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• Multiple column subselect in mysql 5 (5.1.42)

  - by rubber boots

  This one seems to be a simple problem, but I can't make it work in a single select or nested select. Retrieve the authors and (if any) advisers of a paper (article) into one row. I order to explain the problem, here are the two data tables (pseudo) papers (id, title, c_year) persons (id, firstname, lastname) plus a link table w/one extra attribute (pseudo): paper_person_roles( paper_id person_id act_role ENUM ('AUTHOR', 'ADVISER') ) This is basically a list of written papers (table: papers) and a list of staff and/or students (table: persons) An article my have (1,N) authors. An article may have (0,N) advisers. A person can be in 'AUTHOR' or 'ADVISER' role (but not at the same time). The application eventually puts out table rows containing the following entries: TH: || Paper_ID | Author(s) | Title | Adviser(s) | TD: || 21334 |John Doe, Jeff Tucker|Why the moon looks yellow|Brown, Rayleigh| ... My first approach was like: select/extract a full list of articles into the application, eg.SELECT q.id, q.title FROM papers AS q ORDER BY q.c_year and save the results of the query into an array (in the application). After this step, loop over the array of the returned information and retrieve authors and advisers (if any), via prepared statement (? is the paper's id) from the link table like:APPLICATION_LOOP(paper_ids in array) SELECT p.lastname, p.firstname, r.act_role FROM persons AS p, paper_person_roles AS r WHERE p.id=r.person_id AND r.paper_id = ? # The application does further processing from here (pseudo): foreach record from resulting records if record.act_role eq 'AUTHOR' then join to author_column if record.act_role eq 'ADVISER' then join to avdiser_column end print id, author_column, title, adviser_column APPLICATION_LOOP This works so far and gives the desired output. Would it make sense to put the computation back into the DB? I'm not very proficient in nontrivial SQL and can't find a solution with a single (combined or nested) select call. I tried sth. like SELECT q.title (CONCAT_WS(' ', (SELECT p.firstname, p.lastname AS aunames FROM persons AS p, paper_person_roles AS r WHERE q.id=r.paper_id AND r.act_role='AUTHOR') ) ) AS aulist FROM papers AS q, persons AS p, paper_person_roles AS r in several variations, but no luck ... Maybe there is some chance? Thanks in advance r.b.

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• Building a DataTable in C# with one column at a time

  - by Awaken

  I am trying to build a Retirement Calculator as a chance to make something useful and learn C# better. Currently, I am trying to build a DataTable with a dynamic amount of rows/columns. For context, I ask the user for some inputs regarding salary, % of salary being invested, and expected ROI. I have some other stuff too, but it isn't really part of the issue I am having. Because the number of columns I need for the DataTable is unknown until the formula is run (while+for loop completes), I am having trouble doing things as DataColumns. Hopefully the code below will help. I am really trying to build the table one column at a time. I realize I could reverse it to build it one row at a time because the Years before retirement (yearsRetire) is known, but I would prefer not to and I want to learn more. Sorry for the indentation and commenting. I tried to leave some of my commented coding attempts in there. Thanks for any help. public double calcROI() { double testROI = 0.00; double tempRetireAmount = 0; double adjustRetire = goalAmount * (1 + (Math.Pow(inflation,yearsRetire))); // Loop through ROI values until the calculated retire amount with the test ROI // is greater than the target amount adjusted for inflation while (tempRetireAmount < adjustRetire) { //Increment ROI by 1% per while iteration testROI += .01; //Make a new Column to hold the values for ROI for this while iteration //dtMain.Columns.Add(Convert.ToString(testROI)); //DataColumn tempdc = new DataColumn(Convert.ToString(testROI)); //Loop through the number of years entered by user and see the amount //at Retirement with current ROI for (int i = 0; i < yearsRetire; i++) { //Main formula to calculate amount after i years tempRetireAmount = (tempRetireAmount + salary*savingsPct) * (1 + testROI); // Add value for this year/ROI to table/column //DataRow dr = .NewRow(); //dr tempRetireAmount; //tempdc[i] = tempRetireAmount; } //Need to add column of data to my Main DataTable //dtMain.Rows.Add(dr); //dtMain.Columns.Add(tempdc); } return testROI; }

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• Are there any modern GUI toolkits which implement a heirarchical menu buffer zone?

  - by scomar

  In Bruce Tognazzini's quiz on Fitt's Law, the question discussing the bottleneck in the hierarchical menu (as used in almost every modern desktop UI), talks about his design for the original Mac: The bottleneck is the passage between the first-level menu and the second-level menu. Users first slide the mouse pointer down to the category menu item. Then, they must carefully slide the mouse directly across (horizontally) in order to move the pointer into the secondary menu. The engineer who originally designed hierarchicals apparently had his forearm mounted on a track so that he could move it perfectly in a horizontal direction without any vertical component. Most of us, however, have our forarms mounted on a pivot we like to call our elbow. That means that moving our hand describes an arc, rather than a straight line. Demanding that pivoted people move a mouse pointer along in a straight line horizontally is just wrong. We are naturally going to slip downward even as we try to slide sideways. When we are not allowed to slip downward, the menu we're after is going to slam shut just before we get there. The Windows folks tried to overcome the pivot problem with a hack: If they see the user move down into range of the next item on the primary menu, they don't instantly close the second-level menu. Instead, they leave it open for around a half second, so, if users are really quick, they can be inaccurate but still get into the second-level menu before it slams shut. Unfortunately, people's reactions to heightened chance of error is to slow down, rather than speed up, a well-established phenomenon. Therefore, few users will ever figure out that moving faster could solve their problem. Microsoft's solution is exactly wrong. When I specified the Mac hierarchical menu algorthm in the mid-'80s, I called for a buffer zone shaped like a <, so that users could make an increasingly-greater error as they neared the hierarchical without fear of jumping to an unwanted menu. As long as the user's pointer was moving a few pixels over for every one down, on average, the menu stayed open, no matter how slow they moved. (Cancelling was still really easy; just deliberately move up or down.) This just blew me away! Such a simple idea which would result in a huge improvement in usability. I'm sure I'm not the only one who regularly has the next level of a menu slam shut because I don't move the mouse pointer in a perfectly horizontal line. So my question is: Are there any modern UI toolkits which implement this brilliant idea of a < shaped buffer zone in hierarchical menus? And if not, why not?!

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• JPA - Can I create an Entity class, using an @DiscriminatorValue, that doesn't have its own table?

  - by DaveyDaveDave

  Hi - this is potentially a bit complex, so I'll do my best to describe my situation - it's also my first post here, so please forgive formatting mistakes, etc! I'm using JPA with joined inheritance and a database structure that looks like: ACTION --------- ACTION_ID ACTION_MAPPING_ID ACTION_TYPE DELIVERY_CHANNEL_ACTION -------------------------- ACTION_ID CHANNEL_ID OVERRIDE_ADDRESS_ACTION -------------------------- ACTION_ID (various fields specific to this action type) So, in plain English, I have multiple different types of action, all share an ACTION_MAPPING, which is referenced from the 'parent' ACTION table. DELIVERY_CHANNEL_ACTION and OVERRIDE_ADDRESS_ACTION both have extra, supplementary data of their own, and are mapped to ACTION with a FK. Real-world, I also have a 'suppress' action, but this doesn't have any supplementary data of its own, so it doesn't have a corresponding table - all it needs is an ACTION_MAPPING, which is stored in the ACTION table. Hopefully you're with me so far... I'm creating a new project from scratch, so am pretty flexible in what I can do, but obviously would like to get it right from the outset! My current implementation, which works, has three entities loosely defined as follows: @Entity @Table(name="ACTION") @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorValue("SUPPRESS") public class Action @Entity @Table(name="DELIVERY_CHANNEL_ACTION") @DiscriminatorValue("DELIVERY_CHANNEL") public class DeliveryChannelAction extends Action @Entity @Table(name="OVERRIDE_ADDRESS_ACTION") @DiscriminatorValue("OVERRIDE_ADDRESS") public class OverrideAddressAction extends Action That is - I have a concrete base class, Action, with a Joined inheritance strategy. DeliveryChannelAction and OverrideAddressAction both extend Action. What feels wrong here though, is that my Action class is the base class for these two actions, but also forms the concrete implementation for the suppress action. For the time being this works, but at some point more actions are likely to be added, and there's every chance that some of them will, like SUPPRESS, have no supplementary data, which will start to get difficult! So... what I would like to do, in the object model world, is to have Action be abstract, and create a SuppressAction class, which is empty apart from having a @DiscriminatorValue("SUPPRESS"). I've tried doing exactly what is described above, so, changing Action to: @Entity @Table(name="ACTION") @Inheritance(strategy=InheritanceType.JOINED) public abstract class Action and creating: @DiscriminatorValue("SUPPRESS") public class SuppressAction extends Action but no luck - it seems to work fine for DeliveryChannelAction and OverrideAddressAction, but when I try to create a SuppressAction and persist it, I get: java.lang.IllegalArgumentException: Object: com.mypackage.SuppressAction[actionId=null] is not a known entity type. at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:4147) at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:368) at com.mypackage.test.util.EntityTestUtil.createSuppressAction(EntityTestUtil.java:672) at com.mypackage.entities.ActionTest.testCRUDAction(ActionTest.java:27) which I assume is down to the fact that SuppressAction isn't registered as an entity, but I don't know how I can do that, given that it doesn't have an associated table. Any pointers, either complete answers or hints for things to Google (I'm out of ideas!), most welcome :) EDIT: to correct my stacktrace.

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• Exception from Response.Redirect?

