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  • Resume Activity with back button

    - by Hallik
    I have an application I am creating with a DashboardActivity & a SettingsActivity. On the dashboard, I have one object displayed, but when I go into settings, I want to be able to select/deselect X options. Once the user clicks the back button, I save that data locally and to the server. Once the phone receives a success message from the server that it was stored properly, I want to reload the dashboard. I thought I would do this with the onPause and onResume, but they are called when the DashboardActivity is first created. What would be the best way to reload the dashboard by calling my web service after the settings were saved to the server? Here is what I am doing when the back button is hit @Override public boolean onKeyDown(int keyCode, KeyEvent event) { //Save data to the server once the user hits the back button if ((keyCode == KeyEvent.KEYCODE_BACK)) { SchoolSearchActivity.this.divisionProxy = new DivisionProxy(SchoolSearchActivity.this.saveUserDivisionHandler); SchoolSearchActivity.this.divisionProxy.submitUserDivisions(SchoolSearchActivity.this.userDivisions, SchoolSearchActivity.this.user_id); //SchoolSearchActivity.this.finish(); //Toast.makeText(SchoolSearchActivity.this, "Divisions Saved",Toast.LENGTH_LONG).show(); } return true; } The above opens an HTTP connection, and when the response is received, the handler processes the response. I am going to: 1) throw up a progress dialog box letting the user know it's being submitted to the server, and once a response is received, 2) go back to the previous activity and call the "refresh" webservice again. What's the best way to accomplish 1 & 2?

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  • MsSql Server high Resource Waits and Head Blocker

    - by MartinHN
    Hi I have a MS SQL Server 2008 Standard installation running a database for a webshop. The current size of the database is 2.5 GB. Running on Windows 2008 Standard. Dual Intel Xeon X5355 @ 2.00 GHz. 4 GB RAM. When I open the Activity Monitor, I see that I have a Wait Time (ms/sec) of 5000 in the "Other" category. In the Processes list, all connections from the webshop, the Head Blocker value is 1. I see every day that when I try to access the website, it can take 20-30 secs before it even starts to "work". I know that it is not network latency. (I have a 301 redirect from the same server that is executed instantly). When the first request has been served, it seems as if it's not a sleep anymore and every subsequent request is served instantly with the speed of light. The problem was worse two weeks ago, until I changed every query to include WITH (NOLOCK). But I still experience the problem, and the Wait times in the Activity Monitor is about the same. The largest table (Images) has 32764 rows (448576 KB). Some tables exceed 300000 rows, thought they're much smaller in size than the Images table. I have the default clustered index for every primary key column, only. Any ideas?

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  • DataReader-DataSet Hybrid solution

    - by G33kKahuna
    My solution architects and I have exhausted both pure Dataset and Datareader solutions. Basically we have a Microsoft.NET 2.0 windows service application that pulls data based on a query and processes additional tasks per record; almost a poor mans workflow system. The recordsets are broader (in terms of the columns) and deeper (in terms of number of records). We observed that DataSet performs much better in terms of performance but runs into contraints as # of records increase say 100K+ we start seeing System.OutOfMemoryException on a 4G machine with processModel configured to run at memoryLimit set to 85. Since this is a multi-threaded app, there could be multiple threads processing different queries and building different DataSets, so we run into the exception sooner in that case DataReader on the other hand works but is a lot slower and hits other contraints; if there is some sort of disconnect it has to start over again or leaves open connections on the DB side and worst case takes down the service completely etc. So, we decided the best option would be some sort of hybrid solution. I'm open to guidance and suggestions. Are there any hybrid solutions available? Any other suggestions

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  • How can I validate/secure/authenticate a JavaScript-based POST request?

