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https://issues.apache.org/jira/browse/CASSANDRA-12763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15563219#comment-15563219
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Jeremy Hanna commented on CASSANDRA-12763:
------------------------------------------
With some other context, it sounds like the smaller sstables may be created as
a product of using LCS with 256 vnodes and then the repair creates the tiny
sstables. In that case it's probably better to use a smaller number of vnodes
(perhaps 32) in Cassandra 3+ with CASSANDRA-7032 so you don't have as much skew
and aren't as vulnerable to small sstables with repair.
Keep in mind that if you add a new datacenter, that 7032 relies on getting the
replication factor to reduce the skew at smaller vnode numbers. So you'd need
to create a node in each rack in the new datacenter with
{{auto_bootstrap=false}}, then you can create an empty keyspace and table with
replication in that datacenter and add the rest of the nodes with the 7032
algorithm.
> 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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