  - by allencoded

  I keep getting an error: A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code The thread '' (0x27ee4) has exited with code 0 (0x0). I was told it was related to this: protected void Button1_Click(object sender, EventArgs e) { Response.Redirect("Results.aspx?Keywords=" + searchString.Text); } I figured it may help to include my complete code. The code above is the only C# code on my first asp page. That code relates to this code on this page. It is also the only C# code I have on my second page. I am simply just trying to pass a keyword from a search form to this block of code: if (Request.QueryString["Keywords"] != null){ string keywords = Request.QueryString["Keywords"]; string myAppID = "HIDDEN"; var xml = XDocument.Load("http://svcs.ebay.com/services/search/FindingService/v1?OPERATION-NAME=findItemsByKeywords&SERVICE-VERSION=1.0.0&SECURITY-APPNAME=" + myAppID + "&RESPONSE-DATA-FORMAT=XML&REST-PAYLOAD&keywords=" + keywords + "&paginationInput.entriesPerPage=5"); XNamespace ns = "http://www.ebay.com/marketplace/search/v1/services"; var titles = from item in xml.Root.Descendants(ns + "title") select new{ title = xml.Descendants(ns + "title").Select (x => x.Value), }; foreach (var item in titles){ Label1.Text += item; } } This block of code calls the keyword value and uses it in an api to perform a search. The code of the xml(api) formats like this: <findItemsByKeywordsResponse xmlns="http://www.ebay.com/marketplace/search/v1/services"> <searchReslut count="5"> <item> <title></title> </item> <item> <title></title> </item> <item> <title></title> </item> Why am I getting this error how do you fix it?

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• Need help with 2 MySql Queries. Join vs Subqueries.

  - by BugBusterX

  I have 2 tables: user: id, name message: sender_id, receiver_id, message, read_at, created_at There are 2 results I need to retrieve and I'm trying to find the best solution. I have included queries that I'm using in the very end. I need to retrieve a list of users, and also with each user have information available whether there are any unread messages from each user (them as sender, me as receiver) and whether or not there are any read messages between us ( they send I'm receiver or I send they are receivers) I need Same as above, but only those members where there has been any messaging between us, sorted by unread first, then by last message received. Can you advise please? Should this be done with joins or subqueries? In first case I do not need the count, I just need to know whether or not there is at least one unread message. I'm posting code and my current queries, please have a look when you get a chance: BTW, everything is the way I want in fist query. My concern is: In second query I would like to order by messages.created_at, but I dont think I can do that with grouping? And also I dont know if this approach is the most optimized and fast. CREATE TABLE `user` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, PRIMARY KEY (`id`) ) INSERT INTO `user` VALUES (1,'User 1'),(2,'User 2'),(3,'User 3'),(4,'User 4'),(5,'User 5'); CREATE TABLE `message` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `sender_id` bigint(20) DEFAULT NULL, `receiver_id` bigint(20) DEFAULT NULL, `message` text, `read_at` datetime DEFAULT NULL, `created_at` datetime NOT NULL, PRIMARY KEY (`id`) ) INSERT INTO `message` VALUES (1,3,1,'Messge',NULL,'2010-10-10 10:10:10'),(2,1,4,'Hey','2010-10-10 10:10:12','2010-10-10 10:10:11'),(3,4,1,'Hello','2010-10-10 10:10:19','2010-10-10 10:10:15'),(4,1,4,'Again','2010-10-10 10:10:25','2010-10-10 10:10:21'),(5,3,1,'Hiii',NULL,'2010-10-10 10:10:21'); SELECT u.*, m_new.id as have_new, m.id as have_any FROM user u LEFT JOIN message m_new ON (u.id = m_new.sender_id AND m_new.receiver_id = 1 AND m_new.read_at IS NULL) LEFT JOIN message m ON ((u.id = m.sender_id AND m.receiver_id = 1) OR (u.id = m.receiver_id AND m.sender_id = 1)) GROUP BY u.id SELECT u.*, m_new.id as have_new, m.id as have_any FROM user u LEFT JOIN message m_new ON (u.id = m_new.sender_id AND m_new.receiver_id = 1 AND m_new.read_at IS NULL) LEFT JOIN message m ON ((u.id = m.sender_id AND m.receiver_id = 1) OR (u.id = m.receiver_id AND m.sender_id = 1)) where m.id IS NOT NULL GROUP BY u.id

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• template; operator (int)

  - by Oops

  Hi, regarding my Point struct already mentioned here: http://stackoverflow.com/questions/2794369/template-class-ctor-against-function-new-c-standard is there a chance to replace the function toint() with a cast-operator (int)? namespace point { template < unsigned int dims, typename T > struct Point { T X[ dims ]; //umm??? template < typename U > Point< dims, U > operator U() const { Point< dims, U > ret; std::copy( X, X + dims, ret.X ); return ret; } //umm??? Point< dims, int > operator int() const { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } //OK Point<dims, int> toint() { Point<dims, int> ret; std::copy( X, X + dims, ret.X ); return ret; } }; //struct Point template < typename T > Point< 2, T > Create( T X0, T X1 ) { Point< 2, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; return ret; } }; //namespace point int main(void) { using namespace point; Point< 2, double > p2d = point::Create( 12.3, 34.5 ); Point< 2, int > p2i = (int)p2d; //äähhm??? std::cout << p2d.str() << std::endl; char c; std::cin >> c; return 0; } I think the problem is here that C++ cannot distinguish between different return types? many thanks in advance. regards Oops

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• Advice needed: stay with Java team or move to C++ team?

  - by user68759

  Some background - I have been programming in Java as a professional for the last few years. This is mainly using Java SE. I have also touched bits and pieces of other various Java technologies and have some basic knowledge about them. I consider my self as an intermediate Java programmer. I like Java very much. I think it is only going to get bigger. Recently, my manager asked my opinion on whether I would like to be transferred to another team within the company that is developing a product in C++. This is mainly because my current Java team simply didn't make enough money due to poor sales and the economic downturn. Now, I have never had any experience with C++ nor have I ever coded a single line of code in C++. I have always wanted to learn it and now is my chance. But I really want to make sure I get benefit out of it in the future, in the sense that I will have the skills that will still be on-demand in the future. So, what do you experts think? Is C++ still the language to learn these days to secure yourself for the future? What will I learn more in C++ but not in Java? And are they worthy to learn considering the current and possible future demands in IT industry? (Apart from the obvious more control over memory management and something along that line.) What is a good excuse to refuse the offer in order to stay with the Java team? I don't want to blatantly refuse it because you can never predict the future and I could possibly come back to my manager in the future and ask him to transfer me to the C++ team. How do I say it nicely that I am taking the offer but I would like to still be involved with Java one way or another, such as when there is a new Java project I would like to be considered. I have to admit that I am kind of 50-50 at the moment. I want to learn C++ for the sake of improving my skills and also helping my company to reduce the fund required for the Java team. But it is also hard for me to leave Java because I know Java is going to get bigger, so I am afraid of getting behind when I start concentrating on C++. I could, of course, decide to just join the C++ team, and then spend my free time reading about Java to keep in touch with it, but I thought I would ask anyway in case some people can point out the strong points of either over the other given the current and possibly future circumstances.

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• How dangerous is e.preventDefault();, and can it be replaced by keydown/mousedown tracking?

  - by yc

  I'm working on a tracking script for a fairly sophisticated CRM for tracking form actions in Google Analytics. I'm trying to balance the desire to track form actions accurately with the need to never prevent a form from not working. Now, I know that doing something like this doesn't work. $('form').submit(function(){ _gaq.push('_trackEvent', 'Form', 'Submit', $(this).attr('action')) }); The DOM unloads before this has a chance to process. So, a lot of sample code recommends something like this: $('form').submit(function(e){ e.preventDefault(); var form = this; _gaq.push('_trackEvent', 'Form', 'Submit', $(this).attr('action')); //...do some other tracking stuff... setTimeout(function(){ form.submit(); }, 400); }); This is reliable in most cases, but it makes me nervous. What if something happens between e.preventDefault();and when I get around to triggering the DOM based submit? I've totally broken the form. I've been poking around some other analytics implementations, and I've noticed something like this: $('form').mousedown(function(){ _gaq.push('_trackEvent', 'Form', 'Submit', $(this).attr('action')); }); $('form').keydown(function(e){ if(e.which===13) //if the keydown is the enter key _gaq.push('_trackEvent', 'Form', 'Submit', $(this).attr('action')); }); Basically, instead of interrupting the form submit, preempting it by assuming that if someone is mousing down or keying down on Enter, than that form is submitted. Obviously, this will result in a certain amount of false positives, but it completely eliminates use of e.preventDefault();, which in my mind eliminates the risk that I might ever prevent a form from successfully submitting. So, my question: Is it possible to take the standard form tracking snippet and prevent it from ever fully preventing the form from submitting? Is the mousedown/keydown alternative viable? Are there any submission cases it may miss? Specifically, are there other ways to end up submitting besides the mouse and the keyboard enter? And will the browser always have time to process javascript before beginning to unload the page?

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• Single entity with single view or two views in mvc3 vs2010?

