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  • Question on a tutorial

    - by hansa
    Hello, i´m trying to get following tutorial to run and understand: http://www.ibm.com/developerworks/web/library/wa-cometjava/index.html In the example code which can be downloaded at the bottom of the page is everything in one class with two inner classes. How can i make the the thread of "MessageSender" (Listing 3) visible to "The Weatherman" (Listing 4) so i can use it in the run method without using inner classes? Thank you hansa Reformulation of Question: How to make the send-method of inner class MessageSender make accessible in ClassThatDoSomething. Example-Code: public class Example extends HttpServlet implements CometProcessor { private MessageSender messageSender = null; @Override public void init() throws ServletException { // starts thread MessageSender } public event(CometEvent) { // Object of ClassThatDoSomething gets created started } private class ClassThatDoSomething { public void start() { Runnable runnable = new Runnable() { public void run(){ messageSender.send(message); } Thread thread = new Thread(runnable); thread.start(); } } private class MessageSender implements Runnable { public void send(String message) { //... } public void run() { //...} } }

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  • How can I make a dashboard with all pending tasks using Celery?

    - by e-satis
    I want to have some place where I can watch all the pendings tasks. I'm not talking about the registered functions/classes as tasks, but the actual scheduled jobs for which I could display: name, task_id, eta, worker, etc. Using Celery 2.0.2 and djcelery, I found `inspect' in the documentation. I tried: from celery.task.control import inspect def get_scheduled_tasks(nodes=None): if nodes: i = inspect(nodes) else: i = inspect() scheduled_tasks = [] dump = i.scheduled() if dump: for worker, tasks in dump: for task in tasks: scheduled_task = {} scheduled_task.update(task["request"]) del task["request"] scheduled_task.update(task) scheduled_task["worker"] = worker scheduled_tasks.append(scheduled_task) return scheduled_tasks But it hangs forever on dump = i.scheduled(). Strange, because otherwise everything works. Using Ubuntu 10.04, django 1.0 and virtualenv.

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  • How to know who kills my threads

    - by mcabral
    I got a thread that is just banishing.. i'd like to know who is killing my thread and why. It occurs to me my thread is being killed by the OS, but i'd like to confirm this and if possible to know why it's killing it. As for the thread, i can assert it has at least 40 min of execution before dying, but it suddenly dies around 5 min. public void RunWorker() { Thread worker = new Thread(delegate() { DoSomethingForALongLongTime(); }); worker.IsBackground = true; worker.SetApartmentState(System.Threading.ApartmentState.STA); worker.Start(); }

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  • GetMessage with a timeout

    - by qdii
    I have an application which second thread calls GetMessage() in a loop. At some point the first thread realizes that the user wants to quit the application and notifies the second thread that he should terminate. As the first thread is stuck on GetMessage(), the program never quits. Is there a way to wait for messages with a timeout? I’m open to other ideas too. EDIT: (additional explanations) The second thread runs that snippet of code: while ( !m_quit && GetMessage( &msg, NULL, 0, 0 ) ) { TranslateMessage( &msg ); DispatchMessage( &msg ); } The first thread sets m_quit to true.

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  • C# BackgroundWorker RunWorkerCompleted Event

    - by Jim Fell
    My C# application has several background workers. Sometimes one background worker will fire off another. When the first background worker completes and the RunWorkerCompleted event is fired, on which thread will that event fire, the UI or the first background worker from which RunWorkerAsync was called? I am using Microsoft Visual C# 2008 Express Edition. Any thoughts or suggestions you may have would be appreciated. Thanks.

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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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  • Sorted queue with dropping out elements

    - by ffriend
    I have a list of jobs and queue of workers waiting for these jobs. All the jobs are the same, but workers are different and sorted by their ability to perform the job. That is, first person can do this job best of all, second does it just a little bit worse and so on. Job is always assigned to the person with the highest skills from those who are free at that moment. When person is assigned a job, he drops out of the queue for some time. But when he is done, he gets back to his position. So, for example, at some moment in time worker queue looks like: [x, x, .83, x, .7, .63, .55, .54, .48, ...] where x's stand for missing workers and numbers show skill level of left workers. When there's a new job, it is assigned to 3rd worker as the one with highest skill of available workers. So next moment queue looks like: [x, x, x, x, .7, .63, .55, .54, .48, ...] Let's say, that at this moment worker #2 finishes his job and gets back to the list: [x, .91, x, x, .7, .63, .55, .54, .48, ...] I hope the process is completely clear now. My question is what algorithm and data structure to use to implement quick search and deletion of worker and insertion back to his position. For the moment the best approach I can see is to use Fibonacci heap that have amortized O(log n) for deleting minimal element (assigning job and deleting worker from queue) and O(1) for inserting him back, which is pretty good. But is there even better algorithm / data structure that possibly take into account the fact that elements are already sorted and only drop of the queue from time to time?

