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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4391) Provide support for asynchronous operations over streams
Date Fri, 04 Nov 2016 09:06:58 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15635736#comment-15635736
] 

ASF GitHub Bot commented on FLINK-4391:
---------------------------------------

Github user bjlovegithub commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2629#discussion_r86507829
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/async/AsyncCollectorBuffer.java
---
    @@ -0,0 +1,494 @@
    +/*
    + * 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.LatencyMarker;
    +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 final int bufferSize;
    +
    +	private final AsyncDataStream.OutputMode mode;
    +
    +	private final AsyncWaitOperator<IN, OUT> operator;
    +
    +	/**
    +	 * {@link AsyncCollector} queue.
    +	 */
    +	private final SimpleLinkedList<AsyncCollector<IN, OUT>> queue = new SimpleLinkedList<>();
    +	/**
    +	 * A hash map keeping {@link AsyncCollector} and their corresponding {@link StreamElement}
    +	 */
    +	private final Map<AsyncCollector<IN, OUT>, StreamElement> collectorToStreamElement
= new HashMap<>();
    +	/**
    +	 * A hash map keeping {@link AsyncCollector} and their node references in the #queue.
    +	 */
    +	private final Map<AsyncCollector<IN, OUT>, SimpleLinkedList.Node> collectorToQueue
= new HashMap<>();
    +
    +	private final 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 final Lock lock;
    +	private final Condition notFull;
    +	private final Condition taskDone;
    +	private final Condition isEmpty;
    +
    +	/**
    +	 * Error from user codes.
    +	 */
    +	private volatile Exception error;
    +
    +	private final Emitter emitter;
    +	private final Thread emitThread;
    +
    +	private boolean isCheckpointing;
    +
    +	public AsyncCollectorBuffer(int maxSize, AsyncDataStream.OutputMode mode, AsyncWaitOperator
operator) {
    +		Preconditions.checkArgument(maxSize > 0, "Future buffer size should be greater than
0.");
    +
    +		this.bufferSize = maxSize;
    +		this.mode = mode;
    +		this.operator = operator;
    +
    +		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 {
    +		return processMark(watermark);
    +	}
    +
    +	/**
    +	 * Add a {@link LatencyMarker} into queue. A new AsyncCollector will be created and
returned.
    +	 * <p>
    +	 * If queue is full, caller will be blocked here.
    +	 *
    +	 * @param latencyMarker LatencyMarker
    +	 * @return AsyncCollector
    +	 * @throws Exception Exceptions from async operation.
    +	 */
    +	public AsyncCollector<IN, OUT> add(LatencyMarker latencyMarker) throws Exception
{
    +		return processMark(latencyMarker);
    +	}
    +
    +	private AsyncCollector<IN, OUT> processMark(StreamElement mark) 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, mark);
    +
    +			// 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) {
    --- End diff --
    
    fixed


> Provide support for asynchronous operations over streams
> --------------------------------------------------------
>
>                 Key: FLINK-4391
>                 URL: https://issues.apache.org/jira/browse/FLINK-4391
>             Project: Flink
>          Issue Type: New Feature
>          Components: DataStream API
>            Reporter: Jamie Grier
>            Assignee: david.wang
>
> Many Flink users need to do asynchronous processing driven by data from a DataStream.
 The classic example would be joining against an external database in order to enrich a stream
with extra information.
> It would be nice to add general support for this type of operation in the Flink API.
 Ideally this could simply take the form of a new operator that manages async operations,
keeps so many of them in flight, and then emits results to downstream operators as the async
operations complete.



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