  - by user2905798

  I have the following entity model public class Employee { public int Employee ID{get;set;} public string employeename{get;set;} public datetime employeeDOb{get;set;} public datetime? employeeDateOfJoin{get;set;} public string empFamilyname{get;set;} public datetime empFamilyDob{get;set;} } here I have to design a view for collecting employee information and employee family information. Since I am working on already available data, where in empFamilyDob was not mandatory. But now it is being made mandatory, the previous data doesn't contain EmpFamilyDob. So naturally I have added this new property EmpFamilyDob to the Model and made it required through DataAnnotations. Now there are two set of views to be developed. 1. A view which simply allows to collect the employee information without employee family information. i.e, empFamilyName and EmpFamilyDob.--This view is used by the Hr section to insert empplyee details Since the empFamilyname and EmpFamilyDob being now made mandatory, some other section will edit the data and update the EmpFamilyName and EmpFamilyDob as and when the information about employee family details are received. I have action controller for CreateNew and Edit Which is being generated by using the default model. There are two user actions being performed. 1.When the user clicks the Create new -- he will be able to update only the Employee information 2.As and when the other section receives the employee family details they update the familyname and family date of birth. i.e, EmployeeFamilyname and EmployeFamilyDob. While creating new record the uses should be able to update employee information only and while editing the information he should be able to update the employeefamily information. Since I have a single view with most of these fields as required and not allowing null , How can I achieve this in a sincle view? I have recorrected the model like this public class Employee { public int Employee ID{get;set;} public string employeename{get;set;} public datetime employeeDOb{get;set;} public datetime? employeeDateOfJoin{get;set;} public string empFamilyname{get;set;} public datetime? empFamilyDob{get;set;} } Now by default I hope the createnew action would insert null value for empFamilyname(string datatype) and empFamilyDob . In the Edit action the user should be made to enter empFamilyname and empFamilyDob(mandatory). As there is every chance that the user might edit other information about the employee(like employeeDob) I don't want to go for partial views. Can you help me out with some illustration. Thanks in advance

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• HTTP 500 Internal Server Error on IIS 7.5 with MVC3

  - by Tor Haugen

  I am trying to install an MVC3 application on our production server with no luck. The application is from a 3rd party (compiled), and so debugging is not available to me. Besides, I strongly suspect the error occurs before any code in the site has a chance to execute. Our staging server is - as far as I can determine - set up excactly like the production server. Both run Windows Server 2008 Standard R2, both also run a Sharepoint 2010 site (though this install doesn't touch that in any way). IIS is version 7.5, and .NET Framework 4.0 (required by the MVC app) is (recently) installed (by me, with a reboot after). The application is very small and simple and, as far as I can tell sticks to fairly standard functionality - including forms authentication (ie. it doesnt' pull any dirty tricks). The error message shown in the browser is very general: HTTP Error 500.0 - Internal Server Error An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur. The bit about 'An error message detailing the cause' being in the application event log seems to be just speculation - a pious hope that whatever code actually caused the error will log it. Nothing useful is to be found in the event log (only the very same message, logged by IIS). Module: AspNetInitClrHostFailureModule Notification: BeginRequest Handler: StaticFile Error Code: 0x80070002 Requested URL: http://xxxxxx.xxxxxx.xx:80/ Physical Path: C:\Xxxxxxx\Prod\WebClient Logon Method: Not yet determined Logon User: Not yet determined Using Failed Request Tracing, I have been able to track the error (as also indicated above) to the AspNetInitClrHostFailureModule: 103. -NOTIFY_MODULE_START ModuleName AspNetInitClrHostFailureModule Notification 1 fIsPostNotification false Notification BEGIN_REQUEST 104. -SET_RESPONSE_ERROR_DESCRIPTION ErrorDescription An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur. 105. -MODULE_SET_RESPONSE_ERROR_STATUS ModuleName AspNetInitClrHostFailureModule Notification 1 HttpStatus 500 HttpReason Internal Server Error HttpSubStatus 0 ErrorCode 2147942402 ConfigExceptionInfo Notification BEGIN_REQUEST ErrorCode The system cannot find the file specified. (0x80070002) So there you have it. Seemingly, the AspNetInitClrHostFailureModule fails to find some file. So some questions are: What is the AspNetInitClrHostFailureModule? It is not listed in the fairly exhausting list of modules configurable in IIS manager for the site. I have had no success googling it either. Maybe it's secret.. I access the root URL of the site. This is supposed to be redirected to /Account/LogOn by the FormsAuthenticationModule. Why then is the handler StaticFile? Is that a clue? I have tried removing the infamous system.webserver/modules/runAllManagedModulesForAllRequests attribute, and that makes the error go away (but MVC not actually working, of course). I am prepared to specify all necessary modules manually if that's what it takes, but if the AspNetInitClrHostFailureModule is actually needed, I will be just as stuck. Does anyone know, or can anyone direct me to someone who knows, exactly what modules a typical MVC3 application actually needs? This question might well be a duplicate of this one, but he didn't get any useful answer, and also asked less specific questions. So I'll have my own go. Hoping for some help here :) Edit: I have now tried setting up a trivial MVC 3 project on the server. I created a new project using the MVC Application template, compiled it and deployed it to the server. It behaves in exactly the same way. The server simply cannot run MVC 3 projects.

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• What are the pitfalls of hardlinked files on my desktop PC?

  - by MountainX

  All the identical-content files on my PC are now hardlinked. (My data is completely de-duplicated. It is a consequence of the way I copied my data from my old computer.) What pitfalls do I need to be aware of now that certain actions on one file could silently affect a number of other files? I know that deleting the file I'm working on is not a problem (assuming I deleted it on purpose). It doesn't affect any of the other hardlinked files and I don't see that the delete action would lead to unexpected side effects. Moving or renaming the file is not a problem. I don't see any unexpected consequences. I don't think copying hardlinked files is a problem, but I'm not as confident about any unexpected consequences in this regard. What I have seen is that making a copy (to the same disk) of a hardlinked file with cp keeps the copy hardlinked (i.e., inode number doesn't change in the copy). Copying to another filesystem obviously breaks the hardlink. (I guess one pitfall is forgetting this fact, given that my PC has 3 hard disks.) Changing permissions does affect all linked files. So far this has proven handy. (I made a large number of the hardlinked files read-only.) None of the operations above seem to produce any major unexpected consequences. However, as was pointed out to me by Daniel Beck in a comment, editing or modifying a file can sometimes be a problem. It depends on the tool and maybe the type of edit. (For example, editing small text files using sed seems to always break the link while using nano doesn't.) This introduces the chance that editing one file could affect all the hardlinked files (i.e., alter the original inode). My proposed solution to this is to make all hardlinked files read-only (and that is already mostly the case). If I can't do that for some files, I will unlink those particular files. Is there any problem with this read-only approach? I'm assuming that if I go to edit a file and find it to be read-only, I'll remember to unlink that filename while making it writable. So one pitfall might be forgetting this rule. In that case, I'll have to rely on my backups. Am I correct in the above statements? And what else do I need to know? BTW, I'm running Kubuntu 12.04. I'm also using btrfs. (I have 2 SSD's and 1 HDD in the PC. I will also be adding an external USB HDD. I'm also connected to a network and I mount some NFS shares. I don't assume any of these last bits are relevant to the question, but I'm adding them just in case.) BTW, since I have more than one drive (with separate file systems), to unlink any file all I have to do is copy it to another drive, then move it back. However, using sed also works (in my testing). Here's my script: sed -i 's/\(.\)/\1/' file1 Surprisingly, this even unlinks zero byte files. In my testing it also appears to work on non-text files without any special options. (But I understand that the --binary option might be needed on Windows, MS-DOS and Cygwin.) However, copying to another disk and moving back may be the best way to unlink. For my use-case, unlink command doesn't really "unlink", rather it "removes".

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• SQL Server Issue: Could not allocate space for object ... primary filegroup is full

  - by Luke

  Trying to figure out a problem at an office that has SQL Server 2005 installed on Windows SBS Server 2008. Here's the setup: It's an office, and the person who set this all up is nowhere to be found. I'm the best hope they have... One of the programs they use on a workstation gives them an error of "Could not allocate space for object 'Billing' in database "MyDatabase" because primary filegroup is full" when trying to save an entry in their software. I searched around for hours, looking for possible solutions. One was to check for available disk space, and another was to defrag. I checked the hard drives on the server, and there is plenty of space free. I also defragged, which may have helped the problem somewhat. It's hard to say, because it seems like with the nature of the error, if you try over and over you might get it to actually save. My next step was to try to see if autogrowth was enabled on the database. This would seem to be a likely / possible solution, but I can't access the database! If I run the SQL Management Studio, I can log in as my Windows user and view the list of databases. However, if I try to do anything (actually view the database, view the properties, add or edit users), I get errors that I don't have permission. For what it's worth, I also tried runing Management Studio as Administrator, in case that would help. No difference, though. Now, what I'm guessing is going on -- from my limited knowledge of SQL and from reading online -- is that though I'm logged in as a Windows administrator, that account does NOT have SQL access. I do see a list of SQL users, including SA, but I again don't have permission to add one or to change the password on an existing one. And nobody at the office has any idea what the SQL passwords could be. So... here's my thinking thus far: 1 - The "Could not allocate" error likely points to a database that needs to be allowed to autogrow. Especially since I verified there is plenty of free space and the HD has been defragmented. 2 - Enabling autogrow would be very easy to do if I had the proper access within SQL Management Stuido. That leads me to this link: http://blogs.technet.com/b/sqlman/archive/2011/06/14/tips-amp-tricks-you-have-lost-access-to-sql-server-now-what.aspx It sounds like it's a step-by-step guide for giving me the access I need to SQL. I'm guessing that if I followed this guide, I would be able to then log in to the SQL server via Management Studio with the proper permissions, and would be able to enable autogrow (or simply view the status of the existing database), and hopefully solve the "Could not allocate space" problem! So I guess I have a few questions: 1 - Would you guys agree with my "diagnosis"? Think I'm barking up the right tree? 2 - Is there any risk at all in hurting / disabling / wrecking the current SQL database or setup with me going through the guide to regain SQL access? I understand that per the guide, I would have to temporarily shut down SQL, so obviously it wouldn't be accessible during that time. But it wouldn't be worth the risk if there's a chance I could mess anything up... Like I said, the workstations ARE currently accessing the database somehow, but nobody knows with what login info or anything. Basically, it's set up, it works (usually), but if they had to reload the software, nobody would know how. Any feedback would be appreciated!! The problem is such that it's not an emergency for them, but an annoyance. If I could fix it, it would be wonderful. But if not, I think they'll manage, especially as they are going to eventually stop using this software. Thank you so much for your time! Luke

