ThreadPoolExecutor Block When Queue Is Full?

Question

I am trying to execute lots of tasks using a ThreadPoolExecutor. Below is a hypothetical example:

def workQueue = new ArrayBlockingQueue(3, f         


        

Answer 1

Ok, old thread but this is what I found when searching for blocking thread executor. My code tries to get a semaphore when the task is submitted to the task queue. This blocks if there are no semaphores left. As soon as a task is done the semaphore is released with the decorator. Scary part is that there is a possibility of losing semaphore but that could be solved with for example a timed job that just clears semaphores on a timed basis.

So here my solution:

class BlockingThreadPoolTaskExecutor(concurrency: Int) : ThreadPoolTaskExecutor() {
    companion object {
        lateinit var semaphore: Semaphore
    }

    init {
        semaphore = Semaphore(concurrency)
        val semaphoreTaskDecorator = SemaphoreTaskDecorator()
        this.setTaskDecorator(semaphoreTaskDecorator)
    }

    override fun  submit(task: Callable): Future {
        log.debug("submit")
        semaphore.acquire()
        return super.submit(task)
    }
}

private class SemaphoreTaskDecorator : TaskDecorator {
    override fun decorate(runnable: Runnable): Runnable {
        log.debug("decorate")
        return Runnable {
            try {
                runnable.run()
            } finally {
                log.debug("decorate done")
                semaphore.release()
            }
        }
    }
}