Bug: OOM because repair session thread not closed when terminating repair
Status: Resolved
Priority: Normal
Resolution: Fixed
Created: 25/Jun/20 13:50
Resolved: 28/Oct/20 14:01

In our cluster, after a while some nodes running slowly out of memory. On that nodes we observed that Cassandra Reaper terminate repairs with a JMX call to {{StorageServiceMBean.forceTerminateAllRepairSessions()}} because reaching timeout of 30 min.

In the memory heap dump we see lot of instances of {{io.netty.util.concurrent.FastThreadLocalThread}} occupy most of the memory:
{noformat}
119 instances of "io.netty.util.concurrent.FastThreadLocalThread", loaded by "sun.misc.Launcher$AppClassLoader @ 0x51a800000" occupy 8.445.684.480 (93,96 %) bytes. {noformat}
In the thread dump we see lot of repair threads:
{noformat}
grep "Repair#" threaddump.txt | wc -l
      50 {noformat}
 

The repair jobs are waiting for the validation to finish:
{noformat}
"Repair#152:1" #96170 daemon prio=5 os_prio=0 tid=0x0000000012fc5000 nid=0x542a waiting on condition [0x00007f81ee414000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000007939bcfc8> (a com.google.common.util.concurrent.AbstractFuture$Sync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
        at com.google.common.util.concurrent.AbstractFuture$Sync.get(AbstractFuture.java:285)
        at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:116)
        at com.google.common.util.concurrent.Uninterruptibles.getUninterruptibly(Uninterruptibles.java:137)
        at com.google.common.util.concurrent.Futures.getUnchecked(Futures.java:1509)
        at org.apache.cassandra.repair.RepairJob.run(RepairJob.java:160)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at org.apache.cassandra.concurrent.NamedThreadFactory.lambda$threadLocalDeallocator$0(NamedThreadFactory.java:81)
        at org.apache.cassandra.concurrent.NamedThreadFactory$$Lambda$13/480490520.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748) {noformat}
 

Thats the line where the threads stuck:
{noformat}
// Wait for validation to complete
Futures.getUnchecked(validations); {noformat}
 

The call to {{StorageServiceMBean.forceTerminateAllRepairSessions()}} stops the thread pool executor. It looks like that futures which are in progress will therefor never be completed and the repair thread waits forever and won't be finished.

 

Environment:

Cassandra version: 3.11.4 and 3.11.6

Cassandra Reaper: 1.4.0

JVM memory settings:
{noformat}
-Xms11771M -Xmx11771M -XX:+UseG1GC -XX:MaxGCPauseMillis=100 -XX:+ParallelRefProcEnabled -XX:MaxMetaspaceSize=100M {noformat}
on another cluster with same issue:
{noformat}
-Xms31744M -Xmx31744M -XX:+UseG1GC -XX:MaxGCPauseMillis=100 -XX:+ParallelRefProcEnabled -XX:MaxMetaspaceSize=100M {noformat}
Java Runtime:
{noformat}
openjdk version "1.8.0_212"
OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_212-b03)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.212-b03, mixed mode) {noformat}
 

The same issue described in this comment: https://issues.apache.org/jira/browse/CASSANDRA-14355?focusedCommentId=16992973&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16992973

As suggested in the comments I created this new specific ticket.