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Date: Wed, 10 Jun 2015 16:20:01 +0000 (UTC)
From: "Alan Boudreault (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-9573) OOM when loading compressed
 sstables (system.hints)
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    [ https://issues.apache.org/jira/browse/CASSANDRA-9573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14580728#comment-14580728 ] 

Alan Boudreault commented on CASSANDRA-9573:
--------------------------------------------

No. everything is good on 2.1


> OOM when loading compressed sstables (system.hints)
> ---------------------------------------------------
>
>                 Key: CASSANDRA-9573
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9573
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Alan Boudreault
>            Priority: Critical
>             Fix For: 2.2.0 rc2
>
>         Attachments: hs_err_pid11243.log, java-hints-issue-2015-06-09.snapshot, system.log, yourkit.ss.tar.gz
>
>
> [~andrew.tolbert] discovered an issue while running endurance tests on 2.2. A Node was not able to start and was killed by the OOM Killer.
> Briefly, Cassandra use an excessive amount of memory when loading compressed sstables (off-heap?). We have initially seen the issue with system.hints before knowing it was related to compression. system.hints use lz4 compression by default. If we have a sstable of, say 8-10G, Cassandra will be killed by the OOM killer after 1-2 minutes. I can reproduce that bug everytime locally. 
> * the issue also happens if we have 10G of data splitted in 13MB sstables.
> * I can reproduce the issue if I put a lot of data in the system.hints table.
> * I cannot reproduce the issue with a standard table using the same compression (LZ4). Something seems to be different when it's hints?
> You wont see anything in the node system.log but you'll see this in /var/log/syslog.log:
> {code}
> Out of memory: Kill process 30777 (java) score 600 or sacrifice child
> {code}
> The issue has been introduced in this commit but is not related to the performance issue in CASSANDRA-9240: https://github.com/apache/cassandra/commit/aedce5fc6ba46ca734e91190cfaaeb23ba47a846
> Here is the core dump and some yourkit snapshots in attachments. I am not sure you will be able to get useful information from them.
> core dump: http://dl.alanb.ca/core.tar.gz
> Not sure if this is related, but all dumps and snapshot points to EstimatedHistogramReservoir ... and we can see many javax.management.InstanceAlreadyExistsException: org.apache.cassandra.metrics:... exceptions in system.log before it hangs then crash.
> To reproduce the issue: 
> 1. created a cluster of 3 nodes
> 2. start the whole cluster
> 3. shutdown node2 and node3
> 4. writes 10-15G of data on node1 with replication factor 3. You should see a lot of hints.
> 5. stop node1
> 6. start node2 and node3
> 7. start node1, you should OOM.
> //cc [~tjake] [~benedict] [~andrew.tolbert]


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