| package org.osgi.util.pushstream; |
| |
| import static java.util.concurrent.TimeUnit.MILLISECONDS; |
| import static org.osgi.util.pushstream.AbstractPushStreamImpl.State.CLOSED; |
| import static org.osgi.util.pushstream.PushEventConsumer.ABORT; |
| |
| import java.util.concurrent.BlockingQueue; |
| import java.util.concurrent.Executor; |
| import java.util.concurrent.ScheduledExecutorService; |
| import java.util.concurrent.Semaphore; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| import java.util.function.Function; |
| |
| class BufferedPushStreamImpl<T, U extends BlockingQueue<PushEvent< ? extends T>>> |
| extends UnbufferedPushStreamImpl<T,U> implements PushStream<T> { |
| |
| private final U eventQueue; |
| |
| private final Semaphore semaphore; |
| |
| private final Executor worker; |
| |
| private final QueuePolicy<T, U> queuePolicy; |
| |
| private final PushbackPolicy<T, U> pushbackPolicy; |
| |
| /** |
| * Indicates that a terminal event has been received, that we should stop |
| * collecting new events, and that we must drain the buffer before |
| * continuing |
| */ |
| private final AtomicBoolean softClose = new AtomicBoolean(); |
| |
| private final int parallelism; |
| |
| BufferedPushStreamImpl(PushStreamProvider psp, |
| ScheduledExecutorService scheduler, U eventQueue, |
| int parallelism, Executor worker, QueuePolicy<T,U> queuePolicy, |
| PushbackPolicy<T,U> pushbackPolicy, |
| Function<PushEventConsumer<T>,AutoCloseable> connector) { |
| super(psp, worker, scheduler, connector); |
| this.eventQueue = eventQueue; |
| this.parallelism = parallelism; |
| this.semaphore = new Semaphore(parallelism); |
| this.worker = worker; |
| this.queuePolicy = queuePolicy; |
| this.pushbackPolicy = pushbackPolicy; |
| } |
| |
| @Override |
| protected long handleEvent(PushEvent< ? extends T> event) { |
| |
| // If we have already been soft closed, or hard closed then abort |
| if (!softClose.compareAndSet(false, event.isTerminal()) |
| || closed.get() == CLOSED) { |
| return ABORT; |
| } |
| |
| try { |
| queuePolicy.doOffer(eventQueue, event); |
| long backPressure = pushbackPolicy.pushback(eventQueue); |
| if(backPressure < 0) { |
| close(); |
| return ABORT; |
| } |
| if(semaphore.tryAcquire()) { |
| startWorker(); |
| } |
| return backPressure; |
| } catch (Exception e) { |
| close(PushEvent.error(e)); |
| return ABORT; |
| } |
| } |
| |
| private void startWorker() { |
| worker.execute(() -> { |
| try { |
| PushEvent< ? extends T> event; |
| while ((event = eventQueue.poll()) != null) { |
| if (event.isTerminal()) { |
| // Wait for the other threads to finish |
| semaphore.acquire(parallelism - 1); |
| } |
| |
| long backpressure = super.handleEvent(event); |
| if(backpressure < 0) { |
| close(); |
| return; |
| } else if(backpressure > 0) { |
| scheduler.schedule(this::startWorker, backpressure, |
| MILLISECONDS); |
| return; |
| } |
| } |
| |
| semaphore.release(); |
| } catch (Exception e) { |
| close(PushEvent.error(e)); |
| } |
| if(eventQueue.peek() != null && semaphore.tryAcquire()) { |
| try { |
| startWorker(); |
| } catch (Exception e) { |
| close(PushEvent.error(e)); |
| } |
| } |
| }); |
| |
| } |
| } |