.so(zend_destroy_modules+0x3c)[0xb5d506cc] /usr/lib/apache2/modules/libphp5.so(+0x30c743)[0xb5d4a743] /usr/lib/apache2/modules/libphp5.so(php_module_shutdown+0x42)[0xb5ce5172] /usr/lib/apache2/modules/libphp5.so(php_module_shutdown_wrapper+0x17)[0xb5ce5257] /usr/lib/apache2/modules/libphp5.so(+0x3bebe1)[0xb5dfcbe1] /usr/lib/libapr-1.so.0(+0x19846)[0xb76f2846] /usr/lib/libapr-1.so.0(apr_pool_destroy+0x52)[0xb76f19ec] /usr/sbin/apache2(+0x4ccee)[0xb77eccee] ======= Memory map: ======== b2e18000-b2e2c000 rw-s 00000000 00:04 8841030 /dev/zero (deleted) b2e2c000-b2eaa000 rw-s 00000000 00:04 8841029 /dev/zero (deleted) b2eaa000-b2eab000 ---p 00000000 00:00 0 b2eab000-b36ab000 rw-p 00000000 00:00 0 b5900000-b5921000 rw-p 00000000 00:00 0 b5921000-b5a00000 ---p 00000000 00:00 0 b5a3e000-b60bd000 r-xp 00000000 ca:00 44137 /usr/lib/apache2/modules/libphp5.so b60bd000-b611e000 r--p 0067f000 ca:00 44137 /usr/lib/apache2/modules/libphp5.so b611e000-b6123000 rw-p 006e0000 ca:00 44137 /usr/lib/apache2/modules/libphp5.so b6123000-b6142000 rw-p 00000000 00:00 0 b6142000-b6147000 r-xp 00000000 ca:00 24570 /lib/i386-linux-gnu/libnss_dns-2.13.so b6147000-b6148000 r--p 00004000 ca:00 24570 /lib/i386-linux-gnu/libnss_dns-2.13.so b6148000-b6149000 rw-p 00005000 ca:00 24570 /lib/i386-linux-gnu/libnss_dns-2.13.so b6149000-b6175000 rw-p 00000000 00:00 0 b6175000-b6180000 r-xp 00000000 ca:00 24572 /lib/i386-linux-gnu/libnss_files-2.13.so b6180000-b6181000 r--p 0000a000 ca:00 24572 /lib/i386-linux-gnu/libnss_files-2.13.so b6181000-b6182000 rw-p 0000b000 ca:00 24572 /lib/i386-linux-gnu/libnss_files-2.13.so b6182000-b618c000 r-xp 00000000 ca:00 24576 /lib/i386-linux-gnu/libnss_nis-2.13.so b618c000-b618d000 r--p 00009000 ca:00 24576 /lib/i386-linux-gnu/libnss_nis-2.13.so b618d000-b618e000 rw-p 0000a000 ca:00 24576 /lib/i386-linux-gnu/libnss_nis-2.13.so b618e000-b6196000 r-xp 00000000 ca:00 24562 /lib/i386-linux-gnu/libnss_compat-2.13.so b6196000-b6197000 r--p 00007000 ca:00 24562 /lib/i386-linux-gnu/libnss_compat-2.13.so b6197000-b6198000 rw-p 00008000 ca:00 24562 /lib/i386-linux-gnu/libnss_compat-2.13.so b6198000-b6270000 rw-p 00000000 00:00 0 b6270000-b6274000 rw-p 00000000 00:00 0 b6468000-b6474000 rw-p 00000000 00:00 0 b6475000-b6479000 rw-p 00000000 00:00 0 b6479000-b649a000 r-xp 00000000 ca:00 65670 /usr/lib/php5/220100525+lfs/apc.so b649a000-b649b000 r--p 00021000 ca:00 65670 /usr/lib/php5/220100525+lfs/apc.so b649b000-b649c000 rw-p 00022000 ca:00 65670 /usr/lib/php5/220100525+lfs/apc.so b649c000-b64a1000 rw-p 00000000 00:00 0 b64a1000-b64a6000 rw-p 00000000 00:00 0 b64a7000-b64aa000 rw-p 00000000 00:00 0 b64aa000-b64af000 rw-p 00000000 00:00 0 b64b0000-b64b3000 rw-p 00000000 00:00 0 b64bf000-b64c4000 rw-p 00000000 00:00 0 b64c4000-b64c9000 rw-p 00000000 00:00 0 b64c9000-b64cc000 rw-p 00000000 00:00 0 b64cd000-b64cf000 rw-p 00000000 00:00 0 b64ea000-b64fd000 r-xp 00000000 ca:00 24598 /lib/i386-linux-gnu/libresolv-2.13.so b64fd000-b64fe000 r--p 00012000 ca:00 24598 /lib/i386-linux-gnu/libresolv-2.13.so b64fe000-b64ff000 rw-p 00013000 ca:00 24598 /lib/i386-linux-gnu/libresolv-2.13.so b64ff000-b6501000 rw-p 00000000 00:00 0 b650e000-b652a000 r-xp 00000000 ca:00 22450 /lib/i386-linux-gnu/libgcc_s.so.1 b652a000-b652b000 r--p 0001b000 ca:00 22450 /lib/i386-linux-gnu/libgcc_s.so.1 b652b000-b652c000 rw-p 0001c000 ca:00 22450 /lib/i386-linux-gnu/libgcc_s.so.1 b652c000-b6534000 rw-p 00000000 00:00 0 b65dd000-b65df000 rw-p 00000000 00:00 0 b67ad000-b67c2000 r-xp 00000000 ca:00 22063 /lib/i386-linux-gnu/libnsl-2.13.so b67c2000-b67c3000 r--p 00015000 ca:00 22063 /lib/i386-linux-gnu/libnsl-2.13.so b67c3000-b67c4000 rw-p 00016000 ca:00 22063 /lib/i386-linux-gnu/libnsl-2.13.so b67c4000-b67c6000 rw-p 00000000 00:00 0 b67c6000-b67ee000 r-xp 00000000 ca:00 21904 /lib/i386-linux-gnu/libm-2.13.so b67ee000-b67ef000 r--p 00028000 ca:00 21904 /lib/i386-linux-gnu/libm-2.13.so b67ef000-b67f0000 rw-p 00029000 ca:00 21904 /lib/i386-linux-gnu/libm-2.13.so b67f0000-b67f7000 r-xp 00000000 ca:00 24600 /lib/i386-linux-gnu/librt-2.13.so b67f7000-b67f8000 r--p 00006000 ca:00 24600 /lib/i386-linux-gnu/librt-2.13.so b67f8000-b67f9000 rw-p 00007000 ca:00 24600 /lib/i386-linux-gnu/librt-2.13.so b6886000-b69af000 rw-p 00000000 00:00 0 b69af000-b6b3c000 r-xp 00000000 ca:00 23592 /lib/i386-linux-gnu/libcrypto.so.1.0.0 b6b3c000-b6b4a000 r--p 0018d000 ca:00 23592 /lib/i386-linux-gnu/libcrypto.so.1.0.0 b6b4a000-b6b50000 rw-p 0019b000 ca:00 23592 /lib/i386-linux-gnu/libcrypto.so.1.0.0 b6b50000-b6b53000 rw-p 00000000 00:00 0 b6b53000-b6b9b000 r-xp 00000000 ca:00 23621 /lib/i386-linux-gnu/libssl.so.1.0.0 b6b9b000-b6b9d000 r--p 00047000 ca:00 23621 /lib/i386-linux-gnu/libssl.so.1.0.0 b6b9d000-b6ba0000 rw-p 00049000 ca:00 23621 /lib/i386-linux-gnu/libssl.so.1.0.0 b6ba0000-b6c7e000 r-xp 00000000 ca:00 9878 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.16 b6c7e000-b6c7f000 ---p 000de000 ca:00 9878 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.16 b6c7f000-b6c83000 r--p 000de000 ca:00 9878 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.16 b6c83000-b6c84000 rw-p 000e2000 ca:00 9878 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.16 b6c84000-b6c8b000 rw-p 00000000 00:00 0 b6c93000-b6cd4000 rw-p 00000000 00:00 0 b6cd4000-b6ce0000 rw-p 00000000 00:00 0 b6cea000-b6cef000 r-xp 00000000 ca:00 45178 /usr/lib/apache2/modules/mod_status.so b6cef000-b6cf0000 r--p 00004000 ca:00 45178 /usr/lib/apache2/modules/mod_status.so b6cf0000-b6cf1000 rw-p 00005000 ca:00 45178 /usr/lib/apache2/modules/mod_status.so b6cf1000-b6d19000 r-xp 00000000 ca:00 45175 /usr/lib/apache2/modules/mod_ssl.so b6d19000-b6d1a000 ---p 00028000 ca:00 45175 /usr/lib/apache2/modules/mod_ssl.so b6d1a000-b6d1b000 r--p 00028000 ca:00 45175 /usr/lib/apache2/modules/mod_ssl.so b6d1b000-b6d1c000 rw-p 00029000 ca:00 45175 /usr/lib/apache2/modules/mod_ssl.so b6d1c000-b6d1e000 rw-p 00000000 00:00 0 b6d1e000-b6d20000 r-xp 00000000 ca:00 45166 /usr/lib/apache2/modules/mod_setenvif.so b6d20000-b6d21000 r--p 00001000 ca:00 45166 /usr/lib/apache2/modules/mod_setenvif.so b6d21000-b6d22000 rw-p 00002000 ca:00 45166 /usr/lib/apache2/modules/mod_setenvif.so b6d22000-b6d30000 r-xp 00000000 ca:00 45195 /usr/lib/apache2/modules/mod_rewrite.so b6d30000-b6d31000 r--p 0000e000 ca:00 45195 /usr/lib/apache2/modules/mod_rewrite.so b6d31000-b6d32000 rw-p 0000f000 ca:00 45195 /usr/lib/apache2/modules/mod_rewrite.so b6d32000-b6d45000 r-xp 00000000 ca:00 45168 /usr/lib/apache2/modules/mod_proxy.so b6d45000-b6d46000 r--p 00012000 ca:00 45168 /usr/lib/apache2/modules/mod_proxy.so b6d46000-b6d47000 rw-p 00013000 ca:00 45168 /usr/lib/apache2/modules/mod_proxy.so b6d47000-b6d4e000 r-xp 00000000 ca:00 9904 /usr/lib/i386-linux-gnu/libkrb5support.so.0.1 b6d4e000-b6d4f000 r--p 00006000 ca:00 9904 /usr/lib/i386-linux-gnu/libkrb5support.so.0.1 b6d4f000-b6d50000 rw-p 00007000 ca:00 9904 /usr/lib/i386-linux-gnu/libkrb5support.so.0.1 b6d50000-b6e97000 r-xp 00000000 ca:00 3416 /usr/lib/libxml2.so.2.7.8 b6e97000-b6e9b000 r--p 00147000 ca:00 3416 /usr/lib/libxml2.so.2.7.8 b6e9b000-b6e9c000 rw-p 0014b000 ca:00 3416 /usr/lib/libxml2.so.2.7.8 b6e9c000-b6e9d000 rw-p 00000000 00:00 0 b6e9d000-b6ec4000 r-xp 00000000 ca:00 12282 /usr/lib/i386-linux-gnu/libk5crypto.so.3.1 b6ec4000-b6ec5000 r--p 00026000 ca:00 12282 /usr/lib/i386-linux-gnu/libk5crypto.so.3.1 b6ec5000-b6ec6000 rw-p 00027000 ca:00 12282 /usr/lib/i386-linux-gnu/libk5crypto.so.3.1 b6ec6000-b6f88000 r-xp 00000000 ca:00 13335 /usr/lib/i386-linux-gnu/libkrb5.so.3.3 b6f88000-b6f8e000 r--p 000c1000 ca:00 13335 /usr/lib/i386-linux-gnu/libkrb5.so.3.3 b6f8e000-b6f8f000 rw-p 000c7000 ca:00 13335 /usr/lib/i386-linux-gnu/libkrb5.so.3.3 b6f8f000-b6fca000 r-xp 00000000 ca:00 9854 /usr/lib/i386-linux-gnu/libgssapi_krb5.so.2.2 b6fca000-b6fcb000 ---p 0003b000 ca:00 9854 /usr/lib/i386-linux-gnu/libgssapi_krb5.so.2.2 b6fcb000-b6fcc000 r--p 0003b000 ca:00 9854 /usr/lib/i386-linux-gnu/libgssapi_krb5.so.2.2 b6fcc000-b6fcd000 rw-p 0003c000 ca:00 9854 /usr/lib/i386-linux-gnu/libgssapi_krb5.so.2.2 b6fcd000-b6fdc000 r-xp 00000000 ca:00 21797 /lib/libbz2.so.1.0.4 b6fdc000-b6fdd000 r--p 0000e000 ca:00 21797 /lib/libbz2.so.1.0.4 b6fdd000-b6fde000 rw-p 0000f000 ca:00 21797 /lib/libbz2.so.1.0.4 b6fde000-b702a000 r-xp 00000000 ca:00 2505 /usr/lib/libqdbm.so.14.13.0 b702a000-b702b000 r--p 0004c000 ca:00 2505 /usr/lib/libqdbm.so.14.13.0 b702b000-b702c000 rw-p 0004d000 ca:00 2505 /usr/lib/libqdbm.so.14.13.0 b702c000-b71aa000 r-xp 00000000 ca:00 10201 /usr/lib/i386-linux-gnu/libdb-4.8.so b71aa000-b71ac000 r--p 0017d000 ca:00 10201 /usr/lib/i386-linux-gnu/libdb-4.8.so b71ac000-b71ad000 rw-p 0017f000 ca:00 10201 /usr/lib/i386-linux-gnu/libdb-4.8.so b71ad000-b71f7000 r-xp 00000000 ca:00 23521 /lib/libssl.so.0.9.8 b71f7000-b71f8000 r--p 0004a000 ca:00 23521 /lib/libssl.so.0.9.8 b71f8000-b71fb000 rw-p 0004b000 ca:00 23521 /lib/libssl.so.0.9.8 b71fb000-b7359000 r-xp 00000000 ca:00 835379 /lib/libcrypto.so.0.9.8 b7359000-b735a000 ---p 0015e000 ca:00 835379 /lib/libcrypto.so.0.9.8 b735a000-b7362000 r--p 0015e000 ca:00 835379 /lib/libcrypto.so.0.9.8 b7362000-b7371000 rw-p 00166000 ca:00 835379 /lib/libcrypto.so.0.9.8 b7371000-b7374000 rw-p 00000000 00:00 0 b7374000-b73ba000 r-xp 00000000 ca:00 2503 /usr/lib/libonig.so.2.0.0 b73ba000-b73bd000 rw-p 00045000 ca:00 2503 /usr/lib/libonig.so.2.0.0 b73be000-b73c0000 rw-p 00000000 00:00 0 b73c0000-b73c7000 r-xp 00000000 ca:00 45171 /usr/lib/apache2/modules/mod_proxy_http.so b73c7000-b73c8000 r--p 00006000 ca:00 45171 /usr/lib/apache2/modules/mod_proxy_http.so b73c8000-b73c9000 rw-p 00007000 ca:00 45171 /usr/lib/apache2/modules/mod_proxy_http.so b73c9000-b73dc000 r-xp 00000000 ca:00 22461 /lib/i386-linux-gnu/libz.so.1.2.3.4 b73dc000-b73dd000 r--p 00012000 ca:00 22461 /lib/i386-linux-gnu/libz.so.1.2.3.4 b73dd000-b73de000 rw-p 00013000 ca:00 22461 /lib/i386-linux-gnu/libz.so.1.2.3.4 b73de000-b73e3000 rw-p 00000000 00:00 0 b73e3000-b73ea000 r-xp 00000000 ca:00 45188 /usr/lib/apache2/modules/mod_negotiation.so b73ea000-b73eb000 r--p 00006000 ca:00 45188 /usr/lib/apache2/modules/mod_negotiation.so b73eb000-b73ec000 rw-p 00007000 ca:00 45188 /usr/lib/apache2/modules/mod_negotiation.so b73ec000-b73f1000 rw-p 00000000 00:00 0 b73f2000-b73f5000 r-xp 00000000 ca:00 45149 /usr/lib/apache2/modules/mod_reqtimeout.so b73f5000-b73f6000 r--p 00002000 ca:00 45149 /usr/lib/apache2/modules/mod_reqtimeout.so b73f6000-b73f7000 rw-p 00003000 ca:00 45149 /usr/lib/apache2/modules/mod_reqtimeout.so b73f7000-b73fc000 rw-p 00000000 00:00 0 b73fc000-b73fe000 rw-p 00000000 00:00 0 b73fe000-b7400000 r-xp 00000000 ca:00 22437 /lib/i386-linux-gnu/libkeyutils.so.1.3 b7400000-b7401000 r--p 00001000 ca:00 22437 /lib/i386-linux-gnu/libkeyutils.so.1.3 b7401000-b7402000 rw-p 00002000 ca:00 22437 /lib/i386-linux-gnu/libkeyutils.so.1.3 b7402000-b7407000 rw-p 00000000 00:00 0 b7407000-b7409000 r-xp 00000000 ca:00 22344 /lib/i386-linux-gnu/libcom_err.so.2.1 b7409000-b740a000 r--p 00001000 ca:00 22344 /lib/i386-linux-gnu/libcom_err.so.2.1 b740a000-b740b000 rw-p 00002000 ca:00 22344 /lib/i386-linux-gnu/libcom_err.so.2.1 b740b000-b7410000 rw-p 00000000 00:00 0 b7411000-b7413000 rw-p 00000000 00:00 0 b7413000-b7416000 rw-p 00000000 00:00 0 b7416000-b7418000 rw-p 00000000 00:00 0 b7418000-b741c000 r-xp 00000000 ca:00 45176 /usr/lib/apache2/modules/mod_mime.so b741c000-b741d000 r--p 00003000 ca:00 45176 /usr/lib/apache2/modules/mod_mime.so b741d000-b741e000 rw-p 00004000 ca:00 45176 /usr/lib/apache2/modules/mod_mime.so b741e000-b7422000 r-xp 00000000 ca:00 45162 /usr/lib/apache2/modules/mod_headers.so b7422000-b7423000 r--p 00003000 ca:00 45162 /usr/lib/apache2/modules/mod_headers.so b7423000-b7424000 rw-p 00004000 ca:00 45162 /usr/lib/apache2/modules/mod_headers.so b7424000-b7426000 r-xp 00000000 ca:00 45161 /usr/lib/apache2/modules/mod_expires.so b7426000-b7427000 r--p 00001000 ca:00 45161 /usr/lib/apache2/modules/mod_expires.so b7427000-b7428000 rw-p 00002000 ca:00 45161 /usr/lib/apache2/modules/mod_expires.so b7428000-b742a000 r-xp 00000000 ca:00 45189 /usr/lib/apache2/modules/mod_dir.so b742a000-b742b000 r--p 00001000 ca:00 45189 /usr/lib/apache2/modules/mod_dir.so b742b000-b742c000 rw-p 00002000 ca:00 45189 /usr/lib/apache2/modules/mod_dir.so b742c000-b742e000 rw-p 00000000 00:00 0 b742f000-b7430000 r-xp 00000000 ca:00 45158 /usr/lib/apache2/modules/mod_env.so b7430000-b7431000 r--p 00000000 ca:00 45158 /usr/lib/apache2/modules/mod_env.so b7431000-b7432000 rw-p 00001000 ca:00 45158 /usr/lib/apache2/modules/mod_env.so b7432000-b7437000 rw-p 00000000 00:00 0 b7437000-b743c000 r-xp 00000000 ca:00 45155 /usr/lib/apache2/modules/mod_deflate.so b743c000-b743d000 r--p 00004000 ca:00 45155 /usr/lib/apache2/modules/mod_deflate.so b743d000-b743e000 rw-p 00005000 ca:00 45155 /usr/lib/apache2/modules/mod_deflate.so b743e000-b7443000 rw-p 00000000 00:00 0 b7443000-b7448000 r-xp 00000000 ca:00 45184 /usr/lib/apache2/modules/mod_cgi.so b7448000-b7449000 r--p 00004000 ca:00 45184 /usr/lib/apache2/modules/mod_cgi.so b7449000-b744a000 rw-p 00005000 ca:00 45184 /usr/lib/apache2/modules/mod_cgi.so b744a000-b744f000 rw-p 00000000 00:00 0 b744f000-b7457000 r-xp 00000000 ca:00 45179 /usr/lib/apache2/modules/mod_autoindex.so b7457000-b7458000 r--p 00007000 ca:00 45179 /usr/lib/apache2/modules/mod_autoindex.so b7458000-b7459000 rw-p 00008000 ca:00 45179 /usr/lib/apache2/modules/mod_autoindex.so b7459000-b745e000 rw-p 00000000 00:00 0 b745e000-b745f000 r-xp 00000000 ca:00 45136 /usr/lib/apache2/modules/mod_authz_user.so b745f000-b7460000 r--p 00000000 ca:00 45136 /usr/lib/apache2/modules/mod_authz_user.so b7460000-b7461000 rw-p 00001000 ca:00 45136 /usr/lib/apache2/modules/mod_authz_user.so b7461000-b7466000 rw-p 00000000 00:00 0 b7466000-b7468000 r-xp 00000000 ca:00 45134 /usr/lib/apache2/modules/mod_authz_host.so b7468000-b7469000 r--p 00001000 ca:00 45134 /usr/lib/apache2/modules/mod_authz_host.so b7469000-b746a000 rw-p 00002000 ca:00 45134 /usr/lib/apache2/modules/mod_authz_host.so b746a000-b746f000 rw-p 00000000 00:00 0 b746f000-b7471000 r-xp 00000000 ca:00 45135 /usr/lib/apache2/modules/mod_authz_groupfile.so b7471000-b7472000 r--p 00001000 ca:00 45135 /usr/lib/apache2/modules/mod_authz_groupfile.so b7472000-b7473000 rw-p 00002000 ca:00 45135 /usr/lib/apache2/modules/mod_authz_groupfile.so b7473000-b7478000 rw-p 00000000 00:00 0 b7478000-b7479000 r-xp 00000000 ca:00 45140 /usr/lib/apache2/modules/mod_authz_default.so b7479000-b747a000 r--p 00000000 ca:00 45140 /usr/lib/apache2/modules/mod_authz_default.so b747a000-b747b000 rw-p 00001000 ca:00 45140 /usr/lib/apache2/modules/mod_authz_default.so b747b000-b7480000 rw-p 00000000 00:00 0 b7480000-b7481000 r-xp 00000000 ca:00 44436 /usr/lib/apache2/modules/mod_authn_file.so b7481000-b7482000 ---p 00001000 ca:00 44436 /usr/lib/apache2/modules/mod_authn_file.so b7482000-b7483000 r--p 00001000 ca:00 44436 /usr/lib/apache2/modules/mod_authn_file.so b7483000-b7484000 rw-p 00002000 ca:00 44436 /usr/lib/apache2/modules/mod_authn_file.so b7484000-b7489000 rw-p 00000000 00:00 0 b7489000-b748b000 r-xp 00000000 ca:00 45141 /usr/lib/apache2/modules/mod_auth_basic.so b748b000-b748c000 r--p 00001000 ca:00 45141 /usr/lib/apache2/modules/mod_auth_basic.so b748c000-b748d000 rw-p 00002000 ca:00 45141 /usr/lib/apache2/modules/mod_auth_basic.so b748d000-b7492000 rw-p 00000000 00:00 0 b7492000-b7495000 r-xp 00000000 ca:00 45194 /usr/lib/apache2/modules/mod_alias.so b7495000-b7496000 r--p 00002000 ca:00 45194 /usr/lib/apache2/modules/mod_alias.so b7496000-b7497000 rw-p 00003000 ca:00 45194 /usr/lib/apache2/modules/mod_alias.so b7497000-b74d8000 rw-p 00000000 00:00 0 b74d8000-b74db000 r-xp 00000000 ca:00 21902 /lib/i386-linux-gnu/libdl-2.13.so b74db000-b74dc000 r--p 00002000 ca:00 21902 /lib/i386-linux-gnu/libdl-2.13.so b74dc000-b74dd000 rw-p 00003000 ca:00 21902 /lib/i386-linux-gnu/libdl-2.13.so b74dd000-b74de000 rw-p 00000000 00:00 0 b74de000-b74e2000 r-xp 00000000 ca:00 22401 /lib/i386-linux-gnu/libuuid.so.1.3.0 b74e2000-b74e3000 r--p 00003000 ca:00 22401 /lib/i386-linux-gnu/libuuid.so.1.3.0 b74e3000-b74e4000 rw-p 00004000 ca:00 22401 /lib/i386-linux-gnu/libuuid.so.1.3.0 b74e4000-b750a000 r-xp 00000000 ca:00 22420 /lib/i386-linux-gnu/libexpat.so.1.5.2 b750a000-b750b000 ---p 00026000 ca:00 22420 /lib/i386-linux-gnu/libexpat.so.1.5.2 b750b000-b750d000 r--p 00026000 ca:00 22420 /lib/i386-linux-gnu/libexpat.so.1.5.2 b750d000-b750e000 rw-p 00028000 ca:00 22420 /lib/i386-linux-gnu/libexpat.so.1.5.2 b750e000-b7516000 r-xp 00000000 ca:00 21889 /lib/i386-linux-gnu/libcrypt-2.13.so b7516000-b7517000 r--p 00007000 ca:00 21889 /lib/i386-linux-gnu/libcrypt-2.13.so b7517000-b7518000 rw-p 00008000 ca:00 21889 /lib/i386-linux-gnu/libcrypt-2.13.so b7518000-b753f000 rw-p 00000000 00:00 0 b753f000-b76b7000 r-xp 00000000 ca:00 21864 /lib/i386-linux-gnu/libc-2.13.so b76b7000-b76b9000 r--p 00178000 ca:00 21864 /lib/i386-linux-gnu/libc-2.13.so b76b9000-b76ba000 rw-p 0017a000 ca:00 21864 /lib/i386-linux-gnu/libc-2.13.so b76ba000-b76bd000 rw-p 00000000 00:00 0 b76bd000-b76d4000 r-xp 00000000 ca:00 24594 /lib/i386-linux-gnu/libpthread-2.13.so b76d4000-b76d5000 r--p 00016000 ca:00 24594 /lib/i386-linux-gnu/libpthread-2.13.so b76d5000-b76d6000 rw-p 00017000 ca:00 24594 /lib/i386-linux-gnu/libpthread-2.13.so b76d6000-b76d9000 rw-p 00000000 00:00 0 b76d9000-b770c000 r-xp 00000000 ca:00 6233 /usr/lib/libapr-1.so.0.4.5 b770c000-b770d000 r--p 00032000 ca:00 6233 /usr/lib/libapr-1.so.0.4.5 b770d000-b770e000 rw-p 00033000 ca:00 6233 /usr/lib/libapr-1.so.0.4.5 b770e000-b772f000 r-xp 00000000 ca:00 6236 /usr/lib/libaprutil-1.so.0.3.12 b772f000-b7730000 r--p 00020000 ca:00 6236 /usr/lib/libaprutil-1.so.0.3.12 b7730000-b7731000 rw-p 00021000 ca:00 6236 /usr/lib/libaprutil-1.so.0.3.12 b7731000-b776e000 r-xp 00000000 ca:00 22336 /lib/i386-linux-gnu/libpcre.so.3.12.1 b776e000-b776f000 r--p 0003c000 ca:00 22336 /lib/i386-linux-gnu/libpcre.so.3.12.1 b776f000-b7770000 rw-p 0003d000 ca:00 22336 /lib/i386-linux-gnu/libpcre.so.3.12.1 b7770000-b7780000 rw-p 00000000 00:00 0 b7780000-b779e000 r-xp 00000000 ca:00 21844 /lib/i386-linux-gnu/ld-2.13.so b779e000-b779f000 r--p 0001d000 ca:00 21844 /lib/i386-linux-gnu/ld-2.13.so b779f000-b77a0000 rw-p 0001e000 ca:00 21844 /lib/i386-linux-gnu/ld-2.13.so b77a0000-b7803000 r-xp 00000000 ca:00 44432 /usr/lib/apache2/mpm-prefork/apache2 b7803000-b7805000 r--p 00063000 ca:00 44432 /usr/lib/apache2/mpm-prefork/apache2 b7805000-b7807000 rw-p 00065000 ca:00 44432 /usr/lib/apache2/mpm-prefork/apache2 b7807000-b780a000 rw-p 00000000 00:00 0 b7a17000-b7a55000 rw-p 00000000 00:00 0 [heap] b7a55000-b7b9f000 rw-p 00000000 00:00 0 [heap] b7b9f000-b7c1a000 rw-p 00000000 00:00 0 [heap] bf9a1000-bf9c2000 rw-p 00000000 00:00 0 [stack] f57fe000-f57ff000 r-xp 00000000 00:00 0 [vdso] [Tue Jun 26 13:15:10 2012] [notice] child pid 26840 exit signal Aborted (6) Sometimes it recovers, but sometimes it kills the server. It's unclear to me what glibc is doing to crash.. can anyone decipher what's crashing in this error log?

