CODEWITHSUNDEEP
javamultithreadingthreadpool
Al Star
Al Star

Reputation: 13

Looking for Java's ThreadPool with the ability to fallback to serial execution

I'm looking for a threadpool implementation that will not wait when no threads are immediately available in the pool and instead either resort to a serial execution or somehow else let caller know that some tasks that are scheduled for executions would have to wait until thread pool gets back threads that are currently busy.

The net effect I'm trying to achieve is to have parallel executions when possible and when thread pool is fully saturated execute remaining tasks serially in the current thread - that is, where scheduling attempt has been made - without waiting until threadpool gets back another thread.

While this seems doable, I still feel that doing it right would be a significant amount of work - perhaps mostly testing-wise, making sure that all corner cases are properly addressed, etc).

I'd like to avoid reinventing the wheel if this support is readily available in one form or the other in one of the JDK's threading-related library classes.

If some other widely known libraries like Guava or Apache Commons offer that functionality I'd be curious knowing that too.

Upvotes: 0

Views: 290

Answers (1)

Joni
Joni

Reputation: 111339

You can achieve what you want with the standard ThreadPoolExecutor:

  • To stop tasks from queueing when no threads are available, use SynchronousQueue as the queue implementation.
  • To have the caller run the submitted task when no thread is available in the pool, use ThreadPoolExecutor.CallerRunsPolicy as the task rejection policy.

These two parameters can be set by calling the constructor:

ExecutorService executor = new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, timeUnit,
    new SynchronousQueue<>(), new ThreadPoolExecutor.CallerRunsPolicy())

Upvotes: 2

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