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POMulti-threading a stage in the pipeline pattern with ExecutorService
 

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  1. POMulti-threading a stage in the pipeline pattern with ExecutorService
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    <p>I have a multi-stage pipeline. Each stage runs in a separate thread with communication happening using bounded BlockingArrayQueues. I'm trying to multi-thread the slowest stage to improve throughput.</p> <p>Question: What is the recommended implementation for this? Is there a library that would make this implementation simpler &amp; easier to read?</p> <p>Input Queue -> Stage 1 (4 threads) -> Bounded Queue -> Stage 2</p> <p><strong>Requirements</strong>:</p> <ul> <li><p>Work units on the input queue are independent. </p></li> <li><p>Work units are strictly ordered -- output should be in the same order as input. </p></li> <li><p>Stage 1 must be throttled -- it must stop if the output exceeds a certain size. </p></li> <li><p>Exceptions in Stage 1 should result in a "poison pill" on the output queue and terminate the ExecutorService. Queued tasks should be discarded best effort.</p></li> </ul> <p>** My proposed implementation:**</p> <p>I'm thinking of using a ThreadPoolExecutor with a limited # of threads.</p> <p>Strict ordering will be enforced with a CountDown latch on each work unit. A thread can only push the result if the previous work unit's latch is 0 and there's space on the queue. This also takes care of throttling since the thread will block until there's room on the output queue.</p> <pre><code>class WorkUnit { CountDownLatch previousLatch; CountDownLatch myLatch; } class MyRunnable extends Runnable { public void run() { //do work... previousLatch.await(); ouputQueue.put( result ); myLatch.countDown(); } } </code></pre> <p>Exception handling is where I'm a little stumped. I'm thinking of overriding ThreadPoolExecutor.afterExecute() which will call shutdownNow() if there's an exception.</p> <pre><code>class MyThreadPoolExecutor extends ThreadPoolExecutor { protected void afterExecute(Runnable r, Throwable t) { if(t != null) { //record exection, log, alert, etc ouput.put(POISON_PILL); shutdownNow(); } } } </code></pre>
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    1. USSteve Brisk
    1. USSteve Brisk
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      1. POMulti-threading a stage in the pipeline pattern with ExecutorService
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    1. COI would use an ExecutorService at each stage. I would design it so the thread pools are running all the time and not shutdown.
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      1. USPeter Lawrey
    2. COwhat is your question?
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      1. USamphibient
    3. CO@foampile My question is what is the best solution to this problem...is there a design pattern, library, etc that would cleanly achieve what I'm looking for
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      1. USSteve Brisk
 

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