    - by Bungle
    A product I'm helping to develop will basically work like this: A Web publisher creates a new page on their site that includes a <script> from our server. When a visitor reaches that new page, that <script> gathers the text content of the page and sends it to our server via a POST request (cross-domain, using a <form> inside of an <iframe>). Our server processes the text content and returns a response (via JSONP) that includes an HTML fragment listing links to related content around the Web. This response is cached and served to subsequent visitors until we receive another POST request with text content from the same URL, at which point we regenerate a "fresh" response. These POSTs only happen when our cached TTL expires, at which point the server signifies that and prompts the <script> on the page to gather and POST the text content again. The problem is that this system seems inherently insecure. In theory, anyone could spoof the HTTP POST request (including the referer header, so we couldn't just check for that) that sends a page's content to our server. This could include any text content, which we would then use to generate the related content links for that page. The primary difficulty in making this secure is that our JavaScript is publicly visible. We can't use any kind of private key or other cryptic identifier or pattern because that won't be secret. Ideally, we need a method that somehow verifies that a POST request corresponding to a particular Web page is authentic. We can't just scrape the Web page and compare the content with what's been POSTed, since the purpose of having JavaScript submit the content is that it may be behind a login system. Any ideas? I hope I've explained the problem well enough. Thanks in advance for any suggestions.

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  • Is it legal to have different SOAP namespaces/versions between the request and response?

    - by Lord Torgamus
    THIRD EDIT: I now believe that this problem is due to a SOAP version mismatch (1.1 request, 1.2 response) masquerading as a namespace problem. Is it illegal to mix versions, or just bad style? Am I completely out of luck if I can't change my SOAP version or the service's? SECOND EDIT: Clarified error message, and tried to reduce "tl;dr"-ness. EDIT: [Link deleted, not related] Using soapUI, I'm sending a request that starts with: <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" ... and getting a response that starts with: <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" ... I know the service is getting the info, because processes down the line are working. However, my soapUI teststep fails. It has two active assertions: "SOAP Response" and "Not SOAP Fault." The failure marker is next to "SOAP Response," with the following message: line -1: Element Envelope@http://www.w3.org/2003/05/soap-envelope is not a valid Envelope@http://schemas.xmlsoap.org/soap/envelope/ document or a valid substitution. I have tried mixing and matching the namespace prefixes and schema URLs. Changing prefixes seems to have no effect; changing URLs causes a VersionMismatch error. I have also tried to use a substitution group, but that doesn't seem to be legal.

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  • Naming multi-instance performance counters in .NET

    - by Roger Lipscombe
    Most multiple instance performance counters in Windows seem to automatically(?) have a #n on the end if there's more than one instance with the same name. For example: if, in Perfmon, you look under the Process category, you'll see: ... dwm explorer explorer#1 ... I have two explorer.exe processes, so the second counter has #1 appended to its name. When I attempt to do this in a .NET application: I can create the category, and register the instance (using the PerformanceCounterCategory.Create that takes a CounterCreationDataCollection). I can open the counter for write and write to it. When I open the counter a second time, it opens the same counter. This means that I have two applications fighting over the counters. The documentation for PerformanceCounter.InstanceName states that # is not allowed in the name. So: how do I have multiple-instance performance counters that are actually multiple instance? And where the second (and subsequent) instances get #n appended to the name? That is: I know that I can put the process ID (e.g.) on the instance name. This works, but has the unfortunate side effect that restarting the process results in a new PID, and Perfmon continues monitoring the old counter.

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  • svnsync loses revision properties although hook installed

    - by roesslerj
    Hello all! I have a pretty weird problem. We have setup an SVN-Mirror via cronjob (because it needs to go from inside to outside of a firewall, so no post-commit-hook possible) and svnsync. We installed a pre-revprop-hook just as told. Everything seems to work fine, except that it doesn't. E.g. when manually executing the script. # svnsync --non-interactive sync file://<path-to-mirror> --source-username <usr> --source-password <pwd> Committed revision 19817. Copied properties for revision 19817. No error, no complaints. But if checking for the revision properties it says: # svnlook info <path-to-mirror> 0 # svn info -r HEAD file://<path-to-mirror> 2>&1 Path: <root-of-mirror> URL: file://<path-to-mirror> Repository Root: file://<path-to-mirror> Repository UUID: <uid> Revision: 19817 Node Kind: directory Last Changed Rev: 19817 So somehow the author and timestamp information gets lost. But we need that information for our internal processes. Since no error or warning is produced I have absolutely no idea even where to start to look. Everything is local (except for the remote master), so there are no server-logs to look at. I also tried to manually recopy via svnsync copy-revprops (http://chestofbooks.com/computers/revision-control/subversion-svn/svnsync-Copy-revprops-Ref-svnsync-C-Copy-revprops.html). It says Copied properties for revision 19885. But when I query them, it's just the same. Any ideas how I could approach that problem, or even better -- how to solve it? Any ideas appreciated.

