Eric Chang created KAFKA-21152:
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Summary: LogCompactionTester stops at the first empty poll and
misses data after compaction
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
Attachments: build948-trimmed.log
{{LogCompactionTest.test_log_compaction}} is flaky.
{{LogCompactionTester.consumeMessages()}} stops when {{poll()}} returns no
records:
{code:java}
if (consumerRecords.isEmpty()) return consumedFilePath;
{code}
Since KAFKA-12980 (3.2.0), an empty {{poll()}} does not mean the end of the
log. 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 no records
right away. The tester then stops early and the validation fails.
In the 4.4.0-rc1 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. This is
not a 4.4 regression and should not block the release: the consumer behavior
exists since 3.2.0, and the tester code is even older. The trimmed logs are
attached.
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}
The consumer behavior is expected (KAFKA-14865 tracks it). This ticket only
fixes the tester.
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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