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问题描述

不同情况下需要找对应的解决方法，这里介绍的解决方法不能拓展到别的场景。

场景描述： flink job 的开发过程中遇到这样的需求，需要先 map 处理，然后把返回的 DataStream 作为输入，流入别的 map 中。这里我们遇到的场景是从原来的 map 流到 AsyncDataStream 中。
大概的 java 代码为：

        SingleOutputStreamOperator<xxxxx> task = source.rebalance().map(new XXXXMapFunction()).uid("xxxxxx").name("xxxx");DataStream<yyyyy> dataStreamHyKontrast = AsyncDataStream.unorderedWait(task, new YYYYRequestMapFunction(), defaultTimeoutMills, TimeUnit.SECONDS).name("yyyyyy").uid("yyyyyy");.......

问题描述： 开发完成本地运行flink入口 main 方法的时候，错误提示如下：

Caused by: java.lang.RuntimeException: Assigned key must not be null!at org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:103)at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:87)at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:43)at org.apache.flink.streaming.api.operators.CountingOutput.collect(CountingOutput.java:50)at org.apache.flink.streaming.api.operators.CountingOutput.collect(CountingOutput.java:28)at org.apache.flink.streaming.api.operators.StreamMap.processElement(StreamMap.java:38)at org.apache.flink.streaming.runtime.tasks.CopyingChainingOutput.pushToOperator(CopyingChainingOutput.java:71)at org.apache.flink.streaming.runtime.tasks.CopyingChainingOutput.collect(CopyingChainingOutput.java:46)at org.apache.flink.streaming.runtime.tasks.CopyingChainingOutput.collect(CopyingChainingOutput.java:26)at org.apache.flink.streaming.api.operators.TimestampedCollector.collect(TimestampedCollector.java:50)at org.apache.flink.streaming.api.operators.async.queue.StreamRecordQueueEntry.emitResult(StreamRecordQueueEntry.java:64)at org.apache.flink.streaming.api.operators.async.queue.UnorderedStreamElementQueue$Segment.emitCompleted(UnorderedStreamElementQueue.java:272)at org.apache.flink.streaming.api.operators.async.queue.UnorderedStreamElementQueue.emitCompletedElement(UnorderedStreamElementQueue.java:159)at org.apache.flink.streaming.api.operators.async.AsyncWaitOperator.outputCompletedElement(AsyncWaitOperator.java:298)at org.apache.flink.streaming.api.operators.async.AsyncWaitOperator.access$100(AsyncWaitOperator.java:78)at org.apache.flink.streaming.api.operators.async.AsyncWaitOperator$ResultHandler.processResults(AsyncWaitOperator.java:371)at org.apache.flink.streaming.api.operators.async.AsyncWaitOperator$ResultHandler.lambda$processInMailbox$0(AsyncWaitOperator.java:352)at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$1.runThrowing(StreamTaskActionExecutor.java:50)at org.apache.flink.streaming.runtime.tasks.mailbox.Mail.run(Mail.java:90)at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.processMail(MailboxProcessor.java:317)at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMailboxLoop(MailboxProcessor.java:189)at org.apache.flink.streaming.runtime.tasks.StreamTask.runMailboxLoop(StreamTask.java:609)at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:573)at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:755)at org.apache.flink.runtime.taskmanager.Task.run(Task.java:570)at java.lang.Thread.run(Thread.java:750)

解决方法

我们避免数据直接从第一个 map 过程后直接流向第二个 AsynMap，中间添加一个处理过程，尽管这个处理过程我们啥也不干。

        SingleOutputStreamOperator<xxxxx> task = source.rebalance().map(new XXXXMapFunction()).uid("xxxxxx").name("xxxx");// 这里添加一个处理过程，task -> process ，然后process到下一个 mapSingleOutputStreamOperator<KontrastAlgoTaskStated> process = task.process(new DefaultProcessFunction<>());DataStream<yyyyy> dataStreamHyKontrast = AsyncDataStream.unorderedWait(process, new YYYYRequestMapFunction(), defaultTimeoutMills, TimeUnit.SECONDS).name("yyyyyy").uid("yyyyyy");

其中的 DefaultProcessFunction 是我自己编写的，就是什么也不做。

import org.apache.flink.streaming.api.functions.ProcessFunction;
import org.apache.flink.util.Collector;/*** 默认的 collect，用于处理 map 后不做任何处理直接到下一个结点* @author smileyan* @param <IN> 对应的实体类*/
public final class DefaultProcessFunction<IN> extends ProcessFunction<IN, IN> {@Overridepublic void processElement(IN value, ProcessFunction<IN, IN>.Context ctx, Collector<IN> out) throws Exception {out.collect(value);}
}

总结

遇到问题后查了一下，都没有找到我这种情况的博客。后来折腾了一会儿发现如上方法可以解决问题，特此记录，希望可能帮到遇到相同问题的小伙伴 ~ 感谢阅览 ~

Smileyan
2023.07.18 10:12