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  • Load Spikes on a Apache MySQL Server with Wordpress MU

    - by Vikram Goyal
    Hi there, I am trying to investigate the reasons for some mysterious load spikes on a Linux Apache server (2.2.14) running PHP 5.2.9 on a dedicated server with enough processing power and memory. My primary web application is a Wordpress MU (2.9.2) installation. I have investigated and ruled out DOS attack, MySQL or Apache configuration issues. The log files don't give me anything of interest, except to tell me that there is severe load. The load (which can go up to 100) just seems to come and go. It helps that I have a script that checks every 3 minutes for the load, and restarts Apache. Restarting it helps, and the server comes back, till it happens again. There seems to be no set time frame, or visitor numbers on the site that can trigger this. Even a low number of concurrent visitors (20) can trigger it. I am almost convinced that there is a rewrite loop somewhere that is causing Apache to go mad. Apache is trying to serve something that is causing it to spawn more and more processes till it keels over. My question is: Given that I am convinced that this is a rewrite issue or something similar, how can I try and figure out what the issue is? What should I monitor? Apache logs are voluminous, and not very helpful. Of course, if this is not the issue, then at least knowing what to look for will help me eliminate this as an issue and look for something else. Thanks! Vikram

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  • Is it possible to store pointers in shared memory without using offsets?

    - by Joseph Garvin
    When using shared memory, each process may mmap the shared region into a different area of their address space. This means that when storing pointers within the shared region, you need to store them as offsets of the start of the shared region. Unfortunately, this complicates use of atomic instructions (e.g. if you're trying to write a lock free algorithm). For example, say you have a bunch of reference counted nodes in shared memory, created by a single writer. The writer periodically atomically updates a pointer 'p' to point to a valid node with positive reference count. Readers want to atomically write to 'p' because it points to the beginning of a node (a struct) whose first element is a reference count. Since p always points to a valid node, incrementing the ref count is safe, and makes it safe to dereference 'p' and access other members. However, this all only works when everything is in the same address space. If the nodes and the 'p' pointer are stored in shared memory, then clients suffer a race condition: x = read p y = x + offset Increment refcount at y During step 2, p may change and x may no longer point to a valid node. The only workaround I can think of is somehow forcing all processes to agree on where to map the shared memory, so that real pointers rather than offsets can be stored in the mmap'd region. Is there any way to do that? I see MAP_FIXED in the mmap documentation, but I don't know how I could pick an address that would be safe.

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  • Which apache worker to use with passenger and how?

    - by Millisami
    I've this config in my apache2.conf <IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 150 MaxRequestsPerChild 0 </IfModule> # worker MPM # StartServers: initial number of server processes to start # MaxClients: maximum number of simultaneous client connections # MinSpareThreads: minimum number of worker threads which are kept spare # MaxSpareThreads: maximum number of worker threads which are kept spare # ThreadsPerChild: constant number of worker threads in each server process # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_worker_module> StartServers 2 MaxClients 15 MinSpareThreads 4 MaxSpareThreads 5 ThreadsPerChild 15 MaxRequestsPerChild 50000 </IfModule> Now I'm confused here. Which module gets loaded on which conditions? The phusion guys have suggested to use the worker module. Since both are present in apache conf file, do I have to comment the mpm_prefork_module or leave it as it is? Following is my passenger conf file for apache: LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/ext/apache2/mod_passenger.so PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4 PassengerRuby /usr/bin/ruby1.8 PassengerMaxPoolSize 3 PassengerPoolIdleTime 999999 RailsFrameworkSpawnerIdleTime 0 RailsAppSpawnerIdleTime 0 I'm running just a single Rails 2.3.2 app on 256MB slice at slicehost. I'm not quite satisfied with the performance yet. Are the settings above are any good??

