Examples with SynchronousQueue java.util.concurrent.SynchronousQueue used on opensource projects

Example 46 with SynchronousQueue

use of java.util.concurrent.SynchronousQueue in project cdap by caskdata.

the class AbstractProgramController method addListener.

@Override
public final Cancellable addListener(Listener listener, final Executor listenerExecutor) {
    Preconditions.checkNotNull(listener, "Listener shouldn't be null.");
    Preconditions.checkNotNull(listenerExecutor, "Executor shouldn't be null.");
    final ListenerCaller caller = new ListenerCaller(listener, listenerExecutor);
    final Cancellable cancellable = new Cancellable() {

        @Override
        public void cancel() {
            // Simply remove the listener from the map through the executor and block on the completion
            Futures.getUnchecked(executor.submit(new Runnable() {

                @Override
                public void run() {
                    listeners.remove(caller);
                }
            }));
        }
    };
    try {
        // Use a synchronous queue to communicate the Cancellable to return
        final SynchronousQueue<Cancellable> result = new SynchronousQueue<>();
        // Use the single thread executor to add the listener and call init
        executor.submit(new Callable<Void>() {

            @Override
            public Void call() throws Exception {
                Cancellable existing = listeners.get(caller);
                if (existing == null) {
                    listeners.put(caller, cancellable);
                    result.put(cancellable);
                    caller.init(getState(), getFailureCause());
                } else {
                    result.put(existing);
                }
                return null;
            }
        });
        return result.take();
    } catch (Exception e) {
        // there shouldn't be interrupted exception as well.
        throw Throwables.propagate(Throwables.getRootCause(e));
    }
}