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• Scenarios for Bazaar and SVN interaction

  - by Adam Badura

  At our company we are using SVN repository. I'm doing programming from both work (main place) and home (mostly experiments and refactoring). Those are two different machines, in different networks and almost never turned on at the same time (after all I'm either at work or at home...) I wanted to give a chance to some distributed version control system and solve some of the issues associated with SVN based process and having two machines. From git, Mercurial and Bazaar I chose to start with Bazaar since it claims that it is designed do be used by human beings. Its my first time with distributed system and having nice and easy user interface was important for me. Features I wanted to achieve were: Being able to update from SVN repository and commit to it. Being able to commit locally steps of my work on a task. Being able to have few separate tasks at the same time in their own local branches. Being able to share those branches between my work and home computer. As a means of transport between work and home computer I wanted to use a pen-drive. Company server will not work since I may not instal there anything. Neither will work a web service repository as I may not upload source code to web (especially if it would be public which seems to be a common case in free web services). This transport should be Bazaar-based (or what ever else I will end with) so it can be done more or less automatically but manual copying and pasting some folders or generating patch files (providing they would work - I have bad experience with patch files in SVN) would work as well if there is no better solution. Yet the pen-drive should only be used for transportation. I do not want to edit or build there. I tried following Bazaar guidelines for integration with SVN. But I failed. I tried both bzr svn-import and bzr checkout providing URL from my repository as both https://... and svn+https://.... In some cases it had some issues with certificates but the output specified argument to ignore them so I did that. Sometimes it asked me to log in (in other cases maybe it remembered... I don't know) which I did. All were running very slow (this could be our server issue) and at some point were interrupted due to connection interruption (this almost for sure is our server issue: it truncates the connection after some time). But since (as opposed to SVN) restarting starts a new rather than from point where it was interrupted I was unable to reach all the ~19000 revisions (ending usually somewhere around 150). What and how should I do with Bazaar? Is is possible to somehow import SVN repository from the local checkout (so that I do not suffer the connection truncation)? I was told that a colleague that used to work with us has done something similar (importing SVN repository with full history) with Mercurial like in no time. So I'm seriously considering now trying Mercurial even if only to see if that will work. But also what are your general guidelines to achieve the listed features?

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• Random Slow Response

  - by ARehman

  We have an ASP.NET MVC 1.0 application running on Windows Server 2008 – Standard (32 –bit), Dual Core Xeon (3.0 GHz), 2 G.B R.A.M. Most of the times application renders response in 3-4 seconds, but sometimes users get very late response and delay is up to 40 seconds or more than a minute. It happens in following way: User browsed a page, idle for 5, 10 or 15 minutes, tried to browse same page or some other. Now, there is a chance that he will see late response whereas the app pool is still up and running. This can happen with any arbitrary page. We have tried followings/observations. Moved the application to stand alone web server App Pool idle shutdown time is 60 minutes. There are no abrupt shut downs/restarts. CPU or memory doesn’t spike. No delays in SQL queries. Modified App Pool setting to run in classic-mode. It didn’t help. Plugged-in custom module to log all those requests which took more than 5 seconds to complete. It didn’t pick any request of interest. Enabled ‘Failed Request Tracing’ to log all those requests which take 20 or more seconds to complete. It didn’t log anything. Event Viewer, HTTPER log, W3SVC logs or WAS logs don’t indicate anything. HTTPERR only has ‘_ _ Timer_ConnectionIdle _ _’ entries. There is not much traffic to server. This can happen also if only two users are active. Next we captured TCP/IP terrific on both a user and server end with Wireshark and below are details in brief of this slowness: Browser sends a request for ~/User/Home/ (GET Request) by setting up a receiving end point using port 'wlbs(port-2504)'. I'm not sure if this could be a problem in some way that browser didn't hand-shake with the server first and assumed that last connection is still open, whereas, I browsed the same page 4 minutes ago and didn't perform any activity with site after that. If I see the HTTPERR log, it indicates that it has ‘_ _ Timer_ConnectionIdle _ _ _’ entry for my last activity with server. Browser (I was using Chrome) waits for any response from the server, doesn’t find any then starts retransmitting the same request using same end point after incrementing wait intervals, e.g. after 8, 18, 29, 40, 62, and 92 seconds. All these GET requests were received by server as well. But, server didn’t send any packet to client. Browser didn't see any response on the end point it set up in point 1, it opened a new end point 'optiwave-lm (port-2524)', did a hand shake with the server and transmitted the same request again. Server received, processed it, and returned successful response. What happened to earlier 6-7 requests? Whether they were passed on to HTTP.SYS or not? Why Failed Request Tracing not logged anything, we didn't find any clue yet. Server served the same page successfully just 4 minutes ago. Looking forward for more suggestions/solutions. -- Thanks

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• Win 7 Netbook refuses to ping JetDirect card (all other PCs work)

  - by Luke Puplett

  I have an odd thing occuring here. From a Windows 7 netbook, I cannot ping an HP printer on the network, while all other machines (Win7/Vista) can. And the netbook can also ping everything else on the LAN. Example showing that the netbook can ping 192.168.3.4 but not 3.6. C:\Users\backdoor>ping w7ue1m Pinging w7ue1m.corp.biz.co.uk [192.168.3.4] with 32 bytes of data: Reply from 192.168.3.4: bytes=32 time=7ms TTL=128 Reply from 192.168.3.4: bytes=32 time=4ms TTL=128 Reply from 192.168.3.4: bytes=32 time=2ms TTL=128 Reply from 192.168.3.4: bytes=32 time=2ms TTL=128 Ping statistics for 192.168.3.4: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 2ms, Maximum = 7ms, Average = 3ms C:\Users\backdoor>ping uktnprint1 Pinging uktnprint1.corp.biz.co.uk [192.168.3.6] with 32 bytes of data: Reply from 192.168.3.0: Destination host unreachable. Reply from 192.168.3.0: Destination host unreachable. Reply from 192.168.3.0: Destination host unreachable. Reply from 192.168.3.0: Destination host unreachable. Ping statistics for 192.168.3.6: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),`enter code here` The IPCONFIG result for the netbook is fine. IPv4 Address. . . . . . . . . . . : 192.168.3.0 Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : 192.168.1.1 Most unusual network thing I've seen in years. I must reiterate that only this netbook is having trouble pinging/printing. Thanks, Luke ** UPDATE ** Am now on a Vista box, and here's the IPCONFIG: IPv4 Address. . . . . . . . . . . : 192.168.3.3 Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : 192.168.1.1 Pinging uktnprint1.corp.biz.co.uk [192.168.3.6] with 32 bytes of data: Reply from 192.168.3.6: bytes=32 time=2ms TTL=60 Firewall is off. I'll look into the chance of an IP conflict because it's the only thing I can think of - compare arp caches of each machine. Cheers!

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• Just a few questions about Hyper-V virtual machines and clustering

  - by René Kåbis

  I have been using Microsoft’s Hyper-V technology for a little while now, but I am just now dipping my toe into clustering. In particular, I am trying to implement a fault-tolerant SQL DB. This involves setting up two VMs, clustering them via Failover Cluster, and then installing SQL Server in some fashion. I have two physical machines - one high-end and rather beefy “heavy lifter” to contain the majority of the VMs, and another “backup” (a repurposed desktop) to hold the essential “secondary” (or failover) AD-DC, SQL and FS VMs. The main reason why I find the failover cluster at the VM level so attractive is that it presents a single IP and DNS entry to the network as a whole - if one machine (physical or virtual) goes down, you might loose some ping and the connections get reset, but the network applications (Microsoft RMS connection to backend SQL) can still connect to a viable DB without having to mess around with the settings at all. My first question is in terms of SQL Server itself. If I have a cluster between two VMs, does it make more sense to install the SQL Server in Failover Cluster configuration or should I simply install it in a stand-alone config and mirror the DBs? For example, this post suggests just mirroring the DBs, but do I just mirror standalone DBs on standalone VMs, or can I get the network and failover benefits of clustered VMs while still utilizing (on each clustered VM) standalone DBs that have been mirrored between each other? As well, I have come across a lot of documentation about SQL clustering, but most assume a number (#2) of physical machines to hold not only the actual SQL VMs but also the Quorum and Witness stores. I will not be able to muster more than two physical machines. As such, I will have to be satisfied with a VM cluster that does not exceed two VMs (one for each physical machine). Another issue involves MSDTC - the Distributed Transaction Coordinator. When attempting to install the SQL Failover Cluster (I never completed it for this reason) it threw a hissy fit because MSDTC had not been clustered. Search as I might, I have not yet found a way to do so under Windows Server 2012 R2. I have found plenty of docs for Windows 2008 and 2008 R2, but these instructions don’t align with 2012 R2 (at least, not in a way that allows me to successfully cluster MSDTC). Plus, some of the instructions that I have found for SQL Server Failover Cluster installation suggest that a third “network device” - shared network storage (a SAN) - is required for the DB itself (and other functionality). I do not have this, and won’t be getting this. Most of my storage exists on the “heavy lifter” that was designed for all of the “primary” VMs. If that physical machine goes down, so does the storage. The secondary server does have enough resources for an AD-DC Server, an SQL server and a File Server, so it will handle the “secondary” failover versions of those VMs (clustered or not). My final question involves file servers. If I cluster file servers between two VMs (one on my “heavy lifter” and another on my “backup”, how do I mirror the data between them? Clustering VMs only provides a single point of access on the network for a resource, it doesn’t exactly replicate data between the two - that is left to the services that serve up that data. I am unsure how I can ensure that file server data between two clustered file server VMs can be properly mirrored. Remember, I only have two devices to be used here - my primary machine and a backup secondary. There is no chance of me obtaining a SAN or any other type of network attached storage. What exists on the machines must act as the storage. Thanks in advance for any suggestions.

