Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/2629#discussion_r83382895
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/async/AsyncCollectorBuffer.java
---
@@ -0,0 +1,469 @@
+/*
+ * 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.flink.streaming.api.operators.async;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.streaming.api.datastream.AsyncDataStream;
+import org.apache.flink.streaming.api.operators.Output;
+import org.apache.flink.streaming.api.operators.TimestampedCollector;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.streaming.runtime.streamrecord.StreamElement;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.util.Preconditions;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * AsyncCollectorBuffer will hold all {@link AsyncCollector} in its
internal buffer,
+ * and emit results from {@link AsyncCollector} to the next operators
following it by
+ * calling {@link Output#collect(Object)}
+ */
+@Internal
+public class AsyncCollectorBuffer<IN, OUT> {
+ private static final Logger LOG =
LoggerFactory.getLogger(AsyncCollectorBuffer.class);
+
+ /**
+ * Max number of {@link AsyncCollector} in the buffer.
+ */
+ private int bufferSize;
+
+ private AsyncDataStream.OutputMode mode;
+
+ /**
+ * {@link AsyncCollector} queue.
+ */
+ private SimpleLinkedList<AsyncCollector<IN, OUT>> queue = new
SimpleLinkedList<>();
+ /**
+ * A hash map keeping {@link AsyncCollector} and their corresponding
{@link StreamElement}
+ */
+ private Map<AsyncCollector<IN, OUT>, StreamElement>
collectorToStreamElement = new HashMap<>();
+ /**
+ * A hash map keeping {@link AsyncCollector} and their node references
in the #queue.
+ */
+ private Map<AsyncCollector<IN, OUT>, SimpleLinkedList.Node>
collectorToQueue = new HashMap<>();
+
+ private LinkedList<AsyncCollector> finishedCollectors = new
LinkedList<>();
+
+ /**
+ * {@link TimestampedCollector} and {@link Output} to collect results
and watermarks.
+ */
+ private TimestampedCollector<OUT> timestampedCollector;
+ private Output<StreamRecord<OUT>> output;
+
+ /**
+ * Locks and conditions to synchronize with main thread and emitter
thread.
+ */
+ private Lock lock;
+ private Condition notFull;
+ private Condition taskDone;
+ private Condition isEmpty;
+
+ /**
+ * Error from user codes.
+ */
+ private volatile Exception error;
+
+ private Emitter emitter;
+ private Thread emitThread;
+
+ private boolean isCheckpointing;
+
+ public AsyncCollectorBuffer(int maxSize, AsyncDataStream.OutputMode
mode) {
+ Preconditions.checkArgument(maxSize > 0, "Future buffer size
should be greater than 0.");
+
+ this.bufferSize = maxSize;
+ this.mode = mode;
+
+ this.lock = new ReentrantLock(true);
+ this.notFull = this.lock.newCondition();
+ this.taskDone = this.lock.newCondition();
+ this.isEmpty = this.lock.newCondition();
+
+ this.emitter = new Emitter();
+ this.emitThread = new Thread(emitter);
+ }
+
+ /**
+ * Add an {@link StreamRecord} into the buffer. A new {@link
AsyncCollector} will be created and returned
+ * corresponding to the input StreamRecord.
+ * <p>
+ * If buffer is full, caller will wait until new space is available.
+ *
+ * @param record StreamRecord
+ * @return An AsyncCollector
+ * @throws Exception InterruptedException or exceptions from
AsyncCollector.
+ */
+ public AsyncCollector<IN, OUT> add(StreamRecord<IN> record) throws
Exception {
+ try {
+ lock.lock();
+
+ notifyCheckpointDone();
+
+ while (queue.size() >= bufferSize) {
+ notFull.await();
+ }
+
+ // propagate error to the main thread
+ if (error != null) {
+ throw error;
+ }
+
+ AsyncCollector<IN, OUT> collector = new
AsyncCollector(this);
+
+ collectorToQueue.put(collector, queue.add(collector));
+ collectorToStreamElement.put(collector, record);
+
+ return collector;
+ }
+ finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Add a {@link Watermark} into queue. A new AsyncCollector will be
created and returned.
+ * <p>
+ * If queue is full, caller will be blocked here.
+ *
+ * @param watermark Watermark
+ * @return AsyncCollector
+ * @throws Exception Exceptions from async operation.
+ */
+ public AsyncCollector<IN, OUT> add(Watermark watermark) throws
Exception {
+ try {
+ lock.lock();
+
+ notifyCheckpointDone();
+
+ while (queue.size() >= bufferSize)
+ notFull.await();
+
+ if (error != null) {
+ throw error;
+ }
+
+ AsyncCollector<IN, OUT> collector = new
AsyncCollector(this, true);
+
+ collectorToQueue.put(collector, queue.add(collector));
+ collectorToStreamElement.put(collector, watermark);
+
+ // signal emitter thread that current collector is ready
+ mark(collector);
+
+ return collector;
+ }
+ finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Notify the Emitter Thread that an AsyncCollector has completed.
+ *
+ * @param collector Completed AsyncCollector
+ */
+ void mark(AsyncCollector<IN, OUT> collector) {
+ try {
+ lock.lock();
+
+ if (mode == AsyncDataStream.OutputMode.UNORDERED) {
+ finishedCollectors.add(collector);
+ }
+
+ taskDone.signal();
+ }
+ finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Caller will wait here if buffer is not empty, meaning that not all
async i/o tasks have returned yet.
+ *
+ * @throws Exception InterruptedException or Exceptions from
AsyncCollector.
+ */
+ void waitEmpty() throws Exception {
+ try {
+ lock.lock();
+
+ notifyCheckpointDone();
+
+ while (queue.size() != 0)
+ isEmpty.await();
+
+ if (error != null) {
+ throw error;
+ }
+ }
+ finally {
+ lock.unlock();
+ }
+ }
+
+ public void startEmitterThread() {
+ this.emitThread.start();
+ }
+
+ public void stopEmitterThread() {
+ if (emitter != null) {
--- End diff --
`emitter` and `emitThread` can probably never be `null`.
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