How many Runnable's can be added to the queue in a fixed/cached Thread Pool?

Question

Is there practically any limit on how many number of Runnable's that can be added to the queue in a fixed/cached Thread Pool of say 10 worker Threads..??

In my application, I am trying to add 100000 Runnable's.

for (int i=0; i<100000; i++) {
    executor.execute(new Task(i));
}

Will it actually process all the Runnable's added to the Queue..? Or will it throw an Exception?

there is no single answer, it depends on how the executor is configured. — jtahlborn, Aug 25 '14 at 18:09
I suspect that among the limiting factors one will be the amount of RAM. — 9000, Aug 25 '14 at 18:11
It should process them until at least memory exhaustion. 100000 is not that big, but it depends on what those task do. — NoDataFound, Aug 25 '14 at 18:55
Although JVM heap space is the ultimate factor, in the OpenJDK, the number of Runnables in the queue cannot exceed Integer.MAX_INT. For most practical applications, this wouldn't matter, but in some applications this hard limit is a factor as well. — therealrootuser, Aug 25 '14 at 19:21

score 4 · Accepted Answer · edited Aug 25 '14 at 19:08

4

Maximum number of Runnable's that can be added to the Queue in fixed/cached Thread Pool is decided by the memory allocated to the JVM.

Once all of the memory is consumed, JVM will throw

Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native thread

error message.

edited Aug 25 '14 at 19:08

msrd0

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answered Aug 25 '14 at 18:52

crashstorm

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score 1 · Answer 2 · answered Aug 25 '14 at 19:05

Assuming that you are using the java.util.concurrent.Executors.newFixedThreadPool() method, the limit is Integer.MAX_INT, at least in the OpenJDK implementation.

The OpenJDK 8 implementation of this method creates a new LinkedBlockingQueue, which defaults to a max size of Integer.MAX_INT.

Thus, the maximum number of Runnables in the default fixed thread pool is Integer.MAX_INT. Note however, that if your heap is not large enough to store that many Runnables, then you will still be limited by the size of your heap.

How many Runnable's can be added to the queue in a fixed/cached Thread Pool?

2 Answers2