db: fix obsolete file metric underflows #4839
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RaduBerinde
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Jun 6, 2025
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Nice find!
Reviewable status: 0 of 4 files reviewed, 1 unresolved discussion
obsolete_files.go line 38 at r1 (raw file):
opts *Options objProvider objstorage.Provider onTableDeleteFn func(fileSize uint64, isLocal bool)
Nice to see this gone!
db.go line 460 at r1 (raw file):
// reference count to prohibit file cleaning. See // DB.{disable,enable}FileDeletions(). disabled int
[nit] disableCount
Previously a race existed in the calculation of obsolete file metrics resulting
in underflow. The values within versionSet.metrics were reset and recalculated
to reflect the set of files in versionSet.obsolete{Tables,Blobs} whenever new
files were added to obsoleteFiles. Additionally, the cleanup manager invoked a
callback to decrease versionSet.metrics whenever a table was deleted.
The recalculation of versionSet.metrics could reset the metrics to less than
the sum of outstanding pending deletes. When the cleanup manager eventually
deleted the pending tables, these metrics would underflow.
This commit fixes the bug by maintaining separate stats for all files that have
been enqueued for the cleanup manager and all files that have been successfully
deleted. The volume of outstanding, pending deletions is the difference between
the two.
For now, there's an additional wart that the set of files that are sitting in
versionSet.obsolete{Table,Blobs} are still separately tracked.
Fix cockroachdb#4811.
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jbowens
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Jun 6, 2025
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TFTR!
Reviewable status: 0 of 4 files reviewed, all discussions resolved (waiting on @RaduBerinde)
db.go line 460 at r1 (raw file):
Previously, RaduBerinde wrote…
[nit] disableCount
Done
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Previously a race existed in the calculation of obsolete file metrics resulting in underflow. The values within versionSet.metrics were reset and recalculated to reflect the set of files in versionSet.obsolete{Tables,Blobs} whenever new files were added to obsoleteFiles. Additionally, the cleanup manager invoked a callback to decrease versionSet.metrics whenever a table was deleted.
The recalculation of versionSet.metrics could reset the metrics to less than the sum of outstanding pending deletes. When the cleanup manager eventually deleted the pending tables, these metrics would underflow.
This commit fixes the bug by maintaining separate stats for all files that have been enqueued for the cleanup manager and all files that have been successfully deleted. The volume of outstanding, pending deletions is the difference between the two.
For now, there's an additional wart that the set of files that are sitting in versionSet.obsolete{Table,Blobs} are still separately tracked.
Fix #4811.