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https://issues.apache.org/jira/browse/CASSANDRA-9681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14607913#comment-14607913
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mlowicki commented on CASSANDRA-9681:
-------------------------------------
https://www.dropbox.com/s/cnv36bbdznbwc0g/Screenshot%202015-06-30%2010.07.27.png?dl=0
- this if chart from the box I was creating heap dump. Please keep in mind
that the metric changes rapidly. It can grow from ~300MB to over 1GB within 3
minutes. I'll prepare heap dump today once again.
I'm using jmap:
{code}
root@db5:/var# jmap -F -dump:file=cassandra.bin 19189
{code}
and this C* node is dead for the rest of the cluster for ~40minutes. Can this
be avoided?
> Memtable heap size grows and many long GC pauses are triggered
> --------------------------------------------------------------
>
> Key: CASSANDRA-9681
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9681
> Project: Cassandra
> Issue Type: Bug
> Environment: C* 2.1.7, Debian Wheezy
> Reporter: mlowicki
> Assignee: Benedict
> Priority: Critical
> Fix For: 2.1.x
>
> Attachments: cassandra.yaml, system.log.6.zip, system.log.7.zip,
> system.log.8.zip, system.log.9.zip
>
>
> C* 2.1.7 cluster is behaving really bad after 1-2 days.
> {{gauges.cassandra.jmx.org.apache.cassandra.metrics.ColumnFamily.AllMemtablesHeapSize.Value}}
> jumps to 7 GB
> (https://www.dropbox.com/s/vraggy292erkzd2/Screenshot%202015-06-29%2019.12.53.png?dl=0)
> on 3/6 nodes in each data center and then there are many long GC pauses.
> Cluster is using default heap size values ({{-Xms8192M -Xmx8192M -Xmn2048M}})
> Before C* 2.1.5 memtables heap size was basically constant ~500MB
> (https://www.dropbox.com/s/fjdywik5lojstvn/Screenshot%202015-06-29%2019.30.00.png?dl=0)
> After restarting all nodes is behaves stable for 1-2days. Today I've done
> that and long GC pauses are gone (~18:00
> https://www.dropbox.com/s/7vo3ynz505rsfq3/Screenshot%202015-06-29%2019.28.37.png?dl=0).
> The only pattern we've found so far is that long GC pauses are happening
> basically at the same time on all nodes in the same data center - even on the
> ones where memtables heap size is not growing.
> Cliffs on the graphs are nodes restarts.
> Used memory on boxes where {{AllMemtabelesHeapSize}} grows, stays at the same
> level -
> https://www.dropbox.com/s/tes9abykixs86rf/Screenshot%202015-06-29%2019.37.52.png?dl=0.
> Replication factor is set to 3.
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