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• How to change the language of driver interface for Canon Pixma printers?

  - by Sammy

  Is there a way to change the language of the driver interface for Canon Pixma printers? Which language is used seems to be determined by the language of the OS or the Windows localization settings. I really don't want that, I want to be able to set the language manually to my own liking, either during the driver installation or afterwards. I have found a workaround for Pixma IP2770 where you edit the setup.ini file by replacing the language names and the DLL search paths with <SELECT> under the LANGUAGES section. So instead of... 0000=<SELECT> 0001=Arabic,RES\STRING\IJInstAR.ini,RES\DLL\IJInstAR.dll 0804=Simplified Chinese,RES\STRING\IJInstCN.ini,RES\DLL\IJInstCN.dll 0404=Traditional Chinese,RES\STRING\IJInstTW.ini,RES\DLL\IJInstTW.dll 0005=Czech,RES\STRING\IJInstCZ.ini,RES\DLL\IJInstCZ.dll 0006=Danish,RES\STRING\IJInstDK.ini,RES\DLL\IJInstDK.dll 0007=German,RES\STRING\IJInstDE.ini,RES\DLL\IJInstDE.dll 0008=Greek,RES\STRING\IJInstGR.ini,RES\DLL\IJInstGR.dll 0009=English,RES\STRING\IJInstUS.ini,RES\DLL\IJInstUS.dll 000A=Spanish,RES\STRING\IJInstES.ini,RES\DLL\IJInstES.dll 000B=Finnish,RES\STRING\IJInstFI.ini,RES\DLL\IJInstFI.dll 000C=French,RES\STRING\IJInstFR.ini,RES\DLL\IJInstFR.dll 000E=Hungarian,RES\STRING\IJInstHU.ini,RES\DLL\IJInstHU.dll 0010=Italian,RES\STRING\IJInstIT.ini,RES\DLL\IJInstIT.dll 0011=Japanese,RES\STRING\IJInstJP.ini,RES\DLL\IJInstJP.dll 0012=Korean,RES\STRING\IJInstKR.ini,RES\DLL\IJInstKR.dll 0013=Dutch,RES\STRING\IJInstNL.ini,RES\DLL\IJInstNL.dll 0014=Norwegian,RES\STRING\IJInstNO.ini,RES\DLL\IJInstNO.dll 0015=Polish,RES\STRING\IJInstPL.ini,RES\DLL\IJInstPL.dll 0016=Portuguese,RES\STRING\IJInstPT.ini,RES\DLL\IJInstPT.dll 0019=Russian,RES\STRING\IJInstRU.ini,RES\DLL\IJInstRU.dll 001D=Swedish,RES\STRING\IJInstSE.ini,RES\DLL\IJInstSE.dll 001E=Thai,RES\STRING\IJInstTH.ini,RES\DLL\IJInstTH.dll 001F=Turkish,RES\STRING\IJInstTR.ini,RES\DLL\IJInstTR.dll 0021=Indonesian,RES\STRING\IJInstID.ini,RES\DLL\IJInstID.dll You get.... 0000=<SELECT> 0001=<SELECT> 0804=<SELECT> 0404=<SELECT> 0005=<SELECT> 0006=<SELECT> 0007=<SELECT> 0008=<SELECT> 0009=English,RES\STRING\IJInstUS.ini,RES\DLL\IJInstUS.dll 000A=<SELECT> 000B=<SELECT> 000C=<SELECT> 000E=<SELECT> 0010=<SELECT> 0011=<SELECT> 0012=<SELECT> 0013=<SELECT> 0014=<SELECT> 0015=<SELECT> 0016=<SELECT> 0019=<SELECT> 001D=<SELECT> 001E=<SELECT> 001F=<SELECT> 0021=<SELECT> .... in case English is the preferred language. It's a way to force the installation program to only install the English language support. IP2770 is a model for the Asian market, so if you want to check this out you need to go to the Canon India download page (for instance) to get the driver. Unfortunately this method is not possible with my IP4000. There is no driver even available for it to download for Windows Vista. But is there really no way of changing the language of the UI in any normal way, you know... without having to hack it? Besides, the driver for my printer comes with Windows Vista, so I don't even have to install any drivers. And little do I get the chance to set the language, knowing that the installation never happens. Any ideas?...

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• Hard drive after PCB swap strange stuff

  - by ramyy

  I’ve done a PCB swap to my HDD. The HDD model is: WD6400AAKS-00A7B2. The original PCB PN matches the new one (first three letter groups), though the cache mismatches (16MB original, 8MB new). The Hardware store that made the swap told me it was hard to do the swap, they have done firmware adaptation. I can see that this firmware version does not match the original, (01.03B01 original, 05.04E05 new). Still I can see that the serial number and model of the drive is correct, the hard drive appeared normal in the BIOS, all the partitions show and everything appears normal. I have encountered three things though, I have left the drive non operated for 2-3 weeks after the swap to avoid corrupting the data or anything else the new PCB might cause, until I buy a new drive and backup the data. I got a drive, and when I powered the old drive manually (I have a laptop, I use a normal desktop power supply and a USB/SATA connector), I heard the motor start and I could hear ticking as if the motor’s somehow struggling to start, and then the motor sound starts again then the ticking, and so on.. I tried powering again it happened again. The third time it started normally and I could see everything normally. I took the chance and copied all the data over to the new drive. When I was done, I powered off the drive (after more than 25 hours of continuous operation), tried to power it up again and it did so normally, and so are the times I powered it up later; but I got very suspicious now. What could be the problem here? And what happened new, it used to power normally after the swap directly? The second thing that happened is that I found size differences with some files; some include movies, songs, (.iso) files for games, and programs. I could find the size is the same, but size on disk is a little more on the new drive for these files. . I’ve tried some of those files (with size differences) they worked fine. They are not too much but still make you suspicious of the integrity of the data copied; one cannot try if all files are working for about (580 GB) worth of data. I tried copying these files on the same partition they exist of the old drive; they are the same in size as when copied to the new drive (allocation unit size not the issue). I took an image of a partition (sector by sector including empty ones) and when I explore it, these file sizes are equal to the original (old drive); I copy them anywhere else their size on disk, increases, i.e becomes equal to the ones I copy from the old drive itself anywhere. Why the size difference and can one trust the integrity of the data?? The third thing is that when I connect my new external USB HDD, the partitions of the old HDD unmount and then mount again. Connected are: (USB mouse + Old HDD) then external HDD. Why that happens?? Considering the following: I compared the SMART reports from after the swap directly and after the copying, no error readings or reallocated sectors where reported. Here they are: http://www.image-share.com/ijpg-1939-219.html I later ran both WD data life guard tests and they came out passed. I’m worried for this drive since I must be sure the data is fine and safe on the new one, and I will consider it backup for the new one, since you can’t trust anything anymore. I hope you can forgive me for the length of the post, but couldn’t ignore any of the details, this hard drive contains very important data to me and I have to deal with the situation with great care.

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• Windows 7, file properties - Is "date accessed" ALWAYS 100% accurate?

  - by Robert

  Hello, Here's the situation: I went on vacation for a couple of weeks, but before I left, I took the harddrive out of my computer and hid it in a different location. Upon coming back on Monday and putting the harddrive back in my computer, I right-clicked on different files to see their properties. Interestingly enough, several files had been accessed during the time I was gone! I right-clicked different files in various locations on the harddrive, and all of these suspect files had been accessed within a certain time range (Sunday, ?January ?09, ?2011, approximately ??between 6:52:16 PM - 7:16:25 PM). Some of them had been accessed at the exact same time--down to the very second. This makes me think that someone must have done a search on my harddrive for certain types of files and then copied all those files to some other medium. The Windows 7 installation on this harddrive is password protected, but NOT encrypted, so they could have easily put the harddrive into an enclosure/toaster to access it from a different computer. Of course I did not right-click every single file on my computer, but did so in different folders. For instance, one of the folders I went through has different types of files: .mp3, ,prproj, .3gp, .mpg, .wmv, .xmp, .txt with file-sizes ranging from 2 KB to 29.7 MB (there is also a sub-folder in this folder which contains only .jpg files); however, of all these different types of files in this folder and its subfolder, all of them had been accessed (including the .jpg files from the sub-folder) EXCEPT the .mp3 files (if it makes any difference, the .mp3 files in this folder range in size from 187 KB to 4881 KB). Additionally, this sub-folder which contained only .jpg files (48 .jpg files to be exact) was not accessed during this time--only the .jpg files within it were accessed-- (between 6:57:03 PM - 6:57:08 PM). I thought that perhaps this was some kind of Windows glitch that was displaying the wrong access date, but then I looked at the "date created" and "date modified" for all of these files in question, and their created/modified dates and times were spot on correct. My first thought was that someone put the harddrive into an enclosure/toaster and viewed the files; but then I realized that this was impossible because several of the files had been accessed at the same exact time down to the second. So this made me think that the only other way the "date accessed" could have changed would have been if someone copied the files. Is there any chance at all whatsoever that this is some kind of Windows glitch or something, or is it a fact that someone was indeed accessing my files (and if someone was accessing my files, am I right about the files in question having been copied)? Is there any other possibility for what could have happened? Do I need to use any kinds of forensics tools to further investigate this matter (and if so, which tools), or is there any other way in which I can be certain of what took place in that timeframe the day before I got back? Or is what I see with Windows 7 good enough (i.e. accurate and truthful)? Thanks in advance, and please let me know if any other details are required on my part.

