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From "Jeff Jirsa (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-9549) Memory leak
Date Mon, 15 Jun 2015 18:15:02 GMT


Jeff Jirsa commented on CASSANDRA-9549:

Throwing a me-too here, copying summary from IRC (on the topic of 2.1.6 showing weird memory
behavior that feels like a leak). Other user was also using DTCS:

11:07 < jeffj> opened CASSANDRA-9597 last night. dtcs + streaming = lots of sstables
that won't compact efficiently and eventually (days after load is stopped) nodes end up ooming
or in gc hell.
11:08 < jeffj> in our case, the PROBLEM is that sstables build up over time due to the
weird way dtcs is selecting candidates to compact, but the symptom is very very very long
gc pauses and eventual ooms.
11:10 < jeffj> i would very much believe there's a leak somewhere in 2.1.6. in our case,
we saw the same behavior in 2.1.5, so i dont think it's a single minor version regression

> Memory leak 
> ------------
>                 Key: CASSANDRA-9549
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         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
>            Priority: Critical
>             Fix For: 2.1.x
>         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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