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https://issues.apache.org/jira/browse/HDFS-9305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14975860#comment-14975860
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Hudson commented on HDFS-9305:
------------------------------
FAILURE: Integrated in Hadoop-Hdfs-trunk-Java8 #541 (See
[https://builds.apache.org/job/Hadoop-Hdfs-trunk-Java8/541/])
HDFS-9305. Delayed heartbeat processing causes storm of subsequent (arp: rev
d8736eb9ca351b82854601ea3b1fbc3c9fab44e4)
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBpServiceActorScheduler.java
> Delayed heartbeat processing causes storm of subsequent heartbeats
> ------------------------------------------------------------------
>
> Key: HDFS-9305
> URL: https://issues.apache.org/jira/browse/HDFS-9305
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 2.7.1
> Reporter: Chris Nauroth
> Assignee: Arpit Agarwal
> Attachments: HDFS-9305.01.patch, HDFS-9305.02.patch
>
>
> A DataNode typically sends a heartbeat to the NameNode every 3 seconds. We
> expect heartbeat handling to complete relatively quickly. However, if
> something unexpected causes heartbeat processing to get blocked, such as a
> long GC or heavy lock contention within the NameNode, then heartbeat
> processing would be delayed. After recovering from this delay, the DataNode
> then starts sending a storm of heartbeat messages in a tight loop. In a
> large cluster with many DataNodes, this storm of heartbeat messages could
> cause harmful load on the NameNode and make overall cluster recovery more
> difficult.
> The bug appears to be caused by incorrect timekeeping inside
> {{BPServiceActor}}. The next heartbeat time is always calculated as a delta
> from the previous heartbeat time, without any compensation for possible long
> latency on an individual heartbeat RPC. The only mitigation would be
> restarting all DataNodes to force a reset of the heartbeat schedule, or
> simply wait out the storm until the scheduling catches up and corrects itself.
> This problem would not manifest after a NameNode restart. In that case, the
> NameNode would respond to the first heartbeat by telling the DataNode to
> re-register, and {{BPServiceActor#reRegister}} would reset the heartbeat
> schedule to the current time. I believe the problem would only manifest if
> the NameNode process kept alive, but processed heartbeats unexpectedly slowly.
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