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  • Threading Issue with WCF Service

    - by helixed
    I'm new to both WCF and threading, so please bear with me. I have a WCF service set up. The service has multiple threads, all of which act upon a single array. This works without a problem so far. However, this service has a method, which, when called, will return the array. My questions: The array is serialized when it is transferred to the client by WCF. Is this a thread safe operation? In other words, can I count on WCF to block all threads from accessing this array while it's being serialized? If I can't count on WCF to do this, then how can I implement it manually? I don't really understand how WCF would facilitate this since the serialization happens after I return from my method call. How can I guarantee a thread will not modify the array after it's been returned by my method but before WCF serializes it?

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  • xpath query in a servlet gives exception

    - by user1401071
    I have a Document object initialized in the init() method of the servlet and use it in the doPost() method to service the requests. selectNodeList() xpath query gives exception when the servlet services many request at same time. The Exception is shown below: Caused by: javax.xml.transform.TransformerException: -1 at org.apache.xpath.XPath.execute(XPath.java:331) at org.apache.xpath.CachedXPathAPI.eval(CachedXPathAPI.java:328) at org.apache.xpath.CachedXPathAPI.selectNodeList(CachedXPathAPI.java:255) at org.apache.xpath.CachedXPathAPI.selectNodeList(CachedXPathAPI.java:235) at com.pro.bb.servlets.Controller.getDataOrPeriodForReport(Controller.java:511) ... 23 more Caused by: java.lang.ArrayIndexOutOfBoundsException: -1 at org.apache.xpath.XPathContext.pushCurrentNode(XPathContext.java:808) at org.apache.xpath.axes.PredicatedNodeTest.acceptNode(PredicatedNodeTest.java:447) at org.apache.xpath.axes.AxesWalker.nextNode(AxesWalker.java:409) at org.apache.xpath.axes.WalkingIterator.nextNode(WalkingIterator.java:176) at org.apache.xpath.axes.NodeSequence.nextNode(NodeSequence.java:320) at org.apache.xpath.axes.NodeSequence.runTo(NodeSequence.java:474) at org.apache.xpath.axes.NodeSequence.setRoot(NodeSequence.java:257) at org.apache.xpath.axes.LocPathIterator.execute(LocPathIterator.java:257) at org.apache.xpath.XPath.execute(XPath.java:308) Help me sort out the issue.

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  • Lucene's nested query evaluation regarding negation

    - by ponzao
    Hi, I am adding Apache Lucene support to Querydsl (which offers type-safe queries for Java) and I am having problems understanding how Lucene evaluates queries especially regarding negation in nested queries. For instance the following two queries in my opinion are semantically the same, but only the first one returns results. +year:1990 -title:"Jurassic Park" +year:1990 +(-title:"Jurassic Park") The simplified object tree in the second example is shown below. query : Query clauses : ArrayList [0] : BooleanClause "MUST" occur : BooleanClause.Occur "year:1990" query : TermQuery [1] : BooleanClause "MUST" occur : BooleanClause.Occur query : BooleanQuery clauses : ArrayList [0] : BooleanClause "MUST_NOT" occur : BooleanClause.Occur "title:"Jurassic Park"" query : TermQuery Lucene's own QueryParser seems to evaluate "AND (NOT" into the same kind of object trees. Is this a bug in Lucene or have I misunderstood Lucene's query evaluation? I am happy to give more information if necessary.

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  • Simple thread-safe non-blocking file logger class in c#

    - by Jason Renlan
    I have a web application, that will log some information to a file. I am looking for a simple thread-safe non-blocking file logger class in c#. I have little experience with threading. I known there are great logging components out there like log4Net, Enterprise Library Logging Block, ELMAH, but I do not want an external dependence for my application. I was thinking about using this queue implementation http://www.codeproject.com/KB/cpp/lockfreeq.aspx

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  • Most popular classroom, bootcamp, or online training for ASP.NET 3.5

    - by Curtis White
    What are the most popular and highest quality training sources for ASP.NET 3.5. I am interested in both "boot camp" class room training and online self-paced training. I am interested in both training that can be applied to certification but also non certification based training in the following areas: ASP.NET 3.5, AJAX, and web security. The training should be geared to real world projects and not memorization. I am most interested to hear from Microsoft MVP's on the matter and those who personally have attended or scheduled such training.

