+ int queueSize = MAX_NOTIFICATION_QUEUE_SIZE;
+ String queueValue = System.getProperty(NOTIFICATION_QUEUE_SIZE_PROPERTY);
+ if (StringUtils.isNotBlank(queueValue)) {
+ try {
+ queueSize = Integer.parseInt(queueValue);
+ logger.trace("Queue size was set to {}", queueSize);
+ } catch (NumberFormatException e) {
+ logger.warn("Cannot parse {} as set by {}, using default {}", queueValue,
+ NOTIFICATION_QUEUE_SIZE_PROPERTY, queueSize);
+ }
+ }
+
+ // Overriding the queue:
+ // ThreadPoolExecutor would not create new threads if the queue is not full, thus adding
+ // occurs in RejectedExecutionHandler.
+ // This impl saturates threadpool first, then queue. When both are full caller will get blocked.
+ final BlockingQueue<Runnable> delegate = new LinkedBlockingQueue<>(queueSize);
+ final BlockingQueue<Runnable> queue = new ForwardingBlockingQueue<Runnable>() {
+ @Override
+ protected BlockingQueue<Runnable> delegate() {
+ return delegate;
+ }
+
+ @Override
+ public boolean offer(final Runnable r) {
+ // ThreadPoolExecutor will spawn a new thread after core size is reached only
+ // if the queue.offer returns false.
+ return false;
+ }
+ };
+
+ final ThreadFactory factory = new ThreadFactoryBuilder()
+ .setDaemon(true)
+ .setNameFormat("md-sal-binding-notification-%d")
+ .build();
+
+ final ThreadPoolExecutor executor = new ThreadPoolExecutor(CORE_NOTIFICATION_THREADS, MAX_NOTIFICATION_THREADS,
+ NOTIFICATION_THREAD_LIFE, TimeUnit.SECONDS, queue, factory,
+ new RejectedExecutionHandler() {
+ // if the max threads are met, then it will raise a rejectedExecution. We then push to the queue.
+ @Override
+ public void rejectedExecution(final Runnable r, final ThreadPoolExecutor executor) {
+ try {
+ executor.getQueue().put(r);
+ } catch (InterruptedException e) {
+ throw new RejectedExecutionException("Interrupted while waiting on the queue", e);
+ }
+ }
+ });
+
+ NOTIFICATION_EXECUTOR = MoreExecutors.listeningDecorator(executor);