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https://issues.apache.org/jira/browse/CASSANDRA-10862?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15321703#comment-15321703
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Chen Shen edited comment on CASSANDRA-10862 at 6/9/16 2:03 AM:
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[~pauloricardomg]
I've done some investigation and I find it might not so easy to schedule a
compaction on L0 table on reception as the only straightforward way to trigger
a compaction is by submitting a task to CompactionManager.submitBackground, and
1) it's not guaranteed to be executed according to my knowledge 2)
submitBackground need a `ColumnFamilyStore` as input, so we need either create
a new CFS, or split the compaction strategy out of CompactionManager, each of
which might need lots of work.
So instead I am doing a different tricky approach: Don't add tables to CFS
until the number of L0 sstables is smaller than a threshold. And subscribe to
`SSTableListChangedNotification` so that the `OnCompletionRunnable` could sleep
and wait on notification.
Is this a right direction? I have a commit here
https://github.com/scv119/cassandra/commit/3b48c092a7381d3074086476b12570db9b16dc16
if you want to take a look. I'm also planing to apply this patch to our
production tier to see if this helps.
was (Author: scv...@gmail.com):
[~pauloricardomg]
I've done some investigation and I find it might not so easy to schedule a
compaction on L0 table on reception as the only straightforward way to trigger
a compaction is by submitting a task to CompactionManager.submitBackground, and
1) it's not guaranteed to be executed according to my knowledge 2)
submitBackground need a `ColumnFamilyStore` as input, so we need either create
a new CFS, or split the compaction strategy out of CompactionManager, each of
which might need lots of work.
So instead I am doing a different tricky approach: Don't add tables to CFS
until the number of L0 sstables is smaller than a threshold. And subscribe to
`SSTableListChangedNotification` so that the `OnCompletionRunnable` could sleep
and wait on notification.
Is this a right direction? I have a commit here
https://github.com/scv119/cassandra/commit/f49013897b1694e006e001df97c6f34399d016ae
if you want to take a look. I'm also planing to apply this patch to our
production tier to see if this helps.
> LCS repair: compact tables before making available in L0
> --------------------------------------------------------
>
> Key: CASSANDRA-10862
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10862
> Project: Cassandra
> Issue Type: Improvement
> Components: Compaction, Streaming and Messaging
> Reporter: Jeff Ferland
> Assignee: Chen Shen
>
> When doing repair on a system with lots of mismatched ranges, the number of
> tables in L0 goes up dramatically, as correspondingly goes the number of
> tables referenced for a query. Latency increases dramatically in tandem.
> Eventually all the copied tables are compacted down in L0, then copied into
> L1 (which may be a very large copy), finally reducing the number of SSTables
> per query into the manageable range.
> It seems to me that the cleanest answer is to compact after streaming, then
> mark tables available rather than marking available when the file itself is
> complete.
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