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  • E-Mails sent from online form are coming in one single mail

    - by HasanGursoy
    I'm using an online form at one of my web sites. Every mail sent from this form is coming in one mail even if the senders IP is different. But I want every single mail to be unique even if the content is same. What I need to do to the mails or which header I need to modify? SmtpClient smtpClient = new SmtpClient(); MailMessage message = new MailMessage(); MailAddress fromAddress = new MailAddress("[email protected]", "NoReply"); MailAddress toAddress = new MailAddress("[email protected]", "Info"); MailAddress toSender = new MailAddress(tEMail.Text, tNameSurname.Text); message.From = fromAddress; message.Bcc.Add(toAddress); message.ReplyTo = toSender; message.Subject = tNameSurname.Text + " : contact"; message.IsBodyHtml = true; message.Body = "some html here"; smtpClient.Send(message);

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  • Sell digital goods online

    - by Adam
    What's the best solution for a photographer wanting to sell image files online? I tried zencart, but it's way over the top and their backend looks like a 3 year old designed it. Is there a free solution out there? One that has easily modifiable templates and isn't too tedious to add hundreds of pictures for sale? I'm seriously thinking learning how to do it myself with the whole paypal IPN thing might be the way to go.. Suggestions is greatly appreciated! Adam

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  • Is this (Lock-Free) Queue Implementation Thread-Safe?

    - by Hosam Aly
    I am trying to create a lock-free queue implementation in Java, mainly for personal learning. The queue should be a general one, allowing any number of readers and/or writers concurrently. Would you please review it, and suggest any improvements/issues you find? Thank you. import java.util.concurrent.atomic.AtomicReference; public class LockFreeQueue<T> { private static class Node<E> { E value; volatile Node<E> next; Node(E value) { this.value = value; } } private AtomicReference<Node<T>> head, tail; public LockFreeQueue() { // have both head and tail point to a dummy node Node<T> dummyNode = new Node<T>(null); head = new AtomicReference<Node<T>>(dummyNode); tail = new AtomicReference<Node<T>>(dummyNode); } /** * Puts an object at the end of the queue. */ public void putObject(T value) { Node<T> newNode = new Node<T>(value); Node<T> prevTailNode = tail.getAndSet(newNode); prevTailNode.next = newNode; } /** * Gets an object from the beginning of the queue. The object is removed * from the queue. If there are no objects in the queue, returns null. */ public T getObject() { Node<T> headNode, valueNode; // move head node to the next node using atomic semantics // as long as next node is not null do { headNode = head.get(); valueNode = headNode.next; // try until the whole loop executes pseudo-atomically // (i.e. unaffected by modifications done by other threads) } while (valueNode != null && !head.compareAndSet(headNode, valueNode)); T value = (valueNode != null ? valueNode.value : null); // release the value pointed to by head, keeping the head node dummy if (valueNode != null) valueNode.value = null; return value; }

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  • Is Structuremap singleton thread safe?

    - by Ben
    Hi, Currently I have the following class: public class PluginManager { private static bool s_initialized; private static object s_lock = new object(); public static void Initialize() { if (!s_initialized) { lock (s_lock) { if (!s_initialized) { // initialize s_initialized = true; } } } } } The important thing here is that Initialize() should only be executed once whilst the application is running. I thought that I would refactor this into a singleton class since this would be more thread safe?: public sealed class PluginService { static PluginService() { } private static PluginService _instance = new PluginService(); public static PluginService Instance { get { return _instance; } } private bool s_initialized; public void Initialize() { if (!s_initialized) { // initialize s_initialized = true; } } } Question one, is it still necessary to have the lock here (I have removed it) since we will only ever be working on the same instance? Finally, I want to use DI and structure map to initialize my servcices so I have refactored as below: public interface IPluginService { void Initialize(); } public class NewPluginService : IPluginService { private bool s_initialized; public void Initialize() { if (!s_initialized) { // initialize s_initialized = true; } } } And in my registry: ForRequestedType<IPluginService>() .TheDefaultIsConcreteType<NewPluginService>().AsSingletons(); This works as expected (singleton returning true in the following code): var instance1 = ObjectFactory.GetInstance<IPluginService>(); var instance2 = ObjectFactory.GetInstance<IPluginService>(); bool singleton = (instance1 == instance2); So my next question, is the structure map solution as thread safe as the singleton class (second example). The only downside is that this would still allow NewPluginService to be instantiated directly (if not using structure map). Many thanks, Ben

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  • How to make Stack.Pop threadsafe

    - by user260197
    I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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  • Testing harness for online teaching?

    - by candeira
    I have been asked to teach an online programming course, and I am looking for a test harness especially geared to education. Some students will have significant coding experience, but others will be total newbies. The course is an introduction to software development, mostly taught in C with some C++ and Java thrown in. In any case, I would like to read their source code only after a test suite has made sure that it compiles and executes properly. The students will also benefit from having a tool they can check their code against before submitting it. However, the Learning Management System my employer is using doesn't have such a system. Do you know of any LMS software that includes this feature? Which testing harness would you recommend in case I have to roll my own?

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  • How can I implement a proper counter bean with EJB 3.0?

