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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9500) datanodesSoftwareVersions map may counting wrong when rolling upgrade
Date Wed, 26 Oct 2016 02:05:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15607096#comment-15607096
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Konstantin Shvachko commented on HDFS-9500:
-------------------------------------------

Good find Erik. I agree we should decrement version count whenever DN is alive. The heartbeat
interval expiration doesn't matter here because the node will be marked alive by that same
method. It should also work for the full version recount in {{countSoftwareVersions()}}. Two
nits
# Could you please add Javadoc
#* to {{shouldCountVersion()}} saying we count versions for all alive nodes
#* and to the new test explaining its purpose
# You do not need to use Mockito for setting fields in {{DatanodeRegistration}}. Can't you
just use a constructor?

> datanodesSoftwareVersions map may counting wrong when rolling upgrade
> ---------------------------------------------------------------------
>
>                 Key: HDFS-9500
>                 URL: https://issues.apache.org/jira/browse/HDFS-9500
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.7.1, 2.6.2
>            Reporter: Phil Yang
>            Assignee: Erik Krogen
>         Attachments: 9500-v1.patch, HDFS-9500.000.patch
>
>
> While rolling upgrading, namenode's website overview will report there are two versions
datanodes in the cluster, for example, 2.6.0 has x nodes and 2.6.2 has y nodes. However, sometimes
when I stop a datanode in old version and start a new version one, namenode only increases
the number of new version but not decreases the number of old version. So the total number
x+y will be larger than the number of datanodes. Even all datanodes are upgraded, there will
still have the messages that there are several datanode in old version. And I must run hdfs
dfsadmin -refreshNodes to clear this message.
> I think this issue is caused by DatanodeManager.registerDatanode. If nodeS in old version
is not alive because of shutting down, it will not pass shouldCountVersion, so the number
of old version won't be decreased. But this method only judges the status of heartbeat and
isAlive at that moment, if namenode has not removed this node which will decrease the version
map and this node restarts in the new version, the decrementVersionCount belongs to this node
will never be executed.
> So the simplest way to fix this is that we always recounting the version map in registerDatanode
since it is not a heavy operation.



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