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  • Two threads in initializer on rails not working

    - by Luccas
    Initially I was using one thread to listen a queue from amazon and works perfectly. aws.rb Thread.new do my_queue = AWS::SQS::Queue.new(SQSADDR['my_queue']) my_queue.poll do |msg| ... but now I appended another thread to listen another queue: ... Thread.new do my_another_queue = AWS::SQS::Queue.new(SQSADDR['my_another_queue']) my_another_queue.poll do |msg| ... and now it seems to not work. Only the last one receives response... What is going on?

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  • Problems related to showing MessageBox from non-GUI threads

    - by Hans Løken
    I'm working on a heavily data-bound Win.Forms application where I've found some strange behavior. The app has separate I/O threads receiving updates through asynchronous web-requests which it then sends to the main/GUI thread for processing and updating of application-wide data-stores (which in turn may be data-bound to various GUI-elements, etc.). The server at the other end of the web-requests requires periodic requests or the session times out. I've gone through several attempted solutions of dealing with thread-issues etc. and I've observed the following behavior: If I use Control.Invoke for sending updates from I/O-thread(s) to main-thread and this update causes a MessageBox to be shown the main form's message pump stops until the user clicks the ok-button. This also blocks the I/O-thread from continuing eventually leading to timeouts on the server. If I use Control.BeginInvoke for sending updates from I/O-thread(s) to main-thread the main form's message pump does not stop, but if the processing of an update leads to a messagebox being shown, the processing of the rest of that update is halted until the user clicks ok. Since the I/O-threads keep running and the message pump keeps processing messages several BeginInvoke's for updates may be called before the one with the message box is finished. This leads to out-of-sequence updates which is unacceptable. I/O-threads add updates to a blocking queue (very similar to http://stackoverflow.com/questions/530211/creating-a-blocking-queuet-in-net/530228#530228). GUI-thread uses a Forms.Timer that periodically applies all updates in the blocking queue. This solution solves both the problem of blocking I/O threads and sequentiality of updates i.e. next update will be never be started until previous is finished. However, there is a small performance cost as well as introducing a latency in showing updates that is unacceptable in the long run. I would like update-processing in the main-thread to be event-driven rather than polling. So to my question. How should I do this to: avoid blocking the I/O-threads guarantee that updates are finished in-sequence keep the main message pump running while showing a message box as a result of an update.

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  • Reading same file from multiple threads in C#

    - by Gustavo Rubio
    Hi. I was googling for some advise about this and I found some links. The most obvious was this one but in the end what im wondering is how well my code is implemented. I have basically two classes. One is the Converter and the other is ConverterThread I create an instance of this Converter class that has a property ThreadNumber that tells me how many threads should be run at the same time (this is read from user) since this application will be used on multi-cpu systems (physically, like 8 cpu) so it is suppossed that this will speed up the import The Converter instance reads a file that can range from 100mb to 800mb and each line of this file is a tab-delimitted value record that is imported to another destination like a database. The ConverterThread class simply runs inside the thread (new Thread(ConverterThread.StartThread)) and has event notification so when its work is done it can notify the Converter class and then I can sum up the progress for all these threads and notify the user (in the GUI for example) about how many of these records have been imported and how many bytes have been read. It seems, however that I'm having some trouble because I get random errors about the file not being able to be read or that the sum of the progress (percentage) went above 100% which is not possible and I think that happens because threads are not being well managed and probably the information returned by the event is malformed (since it "travels" from one thread to another) Do you have any advise on better practices of implementation of threads so I can accomplish this? Thanks in advance.

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  • How do I run different threads in Java?

    - by Cris Carter
    Hey. I'm having some problems with threads. I understand how they work, but since they all use the same method, how do I run different threads that do completely different things, but at the same time? To me, it seems that they always use the same standard method which makes them do the same thing. So, let's say I have a big .txt file where I want to go through each line and do something to the line. In this case, I would like to have each thread do 1/10th of the .txt file, but I don't understand how the threads can communicate with each other, and how they could organize so each thread does the right part? Could anyone explain or help me with this? Would be very much appreciated!

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  • 640 enterprise library caching threads - how?

    - by JohnW
    We have an application that is undergoing performance testing. Today, I decided to take a dump of w3wp & load it in windbg to see what is going on underneath the covers. Imagine my surprise when I ran !threads and saw that there are 640 background threads, almost all of which seem to say the following: OS Thread Id: 0x1c38 (651) Child-SP RetAddr Call Site 0000000023a9d290 000007ff002320e2 Microsoft.Practices.EnterpriseLibrary.Caching.ProducerConsumerQueue.WaitUntilInterrupted() 0000000023a9d2d0 000007ff00231f7e Microsoft.Practices.EnterpriseLibrary.Caching.ProducerConsumerQueue.Dequeue() 0000000023a9d330 000007fef727c978 Microsoft.Practices.EnterpriseLibrary.Caching.BackgroundScheduler.QueueReader() 0000000023a9d380 000007fef9001552 System.Threading.ExecutionContext.runTryCode(System.Object) 0000000023a9dc30 000007fef72f95fd System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) 0000000023a9dc80 000007fef9001552 System.Threading.ThreadHelper.ThreadStart() If i had to give a guess, I'm thinkign that one of these threads are getting spawned for each run of our app - we have 2 app servers, 20 concurrent users, and ran the test approximately 30 times...it's in the neighborhood. Is this 'expected behavior', or perhaps have we implemented something improperly? The test ran hours ago, so i would have expected any timeouts to have occurred already.

