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From "Benedict (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-9549) Memory leak in Ref.GlobalState due to pathological ConcurrentLinkedQueue.remove behaviour
Date Sun, 10 Apr 2016 02:42:25 GMT


Benedict commented on CASSANDRA-9549:

What is obtuse?

bq. how to resolve?

Move to a version >= fixVersion, i.e. 2.1.7

bq. why this happen

The [last comment  with more than one sentence|],
only six comments back, spells out what happened and why.

I realise JIRA noise can be quite an issue in many cases, but in this instance it seems to
me that just a modicum of effort was necessary to find the answers you sought.

> Memory leak in Ref.GlobalState due to pathological ConcurrentLinkedQueue.remove behaviour
> -----------------------------------------------------------------------------------------
>                 Key: CASSANDRA-9549
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>         Environment: Cassandra 2.1.5. 9 node cluster in EC2 (m1.large nodes, 2 cores
7.5G memory, 800G platter for cassandra data, root partition and commit log are on SSD EBS
with sufficient IOPS), 3 nodes/availablity zone, 1 replica/zone
> JVM: /usr/java/jdk1.8.0_40/jre/bin/java 
> JVM Flags besides CP: -ea -javaagent:/usr/share/cassandra/lib/jamm-0.3.0.jar -XX:+CMSClassUnloadingEnabled
-XX:+UseThreadPriorities -XX:ThreadPriorityPolicy=42 -Xms2G -Xmx2G -Xmn200M -XX:+HeapDumpOnOutOfMemoryError
-Xss256k -XX:StringTableSize=1000003 -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled
-XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=1 -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly
-XX:+UseTLAB -XX:CompileCommandFile=/etc/cassandra/conf/hotspot_compiler -XX:CMSWaitDuration=10000
-XX:+CMSParallelInitialMarkEnabled -XX:+CMSEdenChunksRecordAlways -XX:CMSWaitDuration=10000
-Dlogback.configurationFile=logback.xml -Dcassandra.logdir=/var/log/cassandra -Dcassandra.storagedir=
> Kernel: Linux 2.6.32-504.16.2.el6.x86_64 #1 SMP x86_64 x86_64 x86_64 GNU/Linux
>            Reporter: Ivar Thorson
>            Assignee: Benedict
>            Priority: Critical
>             Fix For: 2.1.7
>         Attachments: c4_system.log,, cassandra.yaml, cpu-load.png, memoryuse.png,
ref-java-errors.jpeg, suspect.png, two-loads.png
> We have been experiencing a severe memory leak with Cassandra 2.1.5 that, over the period
of a couple of days, eventually consumes all of the available JVM heap space, putting the
JVM into GC hell where it keeps trying CMS collection but can't free up any heap space. This
pattern happens for every node in our cluster and is requiring rolling cassandra restarts
just to keep the cluster running. We have upgraded the cluster per Datastax docs from the
2.0 branch a couple of months ago and have been using the data from this cluster for more
than a year without problem.
> As the heap fills up with non-GC-able objects, the CPU/OS load average grows along with
it. Heap dumps reveal an increasing number of java.util.concurrent.ConcurrentLinkedQueue$Node
objects. We took heap dumps over a 2 day period, and watched the number of Node objects go
from 4M, to 19M, to 36M, and eventually about 65M objects before the node stops responding.
The screen capture of our heap dump is from the 19M measurement.
> Load on the cluster is minimal. We can see this effect even with only a handful of writes
per second. (See attachments for Opscenter snapshots during very light loads and heavier loads).
Even with only 5 reads a sec we see this behavior.
> Log files show repeated errors in and and "LEAK detected" messages:
> {code}
> ERROR [CompactionExecutor:557] 2015-06-01 18:27:36,978 - Error when closing
> java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@32680b31
rejected from org.apache.cassandra.concurrent.DebuggableScheduledThreadPoolExecutor@573464d6[Terminated,
pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 1644]
> {code}
> {code}
> ERROR [Reference-Reaper:1] 2015-06-01 18:27:37,083 - LEAK DETECTED: a reference
(org.apache.cassandra.utils.concurrent.Ref$State@74b5df92) to class$DescriptorTypeTidy@2054303604:/data2/data/ourtablegoeshere-ka-1151
was not released before the reference was garbage collected
> {code}
> This might be related to [CASSANDRA-8723]?

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