| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.beam.runners.dataflow.worker.windmill; |
| |
| import java.util.concurrent.Phaser; |
| import javax.annotation.concurrent.ThreadSafe; |
| import org.apache.beam.vendor.grpc.v1p13p1.io.grpc.stub.CallStreamObserver; |
| import org.apache.beam.vendor.grpc.v1p13p1.io.grpc.stub.StreamObserver; |
| |
| /** |
| * A {@link StreamObserver} which uses synchronization on the underlying {@link CallStreamObserver} |
| * to provide thread safety. |
| * |
| * <p>Flow control with the underlying {@link CallStreamObserver} is handled with a {@link Phaser} |
| * which waits for advancement of the phase if the {@link CallStreamObserver} is not ready. Creator |
| * is expected to advance the {@link Phaser} whenever the underlying {@link CallStreamObserver} |
| * becomes ready. |
| */ |
| @ThreadSafe |
| public final class DirectStreamObserver<T> implements StreamObserver<T> { |
| private final Phaser phaser; |
| private final CallStreamObserver<T> outboundObserver; |
| |
| public DirectStreamObserver(Phaser phaser, CallStreamObserver<T> outboundObserver) { |
| this.phaser = phaser; |
| this.outboundObserver = outboundObserver; |
| } |
| |
| @Override |
| public void onNext(T value) { |
| int phase = phaser.getPhase(); |
| if (!outboundObserver.isReady()) { |
| try { |
| phaser.awaitAdvanceInterruptibly(phase); |
| } catch (InterruptedException e) { |
| Thread.currentThread().interrupt(); |
| throw new RuntimeException(e); |
| } |
| } |
| synchronized (outboundObserver) { |
| outboundObserver.onNext(value); |
| } |
| } |
| |
| @Override |
| public void onError(Throwable t) { |
| synchronized (outboundObserver) { |
| outboundObserver.onError(t); |
| } |
| } |
| |
| @Override |
| public void onCompleted() { |
| synchronized (outboundObserver) { |
| outboundObserver.onCompleted(); |
| } |
| } |
| } |