Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/2629#discussion_r88676904
--- 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) {
+ synchronized (ctx.getCheckpointLock()) {
+ ctx.collect(start);
+ ++start;
+ }
+ Thread.sleep(10);
+ }
+ }
+
+ @Override
+ public void cancel() {
+ isRunning = false;
+ }
+ }
+
+ private static void printUsage() {
+ System.out.println("To customize example, use: AsyncIOExample
[--fsStatePath <path to fs state>] " +
+ "[--checkpointMode <exactly_once or at_least_once>]
[--maxCount <max number of input from source>] " +
+ "[--sleepFactor <interval to sleep for each stream
element>] [--failRatio <possibility to throw exception>] " +
+ "[--waitMode <ordered or unordered>]
[--waitOperatorParallelism <parallelism for async wait operator>] " +
+ "[--eventType <EventTime or IngestionTime>]");
+ }
+
+ public static void main(String[] args) throws Exception {
+
+ // obtain execution environment
+ StreamExecutionEnvironment env =
StreamExecutionEnvironment.getExecutionEnvironment();
+
+ printUsage();
+
+ // parse parameters
+ final ParameterTool params = ParameterTool.fromArgs(args);
+
+ // check the configuration for the job
+ final String statePath = params.getRequired("fsStatePath");
+ final String cpMode = params.get("checkpointMode",
"exactly_once");
+ final int maxCount = params.getInt("maxCount", 100000);
+ final int sleepFactor = params.getInt("sleepFactor", 100);
+ final float failRatio = params.getFloat("failRatio", 0.001f);
+ final String mode = params.get("waitMode", "ordered");
+ final int taskNum = params.getInt("waitOperatorParallelism",
1);
+ final String timeType = params.get("eventType", "EventTime");
+
+ System.out.println("Job configuration\n"
+ +"\tFS state path="+statePath+"\n"
+ +"\tCheckpoint mode="+cpMode+"\n"
+ +"\tMax count of input from source="+maxCount+"\n"
+ +"\tSleep factor="+sleepFactor+"\n"
+ +"\tFail ratio="+failRatio+"\n"
+ +"\tWaiting mode="+mode+"\n"
+ +"\tParallelism for async wait operator="+taskNum+"\n"
+ +"\tEvent type="+timeType);
+
+ // setup state and checkpoint mode
+ env.setStateBackend(new FsStateBackend(statePath));
+ if (cpMode.equals("exactly_once")) {
+ env.enableCheckpointing(1000,
CheckpointingMode.EXACTLY_ONCE);
+ }
+ else {
+ env.enableCheckpointing(1000,
CheckpointingMode.AT_LEAST_ONCE);
+ env.disableOperatorChaining();
+ }
+
+ // enable watermark or not
+ if (timeType.equals("EventTime")) {
+
env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
+ }
+ else if (timeType.equals("IngestionTime")) {
+
env.setStreamTimeCharacteristic(TimeCharacteristic.IngestionTime);
+ }
+
+ // create input stream of an single integer
+ DataStream<Integer> inputStream = env.addSource(new
SimpleSource(maxCount));
+
+ // create async function, which will *wait* for a while to
simulate the process of async i/o
+ AsyncFunction<Integer, String> function = new
RichAsyncFunction<Integer, String>() {
+ transient ExecutorService executorService;
+ transient Random random;
+
+ @Override
+ public void open(Configuration parameters) throws
Exception {
+ super.open(parameters);
+ executorService =
Executors.newFixedThreadPool(30);
+ random = new Random();
+ }
+
+ @Override
+ public void close() throws Exception {
+ super.close();
+ executorService.shutdown();
+
executorService.awaitTermination(sleepFactor*20, TimeUnit.MILLISECONDS);
+ }
+
+ @Override
+ public void asyncInvoke(final Integer input, final
AsyncCollector<Integer, String> collector) throws Exception {
+ this.executorService.submit(new Runnable() {
+ @Override
+ public void run() {
+ // wait for while to simulate
async operation here
+ int sleep = (int)
(random.nextFloat() * sleepFactor);
+ try {
+ Thread.sleep(sleep);
+ List<String> ret = new
ArrayList<>();
+
ret.add("key-"+(input%10));
--- End diff --
This could also be a singleton list.
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