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  • Culture Sensitive GetHashCode

    - by user114928
    Hi, I'm writing a c# application that will process some text and provide basic query functions. In order to ensure the best possible support for other languages, I am allowing the users of the application to specify the System.Globalization.CultureInfo (via the "en-GB" style code) and also the full range of collation options using the System.Globalization.CompareOptions flags enum. For regular string comparison I'm then using a combination of: a) String.Compare overload that accepts the culture and options b) For some bulk processes I'm caching the byte data (KeyData) from CompareInfo.GetSortKey (overload that accepts the options) and using a byte-by-byte comparison of the KeyData. This seemed fine (although please comment if you think these two methods shouldn't be mixed), but then I had reason to use the HashSet< class which only has an overload for IEqualityComparer<. MS documentation seems to suggest that I should use StringComparer (which implements both IEqualityComparer< and IComparer<), but this only seems to support the "IgnoreCase" option from CompareOptions and not "IgnoreKanaType", "IgnoreSymbols", "IgnoreWidth" etc. I'm assuming that a StringComparer that ignores these other options could produce different hashcodes for two strings that might be considered the same using my other comparison options. I'd therefore get incorrect results from my application. Only thought at the moment is to create my own IEqualityComparer< that generates a hashcode from the SortKey.KeyData and compares eqality be using the String.Compare overload. Any suggestions?

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  • Efficient Method for Preventing Hotlinking via .htaccess

    - by Michael Robinson
    I need to confirm something before I go accuse someone of ... well I'd rather not say. The problem: We allow users to upload images and embed them within text on our site. In the past we allowed users to hotlink to our images as well, but due to server load we unfortunately had to stop this. Current "solution": The method the programmer used to solve our "too many connections" issue was to rename the file that receives and processes image requests (image_request.php) to image_request2.php, and replace the contents of the original with <?php header("HTTP/1.1 500 Internal Server Error") ; ?> Obviously this has caused all images with their src attribute pointing to the original image_request.php to be broken, and is also the wrong code to be sending in this case. Proposed solution: I feel a more elegant solution would be: In .htaccess If the request is for image_request.php Check referrer If referrer is not our site, send the appropriate header If referrer is our site, proceed to image_request.php and process image request What I would like to know is: Compared to simply returning a 500 for each request to image_request.php: How much more load would be incurred if we were to use my proposed alternative solution outlined above? Is there a better way to do this? Our main concern is that the site stays up. I am not willing to agree that breaking all internally linked images is the best / only way to solve this. I refuse to tell our users that because of something WE changed they must now manually change the embed code in all their previously uploaded content.

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  • Atomic int writes on file

    - by Waneck
    Hello! I'm writing an application that will have to be able to handle many concurrent accesses to it, either by threads as by processes. So no mutex'es or locks should be applied to this. To make the use of locks go down to a minimum, I'm designing for the file to be "append-only", so all data is first appended to disk, and then the address pointing to the info it has updated, is changed to refer to the new one. So I will need to implement a small lock system only to change this one int so it refers to the new address. How is the best way to do it? I was thinking about maybe putting a flag before the address, that when it's set, the readers will use a spin lock until it's released. But I'm afraid that it isn't at all atomic, is it? e.g. a reader reads the flag, and it is unset on the same time, a writer writes the flag and changes the value of the int the reader may read an inconsistent value! I'm looking for locking techniques but all I find is either for thread locking techniques, or to lock an entire file, not fields. Is it not possible to do this? How do append-only databases handle this? Thanks! Cauê

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  • pluto or jetspeed on google app engine?