  Read the article

• Slow NFS and GFS2 performance

  - by Tiago

  Recently I've designed and configured a 4 node cluster for a webapp that does lots of file handling. The cluster have been broken down into 2 main roles, webserver and storage. Each role is replicated to a second server using drbd in active/passive mode. The webserver does a NFS mount of the data directory of the storage server and the latter also has a webserver running to serve files to browser clients. In the storage servers I've created a GFS2 FS to hold the data which is wired to drbd. I've chose GFS2 mainly because the announced performance and also because the volume size which has to be pretty high. Since we entered production I've been facing two problems that I think are deeply connected. First of all, the NFS mount on the webservers keeps hanging for a minute or so and then resumes normal operations. By analyzing the logs I've found out that NFS stops answering for a while and outputs the following log lines: Oct 15 18:15:42 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:44 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:46 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:48 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:48 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:51 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:52 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:52 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:55 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:55 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:58 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK In this case, the hang lasted for 16 seconds but sometimes it takes 1 or 2 minutes to resume normal operations. My first guess was this was happening due to heavy load of the NFS mount and that by increasing RPCNFSDCOUNT to a higher value, this would become stable. I've increased it several times and apparently, after a while, the logs started appearing less times. The value is now on 32. After further investigating the issue, I've came across a different hang, despite the NFS messages still appear in the logs. Sometimes, the GFS2 FS simply hangs which causes both the NFS and the storage webserver to serve files. Both stay hang for a while and then they resume normal operations. This hangs leaves no trace on client side (also leaves no NFS ... not responding messages) and, on the storage side, the log system appears to be empty, even though the rsyslogd is running. The nodes connect themselves through a 10Gbps non-dedicated connection but I don't think this is an issue because the GFS2 hang is confirmed but connecting directly to the active storage server. I've been trying to solve this for a while now and I've tried different NFS configuration options, before I've found out the GFS2 FS is also hanging. The NFS mount is exported as such: /srv/data/ <ip_address>(rw,async,no_root_squash,no_all_squash,fsid=25) And the NFS client mounts with: mount -o "async,hard,intr,wsize=8192,rsize=8192" active.storage.vlan:/srv/data /srv/data After some tests, these were the configurations that yielded more performance to the cluster. I am desperate to find a solution for this as the cluster is already in production mode and I need to fix this so that this hangs won't happen in the future and I don't really know for sure what and how I should be benchmarking. What I can tell is that this is happening due to heavy loads as I have tested the cluster earlier and this problems weren't happening at all. Please tell me if you need me to provide configuration details of the cluster, and which do you want me to post. As last resort I can migrate the files to a different FS but I need some solid pointers on whether this will solve this problems as the volume size is extremely large at this point. The servers are being hosted by a third-party enterprise and I don't have physical access to them. Best regards. EDIT 1: The servers are physical servers and their specs are: Webservers: Intel Bi Xeon E5606 2x4 2.13GHz 24GB DDR3 Intel SSD 320 2 x 120GB Raid 1 Storage: Intel i5 3550 3.3GHz 16GB DDR3 12 x 2TB SATA Initially there was a VRack setup between the servers but we've upgraded one of the storage servers to have more RAM and it wasn't inside the VRack. They connect through a shared 10Gbps connection between them. Please note that it is the same connection that is used for public access. They use a single IP (using IP Failover) to connect between them and to allow for a graceful failover. NFS is therefore over a public connection and not under any private network (it was before the upgrade, were the problem still existed). The firewall was configured and tested thoroughly but I disabled it for a while to see if the problem still occurred, and it did. From my knowledge the hosting provider isn't blocking or limiting the connection between either the servers and the public domain (at least under a given bandwidth consumption threshold that hasn't been reached yet). Hope this helps figuring out the problem. EDIT 2: Relevant software versions: CentOS 2.6.32-279.9.1.el6.x86_64 nfs-utils-1.2.3-26.el6.x86_64 nfs-utils-lib-1.1.5-4.el6.x86_64 gfs2-utils-3.0.12.1-32.el6_3.1.x86_64 kmod-drbd84-8.4.2-1.el6_3.elrepo.x86_64 drbd84-utils-8.4.2-1.el6.elrepo.x86_64 DRBD configuration on storage servers: #/etc/drbd.d/storage.res resource storage { protocol C; on <server1 fqdn> { device /dev/drbd0; disk /dev/vg_storage/LV_replicated; address <server1 ip>:7788; meta-disk internal; } on <server2 fqdn> { device /dev/drbd0; disk /dev/vg_storage/LV_replicated; address <server2 ip>:7788; meta-disk internal; } } NFS Configuration in storage servers: #/etc/sysconfig/nfs RPCNFSDCOUNT=32 STATD_PORT=10002 STATD_OUTGOING_PORT=10003 MOUNTD_PORT=10004 RQUOTAD_PORT=10005 LOCKD_UDPPORT=30001 LOCKD_TCPPORT=30001 (can there be any conflict in using the same port for both LOCKD_UDPPORT and LOCKD_TCPPORT?) GFS2 configuration: # gfs2_tool gettune <mountpoint> incore_log_blocks = 1024 log_flush_secs = 60 quota_warn_period = 10 quota_quantum = 60 max_readahead = 262144 complain_secs = 10 statfs_slow = 0 quota_simul_sync = 64 statfs_quantum = 30 quota_scale = 1.0000 (1, 1) new_files_jdata = 0 Storage network environment: eth0 Link encap:Ethernet HWaddr <mac address> inet addr:<ip address> Bcast:<bcast address> Mask:<ip mask> inet6 addr: <ip address> Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:957025127 errors:0 dropped:0 overruns:0 frame:0 TX packets:1473338731 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2630984979622 (2.3 TiB) TX bytes:1648430431523 (1.4 TiB) eth0:0 Link encap:Ethernet HWaddr <mac address> inet addr:<ip failover address> Bcast:<bcast address> Mask:<ip mask> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 The IP addresses are statically assigned with the given network configurations: DEVICE="eth0" BOOTPROTO="static" HWADDR=<mac address> ONBOOT="yes" TYPE="Ethernet" IPADDR=<ip address> NETMASK=<net mask> and DEVICE="eth0:0" BOOTPROTO="static" HWADDR=<mac address> IPADDR=<ip failover> NETMASK=<net mask> ONBOOT="yes" BROADCAST=<bcast address> Hosts file to allow for a graceful NFS failover in conjunction with NFS option fsid=25 set on both storage servers: #/etc/hosts <storage ip failover address> active.storage.vlan <webserver ip failover address> active.service.vlan As you can see, packet errors are down to 0. I've also ran ping for a long time without any packet loss. MTU size is the normal 1500. As there is no VLan by now, this is the MTU used to communicate between servers. The webservers' network environment is similar. One thing I forgot to mention is that the storage servers handle ~200GB of new files each day through the NFS connection, which is a key point for me to think this is some kind of heavy load problem with either NFS or GFS2. If you need further configuration details please tell me. EDIT 3: Earlier today we had a major filesystem crash on the storage server. I couldn't get the details of the crash right away because the server stop responding. After the reboot, I noticed the filesystem was extremely slow, and I was not being able to serve a single file through either NFS or httpd, perhaps due to cache warming or so. Nevertheless, I've been monitoring the server closely and the following error came up in dmesg. The source of the problem is clearly GFS, which is waiting for a lock and ends up starving after a while. INFO: task nfsd:3029 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. nfsd D 0000000000000000 0 3029 2 0x00000080 ffff8803814f79e0 0000000000000046 0000000000000000 ffffffff8109213f ffff880434c5e148 ffff880624508d88 ffff8803814f7960 ffffffffa037253f ffff8803815c1098 ffff8803814f7fd8 000000000000fb88 ffff8803815c1098 Call Trace: [<ffffffff8109213f>] ? wake_up_bit+0x2f/0x40 [<ffffffffa037253f>] ? gfs2_holder_wake+0x1f/0x30 [gfs2] [<ffffffff814ff42e>] __mutex_lock_slowpath+0x13e/0x180 [<ffffffff814ff2cb>] mutex_lock+0x2b/0x50 [<ffffffffa0379f21>] gfs2_log_reserve+0x51/0x190 [gfs2] [<ffffffffa0390da2>] gfs2_trans_begin+0x112/0x1d0 [gfs2] [<ffffffffa0369b05>] ? gfs2_dir_check+0x35/0xe0 [gfs2] [<ffffffffa0377943>] gfs2_createi+0x1a3/0xaa0 [gfs2] [<ffffffff8121aab1>] ? avc_has_perm+0x71/0x90 [<ffffffffa0383d1e>] gfs2_create+0x7e/0x1a0 [gfs2] [<ffffffffa037783f>] ? gfs2_createi+0x9f/0xaa0 [gfs2] [<ffffffff81188cf4>] vfs_create+0xb4/0xe0 [<ffffffffa04217d6>] nfsd_create_v3+0x366/0x4c0 [nfsd] [<ffffffffa0429703>] nfsd3_proc_create+0x123/0x1b0 [nfsd] [<ffffffffa041a43e>] nfsd_dispatch+0xfe/0x240 [nfsd] [<ffffffffa025a5d4>] svc_process_common+0x344/0x640 [sunrpc] [<ffffffff810602a0>] ? default_wake_function+0x0/0x20 [<ffffffffa025ac10>] svc_process+0x110/0x160 [sunrpc] [<ffffffffa041ab62>] nfsd+0xc2/0x160 [nfsd] [<ffffffffa041aaa0>] ? nfsd+0x0/0x160 [nfsd] [<ffffffff81091de6>] kthread+0x96/0xa0 [<ffffffff8100c14a>] child_rip+0xa/0x20 [<ffffffff81091d50>] ? kthread+0x0/0xa0 [<ffffffff8100c140>] ? child_rip+0x0/0x20