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  • Sharing config settings between 2 cocoa apps

    - by bitboxer
    I am new to cocoa development and want to create a little app. For that app I need a background worker that is running all the time and a prefpane-app that gives the user the opportunity to change the settings for that background worker. The gui for the prefpane is ready, the background worker is ready, too. One of the few missing things is how to share the preferences between both apps. How do I notify the worker about changes of the preferences? And how do I store it in a way that both can read/write to it?

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  • More threads and orientation changes questions.

    - by synic
    When it comes to threads and orientation changes, it seems the normal thing to do is something like this: public class Bwent extends Activity { private static Bwent instance; @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); instance = this; } //... That way, if you're making a network request with a thread, and someone changes the orientation of the phone, the thread will know to use the new Activity. However, is it possible that the thread could finish during the time Android is destroying the old Activity and creating a new one? Is there a moment in the process where the thread still might be pointing to the wrong Activity, or a partially destroyed activity? It seems like there shouldn't be, but even using a Handler created in the main thread, I'm having intermittent issues with a thread trying to update an object that no longer exists. It's rare, but it does happen.

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  • How do I know that a process has more than 1 thread?

    - by Richard77
    I'have typed ps -ALF and got the following results. Actually there are more to the tow lines that I typed. UID PID PPID LWP C NLWP SZ RSS PSR STIME TTY TIME CMD root 1 0 1 0 1 5900 1644 1 Nov05 ? 00:00:05 /sbin/init root 2 0 2 0 1 0 0 0 Nov05 ? 00:00:00 [kthreadd] I'm supposed to find which process has more than 1 threads. Which column am I supposed to examine? Thanks for helping

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  • How do I make a lock that allows only ONE thread to read from the resource ?

    - by mare
    I have a file that holds an integer ID value. Currently reading the file is protected with ReaderWriterLockSlim as such: public int GetId() { _fileLock.EnterUpgradeableReadLock(); int id = 0; try { if(!File.Exists(_filePath)) CreateIdentityFile(); FileStream readStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read); StreamReader sr = new StreamReader(readStream); string line = sr.ReadLine(); sr.Close(); readStream.Close(); id = int.Parse(line); return int.Parse(line); } finally { SaveNextId(id); // increment the id _fileLock.ExitUpgradeableReadLock(); } } The problem is that subsequent actions after GetId() might fail. As you can see the GetId() method increments the ID every single time, disregarding what happens after it has issued an ID. The issued ID might be left hanging (as said, exceptions might occur). As the ID is incremented, some IDs might be left unused. So I was thinking of moving the SaveNextId(id) out, remove it (the SaveNextId() actually uses the lock too, except that it's EnterWriteLock). And call it manually from outside after all the required methods have executed. That brings out another problem - multiple threads might enter the GetId() method before the SaveNextId() gets executed and they might all receive the same ID. I don't want any solutions where I have to alter the IDs after the operation, correcting them in any way because that's not nice and might lead to more problems. I need a solution where I can somehow callback into the FileIdentityManager (that's the class that handles these IDs) and let the manager know that it can perform the saving of the next ID and then release the read lock on the file containing the ID. Essentialy I want to replicate the relational databases autoincrement behaviour - if anything goes wrong during row insertion, the ID is not used, it is still available for use but it also never happens that the same ID is issued. Hopefully the question is understandable enough for you to provide some solutions..

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  • Communication between Multiple Threads in a WPF Application

    - by Robert
    I'm creating a WPF application that uses a custom object to populate all the controls. The constructor of that object is initiated by an EventHandler that waits for an API. The problem I'm having is when I try to access any information from that object using a button for example, it returns an error saying "The calling thread cannot access this object because a different thread owns it". I'm assuming this is because the EventHandler creates a new thread which doesn't allow the Main Thread to have access to it. Any ideas on how to get around this? I'm basically having the error "The calling thread cannot access this object because a different thread owns it" when trying to get or set a CollectionViewSource.