    - by Patrick Cornelissen
    I am trying to build something "portlet server"-ish on the google app engine. (as open source) I'd like to use the JSR168/286 standards, but I think that the restrictions of the app engine will make it somewhere between tricky and impossible. Has anyone tried to run jetspeed or an application that uses pluto internally on the google app engine? Based on my current knowledge of portlets and the google app engine I'm anticipating these problems: A war file with portlets is from the deployment standpoint more or less a complete webapp (yes, I know that it doesn't really work without a portal server). The war file may contain it's own web.xml etc. This makes deployment on the app engine rather difficult, because the apps are not visible to each other, so all portlet containing archives need to be included in the war file of the deployed "app engine based portal server". The "portlets" are (at least in liferay) started as permanent servlet processes, based on their portlet.xmls and web.xmls which is located in the same spot for every portlet archive that is loaded. I think this may be problematic in the app engine, because everything is in one big "web app", so it may be tricky to access the portlet.xmls from each archive. This prevents a 100% compatibility in my opinion. Is here anyone who has any experience with the combination of portlets and the app engine? Do you think it's feasible to modify jetspeed, pluto or any other portlet container to be able to run it on the app engine?

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  • Processing XML form input in ASP

    - by Omar Kooheji
    I'm maintaining a legacy application which consists of some ASP.Net pages with c# code behinds and some asp pages. I need to change the way the application accepts it's input from reading a set of parameters from some form fields to reading in one form field which contains contains some XML and parsing to get the parameters out. I've written a C# class that takes an The NameValueCollection from the C# HttpRequest's Form Element. Like so NameValueCollection form = Request.Form; Dictionary<string, string> fieldDictionary = RequestDataExtractor.BuildFieldDictionary(form); The code in the class looks for a particular parameter and if it's there processes the XML and outputs a Dictionary, if its not there it just cycles through the Form parameters and puts them all into the dictionary (Allowing the old method to still work) How would I do this in ASP? Can I use my same class, or a modified version of it? or do I have to write some new code to get this working? If I have to write ASP code Whats the best way to process the XML in ASP? Sorry if this seems like a stupid question but I know next to nothing about ASP and VB.

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  • POST xml to php with apache2

    - by Berry
    I'm working on an application that receives XML data via POST, processes it with a PHP script, and returns an XML response. I'm getting the XML with this PHP code: $requestStr = file_get_contents('php://input'); $requests = simplexml_load_string($requestStr); which works fine on the Linux-based product hardware using nginx as the server. However, for testing I'd like to be able to run it on my MacBook Pro, so I can avoid the "build image, install on product, reboot product, wait, test change" loop while I do targeted development on this XML processor. I enabled "web sharing" which starts up Apache, added a rewrite rule to point a convenient URI at my development source directory and used curl to send a request to my PHP script thus: curl -H "Content-Type:text/xml" -d @request.xml http://localhost/test/path/testscript "testscript" is handled by the PHP script fine, but when it goes to read "php:://input" I get nothing -- the empty string. Anyone have a clue why this would work under Linux with nginx and not under MacOS with Apache? I've googled and searched stackoverlow.com to no avail. Thanks for any answers. UPDATE: I've discovered that at least in this configuration, reading from php://stdin will work fine, while php://input will not. Who knew?

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  • How can I use `pipe` to facilitate interprocess communication in Perl?

    - by Shiftbit
    Can anyone explain how I can successfully get my processes communicating? I find the perldoc on IPC confusing. What I have so far is: $| = 1; $SIG{CHLD} = {wait}; my $parentPid = $$; if ($pid = fork();) ) { if ($pid == 0) { pipe($parentPid, $$); open PARENT, "<$parentPid"; while (<PARENT>) { print $_; } close PARENT; exit(); } else { pipe($parentPid, $pid); open CHILD, ">$pid"; or error("\nError opening: childPid\nRef: $!\n"); open (FH, "<list") or error("\nError opening: list\nRef: $!\n"); while(<FH>) { print CHILD, $_; } close FH or error("\nError closing: list\nRef: $!\n"); close CHILD or error("\nError closing: childPid\nRef: $!\n); } else { error("\nError forking\nRef: $!\n"); } First: What does perldoc pipe mean by READHANDLE, WRITEHANDLE? Second: Can I implement a solution without relying on CPAN or other modules?

