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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 edited comment on CASSANDRA-19597 at 10/9/26 9:11 AM:
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It's a pretty simple feature actually, and would probably be straightforward to 
back port - 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.


was (Author: benedict):
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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