[jira] [Updated] (KAFKA-21152) LogCompactionTester should read until the end offsets instead of stopping at an empty poll

["Eric Chang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-21152?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eric Chang updated KAFKA-21152:
-------------------------------
    Summary: LogCompactionTester should read until the end offsets instead of stopping at an empty poll  (was: LogCompactionTester stops at the first empty poll and misses data after compaction)

> LogCompactionTester should read until the end offsets instead of stopping at an empty poll
> ------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-21152
>                 URL: https://issues.apache.org/jira/browse/KAFKA-21152
>             Project: Kafka
>          Issue Type: Bug
>          Components: system tests, tools
>            Reporter: Eric Chang
>            Assignee: Eric Chang
>            Priority: Minor
>              Labels: flaky-test
>         Attachments: build948-trimmed.log
>
>
> {{LogCompactionTest.test_log_compaction}} is flaky because {{LogCompactionTester}} stops at the first empty {{poll()}}:
> {code:java}
> if (consumerRecords.isEmpty()) return consumedFilePath;
> {code}
> Since KAFKA-12980 (3.2.0), {{poll()}} can return no records even when more data remains. So the tester sometimes stops early and the validation fails. This is a tester bug, not a 4.4 regression: the consumer behavior exists since 3.2.0, and the tester code is even older.
> Why {{poll()}} returns no records: after compaction, a batch keeps its {{lastOffset}} even when its last records are removed. If one {{poll()}} returns exactly {{max.poll.records}} records and the last one is the last live record of a fetch, the next {{poll()}} only moves the position to {{lastOffset + 1}} and returns right away with no records. The consumer behavior is expected (KAFKA-14865 tracks it). This ticket only fixes the tester.
> Simple repro (offsets 5..9 compacted away; {{fetch.max.bytes=1}} for one batch per fetch, {{max.poll.records=5}}):
> {noformat}
> poll#1 count=5 position=5  endOffset=16   (offsets 0..4)
> poll#2 count=0 position=10 endOffset=16   (skips removed offsets 5..9: empty, but not at the end)
> poll#3 count=5 position=15 endOffset=16   (offsets 10..14)
> {noformat}
> Evidence: in the 4.4.0-rc1 system test run (zstd level 10, ISOLATED_KRAFT), the tester read only 7498 of about 191k rows. It stopped at a batch with {{lastOffset}} 649433 whose last live record is 649426. The same case passed 5 out of 5 times on rerun. The trimmed logs are attached.
> Fix: get the end offsets before consuming, and poll until the position of every partition reaches its end offset, with an overall timeout.



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