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From "Anuj Wadehra (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-9146) Ever Growing sstables after every Repair
Date Sat, 06 Jun 2015 19:42:00 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-9146?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Anuj Wadehra updated CASSANDRA-9146:
------------------------------------
    Description: 
Cluster has reached a state where every "repair -pr" operation on CF results in numerous tiny
sstables being flushed to disk.  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 tables are flushed during repair ? What is triggering frequent/premature
flush of  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

  was:
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

        Summary: Ever Growing sstables after every Repair  (was: Ever Growing Secondary Index
sstables after every Repair)

> Ever Growing 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 Wadehra
>         Attachments: sstables.txt, system-modified.log
>
>
> Cluster has reached a state where every "repair -pr" operation on CF results in numerous
tiny sstables being flushed to disk.  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 tables are flushed during repair ? What is triggering frequent/premature
flush of  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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