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https://issues.apache.org/jira/browse/HDFS-14660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16888103#comment-16888103
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Ayush Saxena commented on HDFS-14660:
-------------------------------------
Thanx [~xkrogen]
{quote}Since all negative state IDs are invalid, perhaps we can define a
special constant value (-2 ?) for indicating that the observer should serve the
request without state checking, and clients which haven't set an ID at all (-1)
can be rejected outright.
{quote}
Seems fair enough to me. This way we could provide a way to get the old
behavior too.
> [SBN Read] ObserverNameNode should throw StandbyException for requests not
> from ObserverProxyProvider
> -----------------------------------------------------------------------------------------------------
>
> Key: HDFS-14660
> URL: https://issues.apache.org/jira/browse/HDFS-14660
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Chao Sun
> Assignee: Chao Sun
> Priority: Major
>
> In a HDFS HA cluster with consistent reads enabled (HDFS-12943), clients
> could be using either {{ObserverReadProxyProvider}},
> {{ConfiguredProxyProvider}}, or something else. Since observer is just a
> special type of SBN and we allow transitions between them, a client NOT using
> {{ObserverReadProxyProvider}} will need to have
> {{dfs.ha.namenodes.<nameservice>}} include all NameNodes in the cluster, and
> therefore, it may send request to a observer node.
> For this case, we should check whether the {{stateId}} in the incoming RPC
> header is set or not, and throw an {{StandbyException}} when it is not.
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