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store-gateway: fix loading of series with chunks in multiple segment files #5875

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dimitarvdimitrov
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The bug

Fixes a bug introduced in #5816 (part of r253 and 2.10.0-rc.0) where series with chunks in multiple segment files wouldn't be fetched properly. The cause of the bug was that after 5816 all chunks were in the same chunks range. Since the ID of the segment file is kept once per chunks range, this lead to having chunks from multiple segment files in the same chunks range. The chunks from the second segment file would b e fetched from the first segment file, leading to invalid offsets and overlapping chunks.

The fix

The fix was trivial - reintroduce the usage of partitionChunks which used to partition chunks into multiple ranges based on their segment files. This was the base before 5816 as well.

The side effects in tests

We didn't catch this bug because we don't test large enough blocks that have multiple segment files and series that have multiple chunks. To introduce a test that checks these I had to introduce a few changes to the test setup and the assertions.

Previously the tests in series_refs_test.go would each assert on the chunks' MinTime, MaxTime and their reference. The correct values were found when first writing the tests. This limited how many chunks we can assert against (it's infeasible to hardcode the refs of 100K chunks); see the test cases commented with "There is still no easy way to assert on the refs of 100K chunks, so we skip them."

Now we run prometheus block query code to get the chunk MinTime, MaxTime, and references instead of hardcoding them in the tests. This allows to run with many more chunks and segment files and still do exact assertions. The tradeoff is that we now don't have that strict assertions on the chunk length estimation. I think this is ok, since the estimation doesn't play a huge role in chunks fetching and bugs in it aren't critical.

The changes in the tests will also make the future removals of fine-grained chunks caching easier.

Which issue(s) this PR fixes or relates to

Fixes #

Checklist

  • Tests updated
  • Documentation added
  • CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
@pracucci pracucci self-requested a review August 31, 2023 13:47
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Very subtle bug! Nice work, LGTM!

@@ -1012,7 +1012,7 @@ func (s *loadingSeriesChunkRefsSetIterator) symbolizedSet(ctx context.Context, p
}
case !s.strategy.isNoChunkRefs():
clampLastChunkLength(symbolizedSet.series, metas)
series.chunksRanges = metasToRanges([][]chunks.Meta{metas}, s.blockID, s.minTime, s.maxTime)
series.chunksRanges = metasToRanges(partitionChunks(metas, 1, 1), s.blockID, s.minTime, s.maxTime)
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[for another PR] We can simplify partitionChunks() to not take targetNumRanges, minChunksPerRange at all.

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I was planning to remove partitionChunks and chunks ranges altogether in a future PR. I wanted to do that this week, but this bug took too much time to find and fix, so it will probably roll into next week. Should I still simplify partitionChunks before that its removal?

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Should I still simplify partitionChunks before that its removal?

No :)

@dimitarvdimitrov dimitarvdimitrov merged commit 85be770 into main Aug 31, 2023
28 checks passed
@dimitarvdimitrov dimitarvdimitrov deleted the dimitar/st-gw/add-test-for-chunks-in-multiple-segemtn-files branch August 31, 2023 14:16
grafanabot pushed a commit that referenced this pull request Aug 31, 2023
…files (#5875)

* Add test for series with chunks in multiple segment files

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Partition chunks from multiple segment files into multiple ranges

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Remove redundant upload

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Remove test tool

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

---------

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
(cherry picked from commit 85be770)
grafanabot pushed a commit that referenced this pull request Aug 31, 2023
…files (#5875)

* Add test for series with chunks in multiple segment files

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Partition chunks from multiple segment files into multiple ranges

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Remove redundant upload

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Remove test tool

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

---------

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
(cherry picked from commit 85be770)
colega added a commit that referenced this pull request Sep 1, 2023
…ltiple segment files (#5891)

* store-gateway: fix loading of series with chunks in multiple segment files (#5875)

* Add test for series with chunks in multiple segment files

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Partition chunks from multiple segment files into multiple ranges

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Remove redundant upload

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Remove test tool

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

---------

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
(cherry picked from commit 85be770)

* Update changelog entry

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Update changelog entry

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>

* Update CHANGELOG.md

Co-authored-by: Oleg Zaytsev <mail@olegzaytsev.com>

---------

Signed-off-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
Co-authored-by: Dimitar Dimitrov <dimitar.dimitrov@grafana.com>
Co-authored-by: Oleg Zaytsev <mail@olegzaytsev.com>
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2 participants