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  • C# Spawn Multiple Threads for work then wait until all finished

    - by pharoc
    just want some advice on "best practice" regarding multi-threading tasks. as an example, we have a C# application that upon startup reads data from various "type" table in our database and stores the information in a collection which we pass around the application. this prevents us from hitting the database each time this information is required. at the moment the application is reading data from 10 tables synchronously. i would really like to have the application read from each table in a different thread all running in parallel. the application would wait for all the threads to complete before continuing with the startup of the application. i have looked into BackGroundWorker but just want some advice on accomplishing the above. Does the method sound logical in order to speed up the startup time of our application How can we best handle all the threads keeping in mind that each thread's work is independent of one another, we just need to wait for all the threads to complete before continuing. i look forward to some answers

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  • Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

    - by lazyconfabulator
    I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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  • WebSphere hung threads, how can I track then down?

    - by Puzzled
    We have an application running on WebSphere (unfortunately it is 6.1 which is no longer supported, it has not yet been migrated in production to a later version) which becomes entirely unresponsive because of hung threads. As far as I can tell we entirely exhaust one of the thread pools. I have activated hung thread detection and I get a core/thread dump when hung threads are detected. The server can run for several days without problems but has crashed twice this week. When load the core/thread dump in "IBM Thread and Monitor Dump Analyzer for Java", it tells me that there are a certain number of hung threads (this time it was 2, last time 11) and multiple (usually around 40) threads "waiting on condition" and some running threads. I believe one of the thread pool has around that size (50). Now what I see in there are threads waiting for locks, having locks or in wait. Most of them show a stack track which always ends like this: at java/lang/Object.wait(Native Method) at java/lang/Object.wait(Object.java:231) Now, how can I track this down to either a server configuration problem, application issue, WebSphere problem or something else? How is this supposed to help me track down the problem when almost everything in there refers to IBM code? I cannot ask IBM's help as 6.1 is now an unsupported version of WebSphere and while work has been done to make it work under WebSphere 7 we are not yet ready to switch to it in Production yet.

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  • Tomcat threads vs Java threads

    - by black666
    When using java threads, one has to take care of the basic problems that come with concurrency through synchronization etc. AFAIK Tomcat also works with threads to handle its workload. Why is it, that I don't have to think about making my code threadsafe when it is running in Tomcat?

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  • How to signal a buffer full state between posix threads

    - by mikip
    Hi I have two threads, the main thread 'A' is responsible for message handling between a number of processes. When thread A gets a buffer full message, it should inform thread B and pass a pointer to the buffer which thread B will then process. When thread B has finished it should inform thread A that it has finished. How do I go about implementing this using posix threads using C on linux. I have looked at conditional variables, is this the way to go? . I'm not experienced in multi threaded programming and would like some advice on the best avenue to take. Thanks

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  • Java: Using multiple Threads to paint simultaniously on a JPanel

    - by user347217
    I have a JPanel on which I wish to have several threads painting "animations" on. An "animation" consists of a JLabel with an ImageIcon on it, which is being moved from one area of the screen to another area. Now, problem is - I want several such animations to be portrayed on screen by those threads mentioned. Problem is - the JPanel's "paint()" method can only be trigged by one thread at a time - causing the animations to execute serially, instead of in a parallel way. Any idea how to have several such animations on screen at the same time?

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  • Java ThreadPoolExecutor getting stuck while using ArrayBlockingQueue

