[jira] [Commented] (KAFKA-9572) Sum Computation with Exactly-Once Enabled and Injected Failures Misses Some Records

["Apurva Mehta (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-9572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17040632#comment-17040632 ] 

Apurva Mehta commented on KAFKA-9572:
-------------------------------------

[~guozhang] can you help take a look at this?

> Sum Computation with Exactly-Once Enabled and Injected Failures Misses Some Records
> -----------------------------------------------------------------------------------
>
>                 Key: KAFKA-9572
>                 URL: https://issues.apache.org/jira/browse/KAFKA-9572
>             Project: Kafka
>          Issue Type: Bug
>          Components: streams
>    Affects Versions: 2.4.0
>            Reporter: Bruno Cadonna
>            Priority: Critical
>         Attachments: 7-changelog-1.txt, data-1.txt, streams22.log, streams23.log, streams30.log, sum-1.txt
>
>
> System test {{StreamsEosTest.test_failure_and_recovery}} failed due to a wrongly computed aggregation under exactly-once (EOS). The specific error is:
> {code:java}
> Exception in thread "main" java.lang.RuntimeException: Result verification failed for ConsumerRecord(topic = sum, partition = 1, leaderEpoch = 0, offset = 2805, CreateTime = 1580719595164, serialized key size = 4, serialized value size = 8, headers = RecordHeaders(headers = [], isReadOnly = false), key = [B@6c779568, value = [B@f381794) expected <6069,17269> but was <6069,10698>
> 	at org.apache.kafka.streams.tests.EosTestDriver.verifySum(EosTestDriver.java:444)
> 	at org.apache.kafka.streams.tests.EosTestDriver.verify(EosTestDriver.java:196)
> 	at org.apache.kafka.streams.tests.StreamsEosTest.main(StreamsEosTest.java:69)
> {code} 
> That means, the sum computed by the Streams app seems to be wrong for key 6069. I checked the dumps of the log segments of the input topic partition (attached: data-1.txt) and indeed two input records are not considered in the sum. With those two missed records the sum would be correct. More concretely, the input values for key 6069 are:
> # 147
> # 9250
> # 5340 
> # 1231
> # 1301
> The sum of this values is 17269 as stated in the exception above as expected sum. If you subtract values 3 and 4, i.e., 5340 and 1231 from 17269, you get 10698 , which is the actual sum in the exception above. Somehow those two values are missing.
> In the log dump of the output topic partition (attached: sum-1.txt), the sum is correct until the 4th value 1231 , i.e. 15968, then it is overwritten with 10698.
> In the log dump of the changelog topic of the state store that stores the sum (attached: 7-changelog-1.txt), the sum is also overwritten as in the output topic.
> I attached the logs of the three Streams instances involved.



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