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https://issues.apache.org/jira/browse/KAFKA-7895?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16808185#comment-16808185
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John Roesler commented on KAFKA-7895:
-------------------------------------
Status update: I found a couple of subtle bugs in the logic for restoring
tombstones from the changelog for the suppression buffer. Running with my
patched version of Streams, I was able to restart the application in my
suppress-demo six times in a row without seeing any duplicates. (Previously,
I'd see it on the first restart). So, I feel pretty good about this fix.
I'm cleaning up my branch and will have a PR for review by tomorrow morning.
I think the reason that none of the existing integration/system tests caught it
is just that they don't run over a long enough time scale. I'm working on
regression tests for these specific bugs, which I'll include as a part of my
PR. I'll create a ticket to add a more realistic system test to exercise
Streams better and expose bugs like this.
> Ktable supress operator emitting more than one record for the same key per
> window
> ---------------------------------------------------------------------------------
>
> Key: KAFKA-7895
> URL: https://issues.apache.org/jira/browse/KAFKA-7895
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 2.1.0, 2.1.1
> Reporter: prasanthi
> Assignee: John Roesler
> Priority: Major
> Fix For: 2.2.0, 2.1.2
>
>
> Hi, We are using kstreams to get the aggregated counts per vendor(key) within
> a specified window.
> Here's how we configured the suppress operator to emit one final record per
> key/window.
> {code:java}
> KTable<Windowed<Integer>, Long> windowedCount = groupedStream
> .windowedBy(TimeWindows.of(Duration.ofMinutes(1)).grace(ofMillis(5L)))
> .count(Materialized.with(Serdes.Integer(),Serdes.Long()))
> .suppress(Suppressed.untilWindowCloses(unbounded()));
> {code}
> But we are getting more than one record for the same key/window as shown
> below.
> {code:java}
> [KTABLE-TOSTREAM-0000000010]: [131@1549067040000/1549067100000], 1039
> [KTABLE-TOSTREAM-0000000010]: [131@1549067040000/1549067100000], 1162
> [KTABLE-TOSTREAM-0000000010]: [9@1549067040000/1549067100000], 6584
> [KTABLE-TOSTREAM-0000000010]: [88@1549067040000/1549067100000], 107
> [KTABLE-TOSTREAM-0000000010]: [108@1549067040000/1549067100000], 315
> [KTABLE-TOSTREAM-0000000010]: [119@1549067040000/1549067100000], 119
> [KTABLE-TOSTREAM-0000000010]: [154@1549067040000/1549067100000], 746
> [KTABLE-TOSTREAM-0000000010]: [154@1549067040000/1549067100000], 809{code}
> Could you please take a look?
> Thanks
>
>
> Added by John:
> Acceptance Criteria:
> * add suppress to system tests, such that it's exercised with crash/shutdown
> recovery, rebalance, etc.
> ** [https://github.com/apache/kafka/pull/6278]
> * make sure that there's some system test coverage with caching disabled.
> ** Follow-on ticket: https://issues.apache.org/jira/browse/KAFKA-7943
> * test with tighter time bounds with windows of say 30 seconds and use
> system time without adding any extra time for verification
> ** Follow-on ticket: https://issues.apache.org/jira/browse/KAFKA-7944
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