    - by Ravi Rao
    Hi, I'm working on some application and using ThreadPoolExecutor for handling various tasks. ThreadPoolExecutor is getting stuck after some duration. To simulate this in a simpler environment, I've written a simple code where I'm able to simulate the issue. import java.util.concurrent.ArrayBlockingQueue; import java.util.concurrent.RejectedExecutionHandler; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; public class MyThreadPoolExecutor { private int poolSize = 10; private int maxPoolSize = 50; private long keepAliveTime = 10; private ThreadPoolExecutor threadPool = null; private final ArrayBlockingQueue&lt;Runnable&gt; queue = new ArrayBlockingQueue&lt;Runnable&gt;( 100000); public MyThreadPoolExecutor() { threadPool = new ThreadPoolExecutor(poolSize, maxPoolSize, keepAliveTime, TimeUnit.SECONDS, queue); threadPool.setRejectedExecutionHandler(new RejectedExecutionHandler() { @Override public void rejectedExecution(Runnable runnable, ThreadPoolExecutor threadPoolExecutor) { System.out .println(&quot;Execution rejected. Please try restarting the application.&quot;); } }); } public void runTask(Runnable task) { threadPool.execute(task); } public void shutDown() { threadPool.shutdownNow(); } public ThreadPoolExecutor getThreadPool() { return threadPool; } public void setThreadPool(ThreadPoolExecutor threadPool) { this.threadPool = threadPool; } public static void main(String[] args) { MyThreadPoolExecutor mtpe = new MyThreadPoolExecutor(); for (int i = 0; i &lt; 1000; i++) { final int j = i; mtpe.runTask(new Runnable() { @Override public void run() { System.out.println(j); } }); } } } Try executing this code a few times. It normally print outs the number on console and when all threads end, it exists. But at times, it finished all task and then is not getting terminated. The thread dump is as follows: MyThreadPoolExecutor [Java Application] MyThreadPoolExecutor at localhost:2619 (Suspended) Daemon System Thread [Attach Listener] (Suspended) Daemon System Thread [Signal Dispatcher] (Suspended) Daemon System Thread [Finalizer] (Suspended) Object.wait(long) line: not available [native method] ReferenceQueue&lt;T&gt;.remove(long) line: not available ReferenceQueue&lt;T&gt;.remove() line: not available Finalizer$FinalizerThread.run() line: not available Daemon System Thread [Reference Handler] (Suspended) Object.wait(long) line: not available [native method] Reference$Lock(Object).wait() line: 485 Reference$ReferenceHandler.run() line: not available Thread [pool-1-thread-1] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-2] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-3] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-4] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-6] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-8] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-5] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-10] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-9] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [pool-1-thread-7] (Suspended) Unsafe.park(boolean, long) line: not available [native method] LockSupport.park(Object) line: not available AbstractQueuedSynchronizer$ConditionObject.await() line: not available ArrayBlockingQueue&lt;E&gt;.take() line: not available ThreadPoolExecutor.getTask() line: not available ThreadPoolExecutor$Worker.run() line: not available Thread.run() line: not available Thread [DestroyJavaVM] (Suspended) C:\Program Files\Java\jre1.6.0_07\bin\javaw.exe (Jun 17, 2010 10:42:33 AM) In my actual application,ThreadPoolExecutor threads go in this state and then it stops responding. Regards, Ravi Rao

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  • Linked list example using threads

    - by Carl_1789
    I have read the following code of using CRITICAL_SECTION when working with multiple threads to grow a linked list. what would be the main() part which uses two threads to add to linked list? #include <windows.h> typedef struct _Node { struct _Node *next; int data; } Node; typedef struct _List { Node *head; CRITICAL_SECTION critical_sec; } List; List *CreateList() { List *pList = (List*)malloc(sizeof(pList)); pList->head = NULL; InitializeCriticalSection(&pList->critical_sec); return pList; } void AddHead(List *pList, Node *node) { EnterCriticalSection(&pList->critical_sec); node->next = pList->head; pList->head = node; LeaveCriticalSection(&pList->critical_sec); } void Insert(List *pList, Node *afterNode, Node *newNode) { EnterCriticalSection(&pList->critical_sec); if (afterNode == NULL) { AddHead(pList, newNode); } else { newNode->next = afterNode->next; afterNode->next = newNode; } LeaveCriticalSection(&pList->critical_sec); } Node *Next(List *pList, Node *node) { Node* next; EnterCriticalSection(&pList->critical_sec); next = node->next; LeaveCriticalSection(&pList->critical_sec); return next; }

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  • Need help with threads in a client/server

    - by nunos
    For college, I am developing a local relay chat. I have to program a chat server and client that will only work on sending messages on different terminal windows on the same computer with threads and fifos. The fifos part I am having no trouble, the threads part is the one that is giving me some headaches. The server has one thread for receiving commands from a fifo (used by all clients) and another thread for each client that is connected. For each client that is connected I need to know a certain information. Firstly, I was using global variables, which worked as longs as there was only one client connected, which is much of a chat, to chat alone. So, ideally I would have some data like: -nickname -name -email -etc... per client that is connected. However, I don't know how to do that. I could create a client_data[MAX_NUMBER_OF_THREADS] where client_data was a struct with everything I needed to have access to, but this would require to, in every communication between server and client to ask for the id of the client in the array client_data and that does not seem very pratical I could also instantiate a client_data immediately after creating the thread but it would only be available in that block, and that is not very pratical either. As you can see I am in need of a little guidance here. Any comment, piece of code or link to any relevant information is greatly appreciated. Thanks.

