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https://issues.apache.org/jira/browse/HDFS-6184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14542159#comment-14542159
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Hudson commented on HDFS-6184:
------------------------------
FAILURE: Integrated in Hadoop-Mapreduce-trunk #2142 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/2142/])
HDFS-6184. Capture NN's thread dump when it fails over. Contributed by Ming Ma.
(aajisaka: rev 2463666ecb553dbde1b8c540a21ad3d599239acf)
*
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/ZKFailoverController.java
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/DFSZKFailoverController.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestDFSZKFailoverController.java
*
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/TestDFSZKFailoverController.java
> Capture NN's thread dump when it fails over
> -------------------------------------------
>
> Key: HDFS-6184
> URL: https://issues.apache.org/jira/browse/HDFS-6184
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: Ming Ma
> Assignee: Ming Ma
> Fix For: 2.8.0
>
> Attachments: HDFS-6184-2.patch, HDFS-6184-3.patch, HDFS-6184-4.patch,
> HDFS-6184-5.patch, HDFS-6184-6.patch, HDFS-6184.patch
>
>
> We have seen several false positives in terms of when ZKFC considers NN to be
> unhealthy. Some of these triggers unnecessary failover. Examples,
> 1. SBN checkpoint caused ZKFC's RPC call into NN timeout. The consequence
> isn't bad; just that SBN will quit ZK membership and rejoin it later. But it
> is unnecessary. The reason is checkpoint acquires NN global write lock and
> all rpc requests are blocked. Even though HAServiceProtocol.monitorHealth
> doesn't need to acquire NN lock; it still needs to user service rpc queue.
> 2. When ANN is busy, sometimes the global lock can block other requests.
> ZKFC's RPC call timeout. This will trigger failover. The question is even if
> after the failover, the new ANN might run into similar issue.
> We can increase ZKFC to NN timeout value to mitigate this to some degree. If
> ZKFC can be more accurate in judgment if NN is health or not and can predict
> the failover will help, that will be useful. For example, we can,
> 1. Have ZKFC made decision based on NN thread dump.
> 2. Have a dedicated rpc pool for ZKFC > NN. Given health check doesn't need
> to acquire NN global lock; so it can go through even if NN is doing
> checkpointing or very busy.
> Any comments?
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