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https://issues.apache.org/jira/browse/HDFS-5014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13828830#comment-13828830
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Hudson commented on HDFS-5014:
------------------------------

FAILURE: Integrated in Hadoop-Yarn-trunk #398 (See 
[https://builds.apache.org/job/Hadoop-Yarn-trunk/398/])
HDFS-5014. Process register commands with out holding BPOfferService lock. 
Contributed by Vinay. (umamahesh: 
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1543861)
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* 
/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
* 
/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java


> BPOfferService#processCommandFromActor() synchronization on namenode RPC call 
> delays IBR to Active NN, if Stanby NN is unstable
> -------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-5014
>                 URL: https://issues.apache.org/jira/browse/HDFS-5014
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode, ha
>    Affects Versions: 3.0.0, 2.0.4-alpha
>            Reporter: Vinay
>            Assignee: Vinay
>             Fix For: 3.0.0, 2.3.0, 2.2.1
>
>         Attachments: HDFS-5014-v2.patch, HDFS-5014-v2.patch, 
> HDFS-5014-v2.patch, HDFS-5014-v2.patch, HDFS-5014-v2.patch, 
> HDFS-5014-v2.patch, HDFS-5014.patch, HDFS-5014.patch, HDFS-5014.patch, 
> HDFS-5014.patch, HDFS-5014.patch, HDFS-5014.patch, HDFS-5014.patch
>
>
> In one of our cluster, following has happened which failed HDFS write.
> 1. Standby NN was unstable and continously restarting due to some errors. But 
> Active NN was stable.
> 2. MR Job was writing files.
> 3. At some point SNN went down again while datanode processing the REGISTER 
> command for SNN. 
> 4. Datanodes started retrying to connect to SNN to register at the following 
> code  in BPServiceActor#retrieveNamespaceInfo() which will be called under 
> synchronization.
> {code}      try {
>         nsInfo = bpNamenode.versionRequest();
>         LOG.debug(this + " received versionRequest response: " + nsInfo);
>         break;{code}
> Unfortunately in all datanodes at same point this happened.
> 5. For next 7-8 min standby was down, and no blocks were reported to active 
> NN at this point and writes have failed.
> So culprit is {{BPOfferService#processCommandFromActor()}} is completely 
> synchronized which is not required.



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