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https://issues.apache.org/jira/browse/HDFS-3507?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13437134#comment-13437134
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Aaron T. Myers commented on HDFS-3507:
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My preference is to introduce a new isInSafeMode or getSafeMode function to the
ClientProtocol, instead of parameterizing the check. I've always found it a
little bizarre that a method called "setSafeMode" actually may not set
anything, and may be non-mutative depending upon a parameter. I don't feel
super strongly about this, though. Nicholas, is there some reason you prefer
keeping this as a single method?
Two comments on the correctness of the patch:
# The new parameter in the SetSafeModeRequestProto should be marked optional,
defaulted to false, to maintain compatibility.
# Seems like the calls in DFSAdmin should be passing "true" for isChecked, so
that the the active NN is used.
Another issue related to this: I'm not super happy with the current handling of
setting (not getting) safemode in an HA setup, since an admin command will only
affect a single NN. Imagine the scenario where an operator runs `hdfs dfsadmin
-safemode enter' and then a failure occurs of the active NN, triggering a
failover. Presently, this will have the side effect of causing HDFS to leave
safe mode. I think when an operator calls `safemode -enter' they usually intend
to put the HDFS _service_ into safemode, and not any particular NN. Perhaps we
should make the the DFSAdmin command notice when a logical HA URI is being
used, and make the appropriate RPC call to _all_ of the NNs, instead of just
one? There's some related discussion about this on HDFS-3744, where we discuss
the fact that one must call `hdfs dfsadmin -refreshNodes' on both NNs in an HA
setup.
What are peoples' thoughts on this issue?
> DFS#isInSafeMode needs to execute only on Active NameNode
> ---------------------------------------------------------
>
> Key: HDFS-3507
> URL: https://issues.apache.org/jira/browse/HDFS-3507
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ha
> Affects Versions: 2.1.0-alpha, 3.0.0
> Reporter: Vinay
> Assignee: Vinay
> Priority: Critical
> Attachments: HDFS-3507.patch, HDFS-3507.patch
>
>
> Currently DFS#isInSafeMode is not Checking for the NN state. It can be
> executed on any of the NNs.
> But HBase will use this API to check for the NN safemode before starting up
> its service.
> If first NN configured is in standby then DFS#isInSafeMode will check standby
> NNs safemode but hbase want state of Active NN.
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