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  • Why is CoRegisterClassObject creating two extra threads?

    - by Stijn Sanders
    I'm trying to fix a problem that only recently happens on a number of machine's on a VPN. They each run a client application I wrote that exposes a COM automation object. For some strange reason I haven't been able to discover yet, one thread in the application takes up all of the available CPU time, slowing other operation on the machine. In observing the application's strange behaviour, I've noticed it's the third thread started, and if I debug on my machine I notice the first call to CoRegisterClassObject created two extra threads. If the second of these two threads is the one that gets into an infinite loop, I'm not at all shure how to fix this. Where could I check next about what's wrong? Could it have started by one of the recent patches rolled out by Microsoft this last 'patch tuesday'? I had a go with ProcessExplorer to extract a stack trace of the thread: ntoskrnl.exe!ExReleaseResourceLite+0x1a3 ntoskrnl.exe!PsGetContextThread+0x329 WLDAP32.dll!Ordinal325+0x1231 WLDAP32.dll!Ordinal325+0x129e WLDAP32.dll!Ordinal325+0x1178 ntdll.dll!LdrInitializeThunk+0x24 ntdll.dll!LdrShutdownThread+0xe9 kernel32.dll!ExitThread+0x3e kernel32.dll!FreeLibraryAndExitThread+0x1e ole32.dll!StringFromGUID2+0x65d kernel32.dll!GetModuleFileNameA+0x1ba

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  • Concurrent Threads in C# using BackgroundWorker

    - by Jim Fell
    My C# application is such that a background worker is being used to wait for the acknowledgement of some transmitted data. Here is some psuedo code demonstrating what I'm trying to do: UI_thread { TransmitData() { // load data for tx // fire off TX background worker } RxSerialData() { // if received data is ack, set ack received flag } } TX_thread { // transmit data // set ack wait timeout // fire off ACK background worker // wait for ACK background worker to complete // evaluate status of ACK background worker as completed, failed, etc. } ACK_thread { // wait for ack received flag to be set } What happens is that the ACK BackgroundWorker times out, and the acknowledgement is never received. I'm fairly certain that it is being transmitted by the remote device because that device has not changed at all, and the C# application is transmitting. I have changed the ack thread from this (when it was working)... for( i = 0; (i < waitTimeoutVar) && (!bAckRxd); i++ ) { System.Threading.Thread.Sleep(1); } ...to this... DateTime dtThen = DateTime.Now(); DateTime dtNow; TimeSpan stTime; do { dtNow = DateTime.Now(); stTime = dtNow - dtThen; } while ( (stTime.TotalMilliseconds < waitTimeoutVar) && (!bAckRxd) ); The latter generates a very acurate wait time, as compared to the former. However, I am wondering if removal of the Sleep function is interferring with the ability to receive serial data. Does C# only allow one thread to run at a time, that is, do I have to put threads to sleep at some time to allow other threads to run? Any thoughts or suggestions you may have would be appreciated. I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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  • Why does my ActivePerl program report 'Sorry. Ran out of threads'?

    - by Zaid
    Tom Christiansen's example code (à la perlthrtut) is a recursive, threaded implementation of finding and printing all prime numbers between 3 and 1000. Below is a mildly adapted version of the script #!/usr/bin/perl # adapted from prime-pthread, courtesy of Tom Christiansen use strict; use warnings; use threads; use Thread::Queue; sub check_prime { my ($upstream,$cur_prime) = @_; my $child; my $downstream = Thread::Queue->new; while (my $num = $upstream->dequeue) { next unless ($num % $cur_prime); if ($child) { $downstream->enqueue($num); } else { $child = threads->create(\&check_prime, $downstream, $num); if ($child) { print "This is thread ",$child->tid,". Found prime: $num\n"; } else { warn "Sorry. Ran out of threads.\n"; last; } } } if ($child) { $downstream->enqueue(undef); $child->join; } } my $stream = Thread::Queue->new(3..shift,undef); check_prime($stream,2); When run on my machine (under ActiveState & Win32), the code was capable of spawning only 118 threads (last prime number found: 653) before terminating with a 'Sorry. Ran out of threads' warning. In trying to figure out why I was limited to the number of threads I could create, I replaced the use threads; line with use threads (stack_size => 1);. The resultant code happily dealt with churning out 2000+ threads. Can anyone explain this behavior?

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  • [newbie]Webservice - Threads - close if no active threads, if any activen, then wait till its compl

    - by Raj
    Hi I have an ASP.Net webservice running. When the system date changes, i want to close all the threads and restart them again, if the thread/s aren't doing any work. If any of the thread/s is in the process of doing some work(active threads), then i need to wait till the current thread/s complete its process and then close. This will prevent from aborting any current process. Any ideas on how i can perform such a task? Thanks PS:I am new to ASP.NET and Multithreading.

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