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  • Jasper error: Caused by SQLServerException: Transaction (Process ID 58) was deadlocked on thread | c

    - by Saky
    I got the above error in my jasper report mail. The query that is used in the report is quite complicated (for me). Reading different posts I conclude that to solve this the I have to change the query to SET TRANSACTION ISOLATION LEVEL REPEATABLE READ GO BEGIN TRANSACTION ... my query ... COMMIT TRANSACTION ? I wonder if this is the correct way to solve the error and that if it has any side effects? Has it happened to anyone in the Jasper reports? Does anyone know if there is a better solution exist to the problem? (Although that I have not yet tested the above solution, if anyone can give any insight on this will be helpful.)

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  • Multi-thread conversation in django (like Reddit)

    - by dotty
    Hay, i have an app which essentially a conversation system (much like reddits) Where a post can have multiple replies, and a reply and have multiplies, and a reply to a reply can have multiple replies (etc) I've made the model like this class Discussion(models.Model): message = models.TextField() replies = models.ManyToManyField('self') and the view discussions = Discussions.objects.all() and the template looks like this {% for discussion in discussions %} {{ discussion.message }} {% endfor %} How would i go about making a system where i can output all replies like this discussion reply reply reply reply reply reply Which would go down as far as it needs to to ensure all replies are listed. Thanks

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  • using volatile keyword

    - by sap
    As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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  • Recommendations for an in memory database vs thread safe data structures

    - by yx
    TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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  • C# Thread Queue Synchronize

    - by ikurtz
    Greetings, I am trying to play some audio files without holding up the GUI. Below is a sample of the code: if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(CoordinateProc), fireResult)) { } else { MessageBox.Show("false"); } } if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(FireProc), fireResult)) { } else { MessageBox.Show("false"); } } if (audio) { if (ThreadPool.QueueUserWorkItem(new WaitCallback(HitProc), fireResult)) { } else { MessageBox.Show("false"); } } The situation is the samples are not being played in order. some play before the other and I need to fix this so the samples are played one after another in order. How do I implement this please? Thank you.

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  • Transactional isolation level needed for safely incrementing ids

    - by Knut Arne Vedaa
    I'm writing a small piece of software that is to insert records into a database used by a commercial application. The unique primary keys (ids) in the relevant table(s) are sequential, but does not seem to be set to "auto increment". Thus, I assume, I will have to find the largest id, increment it and use that value for the record I'm inserting. In pseudo-code for brevity: id = select max(id) from some_table id++ insert into some_table values(id, othervalues...) Now, if another thread started the same transaction before the first one finished its insert, you would get two identical ids and a failure when trying to insert the last one. You could check for that failure and retry, but a simpler solution might be setting an isolation level on the transaction. For this, would I need SERIALIZABLE or a lower level? Additionally, is this, generally, a sound way of solving the problem? Are the any other ways of doing it?

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  • Passing data structures to different threads

    - by Robb
    I have an application that will be spawning multiple threads. However, I feel there might be an issue with threads accessing data that they shouldn't be. I'm relatively new to threading so bare with me. Here is the structure of the threaded application (sorry for the crudeness): MainThread / \ / \ / \ Thread A Thread B / \ / \ / \ / \ / \ / \ Thread A_1 Thread A_2 Thread B_1 Thread B_2 Under each lettered thread (which could be many), there will only be two threads and they are fired of sequentially. The issue i'm having is I'm not entirely sure how to pass in a datastructure into these threads. So, the datastructure is created in MainThread, will be modified in the lettered thread (Thread A, etc) specific to that thread and then a member variable from that datastructure is sent to Letter_Numbered threads. Currently, the lettered thread class has a member variable and when the class is constructed, the datastructure from mainthread is passed in by reference, invoking the copy constructor so the lettered thread has it's own copy to play with. The lettered_numbered thread simply takes in a string variable from the data structure within the lettered thread. My question is, is this accceptable? Is there a much better way to ensure each lettered thread gets its own data structure to play with? Sorry for the somewhat poor explanation, please leave comments and i'll try to clarify.

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  • can i know the Thread runnable class attributes in java?