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• How do bots access directories on a server that are not DocumentRoot of public IP address? How do I stop them?

  - by tmsimont

  I have a local network set up with apache2 and "named" running on OpenSuse 13.1 Linux. I used the "named" service to use my computer as a domain server. I set up my router to point to ask my computer for domain lookups, so I have a chance to have it rewrite a bunch of domains on my network to its own local IP, 192.168.0.111 This works great. I use virtual host configuration to allow various domains and subdomains (re-routed to the same IP via named) to pull up different directories in my computer. For example: <VirtualHost *:80> ServerName 192.168.0.111 ServerAlias fmb.wa.net DocumentRoot /home/work/wa.net/fmb </VirtualHost> <VirtualHost *:80> ServerName 192.168.0.111 ServerAlias postrecord.wa.net DocumentRoot /home/work/wa.net/postrecord </VirtualHost> <VirtualHost *:80> ServerName 192.168.0.111 ServerAlias cvalley.wa.net DocumentRoot /home/work/wa.net/cvalley_local </VirtualHost> This makes it possible for me to hit cvalley.wa.net from any device in my network and get the site that lives in /home/work/wa.net/cvalley_local I decided to forward port 80 to this computer, so I could share a few development sites with coworkers. I can't control which site they see with the same named service, because they'd have to use my computer as their domain name server... So I added a line like this: <VirtualHost *:80> ServerName 192.168.0.111 ServerAlias MY.IP.XXX.XX DocumentRoot /home/work/wa.net/cvalley </VirtualHost> Where "MY.IP.XXX.XX" is my public IP address. This works as expected, when you hit my IP address from a public network you see the site that lives in /home/work/wa.net/cvalley. The point of confusion that I have is that there are public IP addresses in my logs in other sites. I would have expected it to be impossible to access other sites in my network, unless the public user somehow figured out what I'm calling my ServerAliases, and is mimicing my domain set up... How can public traffic be hitting my other local sites? How can I recreate this kind of access? Here are some examples of public IP's hitting my VirtualHost sites: 162.253.66.76 - - [15/Aug/2014:19:20:47 -0600] "GET /xmlrpc.php HTTP/1.0" 404 1004 "-" "-" 162.253.66.74 - - [16/Aug/2014:10:50:28 -0600] "GET / HTTP/1.0" 200 262 "-" "masscan/1.0 (https://github.com/robertdavidgraham/masscan)" 185.4.227.194 - - [16/Aug/2014:11:16:45 -0600] "GET http://24x7-allrequestsallowed.com/?PHPSESSID=1rysxtj500143WQMVT%5E_NAZ%5BQ HTTP/1.1" 200 262 "-" "-" 101.226.254.138 - - [16/Aug/2014:13:32:14 -0600] "HEAD / HTTP/1.0" 200 - "-" "-" 162.253.66.74 - - [16/Aug/2014:14:26:19 -0600] "GET / HTTP/1.0" 200 262 "-" "masscan/1.0 (https://github.com/robertdavidgraham/masscan)" 212.129.2.119 - - [16/Aug/2014:16:00:51 -0600] "HEAD / HTTP/1.0" 200 - "-" "-" 91.240.163.111 - - [16/Aug/2014:18:34:32 -0600] "GET / HTTP/1.0" 200 262 "-" "masscan/1.0 (https://github.com/robertdavidgraham/masscan)" 162.253.66.74 - - [16/Aug/2014:19:02:53 -0600] "GET / HTTP/1.0" 200 262 "-" "masscan/1.0 (https://github.com/robertdavidgraham/masscan)" 122.226.223.69 - - [17/Aug/2014:05:53:09 -0600] "GET http://www.k2proxy.com//hello.html HTTP/1.1" 404 1006 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/6.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)" ::1 - - [17/Aug/2014:10:19:26 -0600] "OPTIONS * HTTP/1.0" 200 - "-" "Apache/2.4.6 (Linux/SUSE) OpenSSL/1.0.1e PHP/5.4.20 (internal dummy connection)" 162.209.65.196 - - [17/Aug/2014:15:31:53 -0600] "HEAD / HTTP/1.0" 200 - "-" "-" 111.206.199.163 - - [18/Aug/2014:11:12:56 -0600] "HEAD / HTTP/1.0" 200 - "-" "-" 37.187.180.168 - - [18/Aug/2014:15:40:00 -0600] "HEAD / HTTP/1.0" 200 - "-" "-" 62.210.38.226 - - [18/Aug/2014:18:35:16 -0600] "HEAD / HTTP/1.0" 200 - "-" "-" Is there anything that I can do to reliably deny public access by default, but allow it only in one VirtualHost?

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• Week in Geek: USDA Chooses Microsoft for Cloud Services Edition

  - by Asian Angel

  This week we learned how to create geeky LED holiday lights with old bottles, dig deeper in Windows Defrag via the command prompt, use Google Chrome’s drag/drop feature to upload files easier, find great gift recommendations by looking through the How-To Geek holiday gift guide, and have fun adding Merry Christmas fonts to our computers. Photo by ntr23. Random Geek Links It has been a busy week, so we have extra news link goodness with information that is good for you to know. USDA making the move to Microsoft The U.S. Department of Agriculture has announced that it has chosen Microsoft to host things like e-mail, instant messaging, and collaboration through the software giant’s Business Productivity Online Suite. Google says it was cut off from USDA project bid Google is claiming that it was not given a chance to bid on a cloud-computing project for the U.S. Department of Agriculture, for which the contract was awarded to rival Microsoft. Apache is being forced into a Java Fork When Oracle rolled over Apache and Google’s objections to its Java plans in December, the scene was set for Apache to leave and, eventually, force a Java code fork. Tumblr explains daylong outage After experiencing an outage that started on Sunday afternoon and stretched through most of the day yesterday, Tumblr has explained what happened. Google demos Chrome OS, launches pilot program During a press briefing this week in San Francisco, Google launched the Chrome application store and demonstrated Chrome OS, its browser-centric netbook operating system. Don’t expect Spotify in U.S. this holiday season As of last week, Spotify had yet to sign a single licensing deal with a major label, after spending more than a year negotiating, multiple music sources told CNET. December 2010 Patch Tuesday will come with most bulletins ever According to the Microsoft Security Response Center, Microsoft will issue 17 Security Bulletins addressing 40 vulnerabilities on Tuesday, December 14. It will also host a webcast to address customer questions the following day. Hacker plants back door in Symbian firmware Indian hacker Atul Alex has had a look at the firmware for Symbian S60 smartphones and come up with a back door for it. PC quarantines raise tough complexities The concept of quarantining PCs to prevent widespread infection is “interesting, but difficult to implement, with far too many problems”, said security experts. Symantec: DDoS attacks hard to defend It has surfaced that the distributed denial of service (DDoS) attacks on Visa and MasterCard Web sites on Wednesday were carried out by a toolkit known as low orbit ion cannon (LOIC). Web Sockets and the risks of unfinished standards Enthusiasm for a promising new standard called Web Sockets has quickly cooled in some quarters as a potential security problem led some browser makers to hastily postpone support. Internet Explorer 9 to get tracking protection Microsoft is making changes to Internet Explorer 9’s security features that will better enable users to keep sites from tracking their activity across browsing sessions. NASA sold PCs with sensitive data NASA failed to remove sensitive data from computers that it sold, according to an audit report released this week. Cybercrooks create fake Amazon receipts The bad guys have created yet another online scam, this one involving fake Amazon receipts. World of Warcraft character move fees waived Until December 22, Blizzard will allow free realm transfers from 25 highly populated servers to alleviate log-in queues or performance issues. (The free transfers are one-way and one-time only.) SpaceX Dragon reaches orbit atop a Falcon with a fiery tail The Space Exploration Technologies corporation has become the first nongovernmental entity to put a vehicle into low Earth orbit. Geek Video of the Week If birds have wings, then why are the Angry Birds using slingshots? Photo by Dorkly Bits. Wait… Birds have Wings, Why are the Angry Ones Using Slingshots? Sysadmin Geek Tips How To Setup Email Alerts on Linux Using Gmail or SMTP Linux machines may require administrative intervention in countless ways, but without manually logging into them how would you know about it? Here’s how to setup emails to get notified when your machines want some tender love and attention. Random TinyHacker Links Red Panda Webcam Support Firefox and the Knoxville Zoo’s Red Panda program. Christmas Icons (Icons we like) Superb set of holiday icons by lgp85 at deviantArt. Download the .zip and use as .png or convert to .ico at Convertico.com or with tiny app Imagicon. Super User Questions Enjoy reading the great answers to this week’s popular questions from Super User Useful USB boot disks? DVD/CD burning .zip: is it more reliable, faster, longer lasting to burn a zip of files rather than the files as a folder? What are other ways to backup my files if I do not have an external drive? Anti virus what is the difference between these all? How can I block all Facebook elements/content? How-To Geek Weekly Article Recap Have you had a busy week between work and preparing for the holidays? Get caught up on your HTG reading with our hottest articles of the week. 20 Windows Keyboard Shortcuts You Might Not Know The 50 Best Registry Hacks that Make Windows Better LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology HTG Explains: Which Linux File System Should You Choose? How to Use and Customize Google Chrome Web Apps One Year Ago on How-To Geek This week’s batch of retro geeky goodness is all about customizing Windows 7. ClassicShell Adds Classic Start Menu and Explorer Features to Windows 7 Get an Aero-Styled Classic Start Menu in Windows 7 Customize the Windows 7 Logon Screen Get the Classic Style Network Activity Indicator Back in Windows 7 How To Enable Check Boxes for Items In Windows 7 The Geek Note We would like you to join us in welcoming Jason Fitzpatrick to the writing staff here at How-To Geek. He started with us this past week, so take some time to read through his articles about the Wii, Kindle, & PlayStation 2 Peripherals and leave a friendly comment to say “Hi”! Got a great tip to share? Make sure to send it in to us at [email protected]. Photo by real00. Latest Features How-To Geek ETC The 50 Best Registry Hacks that Make Windows Better The How-To Geek Holiday Gift Guide (Geeky Stuff We Like) LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology The How-To Geek Guide to Learning Photoshop, Part 8: Filters Improve Digital Photography by Calibrating Your Monitor Our Favorite Tech: What We’re Thankful For at How-To Geek Settle into Orbit with the Voyage Theme for Chrome and Iron Awesome Safari Compass Icons Set Escape from the Exploding Planet Wallpaper Move Your Tumblr Blog to WordPress Pytask is an Easy to Use To-Do List Manager for Your Ubuntu System Snowy Christmas House Personas Theme for Firefox