  Read the article

• TCP RST right after FIN/ACK

  - by Nitzan Shaked

  I am having the weirdest issue: I have a web server which sometimes, only on very specific requests, will send a RST to the client after having sent the FIN datagram. First, a description of the setup: The server runs on an Ubuntu 12.04.1 LTS, which itself is a VM guest inside a Win7 x64 host, in bridged mode. ufw is disabled on the host The client runs on a iOS simulator, which runs on OS X Mountain Lion, which is a VM guest (hackintosh) inside a Win7 x64 host, in bridged mode. Both client and server are on the same LAN, one is connected to the home router via an Ethernet cable, and then other thru WiFi. I happened to glimpse over the server's http logs and found that the client sometimes issuing multiple subsequent identical requests. Further investigation led me to discover that this happens when the server sends a RST, and that the client is simply re-trying. I am attaching several tcpdump's: Good1 is the server-side tcpdump of a good session ("good" meaning no RST was generated). Good3 is another sever-side tcpdump of a good session. (The difference between Good1 and Good3 is the order in which ACK's were sent from the server to the client, ACK'ing the client's request. The client's request arives in 2 segements (specifically: one for the http headers, and another for a body containing an empty json object, "{}"). In Good1, the server ACK's both request segments, using 2 ACK segments, after the second request has arrived. In Good3, the server ACK's each request segment with an ACK segment as soon as the request segment arrives. Not that it should make a difference.) Bad1 is a dump, both client- and server-side, of a bad session. Bad2 is another bad session, this time server-side only. Note that in all "bad" sessions, the server ACK's each request segments immediately after having received it. I've looked at a few other bad sessions, and the situation is the same in all of them. But this is also the behavior in "Good3", so I don't see how that observation helps me, of for that matter why it should matter. I can't find any difference between good and bad sessions, or at least one that I think should matter. My question is: why are those RST's being generated? Or at least: how do I go about debugging this, or providing more info here that'll help? Edit 2 new facts that I have learned: Section 4.2.2.13 of the RFC (1122) (and Wikipedia, in the article "TCP", under "Connection Termination") says that a TCP application on one host may close the connection before it has read all of the data in its socket buffer, and in such a case the TCP on the host will sent a RST to the other side, to let it know that not all the data it has sent has been read. I'm not sure I completely understand this, since closing my side of the connection still allows me to read, no? It also means that I can't write any more. I am not sure this is relevant, though, since I see a RST after FIN. There are multiple complaints of this happening with wsgiref (Python's dev-mode HTTP server), which is exactly what I'm using. I'll keep updating as I find out more. Thanks! ~~~~~~~~~~~~~~~~~~~~ Good1 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:02.308319 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [S], seq 94268074, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943308864 ecr 0,sackOK,eol], length 0 13:28:02.308336 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [S.], seq 1726304574, ack 94268075, win 14480, options [mss 1460,sackOK,TS val 326480982 ecr 943308864,nop,wscale 3], length 0 13:28:02.309750 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943308865 ecr 326480982], length 0 13:28:02.310744 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943308865 ecr 326480982], length 350 13:28:02.310766 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943308865 ecr 326480982], length 2 13:28:02.310841 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480983 ecr 943308865], length 0 13:28:02.310918 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480983 ecr 943308865], length 0 13:28:02.315931 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480984 ecr 943308865], length 17 13:28:02.316107 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480984 ecr 943308865], length 666 13:28:02.317651 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943308872 ecr 326480984], length 0 13:28:02.318288 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943308872 ecr 326480984], length 0 13:28:02.318640 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [F.], seq 353, ack 685, win 8192, options [nop,nop,TS val 943308872 ecr 326480984], length 0 13:28:02.318651 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [.], ack 354, win 1944, options [nop,nop,TS val 326480985 ecr 943308872], length 0 ~~~~~~~~~~~~~~~~~~~~ Good3 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:03.311143 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [S], seq 1982901126, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943309853 ecr 0,sackOK,eol], length 0 13:28:03.311155 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [S.], seq 2245063571, ack 1982901127, win 14480, options [mss 1460,sackOK,TS val 326481233 ecr 943309853,nop,wscale 3], length 0 13:28:03.312671 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943309854 ecr 326481233], length 0 13:28:03.313330 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943309855 ecr 326481233], length 350 13:28:03.313337 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326481234 ecr 943309855], length 0 13:28:03.313342 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943309855 ecr 326481233], length 2 13:28:03.313346 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326481234 ecr 943309855], length 0 13:28:03.327942 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326481237 ecr 943309855], length 17 13:28:03.328253 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326481237 ecr 943309855], length 666 13:28:03.329076 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943309868 ecr 326481237], length 0 13:28:03.329688 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943309868 ecr 326481237], length 0 13:28:03.330361 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [F.], seq 353, ack 685, win 8192, options [nop,nop,TS val 943309869 ecr 326481237], length 0 13:28:03.330370 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [.], ack 354, win 1944, options [nop,nop,TS val 326481238 ecr 943309869], length 0 ~~~~~~~~~~~~~~~~~~~~ Bad1 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:01.311876 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [S], seq 920400580, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943307883 ecr 0,sackOK,eol], length 0 13:28:01.311896 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [S.], seq 3103085782, ack 920400581, win 14480, options [mss 1460,sackOK,TS val 326480733 ecr 943307883,nop,wscale 3], length 0 13:28:01.313509 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943307884 ecr 326480733], length 0 13:28:01.315614 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 350 13:28:01.315727 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:01.316229 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 2 13:28:01.316242 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:01.321019 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480735 ecr 943307886], length 17 13:28:01.321294 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 666 13:28:01.321386 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R.], seq 685, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 0 13:28:01.322727 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943307891 ecr 326480735], length 0 13:28:01.322733 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103085800, win 0, length 0 13:28:01.323221 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943307892 ecr 326480736], length 0 13:28:01.323231 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103086467, win 0, length 0 ~~~~~~~~~~~~~~~~~~~~ Bad1 -- Client Side ~~~~~~~~~~~~~~~~~~~~ 13:28:11.374654 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [S], seq 920400580, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943307883 ecr 0,sackOK,eol], length 0 13:28:11.375764 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [S.], seq 3103085782, ack 920400581, win 14480, options [mss 1460,sackOK,TS val 326480733 ecr 943307883,nop,wscale 3], length 0 13:28:11.376352 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943307884 ecr 326480733], length 0 13:28:11.378252 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 350 13:28:11.379027 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 2 13:28:11.379732 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:11.380592 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:11.384968 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480735 ecr 943307886], length 17 13:28:11.385044 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943307891 ecr 326480735], length 0 13:28:11.385586 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 666 13:28:11.385743 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943307892 ecr 326480736], length 0 13:28:11.385966 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R.], seq 685, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 0 13:28:11.387343 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103085800, win 0, length 0 13:28:11.387344 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103086467, win 0, length 0 ~~~~~~~~~~~~~~~~~~~~ Bad2 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:01.319185 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [S], seq 1631526992, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943307889 ecr 0,sackOK,eol], length 0 13:28:01.319197 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [S.], seq 2524685719, ack 1631526993, win 14480, options [mss 1460,sackOK,TS val 326480735 ecr 943307889,nop,wscale 3], length 0 13:28:01.320692 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943307890 ecr 326480735], length 0 13:28:01.322219 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943307890 ecr 326480735], length 350 13:28:01.322336 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480736 ecr 943307890], length 0 13:28:01.322689 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943307890 ecr 326480735], length 2 13:28:01.322700 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307890], length 0 13:28:01.326307 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480737 ecr 943307890], length 17 13:28:01.326614 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480737 ecr 943307890], length 666 13:28:01.326710 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [R.], seq 685, ack 353, win 1944, options [nop,nop,TS val 326480737 ecr 943307890], length 0 13:28:01.328499 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943307896 ecr 326480737], length 0 13:28:01.328509 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [R], seq 2524685737, win 0, length 0 13:28:01.328514 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943307896 ecr 326480737], length 0 13:28:01.328517 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [R], seq 2524686404, win 0, length 0

  Read the article

• Displaying wait cursor in while backgroundworker is running

  - by arc1880

  During the start of my windows application, I have to make a call to a web service to retrieve some default data to load onto my application. During the load of the form, I run a backgroundworker to retrieve this data. I want to display the wait cursor until this data is retrieved. How would I do this? I've tried setting the wait cursor before calling the backgroundworker to run. When I report a progress of 100 then I set it back to the default cursor. The wait cursor comes up but when I move the mouse it disappears. Environment: Windows 7 Pro 64-bit VS2010 C# .NET 4.0 Windows Forms EDIT: I am setting the cursor the way Jay Riggs suggested. It only works if I don't move the mouse. **UPDATE: I have created a button click which does the following: When I do the button click and move my mouse, the wait cursor appears regardless if I move my mouse or not. void BtnClick() { Cursor = Cursors.WaitCursor; Thread.Sleep(8000); Cursor = Cursors.Default; } If I do the following: I see the wait cursor and when I move the mouse it disappears inside the form. If I move to my status bar or the menu bar the wait cursor appears. Cursor = Cursors.WaitCursor; if (!backgroundWorker.IsBusy) { backGroundWorker.RunWorkerAsync(); } void backGroundWorkerDoWork(object sender, DoWorkEventArgs e) { Thread.Sleep(8000); } void backGroundWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { Cursor = Cursors.Default; } If I do the following: The wait cursor appears and when I move the mouse it still appears but will sometimes flicker off and on when moving in text fields. if (!backgroundWorker.IsBusy) { backGroundWorker.RunWorkerAsync(); } void backGroundWorkerDoWork(object sender, DoWorkEventArgs e) { UseWaitCursor = true; Thread.Sleep(8000); } void backGroundWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { UseWaitCursor = false; }