    - by dori naji
    probability this question have been asked before but i cant find anything in my searching mechanism. I am trying to create a multiple threads, in an array list but i want to retrieve them from an arraylist and filter them by the attribute of w1 i used in my code. any ideas ? w1 = new FirstWorker(ProductsList, OrdersList, s); FirstWorkerThread = new Thread(w1); ThreadArrayList.add(FirstWorkerThread); //I know i cant do the code below but i want to do that how ? for(Thread x : ThreadArrayList){ x.ProductsList } this is FirstWorker class import java.lang.String; import java.util.HashMap; /* * To change this template, choose Tools | Templates and open the template in * the editor. */ /** * * @author Dimitris */ public class FirstWorker extends Thread implements Runnable { private OrderList orderlist; private ProductList productlist; private String Worker; boolean Stop; private int speed = 1000; public FirstWorker(ProductList productlist, OrderList orderlist, String Worker) { this.productlist = productlist; this.orderlist = orderlist; this.Worker = Worker; this.Stop = true; } public void run() { if (Stop == true) { try { Thread.sleep(100); } catch (InterruptedException e) { } while (orderlist.returnLengthofOrder() != 0) { if (Thread.interrupted()) { System.out.println("I am in the thread inturrupt"); // We've been interrupted: no more crunching. return; } if (orderlist.getDone() == true) { } else if (orderlist.getDone() == false) { orderlist.setDoneTrue(); orderlist.Purchased(Worker); orderlist.setDoneFalse(); try { Thread.sleep(this.speed); } catch (InterruptedException e) { return; } } } } } public void setWork() { Stop = false; } public void setSpeed(int speed) { this.speed = speed; } }

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  • How to handle large dataset with JPA (or at least with Hibernate)?

    - by Roman
    I need to make my web-app work with really huge datasets. At the moment I get either OutOfMemoryException or output which is being generated 1-2 minutes. Let's put it simple and suppose that we have 2 tables in DB: Worker and WorkLog with about 1000 rows in the first one and 10 000 000 rows in the second one. Latter table has several fields including 'workerId' and 'hoursWorked' fields among others. What we need is: count total hours worked by each user; list of work periods for each user. The most straightforward approach (IMO) for each task in plain SQL is: 1) select Worker.name, sum(hoursWorked) from Worker, WorkLog where Worker.id = WorkLog.workerId group by Worker.name; //results of this query should be transformed to Multimap<Worker, Long> 2) select Worker.name, WorkLog.start, WorkLog.hoursWorked from Worker, WorkLog where Worker.id = WorkLog.workerId; //results of this query should be transformed to Multimap<Worker, Period> //if it was JDBC then it would be vitally //to set resultSet.setFetchSize (someSmallNumber), ~100 So, I have two questions: how to implement each of my approaches with JPA (or at least with Hibernate); how would you handle this problem (with JPA or Hibernate of course)?

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  • Connection Reset by Peer error with Apache and JBoss 7.1.1

    - by vikingz
    We are seeing errors on some of our QA testing scripts that intermittently throw Connection Reset By Peer errors. The Test scripts submit requests via F5 which forwards requests to Apache (2.2.21) with a mod_jk load_balancer with the following setting for each worker in the worker.property worker1 props worker.worker1.type=ajp13 worker.worker1.port=8109 worker.worker1.lbfactor=1 worker.worker1.host=skunkhost1.com worker.worker1.connection_pool_timeout=30 and here is what is in the JBoss domain.xml for the AJP port from JBoss 7.1.1 <unbounded-queue-thread-pool name="SKUNKY.APP.AJP"> <max-threads count="300"/> <keepalive-time time="3" unit="minutes"/> </unbounded-queue-thread-pool> Here is httpd.conf Timeout 300 KeepAlive On KeepAliveTimeout 15 MaxKeepAliveRequests 100 TraceEnable Off My question is that is it posisbe that apache times out and closes the connection while jboss is still ready and working on the request? What might be causing the Connection Reset By Peer error?what am i missing here? Any help is majorly appreciated!! Sincerely KK

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  • Thread signaling basics

    - by Markust
    Hello! I know C# , but I am a total newbie regarding threading and I am having trouble to understand some basic (I think) concepts like signaling. I spent some time looking for some examples, even here, without luck. Maybe some examples or a real simple scenario would be great to understand it. Thanks a lot in advance.