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• Week in Geek: New Security Flaw Confirmed for Internet Explorer Edition

  - by Asian Angel

  This week we learned how to use a PC to stay entertained while traveling for the holidays, create quality photo prints with free software, share links between any browser and any smartphone, create perfect Christmas photos using How-To Geek’s 10 best how-to photo guides, and had fun decorating Firefox with a collection of Holiday 2010 Personas themes. Photo by Repoort. Random Geek Links Photo by Asian Angel. Critical 0-Day Flaw Affects All Internet Explorer Versions, Microsoft Warns Microsoft has confirmed a zero-day vulnerability affecting all supported versions of Internet Explorer, including IE8, IE7 and IE6. Note: Article contains link to Microsoft Security Advisory detailing two work-arounds until a security update is released. Hackers targeting human rights, indie media groups Hackers are increasingly hitting the Web sites of human rights and independent media groups in an attempt to silence them, says a new study released this week by Harvard University’s Berkman Center for Internet & Society. OpenBSD: audits give no indication of back doors So far, the analyses of OpenBSD’s crypto and IPSec code have not provided any indication that the system contains back doors for listening to encrypted VPN connections. But the developers have already found two bugs during their current audits. Sophos: Beware Facebook’s new facial-recognition feature Facebook’s new facial recognition software might result in undesirable photos of users being circulated online, warned a security expert, who urged users to keep abreast with the social network’s privacy settings to prevent the abovementioned scenario from becoming a reality. Microsoft withdraws flawed Outlook update Microsoft has withdrawn update KB2412171 for Outlook 2007, released last Patch Tuesday, after a number of user complaints. Skype: Millions still without service Skype was still working to right itself going into the holiday weekend from a major outage that began this past Wednesday. Mozilla improves sync setup and WebGL in Firefox 4 beta 8 Firefox 4.0 beta 8 brings better support for WebGL and introduces an improved setup process for Firefox Sync that simplifies the steps for configuring the synchronization service across multiple devices. Chrome OS the litmus test for cloud The success or failure of Google’s browser-oriented Chrome OS will be the litmus test to decide if the cloud is capable of addressing user needs for content and services, according to a new Ovum report released Monday. FCC Net neutrality rules reach mobile apps The Federal Communications Commission (FCC) finally released its long-expected regulations on Thursday and the related explanations total a whopping 194 pages. One new item that was not previously disclosed: mobile wireless providers can’t block “applications that compete with the provider’s” own voice or video telephony services. KDE and the Document Foundation join Open Invention Network The KDE e.V. and the Document Foundation (TDF) have both joined the Open Invention Network (OIN) as licensees, expanding the organization’s roster of supporters. Report: SEC looks into Hurd’s ousting from HP The scandal surrounding Mark Hurd’s departure from the world’s largest technology company in August has officially drawn attention from the U.S. Securities and Exchange Commission. Report: Google requests delay of new Google TVs Google TV is apparently encountering a bit of static that has resulted in a programming change. Geek Video of the Week This week we have a double dose of geeky video goodness for you with the original Mac vs PC video and the trailer for the sequel. Photo courtesy of Peacer. Mac vs PC Photo courtesy of Peacer. Mac vs PC 2 Trailer Random TinyHacker Links Awesome Tools To Extract Audio From Video Here’s a list of really useful, and free tools to rip audio from videos. Getting Your iPhone Out of Recovery Mode Is your iPhone stuck in recovery mode? This tutorial will help you get it out of that state. Google Shared Spaces Quickly create a shared space and collaborate with friends online. McAfee Internet Security 2011 – Upgrade not worthy of a version change McAfee has released their 2011 version of security products. And as this review details, the upgrades are minimal when compared to their 2010 products. For more information, check out the review. 200 Countries Plotted Hans Rosling’s famous lectures combine enormous quantities of public data with a sport’s commentator’s style to reveal the story of the world’s past, present and future development. Now he explores stats in a way he has never done before – using augmented reality animation. Super User Questions Enjoy looking through this week’s batch of popular questions and answers from Super User. How to restore windows 7 to a known working state every time it boots? Is there an easy way to mass-transfer all files between two computers? Coffee spilled inside computer, damaged hard drive Computer does not boot after ram upgrade Keyboard not detected when trying to install Ubuntu 10.10 How-To Geek Weekly Article Recap Have you had a super busy week while preparing for the holiday weekend? Then here is your chance to get caught up on your reading with our five hottest articles for the week. Ask How-To Geek: Rescuing an Infected PC, Installing Bloat-free iTunes, and Taming a Crazy Trackpad How to Use the Avira Rescue CD to Clean Your Infected PC Eight Geektacular Christmas Projects for Your Day Off VirtualBox 4.0 Rocks Extensions and a Simplified GUI Ask the Readers: How Many Monitors Do You Use with Your Computer? One Year Ago on How-To Geek Here are more great articles from one year ago for you to read and enjoy during the holiday break. Enjoy Distraction-Free Writing with WriteMonkey Shutter is a State of Art Screenshot Tool for Ubuntu Get Hex & RGB Color Codes the Easy Way Find User Scripts for Your Favorite Websites the Easy Way Access Your Unsorted Bookmarks the Easy Way (Firefox) The Geek Note That “wraps” things up for this week and we hope that everyone enjoys the rest of their holiday break! Found a great tip during the break? Then be sure to send it in to us at [email protected]. Photo by ArSiSa7. Latest Features How-To Geek ETC How to Use the Avira Rescue CD to Clean Your Infected PC The Complete List of iPad Tips, Tricks, and Tutorials Is Your Desktop Printer More Expensive Than Printing Services? 20 OS X Keyboard Shortcuts You Might Not Know HTG Explains: Which Linux File System Should You Choose? HTG Explains: Why Does Photo Paper Improve Print Quality? Simon’s Cat Explores the Christmas Tree! [Video] The Outdoor Lights Scene from National Lampoon’s Christmas Vacation [Video] The Famous Home Alone Pizza Delivery Scene [Classic Video] Chronicles of Narnia: The Voyage of the Dawn Treader Theme for Windows 7 Cardinal and Rabbit Sharing a Tree on a Cold Winter Morning Wallpaper An Alternate Star Wars Christmas Special [Video]

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• ActiveX component can't create Object Error? Check 64 bit Status