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  • LINQ Changeset multi-threading

    - by Xodarap
    I'm using LINQ to SQL and after I submit some changes I want to spawn a thread which looks through all the changes and updates our lucene index as necessary. My code looks vaguely like: (new Thread(() => { UpdateIndex(context.GetChangeSet()); }).Start(); Sometimes though I get an InvalidOperationException, which I think is because context.GetChangeSet() is not thread-safe, and so if the change set is modified in one thread while another thread is enumerating through it, problems arise. Is there a "thread-safe" version of GetChangeSet()? Or some way I can do ChangeSet.clone() or something?

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  • Convert IIS / Tomcat Web Application to a multi-server environment.

    - by bill_the_loser
    I have an existing web application built in .Net, running on IIS that leverages a java servlet that we have running on Tomcat 5.5. We need to scale the application and I'm confused about what relates to our situation and what we need to do to get the servlet running on multiple servers. Right now I have 4 servers that can each individually process results, it almost seems like all I should have to do is add the ajp13 worker processes from three additional machines to the machine hosting the load balancer worker. But I can't imagine it should be that easy. What do I need to do to distribute the Tomcat load to the extra three machines? Thanks. Update: The current configuration is using a workers2.properties configuration file. From all of the documentation online I have not been able to determine the distinction between the workers.properties and the workers2.properties. Most of the examples that I have found are configuring the workers.properties and revolve around adding workers and registering them in the worker.list element. The workers2.properties does not appears to have a worker.list element and the syntax is different enough between the workers.properties and the workers2.properties that I'm doubtful that I can add that element. If I just add my multiple AJP workers to the workers2.properties file do I need to worry about the apparent lack of a worker.list element? [ajp13:localhost:8009] channel=channel.socket:localhost:8009 group=lb [ajp13:host2.mydomain.local:8009] channel=channel.socket:host2.mydomain.local:8009 group=lb [ajp13:host3.mydomain.local:8009] channel=channel.socket:host3.mydomain.local:8009 group=lb A couple of side notes... One I've noticed that sometime Tomcat doesn't seem to reload my changes and I don't know why. Also, I have no idea why this configuration has a workers2.properties and not a workers.properties. I've been assuming that it's based on version but I haven't seen anything to back up that assumption.

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  • How solve consumer/producer task using semaphores

    - by user1074896
    I have SimpleProducerConsumer class that illustrate consumer/producer problem (I am not sure that it's correct). public class SimpleProducerConsumer { private Stack<Object> stack = new Stack<Object>(); private static final int STACK_MAX_SIZE = 10; public static void main(String[] args) { SimpleProducerConsumer pc = new SimpleProducerConsumer(); new Thread(pc.new Producer(), "p1").start(); new Thread(pc.new Producer(), "p2").start(); new Thread(pc.new Consumer(), "c1").start(); new Thread(pc.new Consumer(), "c2").start(); new Thread(pc.new Consumer(), "c3").start(); } public synchronized void push(Object d) { while (stack.size() >= STACK_MAX_SIZE) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } stack.push(new Object()); System.out.println("push " + Thread.currentThread().getName() + " " + stack.size()); notify(); } public synchronized Object pop() { while (stack.size() == 0) try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); } stack.pop(); System.out.println("pop " + Thread.currentThread().getName() + " " + stack.size()); notify(); return null; } class Consumer implements Runnable { @Override public void run() { while (true) { pop(); } } } class Producer implements Runnable { @Override public void run() { while (true) { push(new Object()); } } } } I found simple realization of semaphore(here:http://docs.oracle.com/javase/tutorial/essential/concurrency/guardmeth.html I know that there is concurrency package) How I need to change code to exchange java objects monitors to my custom semaphore. (To illustrate C/P problem using semaphores) Semaphore: class Semaphore { private int counter; public Semaphore() { this(0); } public Semaphore(int i) { if (i < 0) throw new IllegalArgumentException(i + " < 0"); counter = i; } public synchronized void release() { if (counter == 0) { notify(); } counter++; } public synchronized void acquire() throws InterruptedException { while (counter == 0) { wait(); } counter--; } }

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  • What is better and why to use List as thread safe: BlockingCollection or ReaderWriterLockSlim or lock?

    - by theateist
    I have System.Collections.Generic.List _myList and many threads can read from it or add items to it simultaneously. From what I've read I should using 'BlockingCollection' so this will work. I also read about ReaderWriterLockSlim' and 'lock', but I don't figure out how to use them instead ofBlockingCollection`, so my question is can I do the same with: ReaderWriterLockSlim lock instead of using 'BlockingCollection'. If YES, can you please provide simple example and what pros and cons of using BlockingCollection, ReaderWriterLockSlim, lock?

