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https://issues.apache.org/jira/browse/STORM-2430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kushal Bhatt updated STORM-2430:
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Affects Version/s: 1.x
> Potential Race condition in Kafka Spout
> ---------------------------------------
>
> Key: STORM-2430
> URL: https://issues.apache.org/jira/browse/STORM-2430
> Project: Apache Storm
> Issue Type: Bug
> Components: storm-kafka-client
> Affects Versions: 1.0.2, 1.x
> Reporter: Kushal Bhatt
>
> Kafka spout hangs when the number of uncommitted messages exceeds the max
> allowed uncommitted messages and some intermediate tuples have failed in down
> stream bolt.
> Steps of reproduction.
> Create a simple topology with one kafka spout and a slow bolt.
> In kafka spout set the maximum uncommitted messages to a small number like
> 100.
> Bolt should process 10 tuples in second. And program it to fail on some
> random tuples. For eg: say tuple number 10 fails. Also assume there is only
> 1 Kafka partition the spout reads from.
> Spout on first execution of nextTuple() gets 110 records and emits them. At
> this point number of uncommitted message would be 110.
> First 9 tuples are acked by the bolt. 10th tuple is failed by the bolt.
> KafkaSpout puts it on retry queue.
> Tuple number 11 to 110 are acked by bolt . But spout only commits till offset
> 9.[link |
> https://github.com/apache/storm/blob/1.0.x-branch/external/storm-kafka-client/src/main/java/org/apache/storm/kafka/spout/KafkaSpout.java#L510]
> Now, the number of uncommitted messages = 110 - 9 = 101 > 100 (max allowed
> uncommitted messages)
> No new records are polled from kafka.[link |
> https://github.com/apache/storm/blob/1.0.x-branch/external/storm-kafka-client/src/main/java/org/apache/storm/kafka/spout/KafkaSpout.java#L239].
> The spout is stuck as the nothing is polled.
> Solution is to explicitly go through retry queue explicitly and emit tuples
> that are ready on every nextTuple().
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