Here is my use case.

A legacy system updates a database queue table QUEUE.

I want a scheduled recurring job that - checks the contents of QUEUE - if there are rows in the table it locks the row and does some work - deletes the row in QUEUE

If the previous job is still running, then a new thread will be created to do the work. I want to configure the maximum number of concurrent threads.

I am using Spring 3 and my current solution is to do the following (using a fixedRate of 1 millisecond to get the threads to run basically continuously)

@Scheduled(fixedRate = 1)
@Async
public void doSchedule() throws InterruptedException {
    log.debug("Start schedule");
    publishWorker.start();
    log.debug("End schedule");
}

<task:executor id="workerExecutor" pool-size="4" />

This created 4 threads straight off and the threads correctly shared the workload from the queue. However I seem to be getting a memory leak when the threads take a long time to complete.

java.util.concurrent.ThreadPoolExecutor @ 0xe097b8f0                              |              80 |   373,410,496 |     89.74%
|- java.util.concurrent.LinkedBlockingQueue @ 0xe097b940                          |           48 |   373,410,136 |     89.74%
|  |- java.util.concurrent.LinkedBlockingQueue$Node @ 0xe25c9d68

So

1: Should I be using @Async and @Scheduled together?

2: If not then how else can I use spring to achieve my requirements?

3: How can I create the new threads only when the other threads are busy?

Thanks all!

EDIT: I think the queue of jobs was getting infinitely long... Now using

    <task:executor id="workerExecutor"
    pool-size="1-4"
    queue-capacity="10" rejection-policy="DISCARD" />

Will report back with results

spring memory scheduled-tasks
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