  - by Rick Strahl

  If you're running on IIS 7 and a 64 bit operating system you might run into the following error using ASP classic or ASP.NET with COM interop. In classic ASP applications the error will show up as: ActiveX component can't create object   (Error 429) (actually without error handling the error just shows up as 500 error page) In my case the code that's been giving me problems has been a FoxPro COM object I'd been using to serve banner ads to some of my pages. The code basically looks up banners from a database table and displays them at random. The ASP classic code that uses it looks like this: <% Set banner = Server.CreateObject("wwBanner.aspBanner") banner.BannerFile = "wwsitebanners" Response.Write(banner.GetBanner(-1)) %> Originally this code had no specific error checking as above so the ASP pages just failed with 500 error pages from the Web server. To find out what the problem is this code is more useful at least for debugging: <% ON ERROR RESUME NEXT Set banner = Server.CreateObject("wwBanner.aspBanner") Response.Write(err.Number & " - " & err.Description) banner.BannerFile = "wwsitebanners" Response.Write(banner.GetBanner(-1)) %> which results in: 429 - ActiveX component can't create object which at least gives you a slight clue. In ASP.NET invoking the same COM object with code like this: <% dynamic banner = wwUtils.CreateComInstance("wwBanner.aspBanner") as dynamic; banner.cBANNERFILE = "wwsitebanners"; Response.Write(banner.getBanner(-1)); %> results in: Retrieving the COM class factory for component with CLSID {B5DCBB81-D5F5-11D2-B85E-00600889F23B} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)). The class is in fact registered though and the COM server loads fine from a command prompt or other COM client. This error can be caused by a COM server that doesn't load. It looks like a COM registration error. There are a number of traditional reasons why this error can crop up of course. The server isn't registered (run regserver32 to register a DLL server or /regserver on an EXE server) Access permissions aren't set on the COM server (Web account has to be able to read the DLL ie. Network service) The COM server fails to load during initialization ie. failing during startup One thing I always do to check for COM errors fire up the server in a COM client outside of IIS and ensure that it works there first - it's almost always easier to debug a server outside of the Web environment. In my case I tried the server in Visual FoxPro on the server with: loBanners = CREATEOBJECT("wwBanner.aspBanner") loBanners.cBannerFile = "wwsitebanners" ? loBanners.GetBanner(-1) and it worked just fine. If you don't have a full dev environment on the server you can also use VBScript do the same thing and run the .vbs file from the command prompt: Set banner = Server.CreateObject("wwBanner.aspBanner") banner.BannerFile = "wwsitebanners" MsgBox(banner.getBanner(-1)) Since this both works it tells me the server is registered and working properly. This leaves startup failures or permissions as the problem. I double checked permissions for the Application Pool and the permissions of the folder where the DLL lives and both are properly set to allow access by the Application Pool impersonated user. Just to be sure I assigned an Admin user to the Application Pool but still no go. So now what? 64 bit Servers Ahoy A couple of weeks back I had set up a few of my Application pools to 64 bit mode. My server is Server 2008 64 bit and by default Application Pools run 64 bit. Originally when I installed the server I set up most of my Application Pools to 32 bit mainly for backwards compatibility. But as more of my code migrates to 64 bit OS's I figured it'd be a good idea to see how well code runs under 64 bit code. The transition has been mostly painless. Until today when I noticed the problem with the code above when scrolling to my IIS logs and noticing a lot of 500 errors on many of my ASP classic pages. The code in question in most of these pages deals with this single simple COM object. It took a while to figure out that the problem is caused by the Application Pool running in 64 bit mode. The issue is that 32 bit COM objects (ie. my old Visual FoxPro COM component) cannot be loaded in a 64 bit Application Pool. The ASP pages using this COM component broke on the day I switched my main Application Pool into 64 bit mode but I didn't find the problem until I searched my logs for errors by pure chance. To fix this is easy enough once you know what the problem is by switching the Application Pool to Enable 32-bit Applications: Once this is done the COM objects started working correctly again. 64 bit ASP and ASP.NET with DCOM Servers This is kind of off topic, but incidentally it's possible to load 32 bit DCOM (out of process) servers from ASP.NET and ASP classic even if those applications run in 64 bit application pools. In fact, in West Wind Web Connection I use this capability to run a 64 bit ASP.NET handler that talks to a 32 bit FoxPro COM server which allows West Wind Web Connection to run in native 64 bit mode without custom configuration (which is actually quite useful). It's probably not a common usage scenario but it's good to know that you can actually access 32 bit COM objects this way from ASP.NET. For West Wind Web Connection this works out well as the DCOM interface only makes one non-chatty call to the backend server that handles all the rest of the request processing. Application Pool Isolation is your Friend For me the recent incident of failure in the classic ASP pages has just been another reminder to be very careful with moving applications to 64 bit operation. There are many little traps when switching to 64 bit that are very difficult to track and test for. I described one issue I had a couple of months ago where one of the default ASP.NET filters was loading the wrong version (32bit instead of 64bit) which was extremely difficult to track down and was caused by a very sneaky configuration switch error (basically 3 different entries for the same ISAPI filter all with different bitness settings). It took me almost a full day to track this down). Recently I've been taken to isolate individual applications into separate Application Pools rather than my past practice of combining many apps into shared AppPools. This is a good practice assuming you have enough memory to make this work. Application Pool isolate provides more modularity and allows me to selectively move applications to 64 bit. The error above came about precisely because I moved one of my most populous app pools to 64 bit and forgot about the minimal COM object use in some of my old pages. It's easy to forget. To 64bit or Not Is it worth it to move to 64 bit? Currently I'd say -not really. In my - admittedly limited - testing I don't see any significant performance increases. In fact 64 bit apps just seem to consume considerably more memory (30-50% more in my pools on average) and performance is minimally improved (less than 5% at the very best) in the load testing I've performed on a couple of sites in both modes. The only real incentive for 64 bit would be applications that require huge data spaces that exceed the 32 bit 4 gigabyte memory limit. However I have a hard time imagining an application that needs 4 gigs of memory in a single Application Pool :-). Curious to hear other opinions on benefits of 64 bit operation. © Rick Strahl, West Wind Technologies, 2005-2011Posted in COM   ASP.NET  FoxPro  

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• Parallelism in .NET – Part 10, Cancellation in PLINQ and the Parallel class

  - by Reed

  Many routines are parallelized because they are long running processes.  When writing an algorithm that will run for a long period of time, its typically a good practice to allow that routine to be cancelled.  I previously discussed terminating a parallel loop from within, but have not demonstrated how a routine can be cancelled from the caller’s perspective.  Cancellation in PLINQ and the Task Parallel Library is handled through a new, unified cooperative cancellation model introduced with .NET 4.0. Cancellation in .NET 4 is based around a new, lightweight struct called CancellationToken.  A CancellationToken is a small, thread-safe value type which is generated via a CancellationTokenSource.  There are many goals which led to this design.  For our purposes, we will focus on a couple of specific design decisions: Cancellation is cooperative.  A calling method can request a cancellation, but it’s up to the processing routine to terminate – it is not forced. Cancellation is consistent.  A single method call requests a cancellation on every copied CancellationToken in the routine. Let’s begin by looking at how we can cancel a PLINQ query.  Supposed we wanted to provide the option to cancel our query from Part 6: double min = collection .AsParallel() .Min(item => item.PerformComputation()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } We would rewrite this to allow for cancellation by adding a call to ParallelEnumerable.WithCancellation as follows: var cts = new CancellationTokenSource(); // Pass cts here to a routine that could, // in parallel, request a cancellation try { double min = collection .AsParallel() .WithCancellation(cts.Token) .Min(item => item.PerformComputation()); } catch (OperationCanceledException e) { // Query was cancelled before it finished } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, if the user calls cts.Cancel() before the PLINQ query completes, the query will stop processing, and an OperationCanceledException will be raised.  Be aware, however, that cancellation will not be instantaneous.  When cts.Cancel() is called, the query will only stop after the current item.PerformComputation() elements all finish processing.  cts.Cancel() will prevent PLINQ from scheduling a new task for a new element, but will not stop items which are currently being processed.  This goes back to the first goal I mentioned – Cancellation is cooperative.  Here, we’re requesting the cancellation, but it’s up to PLINQ to terminate. If we wanted to allow cancellation to occur within our routine, we would need to change our routine to accept a CancellationToken, and modify it to handle this specific case: public void PerformComputation(CancellationToken token) { for (int i=0; i<this.iterations; ++i) { // Add a check to see if we've been canceled // If a cancel was requested, we'll throw here token.ThrowIfCancellationRequested(); // Do our processing now this.RunIteration(i); } } With this overload of PerformComputation, each internal iteration checks to see if a cancellation request was made, and will throw an OperationCanceledException at that point, instead of waiting until the method returns.  This is good, since it allows us, as developers, to plan for cancellation, and terminate our routine in a clean, safe state. This is handled by changing our PLINQ query to: try { double min = collection .AsParallel() .WithCancellation(cts.Token) .Min(item => item.PerformComputation(cts.Token)); } catch (OperationCanceledException e) { // Query was cancelled before it finished } PLINQ is very good about handling this exception, as well.  There is a very good chance that multiple items will raise this exception, since the entire purpose of PLINQ is to have multiple items be processed concurrently.  PLINQ will take all of the OperationCanceledException instances raised within these methods, and merge them into a single OperationCanceledException in the call stack.  This is done internally because we added the call to ParallelEnumerable.WithCancellation. If, however, a different exception is raised by any of the elements, the OperationCanceledException as well as the other Exception will be merged into a single AggregateException. The Task Parallel Library uses the same cancellation model, as well.  Here, we supply our CancellationToken as part of the configuration.  The ParallelOptions class contains a property for the CancellationToken.  This allows us to cancel a Parallel.For or Parallel.ForEach routine in a very similar manner to our PLINQ query.  As an example, we could rewrite our Parallel.ForEach loop from Part 2 to support cancellation by changing it to: try { var cts = new CancellationTokenSource(); var options = new ParallelOptions() { CancellationToken = cts.Token }; Parallel.ForEach(customers, options, customer => { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // Check for cancellation here options.CancellationToken.ThrowIfCancellationRequested(); // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { theStore.EmailCustomer(customer); customer.LastEmailContact = DateTime.Now; } }); } catch (OperationCanceledException e) { // The loop was cancelled } Notice that here we use the same approach taken in PLINQ.  The Task Parallel Library will automatically handle our cancellation in the same manner as PLINQ, providing a clean, unified model for cancellation of any parallel routine.  The TPL performs the same aggregation of the cancellation exceptions as PLINQ, as well, which is why a single exception handler for OperationCanceledException will cleanly handle this scenario.  This works because we’re using the same CancellationToken provided in the ParallelOptions.  If a different exception was thrown by one thread, or a CancellationToken from a different CancellationTokenSource was used to raise our exception, we would instead receive all of our individual exceptions merged into one AggregateException.

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