Vinay created HDFS-5014:
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Summary: 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: 2.0.4-alpha
Reporter: Vinay
Assignee: Vinay
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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