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https://issues.apache.org/jira/browse/CASSANDRA-6483?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13846987#comment-13846987
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graham sanderson commented on CASSANDRA-6483:
---------------------------------------------
The simplest fix is probably just to precompute an IdentityMap to any of the
mutable data, and use it from within the comparator (since the comparator
happens to be non static)
Alternatively use a List of a new wrapper type and sort that instead.
> Possible Collections.sort assertion failure in STCS.filterColdSSTables
> ----------------------------------------------------------------------
>
> Key: CASSANDRA-6483
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6483
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: graham sanderson
>
> We have observed the following stack trace periodically:
> {code}
> java.lang.IllegalArgumentException: Comparison method violates its general
> contract!
> at java.util.TimSort.mergeLo(TimSort.java:747)
> at java.util.TimSort.mergeAt(TimSort.java:483)
> at java.util.TimSort.mergeCollapse(TimSort.java:410)
> at java.util.TimSort.sort(TimSort.java:214)
> at java.util.TimSort.sort(TimSort.java:173)
> at java.util.Arrays.sort(Arrays.java:659)
> at java.util.Collections.sort(Collections.java:217)
> at
> org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy.filterColdSSTables(SizeTieredCompactionStrategy.java:94)
> at
> org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy.getNextBackgroundSSTables(SizeTieredCompactionStrategy.java:59)
> at
> org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy.getNextBackgroundTask(SizeTieredCompactionStrategy.java:229)
> at
> org.apache.cassandra.db.compaction.CompactionManager$BackgroundCompactionTask.run(CompactionManager.java:191)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
> at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:744)
> {code}
> The comparator ant SizeTieredCompactionStrategy line 94 breaks the assertions
> in the new JDK7 default sort algorithm, because (I think just) the hotness
> value (based on meter) may be modified concurrently by another thread
> This bug appears to have been introduced in CASSANDRA-6109
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