Spring integration concurrency - detecting completion

Question

I have a spring integration workflow that embeds task executors in its channels so as to enable concurrent processing. I manually fire off processing via a gateway and need to block the main thread until all asynchronous processes have completed. Is there a way to accomplish this? I have tried thinking along the lines of barriers, latches, and channel interceptors, but no solution is forthcoming. Any ideas anyone?

Answer 1

To answer my own question, here's what I ended up doing:

• Create a customized ExecutorService that knows when to shutdown - in my case this was simply when releasing the last active thread - i.e. after executing the last piece in the workflow:

public class WorkflowThreadPoolExecutor extends ScheduledThreadPoolExecutor {
    public WorkflowThreadPoolExecutor(int corePoolSize) {
        super(corePoolSize);
    }

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        super.afterExecute(r, t);

        if (getActiveCount() == 1) {
            shutdown();
        }
    }
}

• Await executor termination in main thread as follws:

    try {
        executorService.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);
    } catch (InterruptedException ex) {
        LOG.error("message=Error awaiting termination of executor", ex);
    }

Hope this helps someone else facing a similar issue.