[CASSANDRA-10971] Compressed commit log has no backpressure and can OOM

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 3.0.5, 3.5
• Component/s: Legacy/Local Write-Read Paths
• Severity: Normal
• Assignee: Ariel Weisberg
• Reporter: Ariel Weisberg

Authors

Ariel Weisberg

Reviewers

Benjamin Lerer

• Created: 06/Jan/16 17:37
• Updated: 16/Apr/19 09:30
• Resolved: 16/Mar/16 17:29

Description

I validated this via a unit test that slowed the ability of the log to drain to the filesystem. The compressed commit log will keep allocating buffers pending compression until it OOMs.

I have a fix that am not very happy with because the whole signal a thread to allocate a segment that depends on a resource that may not be available results in some obtuse usage of CompleatableFuture to rendezvous available buffers with CommitLogSegmentManager thread waiting to finish constructing a new segment. The CLSM thread is in turn signaled by the thread(s) that actually wants to write to the next segment, but aren't able to do it themselves.