Dmitry Konstantinov created CASSANDRA-20132:
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Summary: Add metric and tracing event for scanned purgeable
tombstones
Key: CASSANDRA-20132
URL: https://issues.apache.org/jira/browse/CASSANDRA-20132
Project: Apache Cassandra
Issue Type: Improvement
Components: Local/Other
Reporter: Dmitry Konstantinov
Assignee: Dmitry Konstantinov
Currently, Cassandra can read data from SSTables with tombstones and later drop
them silently if the tombstones are older than gc_grace_seconds (aka purgeable
tombstones). Such tombstones are not visible via readTombstoneHistogram metric,
not reported in Cassandra logs if tombstone threshold is crossed and not
mentioned in tracing events. As a result if a partition has a lot of purgeable
tombstones we may have a slow read query without any signs why it is it slow.
This suggested improvement adds:
1) a new metric which tracks number of such tombstones:
PurgeableTombstoneScannedHistogram
2) a new tracing event: "Read {} purgeable tombstone cells" if number of such
tombstones > 0
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