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  • Python sqlite3 and concurrency

    - by RexE
    I have a Python program that uses the "threading" module. Once every second, my program starts a new thread that fetches some data from the web, and stores this data to my hard drive. I would like to use sqlite3 to store these results, but I can't get it to work. The issue seems to be about the following line: conn = sqlite3.connect("mydatabase.db") If I put this line of code inside each thread, I get an OperationalError telling me that the database file is locked. I guess this means that another thread has mydatabase.db open through a sqlite3 connection and has locked it. If I put this line of code in the main program and pass the connection object (conn) to each thread, I get a ProgrammingError, saying that SQLite objects created in a thread can only be used in that same thread. Previously I was storing all my results in CSV files, and did not have any of these file-locking issues. Hopefully this will be possible with sqlite. Any ideas?

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  • How to address thread-safety of service data used for maintaining static local variables in C++?

    - by sharptooth
    Consider the following scenario. We have a C++ function with a static local variable: void function() { static int variable = obtain(); //blahblablah } the function needs to be called from multiple threads concurrently, so we add a critical section to avoid concurrent access to the static local: void functionThreadSafe() { CriticalSectionLockClass lock( criticalSection ); static int variable = obtain(); //blahblablah } but will this be enough? I mean there's some magic that makes the variable being initialized no more than once. So there's some service data maintained by the runtime that indicates whether each static local has already been initialized. Will the critical section in the above code protect that service data as well? Is any extra protection required for this scenario?

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  • Strategy for animation a lot of LED's - thread?, UIView animations? NSOperation? (iPhone)

    - by RickiG
    Hi I have to do some different views containing 72 LED lights. I built an LED Class so I can loop through the LED's and set them to different colors (Green, Red, Orange, Blue None etc.). The LED then loads the appropriate .png. This works fine, I loop over the LED's and set them. Now I know that at some time they will need to not just turn on/off change color, but will have to turn on with a small delay. Like an equalizer. I have a 5-10 views containing the 72 LED's and I would like to achieve the above with the minimum amount of memory/CPU strain. for(LED *l in self.ledArray) { [l display:Green]; } I simply loop as shown above and inside the LED is a switch case that does the correct logic. If this were actual LED's and a microController I would use sleep(100) or similar in the loop, but I would really like to avoid stuff like that for obvious reasons. I was thinking that doing a performOnThread withDelay would really be consuming, so would UIView animation changing the alpha and NSOperation would also be a lot of lifting for a small feature. Is there a both efficient and clever way to go around this? Thanks for any inspiration given:)

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  • In C# is there a thread scheduler for long running threads?

    - by LogicMagic
    Hi, Our scenario is a network scanner. It connects to a set of hosts and scans them in parallel for a while using low priority background threads. I want to be able to schedule lots of work but only have any given say ten or whatever number of hosts scanned in parallel. Even if I create my own threads, the many callbacks and other asynchronous goodness uses the ThreadPool and I end up running out of resources. I should look at MonoTorrent... If I use THE ThreadPool, can I limit my application to some number that will leave enough for the rest of the application to Run smoothly? Is there a threadpool that I can initialize to n long lived threads?

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  • how to make different threads executing different parts in cuda ?

    - by Vickey
    I am working on cuda and I have some problem related to thread synchronization. In my code I need threads to execute different part like one thread - all thread - one thread this is what I want. In the initial part of code only one thread will execute and then some part will be executed by all threads then again single thread. Also the threads are executing in a loop. Can anyone tell me how to do that? It's a kinda urgent. I'll be grateful with any help. Thanks

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  • Data transformation question

    - by tkm
    I have data composed of a list of employers and a list of workers. Each has a many-to-many relationship with the other (so an employer can have many workers, and a worker can have many employers). The way the data is retrieved (and given to me) is as follows: each employer has an array of workers. In other words: employer n has: worker x, worker y etc. So I have a bunch of employer objects each containing an array of workers. I need to transform this data (and basically invert the relationship). I need to have a bunch of worker objects, each containing and array of employers. In other words: worker x has: employer n1, employer n2 etc. The context is hypothetical so please don't comment on why I need this or why I am doing it this way. I would really just like help on the algorithm to perform this transformation (there isn't that much data so I would prefer readability over complex optimizations which reduce complexity). (Oh and I am using Java, but pseudocode would be fine). Thanks!

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