Benedict created CASSANDRA-9593:
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Summary: Compaction may stall due to race condition
Key: CASSANDRA-9593
URL: https://issues.apache.org/jira/browse/CASSANDRA-9593
Project: Cassandra
Issue Type: Bug
Components: Core
Reporter: Benedict
Priority: Minor
Fix For: 2.2.x
If the maximum number of compactions are running, and they all terminate
simultaneously, they can fail to submit any further compaction tasks. Further,
since each only submits one on completion, we only need two of these to race
with each other to reduce the number of active compactions below the configured
concurrency level.
There are a couple of ways to get around this. This simplest is to submit a
task to another thread pool to perform the submitBackgroundTask(), but this may
be unnecessarily delayed. Another is to maintain a separate count of active
compaction tasks, that is decremented while the thread is still serving the
request. A partial solution is to just discount the calling thread from the
count of active tasks, so at least one of any competitors will win.
The problem is mitigated considerably by CASSANDRA-9592, so there's no urgency
to this.
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