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  • exception in thread "main" java.lang.NoclassDefFoundError: cal/class

    - by Gaurav
    enter import java.io.*; class eval { double add(double a,double b) { return (a+b); } double sub(double a,double b) { return (a-b); } double mul(double a,double b) { return (a*b); } double div(double a,double b) { return (a/b); } } class cal extends eval { public static void main(String args[])throws IOException { eval a1=new eval(); try{ System.out.println("1) Add"); System.out.println("2) Subtract"); System.out.println("3) Multiply"); System.out.println("4) Divide"); System.out.println("5) Enter your choice"); BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); int ch;ch=Integer.parseInt(br.readLine()); System.out.println("Enter two number"); double a;a=Integer.parseInt(br.readLine()); double b;b=Integer.parseInt(br.readLine()); switch(ch) { case 1: a1.add(a,b); break; case 2: a1.sub(a,b); break; case 3: a1.mul(a,b); break; case 4: a1.div(a,b); break; } } catch (IOException e) { System.out.println("Error occured, please restart application."); } } }

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  • Threading vs single thread

    - by user177883
    Is it always guaranteed that a multi-threaded application would run faster than a single threaded application? I have two threads that populates data from a data source but different entities (eg: database, from two different tables), seems like single threaded version of the application is running faster than the version with two threads. Why would the reason be? when i look at the performance monitor, both cpu s are very spikey ? is this due to context switching? what are the best practices to jack the CPU and fully utilize it? I hope this is not ambiguous.

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  • Multiprocessing Bomb

    - by iKarampa
    I was working the following example from Doug Hellmann tutorial on multiprocessing: import multiprocessing def worker(): """worker function""" print 'Worker' return if __name__ == '__main__': jobs = [] for i in range(5): p = multiprocessing.Process(target=worker) jobs.append(p) p.start() When I tried to run it outside the if statement: import multiprocessing def worker(): """worker function""" print 'Worker' jobs = [] for i in range(5): p = multiprocessing.Process(target=worker) jobs.append(p) p.start() It started spawning processes non-stop, without any way of to terminating it. Why would that happen? Why it did not generate 5 processes and exit? Why do I need the if statement?

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  • JTextArea thread safe?

    - by Dhaivat Pandya
    Hello everyone, I have some code that does some initialization (including making a JTextArea object), starts three seperate threads, and then these threads try to update the JTextArea (i.e. append() to it), but its not working at all. Nothing shows up on the JTextArea (however, during the initialzation, I print some test lines onto it, and that works fine). What's going on? How can I fix this? Also, each of those threads sleeps a random amount of time every time it has to update the JTextArea. Sorry I haven't provided any code, its all spread out over several files.

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  • Using thread inter-communication to increase my server app's IO throughput; not sure how

    - by Howard Guo
    My server application creates a new thread for each incoming connection. Incoming requests are serialized in a BlockingQueue. There is one worker thread taking items from the queue, produce a response and send the response through socket. I have noticed a throughput issue: Currently, worker thread is responsible of sending the response message through socket, thus severely wasting processing power and throughput. I am considering: rather than sending the response itself, why not telling network IO threads to send the response? However, when I think about thread inter-communication, I cannot yet figure out how to approach it: Worker thread will produce a response, but how will it inform the response message to IO thread? Is there a standard/best practice? Thank you.

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  • How do I read user input in python thread?

    - by Sid H
    I'm trying to read from a thread in python as follows import threading, time, random var = True class MyThread(threading.Thread): def set_name(self, name): self.name = name def run(self): global var while var == True: print "In mythread " + self.name time.sleep(random.randint(2,5)) class MyReader(threading.Thread): def run(self): global var while var == True: input = raw_input("Quit?") if input == "q": var = False t1 = MyThread() t1.set_name("One") t2 = MyReader() t1.start() t2.start() However, if I enter 'q', I see the following error. In mythread One Quit?q Exception in thread Thread-2: Traceback (most recent call last): File "/usr/lib/python2.6/threading.py", line 522, in __bootstrap_inner self.run() File "test.py", line 20, in run input = raw_input("Quit?") EOFError In mythread One In mythread One How does on get user input from a thread?

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