[jira] [Commented] (CASSANDRA-3306) Error in LeveledCompactionStrategy

["Sylvain Lebresne (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13483157#comment-13483157 ] 

Sylvain Lebresne commented on CASSANDRA-3306:
---------------------------------------------

Good analysis Yuki. I'm not really sure what is the right fix though. Given that this should very rarely happen (repair uses a much higher failure detection threshold than the normal one, though maybe we can increase it even more to make this even less likely) and that I don't seen any obvious way to avoid that kind of situation, maybe making DataTracker handle duplicate addition of a SSTableReader is the simplest thing to do. The obvious way to do that would be to change the View sstables List to a Set, which leads me to the current commentary in the code:
{noformat}
        // We can't use a SortedSet here because "the ordering maintained by a sorted set (whether or not an
        // explicit comparator is provided) must be <i>consistent with equals</i>."  In particular,
        // ImmutableSortedSet will ignore any objects that compare equally with an existing Set member.
        // Obviously, dropping sstables whose max column timestamp happens to be equal to another's
        // is not acceptable for us.  So, we use a List instead.
{noformat}
I think that comment is obsolete. Namely, it was added with CASSANDRA-2498 and at the time the list of sstable was kept in max timestamp order at all time. But since then, we've moved the sorting in max timestamp in CollationController directly (which is less fragile), so the order inside DataTracker doesn't matter anymore.
                
> Error in LeveledCompactionStrategy
> ----------------------------------
>
>                 Key: CASSANDRA-3306
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3306
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 1.0.0
>            Reporter: Radim Kolar
>            Assignee: Yuki Morishita
>         Attachments: 0001-CASSANDRA-3306-test.patch
>
>
> during stress testing, i always get this error making leveledcompaction strategy unusable. Should be easy to reproduce - just write fast.
> ERROR [CompactionExecutor:6] 2011-10-04 15:48:52,179 AbstractCassandraDaemon.java (line 133) Fatal exception in thread Thread[CompactionExecutor:6,5,main]
> java.lang.AssertionError
> 	at org.apache.cassandra.db.DataTracker$View.newSSTables(DataTracker.java:580)
> 	at org.apache.cassandra.db.DataTracker$View.replace(DataTracker.java:546)
> 	at org.apache.cassandra.db.DataTracker.replace(DataTracker.java:268)
> 	at org.apache.cassandra.db.DataTracker.replaceCompactedSSTables(DataTracker.java:232)
> 	at org.apache.cassandra.db.ColumnFamilyStore.replaceCompactedSSTables(ColumnFamilyStore.java:960)
> 	at org.apache.cassandra.db.compaction.CompactionTask.execute(CompactionTask.java:199)
> 	at org.apache.cassandra.db.compaction.LeveledCompactionTask.execute(LeveledCompactionTask.java:47)
> 	at org.apache.cassandra.db.compaction.CompactionManager$1.call(CompactionManager.java:131)
> 	at org.apache.cassandra.db.compaction.CompactionManager$1.call(CompactionManager.java:114)
> 	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
> 	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> 	at java.lang.Thread.run(Thread.java:662)
> and this is in json data for table:
> {
>   "generations" : [ {
>     "generation" : 0,
>     "members" : [ 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484 ]
>   }, {
>     "generation" : 1,
>     "members" : [ ]
>   }, {
>     "generation" : 2,
>     "members" : [ ]
>   }, {
>     "generation" : 3,
>     "members" : [ ]
>   }, {
>     "generation" : 4,
>     "members" : [ ]
>   }, {
>     "generation" : 5,
>     "members" : [ ]
>   }, {
>     "generation" : 6,
>     "members" : [ ]
>   }, {
>     "generation" : 7,
>     "members" : [ ]
>   } ]
> }

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