    - by Aaron Digulla
    I have this entity bean: import javax.persistence.*; @Entity public class CounterTest { private int id; private int counter; @Id public int getId() { return id; } public void setId(int id) { this.id = id; } public int getCounter() { return counter; } public void setCounter(int counter) { this.counter = counter; } } and this stateful bean to increment a counter: import java.rmi.RemoteException; import javax.ejb.*; import javax.persistence.*; @Stateful public class CounterTestBean implements CounterTestRemote { @PersistenceContext(unitName = "JavaEE") EntityManager manager; public void initDB() { CounterTest ct = new CounterTest(); ct.setNr(1); ct.setWert(1); manager.persist(ct); } public boolean testCounterWithLock() { try { CounterTest ct = manager.find(CounterTest.class, 1); manager.lock(ct, LockModeType.WRITE); int wert = ct.getWert(); ct.setWert(wert + 1); manager.flush(); return true; } catch (Throwable t) { return false; } } } When I call testCounterWithLock() from three threads 500 times each, the counter gets incremented between 13 and 1279 times. How do I fix this code so that it is incremented 1500 times?

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  • If I'm updating a DataRow, do I lock the entire DataTable or just the DataRow?

    - by Dan Tao
    Suppose I'm accessing a DataTable from multiple threads. If I want to access a particular row, I suspect I need to lock that operation (I could be mistaken about this, but at least I know this way I'm safe): // this is a strongly-typed table OrdersRow row = null; lock (orderTable.Rows.SyncRoot) { row = orderTable.FindByOrderId(myOrderId); } But then, if I want to update that row, should I lock the table (or rather, the table's Rows.SyncRoot object) again, or can I simply lock the row?

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  • ClickOnce Deployment online questions

    - by David Archer
    Hi all, Bit of a strange question, but how do ClickOnce deployments work from a web site? I seem to be having some problems with this. Basically, the setup file will download when you click the "install" button, but then some files are missing. Do you need to be on a Microsoft server to run ClickOnce deployments? I usually do deployments over a local server with UNC, and as this is the first time I've done one online I'm struggling a bit. Any newbie tutorials you can point me to would be great, and if I do need a special host for it, could you please recommend some? Cheers!

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  • Writing re-entrant lexer with Flex

    - by Viet
    I'm newbie to flex. I'm trying to write a simple re-entrant lexer/scanner with flex. The lexer definition goes below. I get stuck with compilation errors as shown below (yyg issue): reentrant.l: /* Definitions */ digit [0-9] letter [a-zA-Z] alphanum [a-zA-Z0-9] identifier [a-zA-Z_][a-zA-Z0-9_]+ integer [0-9]+ natural [0-9]*[1-9][0-9]* decimal ([0-9]+\.|\.[0-9]+|[0-9]+\.[0-9]+) %{ #include <stdio.h> #define ECHO fwrite(yytext, yyleng, 1, yyout) int totalNums = 0; %} %option reentrant %option prefix="simpleit_" %% ^(.*)\r?\n printf("%d\t%s", yylineno++, yytext); %% /* Routines */ int yywrap(yyscan_t yyscanner) { return 1; } int main(int argc, char* argv[]) { yyscan_t yyscanner; if(argc < 2) { printf("Usage: %s fileName\n", argv[0]); return -1; } yyin = fopen(argv[1], "rb"); yylex(yyscanner); return 0; } Compilation errors: vietlq@mylappie:~/Desktop/parsers/reentrant$ gcc lex.simpleit_.c reentrant.l: In function ‘main’: reentrant.l:44: error: ‘yyg’ undeclared (first use in this function) reentrant.l:44: error: (Each undeclared identifier is reported only once reentrant.l:44: error: for each function it appears in.)

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  • Controllers and threads

    - by user72185
    Hi, I'm seeing this code in a project and I wonder if it is safe to do: (ASP.NET MVC 2.0) class MyController { void ActionResult SomeAction() { System.Threading.Thread newThread = new System.Threading.Thread(AsyncFunc); newThread.Start(); } void AsyncFunc() { string someString = HttpContext.Request.UrlReferrer.Authority + Url.Action("Index", new { controller = "AnotherAction" } ); } } Is the controller reused, possibly changing the content of HttpContext.Request and Url, or is this fine (except for not using the thread pool). Thanks for info!

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  • C# - Which is more efficient and thread safe? static or instant classes?

