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https://issues.apache.org/jira/browse/CASSANDRA-14239?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16433655#comment-16433655
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Sergey Kirillov commented on CASSANDRA-14239:
---------------------------------------------

[~jalbersdorfer] I was trying to debug it and it looks like deadlock in 
memtable flush path. This leads to memtables which are never released to the 
pool and eventually you are getting OOM.

However, I still don't understand why those flush/mutation threads are freezing 
and how to resolve this. It would be nice if someone from the devs could take a 
look.

> OutOfMemoryError when bootstrapping with less than 100GB RAM
> ------------------------------------------------------------
>
>                 Key: CASSANDRA-14239
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14239
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Details of the bootstrapping Node
>  * ProLiant BL460c G7
>  * 56GB RAM
>  * 2x 146GB 10K HDD (One dedicated for Commitlog, one for Data, Hints and 
> saved_caches)
>  * CentOS 7.4 on SD-Card
>  * /tmp and /var/log on tmpfs
>  * Oracle JDK 1.8.0_151
>  * Cassandra 3.11.1
> Cluster
>  * 10 existing Nodes (Up and Normal)
>            Reporter: J├╝rgen Albersdorfer
>            Priority: Major
>         Attachments: Objects-by-class.csv, 
> Objects-with-biggest-retained-size.csv, cassandra-env.sh, cassandra.yaml, 
> gc.log.0.current.zip, gc.log.201804111141.zip, jvm.options, jvm_opts.txt, 
> stack-traces.txt
>
>
> Hi, I face an issue when bootstrapping a Node having less than 100GB RAM on 
> our 10 Node C* 3.11.1 Cluster.
> During bootstrap, when I watch the cassandra.log I observe a growth in JVM 
> Heap Old Gen which gets not significantly freed up any more.
> I know that JVM collects on Old Gen only when really needed. I can see 
> collections, but there is always a remainder which seems to grow forever 
> without ever getting freed.
> After the Node successfully Joined the Cluster, I can remove the extra RAM I 
> have given it for bootstrapping without any further effect.
> It feels like Cassandra will not forget about every single byte streamed over 
> the Network over time during bootstrapping, - which would be a memory leak 
> and a major problem, too.
> I was able to produce a HeapDumpOnOutOfMemoryError from a 56GB Node (40 GB 
> assigned JVM Heap). YourKit Profiler shows huge amount of Memory allocated 
> for org.apache.cassandra.db.Memtable (22 GB) 
> org.apache.cassandra.db.rows.BufferCell (19 GB) and java.nio.HeapByteBuffer 
> (11 GB)



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