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From "Anuj (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9146) Ever Growing Secondary Index sstables after every Repair
Date Thu, 09 Apr 2015 14:15:12 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14487406#comment-14487406
] 

Anuj commented on CASSANDRA-9146:
---------------------------------

Yes please analyze as we are facing it in 2.0.3.We may need this fix in 2.0 branch.Upgrading
would take some time and scenario is not easily reproducible but once it occurs in a cluster
this burst of sstables grows with every repair.We need to understand why this premature flushing
is happenning? Whats the work around till we upgrade? If its coldness issue which prevents
auto compaction then any advise to make all sstables hot ( we tried with reads but without
success)? Range scan doesnt contribute to hotness ..thats another open issue I logged sometime
back.

> Ever Growing Secondary Index sstables after every Repair
> --------------------------------------------------------
>
>                 Key: CASSANDRA-9146
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9146
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Anuj
>
> Cluster has reached a state where every "repair -pr" operation on CF results in numerous
tiny sstables being flushed to disk. Most sstables are related to secondary indexes. Due to
thousands of sstables, reads have started timing out. Even though compaction begins for one
of the secondary index, sstable count after repair remains very high (thousands). Every repair
adds thousands of sstables.
> Problems:
> 1. Why burst of tiny secondary index tables are flushed during repair ? What is triggering
frequent/premature flush of secondary index sstable (more than hundred in every burst)? At
max we see one ParNew GC pauses >200ms.
> 2. Why auto-compaction is not compacting all sstables. Is it related to coldness issue(CASSANDRA-8885)
where compaction doesn't works even when cold_reads_to_omit=0 by default? 
>    If coldness is the issue, we are stuck in infinite loop: reads will trigger compaction
but reads timeout as sstable count is in thousands
> 3. What's the way out if we face this issue in Prod?
> Is this issue fixed in latest production release 2.0.13? Issue looks similar to CASSANDRA-8641,
but the issue is fixed in only 2.1.3. I think it should be fixed in 2.0 branch too. 
> Configuration:
> Compaction Strategy: STCS
> memtable_flush_writers=4
> memtable_flush_queue_size=4
> in_memory_compaction_limit_in_mb=32
> concurrent_compactors=12



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