[jira] [Updated] (STORM-2430) Potential Race condition in Kafka Spout

["Kushal Bhatt (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/STORM-2430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kushal Bhatt updated STORM-2430:
--------------------------------
    Component/s:     (was: rm-kafka-client)
                 storm-kafka-client

> 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
>            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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