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From "Sergey Lapukhov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12763) Compaction performance issues when a table has a lot of sstables
Date Tue, 28 Nov 2017 14:48:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16268844#comment-16268844
] 

Sergey Lapukhov commented on CASSANDRA-12763:
---------------------------------------------

What if just maintain a file containing the directory listing and update it every time when
SSTable is added/removed? So instead of calling costly java.io.File.listFiles call instead
the special method that will just read and parse this file. This could give a performance
benefit since this read/parse operation cost will be independent of number of files in the
data directory.

Besides, I believe it could be easier in terms of implementation.

What do you guys think?

> Compaction performance issues when a table has a lot of sstables
> ----------------------------------------------------------------
>
>                 Key: CASSANDRA-12763
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12763
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>            Reporter: Tom van der Woerdt
>              Labels: lcs
>
> An issue with a script flooded my cluster with sstables. There is now a table with 100k
sstables, all on the order of KBytes, and it's taking a long time (ETA 20 days) to compact,
even though the table is only ~30GB.
> Stack trace :
> {noformat}
> "CompactionExecutor:269" #7536 daemon prio=1 os_prio=4 tid=0x00007f4acd40fc00 nid=0x14f8
runnable [0x00007f4798436000]
>    java.lang.Thread.State: RUNNABLE
> 	at java.io.UnixFileSystem.list(Native Method)
> 	at java.io.File.list(File.java:1122)
> 	at java.io.File.listFiles(File.java:1248)
> 	at org.apache.cassandra.db.lifecycle.LogRecord.getExistingFiles(LogRecord.java:268)
> 	at org.apache.cassandra.db.lifecycle.LogRecord.make(LogRecord.java:150)
> 	at org.apache.cassandra.db.lifecycle.LogFile.makeRecord(LogFile.java:293)
> 	at org.apache.cassandra.db.lifecycle.LogFile.add(LogFile.java:283)
> 	at org.apache.cassandra.db.lifecycle.LogTransaction.obsoleted(LogTransaction.java:158)
> 	at org.apache.cassandra.db.lifecycle.Helpers.prepareForObsoletion(Helpers.java:134)
> 	at org.apache.cassandra.db.lifecycle.LifecycleTransaction.doPrepare(LifecycleTransaction.java:193)
> 	at org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.prepareToCommit(Transactional.java:173)
> 	at org.apache.cassandra.io.sstable.SSTableRewriter.doPrepare(SSTableRewriter.java:376)
> 	at org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.prepareToCommit(Transactional.java:173)
> 	at org.apache.cassandra.db.compaction.writers.CompactionAwareWriter.doPrepare(CompactionAwareWriter.java:84)
> 	at org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.prepareToCommit(Transactional.java:173)
> 	at org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.finish(Transactional.java:184)
> 	at org.apache.cassandra.db.compaction.writers.CompactionAwareWriter.finish(CompactionAwareWriter.java:94)
> 	at org.apache.cassandra.db.compaction.CompactionTask.runMayThrow(CompactionTask.java:194)
> 	at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28)
> 	at org.apache.cassandra.db.compaction.CompactionTask.executeInternal(CompactionTask.java:78)
> 	at org.apache.cassandra.db.compaction.AbstractCompactionTask.execute(AbstractCompactionTask.java:61)
> 	at org.apache.cassandra.db.compaction.CompactionManager$BackgroundCompactionCandidate.run(CompactionManager.java:263)
> 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> 	at java.lang.Thread.run(Thread.java:745)
> {noformat}
> listFiles is being called over and over, apparently scaling with the number of files
in the compaction.



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