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https://issues.apache.org/jira/browse/CASSANDRA-19597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18125430#comment-18125430
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Benedict Elliott Smith commented on CASSANDRA-19597:
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It's a pretty simple feature actually, it's a bit silly we haven't fixed this
"bug" for fifteen years or more.
I hadn't looked at the proposed "fix" here though - it is simpler, but much
less complete. I was just mentioning it for information as I happened to be
notified of your message.
> SystemKeyspace CFS flushing blocked by unrelated keyspace flushing/compaction
> -----------------------------------------------------------------------------
>
> Key: CASSANDRA-19597
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19597
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Local/Memtable
> Reporter: Ariel Weisberg
> Assignee: Ariel Weisberg
> Priority: Normal
> Attachments: ci_summary.html
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> There is a single post flush thread and that thread processes tasks in order
> and one of those tasks can be a memtable flush for an unrelated keyspace/cfs,
> and that memtable flush can be blocked by slow IntervalTree building and
> racing with compactors to try and build an interval tree.
> Unless there is a requirement for ordering we probably want to loosen this to
> the actual ordering requirement so that problems in one keyspace can’t effect
> another.
> SystemKeyspace and Gossip in particular cause lots of weird problems like
> nodes marking each other down because Gossip can’t process nodes being
> removed (blocking flush each time in SystemKeyspace.removeNode)
> A very simple fix here might be to queue the post flush task at the same time
> as the flush in a per CFS queue, and then submit the task only once the flush
> is completed.
> If flushes complete out of order the queue will still ensure their
> completions are processed in order.
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