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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 Mon, 21 Nov 2016 11:32:05 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15683273#comment-15683273
] 

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

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

    https://github.com/apache/flink/pull/2629#discussion_r88676017
  
    --- Diff: flink-examples/flink-examples-streaming/src/main/java/org/apache/flink/streaming/examples/async/AsyncIOExample.java
---
    @@ -0,0 +1,219 @@
    +/*
    + * 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.examples.async;
    +
    +import org.apache.flink.api.common.functions.FlatMapFunction;
    +import org.apache.flink.api.java.tuple.Tuple2;
    +import org.apache.flink.api.java.utils.ParameterTool;
    +import org.apache.flink.configuration.Configuration;
    +import org.apache.flink.runtime.state.filesystem.FsStateBackend;
    +import org.apache.flink.streaming.api.CheckpointingMode;
    +import org.apache.flink.streaming.api.TimeCharacteristic;
    +import org.apache.flink.streaming.api.checkpoint.ListCheckpointed;
    +import org.apache.flink.streaming.api.datastream.AsyncDataStream;
    +import org.apache.flink.streaming.api.datastream.DataStream;
    +import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
    +import org.apache.flink.streaming.api.functions.async.AsyncFunction;
    +import org.apache.flink.streaming.api.functions.async.RichAsyncFunction;
    +import org.apache.flink.streaming.api.functions.source.SourceFunction;
    +import org.apache.flink.streaming.api.operators.async.AsyncCollector;
    +import org.apache.flink.util.Collector;
    +
    +import java.util.ArrayList;
    +import java.util.Collections;
    +import java.util.List;
    +import java.util.Random;
    +import java.util.concurrent.ExecutorService;
    +import java.util.concurrent.Executors;
    +import java.util.concurrent.TimeUnit;
    +
    +/**
    + * Example to illustrates how to use {@link org.apache.flink.streaming.api.functions.async.AsyncFunction}
    + */
    +public class AsyncIOExample {
    +
    +	/**
    +	 * A checkpointed source.
    +	 */
    +	private static class SimpleSource implements SourceFunction<Integer>, ListCheckpointed<Integer>
{
    +		private static final long serialVersionUID = 1L;
    +
    +		private volatile boolean isRunning = true;
    +		private int counter = 0;
    +		private int start = 0;
    +
    +		@Override
    +		public List<Integer> snapshotState(long checkpointId, long timestamp) throws
Exception {
    +			return Collections.singletonList(start);
    +		}
    +
    +		@Override
    +		public void restoreState(List<Integer> state) throws Exception {
    +			for (Integer i : state)
    +				this.start = i;
    +		}
    +
    +		public SimpleSource(int maxNum) {
    +			this.counter = maxNum;
    +		}
    +
    +		@Override
    +		public void run(SourceContext<Integer> ctx) throws Exception {
    +			while (start < counter && isRunning) {
    --- End diff --
    
    Can we set the `counter` to `-1` to indicate an infinite input stream?


> 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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