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  • is there a Universal Model for languages?

    - by Smandoli
    Many programming languages share generic and even fairly universal features. For example, if you compared Java, VB6, .NET, PHP, Python, then you would find common functions such as control structures, numeric and string manipulation, etc. What has been done to define these features at a meta-language (or language-agnostic) level? UML offers a descriptive reference of software in every aspect, but the real-world focus seems to be data processes. Is UML relevant? I'm not asking "Why we don't have a single language that replaces the current plethora." We need many different tools (at least in this eon). I'm not asking that all languages fit a template -- assembly vs. compiled languages are different enough to make that unfeasible (and some folks call HTML a language, though I wouldn't). Any attempt would start with a properly narrow scope. In line with this, I wouldn't expect the model to cover even a small selection with full validity. I would expect however that such a model could be used to transpose from one language to another (with limited goals -- think jist translation).

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  • Suggestions for a Cron like scheduler in Python?

    - by jamesh
    I'm looking for a library in Python which will provide at and cron like functionality. I'd quite like have a pure Python solution, rather than relying on tools installed on the box; this way I run on machines with no cron. For those unfamiliar with cron: you can schedule tasks based upon an expression like: 0 2 * * 7 /usr/bin/run-backup # run the backups at 0200 on Every Sunday 0 9-17/2 * * 1-5 /usr/bin/purge-temps # run the purge temps command, every 2 hours between 9am and 5pm on Mondays to Fridays. The cron time expression syntax is less important, but I would like to have something with this sort of flexibility. If there isn't something that does this for me out-the-box, any suggestions for the building blocks to make something like this would be gratefully received. Edit I'm not interested in launching processes, just "jobs" also written in Python - python functions. By necessity I think this would be a different thread, but not in a different process. To this end, I'm looking for the expressivity of the cron time expression, but in Python. Cron has been around for years, but I'm trying to be as portable as possible. I cannot rely on its presence.

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  • Starting and stopping firefox from c#

    - by Lucas Meijer
    When I start /Applications/Firefox.app/Contents/MacOS/firefox-bin on MacOSX using Process.Start() using Mono, the id of the process that gets returned does not match the process that firefox ends up running under. It looks like firefox quickly decides to start another process, and kill the current one. This makes it difficult to stop firefox, and to detect if it is still running. I've tried starting firefox using the -no-remote flag, to no avail. Is there a way to start firefox in such a way that it doesn't do this "I'll quickly make a new process for you" dance? The situation can somewhat be detected by making sure Firefox keeps on running for at least 3 seconds after its start, and when it does not, scan for other firefox processes. However, this technique is shaky at best, as on slow days it might take a bit more than 3 seconds, and then all tests depending on this behaviour fail. It turns out, that this behaviour only happens when asking firefox to start a specific profile using -P MyProfile. (Which I need to do, as I need to start firefox with specific proxyserver settings) If I start firefox "normally" it does stick to its process.

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  • C# Process Binary File, Multi-Thread Processing

    - by washtik
    I have the following code that processes a binary file. I want to split the processing workload by using threads and assigning each line of the binary file to threads in the ThreadPool. Processing time for each line is only small but when dealing with files that might contain hundreds of lines, it makes sense to split the workload. My question is regarding the BinaryReader and thread safety. First of all, is what I am doing below acceptable. I have a feeling it would be better to pass only the binary for each line to the PROCESS_Binary_Return_lineData method. Please note the code below is conceptual. I looking for a but of guidance on this as my knowledge of multi-threading is in its infancy. Perhaps there is a better way to achieve the same result, i.e. split processing of each binary line. var dic = new Dictionary<DateTime, Data>(); var resetEvent = new ManualResetEvent(false); using (var b = new BinaryReader(File.Open(Constants.dataFile, FileMode.Open, FileAccess.Read, FileShare.Read))) { var lByte = b.BaseStream.Length; var toProcess = 0; while (lByte >= DATALENGTH) { b.BaseStream.Position = lByte; lByte = lByte - AB_DATALENGTH; ThreadPool.QueueUserWorkItem(delegate { Interlocked.Increment(ref toProcess); var lineData = PROCESS_Binary_Return_lineData(b); lock(dic) { if (!dic.ContainsKey(lineData.DateTime)) { dic.Add(lineData.DateTime, lineData); } } if (Interlocked.Decrement(ref toProcess) == 0) resetEvent.Set(); }, null); } } resetEvent.WaitOne();

