There are 3 metrics (that goes in every compaction_history entry):
total_tombstone_purge_attempt
total_tombstone_purge_failure_due_to_overlapping_with_memtable
total_tombstone_purge_failure_due_to_overlapping_with_uncompacting_sstable
When a tombstone is not expired (e.g. doesn't satisfy "gc_before" or
grace period), it can be currently accounted as failure due to
overlapping with either memtable or uncompacting sstable.
So those 2 last metrics have noise of *unexpired* tombstones.
What we should do is to only account for expired tombstones in all
those 3 metrics. We lose the info of knowing the amount of tombstones
processed by compaction, now we'll only know about the expired ones.
But those metrics were primarily added for explaining why expired
tombstones cannot be removed.
We could have alternatively added a new field
purge_failure_due_to_being_unexpired or something, but
it requires adding a new field to compaction_history.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-737.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#28669
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