Robert Stupp created CASSANDRA-10998:
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Summary: Snapshots can fail during compactions
Key: CASSANDRA-10998
URL: https://issues.apache.org/jira/browse/CASSANDRA-10998
Project: Cassandra
Issue Type: Improvement
Reporter: Robert Stupp
Priority: Minor
In an unlucky, unlikely and rare situation, a snapshot can fail when sstables
are removed (due to compaction) while the snapshots being taken.
So - for example:
# Compaction starts (compact sstable 1, 2, 3 to 4)
# Snapshot operation starts with sstables 1, 2, 3
# Compaction removes sstables 1, 2, 3
# Snapshot tries to hard link to sstables 1, 2, 3 - failure
I think it's a very rare but still possible race condition manifesting in
{{SSTableReader#createLinks}}, which has been mitigated by CASSANDRA-7066 for
3.0 (introduced a {{File.exists}} before the actual creation of the hard link).
The problem without CASSANDRA-7066 is, that the snapshot just fails. The
problem with the if-clause is that the snapshot is inconsistent as it may not
contain all sstable components or even not all sstables without a failure.
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