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  • How to migrate primary key generation from "increment" to "hi-lo"?

    - by Bevan
    I'm working with a moderate sized SQL Server 2008 database (around 120 tables, backups are around 4GB compressed) where all the table primary keys are declared as simple int columns. At present, primary key values are generated by NHibernate with the increment identity generator, which has worked well thus far, but precludes moving to a multiprocessing environment. Load on the system is growing, so I'm evaluating the work required to allow the use of multiple servers accessing a common database backend. Transitioning to the hi-lo generator seems to be the best way forward, but I can't find a lot of detail about how such a migration would work. Will NHibernate automatically create rows in the hi-lo table for me, or do I need to script these manually? If NHibernate does insert rows automatically, does it properly take account of existing key values? If NHibernate does take care of thing automatically, that's great. If not, are there any tools to help? Update NHibernate's increment identifier generator works entirely in-memory. It's seeded by selecting the maximum value of used identifiers from the table, but from that point on allocates new values by a simple increment, without reference back to the underlying database table. If any other process adds rows to the table, you end up with primary key collisions. You can run multiple threads within the one process just fine, but you can't run multiple processes. For comparison, the NHibernate identity generator works by configuring the database tables with identity columns, putting control over primary key generation in the hands of the database. This works well, but compromises the unit of work pattern. The hi-lo algorithm sits inbetween these - generation of primary keys is coordinated through the database, allowing for multiprocessing, but actual allocation can occur entirely in memory, avoiding problems with the unit of work pattern.

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  • How can I work out what events are being waited for with WinDBG in a kernel debug session

    - by Benj
    I'm a complete WinDbg newbie and I've been trying to debug a WindowsXP problem that a customer has sent me where our software and some third party software prevent windows from logging off. I've reproduced the problem and have verified that only when our software and the customers software are both installed (although not necessarily running at logoff) does the log off problem occur. I've observed that WM_ENDSESSION messages are not reaching the running windows when the user tries to log off and I know that the third party software uses a kernel driver. I've been looking at the processes in WinDbg and I know that csrss.exe would normally send all the windows a WM_ENDSESSION message. When I ran: !process 82356020 6 To look at csrss.exe's stack I can see: WARNING: Frame IP not in any known module. Following frames may be wrong. 00000000 00000000 00000000 00000000 00000000 0x7c90e514 THREAD 8246d998 Cid 0248.02a0 Teb: 7ffd7000 Win32Thread: e1627008 WAIT: (WrUserRequest) UserMode Non-Alertable 8243d9f0 SynchronizationEvent 81fe0390 SynchronizationEvent Not impersonating DeviceMap e1004450 Owning Process 82356020 Image: csrss.exe Attached Process N/A Image: N/A Wait Start TickCount 1813 Ticks: 20748 (0:00:05:24.187) Context Switch Count 3 LargeStack UserTime 00:00:00.000 KernelTime 00:00:00.000 Start Address 0x75b67cdf Stack Init f80bd000 Current f80bc9c8 Base f80bd000 Limit f80ba000 Call 0 Priority 14 BasePriority 13 PriorityDecrement 0 DecrementCount 0 Kernel stack not resident. ChildEBP RetAddr Args to Child f80bc9e0 80500ce6 00000000 8246d998 804f9af2 nt!KiSwapContext+0x2e (FPO: [Uses EBP] [0,0,4]) f80bc9ec 804f9af2 804f986e e1627008 00000000 nt!KiSwapThread+0x46 (FPO: [0,0,0]) f80bca24 bf80a4a3 00000002 82475218 00000001 nt!KeWaitForMultipleObjects+0x284 (FPO: [Non-Fpo]) f80bca5c bf88c0a6 00000001 82475218 00000000 win32k!xxxMsgWaitForMultipleObjects+0xb0 (FPO: [Non-Fpo]) f80bcd30 bf87507d bf9ac0a0 00000001 f80bcd54 win32k!xxxDesktopThread+0x339 (FPO: [Non-Fpo]) f80bcd40 bf8010fd bf9ac0a0 f80bcd64 00bcfff4 win32k!xxxCreateSystemThreads+0x6a (FPO: [Non-Fpo]) f80bcd54 8053d648 00000000 00000022 00000000 win32k!NtUserCallOneParam+0x23 (FPO: [Non-Fpo]) f80bcd54 7c90e514 00000000 00000022 00000000 nt!KiFastCallEntry+0xf8 (FPO: [0,0] TrapFrame @ f80bcd64) This waitForMultipleObjects looks interesting because I'm wondering if csrss.exe is waiting on some event which isn't arriving to allow the logoff. Can anyone tell me how I might find out what event it's waiting for anything else I might do to further investigate the problem?

