ParallelizeDelivery.java

// Parallelizes delivery to multiple devices across a worker pool.
// Begin by initializing lists for the jobs and results we're expecting.
// Then, divide the device information across these jobs, and submit them.
// Finally, call ".get()" on each of the jobs to wait until they're done.
@SuppressWarnings("unchecked")
public void parallelizeDelivery() throws ExecutionException {
    try {
        HashMap[] jobs = new HashMap[numWorkers];
        Future[] results = new Future[numWorkers];
        for(int i=0; i < numWorkers; i++)
            jobs[i] = new HashMap<String, APID.DeliveryInfo>();

        int i = 0;
        for (Entry entry : deliveryInfo.entrySet()) {
            jobs[i % numWorkers].put(entry.getKey(), entry.getValue());
            i++;
        }

        for (int j=0; j < numWorkers; j++)
            results[j] = workerPool.submit(new Deliverer(appKey, push, jobs[j]));

        for (int j=0; j < numWorkers; j++)
            results[j].get();

    } catch (InterruptedException e) { logger.warn("Interrupted during delivery.", e); }
}