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POJava: Producer = Consumer, how to know when to stop?
 

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    <p>I have several workers, that use ArrayBlockingQueue.</p> <p>Every worker takes one object from queue, process it, and in result can get several objects, that will be put into queue for further processing. So, worker = producer + consumer.</p> <p><strong>Worker:</strong></p> <pre><code>public class Worker implements Runnable { private BlockingQueue&lt;String&gt; processQueue = null; public Worker(BlockingQueue&lt;String&gt; processQueue) { this.processQueue = processQueue; } public void run() { try { do { String item = this.processQueue.take(); ArrayList&lt;String&gt; resultItems = this.processItem(item); for(String resultItem : resultItems) { this.processQueue.put(resultItem); } } while(true); } catch(Exception) { ... } } private ArrayList&lt;String&gt; processItem(String item) throws Exception { ... } } </code></pre> <p><strong>Main:</strong></p> <pre><code>public class Test { public static void main(String[] args) throws Exception { new Test().run(); } private void run() throws Exception { BlockingQueue&lt;String&gt; processQueue = new ArrayBlockingQueue&lt;&gt;(10000); processQueue.put("lalala"); Executor service = Executors.newFixedThreadPool(100); for(int i=0; i&lt;100; ++i) { service.execute(new Worker(processQueue)); } } } </code></pre> <p><strong>Whats is the best way to stop workers, when there is no more work ?</strong></p> <p>First, what I have in mind, is to check periodically how many items in queue and how many items are currently in process. If both are equal to zero, then do something like "shutdownNow()" on ExecutorService. But I am not sure this is the best way.</p>
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    1. USOleg Golovanov
    1. USOleg Golovanov
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    1. COMore interesting question is what will be your protection against cyclic patterns, obviously the queue may reproduce itself under some circumstances.
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      1. USOsw
    2. COCould you please clarify the use case? Do you want the app to terminate itself when the queue is empty or that when a request is made to the app to shutdown, it will do so only after the queue is empty?
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    3. CO@Osw, what do you mean with "cyclic pattern" here?
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      1. USOleg Golovanov
 

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