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https://issues.apache.org/jira/browse/CASSANDRA-18762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17817421#comment-17817421
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Brad Schoening commented on CASSANDRA-18762:
--------------------------------------------
It seems setting -XX:MaxDirectMemorySize might be useful to prevent this.
> Repair triggers OOM with direct buffer memory
> ---------------------------------------------
>
> Key: CASSANDRA-18762
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18762
> Project: Cassandra
> Issue Type: Bug
> Components: Consistency/Repair
> Reporter: Brad Schoening
> Priority: Normal
> Labels: OutOfMemoryError
> Attachments: Cluster-dm-metrics-1.PNG,
> image-2023-12-06-15-28-05-459.png, image-2023-12-06-15-29-31-491.png,
> image-2023-12-06-15-58-55-007.png
>
>
> We are seeing repeated failures of nodes with 16GB of heap on a VM with 32GB
> of physical RAM due to direct memory. This seems to be related to
> CASSANDRA-15202 which moved Merkel trees off-heap in 4.0. Using Cassandra
> 4.0.6 with Java 11.
> {noformat}
> 2023-08-09 04:30:57,470 [INFO ] [AntiEntropyStage:1] cluster_id=101
> ip_address=169.0.0.1 RepairSession.java:202 - [repair
> #5e55a3b0-366d-11ee-a644-d91df26add5e] Received merkle tree for table_a from
> /169.102.200.241:7000
> 2023-08-09 04:30:57,567 [INFO ] [AntiEntropyStage:1] cluster_id=101
> ip_address=169.0.0.1 RepairSession.java:202 - [repair
> #5e0d2900-366d-11ee-a644-d91df26add5e] Received merkle tree for table_b from
> /169.93.192.29:7000
> 2023-08-09 04:30:57,568 [INFO ] [AntiEntropyStage:1] cluster_id=101
> ip_address=169.0.0.1 RepairSession.java:202 - [repair
> #5e1dcad0-366d-11ee-a644-d91df26add5e] Received merkle tree for table_c from
> /169.104.171.134:7000
> 2023-08-09 04:30:57,591 [INFO ] [AntiEntropyStage:1] cluster_id=101
> ip_address=169.0.0.1 RepairSession.java:202 - [repair
> #5e69a0e0-366d-11ee-a644-d91df26add5e] Received merkle tree for table_b from
> /169.79.232.67:7000
> 2023-08-09 04:30:57,876 [INFO ] [Service Thread] cluster_id=101
> ip_address=169.0.0.1 GCInspector.java:294 - G1 Old Generation GC in 282ms.
> Compressed Class Space: 8444560 -> 8372152; G1 Eden Space: 7809794048 -> 0;
> G1 Old Gen: 1453478400 -> 820942800; G1 Survivor Space: 419430400 -> 0;
> Metaspace: 80411136 -> 80176528
> 2023-08-09 04:30:58,387 [ERROR] [AntiEntropyStage:1] cluster_id=101
> ip_address=169.0.0.1 JVMStabilityInspector.java:102 - OutOfMemory error
> letting the JVM handle the error:
> java.lang.OutOfMemoryError: Direct buffer memory
> at java.base/java.nio.Bits.reserveMemory(Bits.java:175)
> at java.base/java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:118)
> at java.base/java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:318)
> at org.apache.cassandra.utils.MerkleTree.allocate(MerkleTree.java:742)
> at
> org.apache.cassandra.utils.MerkleTree.deserializeOffHeap(MerkleTree.java:780)
> at org.apache.cassandra.utils.MerkleTree.deserializeTree(MerkleTree.java:751)
> at org.apache.cassandra.utils.MerkleTree.deserialize(MerkleTree.java:720)
> at org.apache.cassandra.utils.MerkleTree.deserialize(MerkleTree.java:698)
> at
> org.apache.cassandra.utils.MerkleTrees$MerkleTreesSerializer.deserialize(MerkleTrees.java:416)
> at
> org.apache.cassandra.repair.messages.ValidationResponse$1.deserialize(ValidationResponse.java:100)
> at
> org.apache.cassandra.repair.messages.ValidationResponse$1.deserialize(ValidationResponse.java:84)
> at
> org.apache.cassandra.net.Message$Serializer.deserializePost40(Message.java:782)
> at org.apache.cassandra.net.Message$Serializer.deserialize(Message.java:642)
> at
> org.apache.cassandra.net.InboundMessageHandler$LargeMessage.deserialize(InboundMessageHandler.java:364)
> at
> org.apache.cassandra.net.InboundMessageHandler$LargeMessage.access$1100(InboundMessageHandler.java:317)
> at
> org.apache.cassandra.net.InboundMessageHandler$ProcessLargeMessage.provideMessage(InboundMessageHandler.java:504)
> at
> org.apache.cassandra.net.InboundMessageHandler$ProcessMessage.run(InboundMessageHandler.java:429)
> at
> java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
> at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
> at
> java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
> at
> java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
> at
> io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
> at java.base/java.lang.Thread.run(Thread.java:834)no* further _formatting_ is
> done here{noformat}
>
> -XX:+AlwaysPreTouch
> -XX:+CrashOnOutOfMemoryError
> -XX:+ExitOnOutOfMemoryError
> -XX:+HeapDumpOnOutOfMemoryError
> -XX:+ParallelRefProcEnabled
> -XX:+PerfDisableSharedMem
> -XX:+ResizeTLAB
> -XX:+UseG1GC
> -XX:+UseNUMA
> -XX:+UseTLAB
> -XX:+UseThreadPriorities
> -XX:-UseBiasedLocking
> -XX:CompileCommandFile=/opt/nosql/clusters/cassandra-101/conf/hotspot_compiler
> -XX:G1RSetUpdatingPauseTimePercent=5
> -XX:G1ReservePercent=20
> -XX:HeapDumpPath=/opt/nosql/data/cluster_101/cassandra-1691623098-pid2804737.hprof
> -XX:InitiatingHeapOccupancyPercent=70
> -XX:MaxGCPauseMillis=200
> -XX:StringTableSize=60013
> -Xlog:gc*:file=/opt/nosql/clusters/cassandra-101/logs/gc.log:time,uptime:filecount=10,filesize=10485760
> -Xms16G
> -Xmx16G
> -Xss256k
>
> From our Prometheus metrics, the behavior shows the direct buffer memory
> ramping up until it reaches the max and then causes an OOM. It would appear
> that direct memory is never being released by the JVM until its exhausted.
>
> !Cluster-dm-metrics.PNG!
> An Eclipse Memory Analyzer
> Class Histogram:
> ||Class Name||Objects||Shallow Heap||Retained Heap||
> |java.lang.Object[]|445,014|42,478,160|>= 4,603,280,344| |
> |io.netty.util.concurrent.FastThreadLocalThread|167|21,376|>= 4,467,294,736|
> Leaks: Problem Suspect 1
> The thread *io.netty.util.concurrent.FastThreadLocalThread @ 0x501dd5930
> AntiEntropyStage:1* keeps local variables with total size *4,295,042,472
> (84.00%)* bytes.
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