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Posted to commits@cassandra.apache.org by "Dimitar Dimitrov (JIRA)" <ji...@apache.org> on 2017/12/06 19:34:00 UTC
[jira] [Comment Edited] (CASSANDRA-13801) CompactionManager
sometimes wrongly determines that a background compaction is running for a
particular table
[ https://issues.apache.org/jira/browse/CASSANDRA-13801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16280752#comment-16280752 ]
Dimitar Dimitrov edited comment on CASSANDRA-13801 at 12/6/17 7:33 PM:
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It turns out that the problem does not necessarily require altering the compaction strategy.
It seems to be rooted in a potential problem with counting the CF compaction requests, that can eventually lead to a skipped background compaction.
The wrong counting can happen if the counting multiset increment [here|https://github.com/apache/cassandra/blob/95b43b195e4074533100f863344c182a118a8b6c/src/java/org/apache/cassandra/db/compaction/CompactionManager.java#L197] gets delayed and happens after the corresponding counting multiset decrement already happened [here|https://github.com/apache/cassandra/blob/95b43b195e4074533100f863344c182a118a8b6c/src/java/org/apache/cassandra/db/compaction/CompactionManager.java#L284].
Here are the branches with the proposed changes, as well as a Byteman test that can be used to demonstrate the issue.
testall results look good (3.0 and trunk each have 1 seemingly unrelated, flaky test failing).
dtest results will be added soon.
| [2.2|https://github.com/apache/cassandra/compare/cassandra-2.2...dimitarndimitrov:c13801-2.2] | [testall|^c13801-2.2-testall.png] |
| [3.0|https://github.com/apache/cassandra/compare/cassandra-3.0...dimitarndimitrov:c13801-3.0] | [testall|^c13801-3.0-testall.png] |
| [3.11|https://github.com/apache/cassandra/compare/cassandra-3.11...dimitarndimitrov:c13801-3.11] | [testall|^c13801-3.11-testall.png] |
| [trunk|https://github.com/apache/cassandra/compare/trunk...dimitarndimitrov:c13801-trunk] | [testall|^c13801-trunk-testall.png] |
was (Author: dimitarndimitrov):
It turns out that the problem does not necessarily require altering the compaction strategy.
It seems to be rooted in a potential problem with counting the CF compaction requests, that can eventually lead to a skipped background compaction.
The wrong counting can happen if the counting multiset increment [here|https://github.com/apache/cassandra/blob/95b43b195e4074533100f863344c182a118a8b6c/src/java/org/apache/cassandra/db/compaction/CompactionManager.java#L197] gets delayed and happens after the corresponding counting multiset decrement already happened [here|https://github.com/apache/cassandra/blob/95b43b195e4074533100f863344c182a118a8b6c/src/java/org/apache/cassandra/db/compaction/CompactionManager.java#L284].
Here are the branches with the proposed changes, as well as a Byteman test that can be used to demonstrate the issue.
testall results look good (3.0 and trunk each have 1 seemingly unrelated, flaky test failing).
dtest results will be added soon.
| [2.2|https://github.com/apache/cassandra/compare/cassandra-2.2...dimitarndimitrov:c13801-2.2] | [testall|^c13801-2.2-testall.png] |
| [3.0|https://github.com/apache/cassandra/compare/cassandra-3.0...dimitarndimitrov:c13801-3.0] | [testall|^c13801-3.0-testall.png] |
| [3.11|https://github.com/apache/cassandra/compare/cassandra-3.11...dimitarndimitrov:c13801-3.11] | [testall|^c13801-3.11-testall.png] |
| [trunk|https://github.com/apache/cassandra/compare/trunk...dimitarndimitrov:c13801-trunk] | [testall|^c13801-2.2-testall.png] |
> CompactionManager sometimes wrongly determines that a background compaction is running for a particular table
> -------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-13801
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13801
> Project: Cassandra
> Issue Type: Bug
> Components: Compaction
> Reporter: Dimitar Dimitrov
> Assignee: Dimitar Dimitrov
> Priority: Minor
> Attachments: c13801-2.2-testall.png, c13801-3.0-testall.png, c13801-3.11-testall.png, c13801-trunk-testall.png
>
>
> Sometimes after writing different rows to a table, then doing a blocking flush, if you alter the compaction strategy, then run background compaction and wait for it to finish, {{CompactionManager}} may decide that there's an ongoing compaction for that same table.
> This may happen even though logs don't indicate that to be the case (compaction may still be running for system_schema tables).
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