Change queue size of a ThreadPoolExecutor

Question

I need to be able to change the size of the task queue of a ThreadPoolExecutor. Of course, the BlockingQueue doesn't support changing the size, and the ThreadPoolExecutor doesn't support changing the queue.

So, the method I've come up with is to use ThreadPoolExecutor.shutdownNow(), which gives me back a list of the Runnables that haven't yet been executed. Then I can create a new executor with the desired queue size and re-submit all of the tasks.

The issue is with the tasks in progress at the time of the shutdownNow() call. As far as I can tell from the javadoc, the executor will call Thread.interrupt() on all threads currently executing a taks. I don't want my tasks to be killed. This question may have been a long-winded way of asking how to write my tasks such that Thread.interrupt() won't have any effect?

Answer 1

Using a mix of "shutdown()" (not shutdownNow()), then polling with getPoolSize()/isTerminated(), you could (a) stop the existing the pool . Then (b) simultaneously (in a separate thread) a new queue with the desired size could be created. You would have a tradeoff here in terms of: can you allow there to temporarily exist more threads than the desired number (while the first pool is shutting down).