  Read the article

• Server cannot set status after HTTP headers have been sent IIS7.5

  - by marcinn

  Hi, Sometimes I get exception in my production environment: Process information Process ID: 3832 Process name: w3wp.exe Account name: NT AUTHORITY\NETWORK SERVICE Exception information Exception type: System.Web.HttpException Exception message: Server cannot set status after HTTP headers have been sent. Request information Request URL: http://www.myulr.pl/logon Request path: /logon User host address: 10.11.9.1 User: user001 Is authenticated: True Authentication Type: Forms Thread account name: NT AUTHORITY\NETWORK SERVICE Thread information Thread ID: 10 Thread account name: NT AUTHORITY\NETWORK SERVICE Is impersonating: False Stack trace: at System.Web.HttpResponse.set_StatusCode(Int32 value) at System.Web.HttpResponseWrapper.set_StatusCode(Int32 value) at System.Web.Mvc.HandleErrorAttribute.OnException(ExceptionContext filterContext) at System.Web.Mvc.ControllerActionInvoker.InvokeExceptionFilters(ControllerContext controllerContext, IList(1) filters, Exception exception) at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) at System.Web.Mvc.Controller.ExecuteCore() at System.Web.Mvc.MvcHandler.<>c__DisplayClass8.<BeginProcessRequest>b__4() at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass1.<MakeVoidDelegate>b__0() at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass8(1).<BeginSynchronous>b__7(IAsyncResult _) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult(1).End() at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& ompletedSynchronously) I didn't noticed this error on my test environment what should I check? I am using ASP.NET MVC 2 (Release Candidate 2)

  Read the article

• Listview Swipe inside viewflipper

  - by Faisal Abid

  Im trying to swipe left and right on a listview and get the viewflipper to swtich. Just like the remeberthemilk app and the default news and weather app on the nexus one (Swiping through news topics). Using various tutorials ive found , i came across on one stackoverflow that shows how to implement a swipe gesture class MyGestureDetector extends SimpleOnGestureListener { @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { try { if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH) return true; // right to left swipe if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { viewFlipper.setInAnimation(slideRightIn); viewFlipper.setOutAnimation(slideRightOut); viewFlipper.showPrevious(); } } catch (Exception e) { // nothing } return true; } } And i got this working by doing lstView.setOnTouchListener(gestureListener); However sometimes what would happen is the listview setOnItemClickListener would be fired when the person is swiping. How do i prevent this from happening, and only get the setOnItemClickListener fired when the user actually clicks on it list item and not just swiping on it. Thanks, Faisal Abid

  Read the article

• HintPath vs ReferencePath in Visual Studio

  - by toasteroven

  What exactly is the difference between the HintPath in a .csproj file and the ReferencePath in a .csproj.user file? We're trying to commit to a convention where dependency DLLs are in a "releases" svn repo and all projects point to a particular release. Since different developers have different folder structures, relative references won't work, so we came up with a scheme to use an environment variable pointing to the particular developer's releases folder to create an absolute reference. So after a reference is added, we manually edit the project file to change the reference to an absolute path using the environment variable. I've noticed that this can be done with both the HintPath and the ReferencePath, but the only difference I could find between them is that HintPath is resolved at build-time and ReferencePath when the project is loaded into the IDE. I'm not really sure what the ramifications of that are though. I have noticed that VS sometimes rewrites the .csproj.user and I have to rewrite the ReferencePath, but I'm not sure what triggers that. I've heard that it's best not to check in the .csproj.user file since it's user-specific, so I'd like to aim for that, but I've also heard that the HintPath-specified DLL isn't "guaranteed" to be loaded if the same DLL is e.g. located in the project's output directory. Any thoughts on this?

  Read the article

• View all ntext column text in SQL Server Management Studio for SQL CE database

  - by Dave

  I often want to do a "quick check" of the value of a large text column in SQL Server Management Studio (SSMS). The maximum number of characters that SSMS will let you view, in grid results mode, is 65535. (It is even less in text results mode.) Sometimes I need to see something beyond that range. Using SQL Server 2005 databases, I often used the trick of converting it to XML, because SSMS lets you view much larger amounts of text that way: SELECT CONVERT(xml, MyCol) FROM MyTable WHERE ... But now I am using SQL CE, and there is no Xml data type. There is still a "Maximum Characters Retreived XML" value under Options; I suppose this is useful when connecting to other data sources. I know I can just get the full value by running a little console app or something, but is there a way within SSMS to see the entire ntext column value? [Edit] OK, this didn't get much attention the first time around (18 views?!). It's not a huge concern, but maybe I'm just obsessed with it. There has to be some good way around this, doesn't there? So a modest bounty is active. What I am willing to accept as answers, in order from best-to-worst: A solution that works just as easy as the XML trick in SQL CE. That is, a single function (convert, cast, etc.) that does the job. A not-too-invasive way to hack SSMS to get it to display more text in the results. An equivalent SQL query (perhaps something that creatively uses SUBSTRING and generates multiple ad-hoc columns??) to see the results. The solution should work with nvarchar and ntext columns of any length in SQL CE from SSMS. Any ideas?

  Read the article

• Abcpdf throwing System.ExecutionEngineException

  - by Tom Tresansky

  I have the binary for several pdf files stored in a collection of Byte arrays. My goal is to concatenate them into a single .pdf file using abcpdf, then stream that newly created file to the Response object on a page of an ASP.Net website. Had been doing it like this: BEGIN LOOP ... 'Create a new Doc Dim doc As Doc = New Doc 'Read the binary of the current PDF doc.Read(bytes) 'Append to the master merged PDF doc _mergedPDFDoc.Append(Doc) END LOOP Which was working fine 95% of the time. Every now and then however, creating a new Doc object would throw a System.ExecutionEngineException and crash the CLR. It didn't seem to be related to a large number of pdfs (sometimes would happen w/ only 2), or with large sized pdfs. It seemed almost completely random. This is a known bug in abcpdf described (not very well) here Item 6.24. I came across a helpful SO post which suggested using a Using block for the abcpdf Doc object. So now I'm doing this: Using doc As New Doc 'Read the binary of the current PDF doc.Read(bytes) 'Append to the master merged PDF doc _mergedPDFDoc.Append(doc) End Using And I haven't seen the problem occur again yet, and have been pounding on a test version as best as I can to get it to. Has anyone had any similar experience with this error? Did this fix it?

  Read the article

• Random pauses with "Key dispatching timed out sending to <null>" when closing Android SurfaceView

  - by kenyee

  When I close an Android SurfaceView Activity, the app sometimes pauses and almost gets an ANR (Application Not Responding) message. Looking at LogCat, it appears to be timing out trying to send keys to it. I tried modifying the code to setFocusable(false) when in the onKeyDown handler for the SurfaceView, but that doesn't seem to affect this. Any other ideas on what might be causing this? Or what these messages in Logcat even mean? ============================= 05-31 19:35:35.285: INFO/WindowManager(586): focus null mToken is null at event dispatch! 05-31 19:35:35.295: WARN/WindowManager(586): Current state: {{KeyEvent{action=1 code=4 repeat=0 meta=0 scancode=158 mFlags=8} to null @ 1275334535292 lw=null lb=null fin=true gfw=true ed=true tts=0 wf=false fp=false mcf=null}} 05-31 19:35:35.305: WARN/WindowManager(586): Continuing to wait for key to be dispatched 05-31 19:35:40.306: WARN/WindowManager(586): Key dispatching timed out sending to 05-31 19:35:40.316: WARN/WindowManager(586): Dispatch state: {{KeyEvent{action=0 code=4 repeat=0 meta=0 scancode=158 mFlags=8} to Window{43763540 com.myapp/com.myapp.DiagramEdit paused=false} @ 1275334499512 lw=Window{43763540 com.myapp/com.myapp.DiagramEdit paused=false} lb=android.os.BinderProxy@43702190 fin=false gfw=true ed=true tts=0 wf=false fp=false mcf=null}} 05-31 19:35:40.326: INFO/WindowManager(586): focus null mToken is null at event dispatch! 05-31 19:35:40.326: WARN/WindowManager(586): Current state: {{KeyEvent{action=1 code=4 repeat=0 meta=0 scancode=158 mFlags=8} to null @ 1275334540327 lw=null lb=null fin=true gfw=true ed=true tts=0 wf=false fp=false mcf=null}} 05-31 19:35:40.326: WARN/WindowManager(586): Continuing to wait for key to be dispatched

  Read the article

• How to organize SQL script files

  - by Mehper C. Palavuzlar

  We have an Oracle 10g database (a huge one) in our company, and I provide employees with data upon their requests. My problem is, I save almost every SQL query I wrote, and now my list has grown too long. I want to organize and rename these .sql files so that I can find the one I want easily. At the moment, I'm using some folders named as Sales Dept, Field Team, Planning Dept, Special etc. and under those folders there are .sql files like Delivery_sales_1, Delivery_sales_2, ... Sent_sold_lostsales_endpoints, ... Sales_provinces_period, Returnrates_regions_bymonths, ... Jack_1, Steve_1, Steve_2, ... I try to name the files regarding their content but this makes file names longer and does not completely meet my needs. Sometimes someone comes and demands a special report, and I give the file his name, but this is also not so good. I know duplicates or very similar files are growing in time but I don't have control over them. Can you show me the right direction to rename all these files and folders and organize my queries for easy and better control? TIA.