    - by Soni Ali
    Consider the following two scenarios: //Data Contract public class MyValue { } Scenario 1: Using a static helper class. public class Broker { private string[] _userRoles; public Broker(string[] userRoles) { this._userRoles = userRoles; } public MyValue[] GetValues() { return BrokerHelper.GetValues(this._userRoles); } } static class BrokerHelper { static Dictionary<string, MyValue> _values = new Dictionary<string, MyValue>(); public static MyValue[] GetValues(string[] rolesAllowed) { return FilterForRoles(_values, rolesAllowed); } } Scenario 2: Using an instance class. public class Broker { private BrokerService _service; public Broker(params string[] userRoles) { this._service = new BrokerService(userRoles); } public MyValue[] GetValues() { return _service.GetValues(); } } class BrokerService { private Dictionary<string, MyValue> _values; private string[] _userRoles; public BrokerService(string[] userRoles) { this._userRoles = userRoles; this._values = new Dictionary<string, MyValue>(); } public MyValue[] GetValues() { return FilterForRoles(_values, _userRoles); } } Which of the [Broker] scenarios will scale best if used in a web environment with about 100 different roles and over a thousand users. NOTE: Feel free to sugest any alternative approach.

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  • Google Chrome Extensions - Online Packaging

    - by Amar Ravikumar
    I am coding something like an online PHP editor. So, now I have this option to port the web applications created using the editor as Chrome extensions (popup). It works okay save the fact that the files created need to be downloaded, packaged (using Chrome or cmd) and re-uploaded. I do have this provision but I find it annoying myself to go through this routine everytime I need to make an update to my application. So, I just want to know if there is some way we can package Chrome extensions from the web itself? Edit: I know this can be done using Ruby or even Python. Want to know if the same can be done in PHP. I tried in vain.

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  • Atomic Instructions and Variable Update visibility

    - by dsimcha
    On most common platforms (the most important being x86; I understand that some platforms have extremely difficult memory models that provide almost no guarantees useful for multithreading, but I don't care about rare counter-examples), is the following code safe? Thread 1: someVariable = doStuff(); atomicSet(stuffDoneFlag, 1); Thread 2: while(!atomicRead(stuffDoneFlag)) {} // Wait for stuffDoneFlag to be set. doMoreStuff(someVariable); Assuming standard, reasonable implementations of atomic ops: Is Thread 1's assignment to someVariable guaranteed to complete before atomicSet() is called? Is Thread 2 guaranteed to see the assignment to someVariable before calling doMoreStuff() provided it reads stuffDoneFlag atomically? Edits: The implementation of atomic ops I'm using contains the x86 LOCK instruction in each operation, if that helps. Assume stuffDoneFlag is properly cleared somehow. How isn't important. This is a very simplified example. I created it this way so that you wouldn't have to understand the whole context of the problem to answer it. I know it's not efficient.

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  • Using EnterCriticalSection in Thread to update VCL label

    - by user257188
    I'm new to threads. I'm using a 3rd party library that uses threads which at times call a procedure I've provided. How do I update update a TLabel.Caption from my procedure when its called by the thread? If I've called InitializeCriticalSection elsewhere, is it as simple as EnterCriticalSection(CritSect); GlobalVariable := 'New TLabel.Caption'; LeaveCriticalSection(CritSect); And then in my main thread: EnterCriticalSection(CritSect); Label1.Caption:= 'New TLable.Caption'; LeaveCriticalSection(CritSect); But, how do I get the main thread code to be called? The thread can use SendMessage? Or is there some better/easier way (.OnIdle could check a flag set by the thread?) Thanks.

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  • java share data between thread

    - by ayush
    i have a java process that reads data from a socket server. Thus i have a BufferedReader and a PrintWriter object corresponding to that socket. Now in the same java process i have a multithreaded java server that accepts client connections. I want to achieve a functionality where all these clients that i accept can read data from the BufferedReader object that i mentioned above.(so that they can multiplex the data) How do i make these individual client threads read the data from BuffereReader single object? Sorry for the confusion.

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  • Need an encrypted online source code backup service.

    - by camelCase
    Please note this is not a question about online/hosted SVN services. I am working on a home based, solo developer, project that now has commercial significance and it is time to think about remote source code backup. There is no need for file level check in/out, all I need is once a day or once a week directory level snapshot to remote storage. Automatic encryption would be a bonus to protect my IP. What I have in mind is some sort of GUI interface app that will squirt a source code snapshot off to an Amazon S3 bucket on an automatic schedule. (My development PC runs on MS Windows.)

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  • System.WIndows.Application static members are thread safe?

    - by Lirik
    The Application static members are supposed to be thread safe: The public static (Shared in Visual Basic) members of this type are thread safe. In addition, the FindResource and TryFindResource methods and the Properties and Resources properties are thread safe.1 How much can we trust that statement in a multithreaded environment when calling static member methods of System.Windows.Application? Update: It's all in reference to this question: http://stackoverflow.com/questions/2463822/threading-errors-with-application-loadcomponent-key-already-exists/2463866#2463866 I never thought I'd see a real bug in the library, but this must be the day for me... that question seems to show a genuine bug. Usually it's "user error," but this doesn't seem to be the case.

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