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  • ActiveRecord exceptions not rescued

    - by zoopzoop
    I have the following code block: unless User.exist?(...) begin user = User.new(...) # Set more attributes of user user.save! rescue ActiveRecord::RecordInvalid, ActiveRecord::RecordNotUnique => e # Check if that user was created in the meantime user = User.exists?(...) raise e if user.nil? end end The reason is, as you can probably guess, that multiple processes might call this method at the same time to create the user (if it doesn't already exist), so while the first one enters the block and starts initializing a new user, setting the attributes and finally calling save!, the user might already be created. In that case I want to check again if the user exists and only raise the exception if it still doesn't (= if no other process has created it in the meantime). The problem is, that regularly ActiveRecord::RecordInvalid exceptions are raised from the save! and not rescued from the rescue block. Any ideas? EDIT: Alright, this is weird. I must be missing something. I refactored the code according to Simone's tip to look like this: unless User.find_by_email(...).present? # Here we know the user does not exist yet user = User.new(...) # Set more attributes of user unless user.save # User could not be saved for some reason, maybe created by another request? raise StandardError, "Could not create user for order #{self.id}." unless User.exists?(:email => ...) end end Now I got the following exception: ActiveRecord::RecordNotUnique: Mysql::DupEntry: Duplicate entry '[email protected]' for key 'index_users_on_email': INSERT INTO `users` ... thrown in the line where it says 'unless user.save'. How can that be? Rails thinks the user can be created because the email is unique but then the Mysql unique index prevents the insert? How likely is that? And how can it be avoided?

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  • C# WinForms MultiThreading in Loop

    - by Goober
    Scenario I have a background worker in my application that runs off and does a bunch of processing. I specifically used this implementation so as to keep my User Interface fluid and prevent it from freezing up. I want to keep the background worker, but inside that thread, spawn off ONLY 3 MORE threads - making them share the processing (currently the worker thread just loops through and processes each asset one-by-one. However I would like to speed this up but using only a limited number of threads. Question Given the code below, how can I get the loop to choose a thread that is free, and then essentially wait if there isn't one free before it continues. CODE foreach (KeyValuePair<int, LiveAsset> kvp in laToHaganise) { Haganise h = new Haganise(kvp.Value, busDate, inputMktSet, outputMktSet, prodType, noOfAssets, bulkSaving); h.DoWork(); } Thoughts I'm guessing that I would have to start off by creating 3 new threads, but my concern is that if I'm instantiating a new Haganise object each time - how can I pass the correct "h" object to the correct thread..... Thread firstThread = new Thread(new ThreadStart(h.DoWork)); Thread secondThread =new Thread(new ThreadStart(h.DoWork)); Thread thirdThread = new Thread(new ThreadStart(h.DoWork)); Help greatly appreciated.

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