  Read the article

• iPhone Inspiration Stories...

  - by Luis Tovar

  So we have all heard of these overnight millionaires in the app store. We know it would be great, but somewhat unlikely to do ourselves. What I do know is, that learning and developing for the iPhone can sometimes be overwhelming. I continue to push on and learn more and more, even when my brain just cant take anymore I turn my mac on and read up on how to do new and different things I haven't done yet in my app yet. I would like to see a few post's of a common day developer's story and how their life has improved now that they are sitting up on the golden pedestal of an iphone developer. I look at these Dice.com jobs on think how nice it would be to be making that kind of money offered for an experienced iphone developer. Im on my way... and while I'm on that road i'd like to look over and see your story... Please include how you got into iPhone development and any apps you have out there and your success with them. Care to share?

  Read the article

• Random DNS Client Issue with BIND9/Windows Server 2003 DNS

  - by upkels

  Within our office, we have a local server running DNS, for internal related "domains", (e.g. .internal, .office, .lan, .vpn, etc.). Randomly, only the hosts configured with those extensions will stop resolving on the Windows-based workstations. Sometimes it'll work for a couple weeks without issue on one machine, then suddenly stop working, or it'll happen on another 15 times per day. It's completely random for all workstations. When troubleshooting, I have opened up a command prompt, and issued various nslookup commands for some of these hosts, and they resolve, however I've been told that nslookup uses different "libraries" for name resolution than other applications such as web browsers, email clients, etc. The only solution thus far, is manually restarting the Windows DNS Client on each workstation when this happens. Issuing the ipconfig /flushdns command multiple times helps every now and then, but is not successful enough to even attempt before restarting the DNS Client. I have tried two different DNS servers; BIND9, and Windows Server 2003 R2 DNS, and the behavior is the same. We have a single Netgear JGS524 switch all workstations and servers are connected to within the office, and a Linksys SR224G switch in another department with workstations attached.

  Read the article

• PDF rendering crashes app Core Graphics

  - by Felixyz

  EDIT: The memory leaks turned out to be unrelated to the crashes. Leaks are fixed but crashes remain, still mysterious. My (iPhone) app does lots of PDF loading and rendering, some of it threaded. Sometime, it seems always after I flush a page cash after getting a memory warning, the app crashes with a bad access when trying to draw a pdf page stored in an NSData object. Here is one example trace: #0 0x3016d564 in CGPDFResourcesGetResource () #1 0x3016d58a in CGPDFResourcesGetResource () #2 0x3016d94e in CGPDFResourcesGetExtGState () #3 0x3015fac4 in CGPDFContentStreamGetExtGState () #4 0x301629a8 in op_gs () #5 0x3016df12 in handle_xname () #6 0x3016dd9e in read_objects () #7 0x3016de6c in CGPDFScannerScan () #8 0x30161e34 in CGPDFDrawingContextDraw () #9 0x3016a9dc in CGContextDrawPDFPage () But sometimes I get this instead: Program received signal: “EXC_BAD_ACCESS”. (gdb) bt #0 0x335625fa in objc_msgSend () #1 0x32c04eba in CFDictionaryGetValue () #2 0x3016d500 in get_value () #3 0x3016d5d6 in CGPDFResourcesGetFont () #4 0x3015fbb4 in CGPDFContentStreamGetFont () #5 0x30163480 in op_Tf () #6 0x3016df12 in handle_xname () #7 0x3016dd9e in read_objects () #8 0x3016de6c in CGPDFScannerScan () #9 0x30161e34 in CGPDFDrawingContextDraw () #10 0x3016a9dc in CGContextDrawPDFPage () Is this an indication that I've mistakenly deallocated an object? It's hard for me to decode what's happening here. This is how I create and retain the various objects involved: // Some data was just loaded from the network and is pointed to by "data" self.pdfData = data; _dataProviderRef = CGDataProviderCreateWithData( NULL, [_pdfData bytes], [_pdfData length], NULL ); _documentRef = CGPDFDocumentCreateWithProvider(_dataProviderRef); _pageRef = CGPDFDocumentGetPage(_documentRef, 1); CGPDFPageRetain(_pageRef); _pdfFrame = CGPDFPageGetBoxRect(_pageRef, kCGPDFArtBox); So the NSData object is retained, and I explicitly retain the page reference. The data provider and the document are already retained by the create-functions. And here is my dealloc method: -(void)dealloc { if (_pageRef) CGPDFPageRelease(_pageRef); if (_documentRef) CGPDFDocumentRelease(_documentRef); if (_dataProviderRef) CGDataProviderRelease(_dataProviderRef); self.pdfData = nil; [super dealloc]; } Am I doing anything wrong? Even an assurance that I'm not, with explanation, would be a help.

  Read the article

• Mixed surrogate composite key insert in JPA 2.0, PostgreSQL and Hibernate 3.5

  - by Gerald

  First off, we are using JPA 2.0 and Hibernate 3.5 as persistence provider on a PostgreSQL database. We successfully use the sequence of the database via the JPA 2.0 annotations as an auto-generated value for single-field-surrogate-keys and all works fine. Now we are implementing a bi-temporal database-scheme that requires a mixed key in the following manner: Table 1: id (pk, integer, auto-generated-sequence) validTimeBegin (pk, dateTime) validTimeEnd (dateTime) firstName (varChar) Now we have a problem. You see, if we INSERT a new element, the field id is auto-generated and that's fine. Only, if we want to UPDATE the field within this scheme, then we have to change the validTimeBegin column WITHOUT changing the id-field and insert it as a new row like so: BEFORE THE UPDATE OF THE ROW: |---|-------------------------|-------------------------|-------------------| | id| validTimeBegin | validTimeEnd | firstName | |---|-------------------------|-------------------------|-------------------| | 1| 2010-05-01-10:00:00.000 | NULL | Gerald | |---|-------------------------|-------------------------|-------------------| AFTER THE UPDATE OF THE ROW happening at exactly 2010-05-01-10:35:01.788 server-time: (we update the person with the id:1 to reflect his new first name...) |---|-------------------------|-------------------------|-------------------| | id| validTimeBegin | validTimeEnd | firstName | |---|-------------------------|-------------------------|-------------------| | 1| 2010-05-01-10:00:00.000 | 2010-05-01-10:35:01.788 | Gerald | |---|-------------------------|-------------------------|-------------------| | 1| 2010-05-01-10:35:01.788 | NULL | Jerry | |---|-------------------------|-------------------------|-------------------| So our problem is, that this doesn't work at all using an auto-generated-sequence for the field id because when inserting a new row then the id ALWAYS is auto-generated although it really is part of a composite key which should sometimes behave differently. So my question is: Is there a way to tell hibernate via JPA to stop auto-generating the id-field in the case I want to generate a new variety of the same person and go on as usual in every other case or do I have to take over the whole id-generation with custom code? Thanks in advance, Gerald

  Read the article

• Alternative to FindAncestor RelativeSource in Silverlight 4 to bind to a property of the page

  - by TimothyP

  Hi, FindAncestor RelativeSource only supports 'Self' and 'TemplatedParent', but I have to bind the width of a popup to the width of the page. Giving the page a name causes problems because sometimes it will throw exceptions saying a control with that name is already present in the visual tree. <Popup IsOpen="True" Width="{Binding ElementName=BordPage, Path=Width}" Height="{Binding ElementName=BordPage, Path=Height}"> Background information: I'm using a SL4 navigation based application here. BordPage is a navigation page, which I'm using multiple times within the application. So giving it a name in the page itself is not really a good idea, but I don't know how else I can bind to the width and height of the page. What I'm trying to do is have a black border (with opacity 0.8) cover the entire screen, (including the controls of the MainPage). Then on top of that I want to display some other controls. Since the application is touch controlled, providing the user with a ComboBox to select a value doesn't really work wel. Instead I want to show this black overlay window with a listbox taking up most of the screen so the user can simply touch the value he wants with a single click. Update: I just realized I can use the ChildWindow class to do this. But my original question remains.

  Read the article

< Previous Page | 252 253 254 255 256 257 258 259 260 261 262 263  | Next Page >