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https://issues.apache.org/jira/browse/HDFS-12976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16524440#comment-16524440
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Konstantin Shvachko commented on HDFS-12976:
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Hey [~csun]. Took me some time, sorry.
So when saying that {{ConfiguredFailoverProxyProvider}} doesn't have notion of
NameNode in HDFS-13687, I meant that the protocol {{<T>}} is completely
obscured from it. The proxy does not know that it is talking to NameNodes and
therefore cannot call {{getServiceStatus()}} or any other NN RPCs. So we should
probably add some interfaces to the type, so that we could actually make the
calls.
I played a bit with your patch. Attaching v. 004 as illustration only, sure
enough it needs more work.
# I added {{<T extends HAServiceProtocol>}} so that we could call
{{getServiceStatus()}} on existing proxies.
# Added {{alignmentContext}} it is needed for passing transaction ids.
# Probably need to write a new implementation of
{{createProxyWithAlignmentContext()}} to avoid nasty casting, etc.
I was also thinking that {{ObserverReadProxyProvider}} now heavily relies on
{{ConfiguredFailoverProxyProvider}}. But there are use cases for
{{IPFailoverProxyProvider}} as well. Would be nice if we could combine them.
But let's first finish this.
> Introduce ObserverReadProxyProvider
> -----------------------------------
>
> Key: HDFS-12976
> URL: https://issues.apache.org/jira/browse/HDFS-12976
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Reporter: Konstantin Shvachko
> Assignee: Chao Sun
> Priority: Major
> Attachments: HDFS-12976-HDFS-12943.000.patch,
> HDFS-12976-HDFS-12943.001.patch, HDFS-12976-HDFS-12943.002.patch,
> HDFS-12976-HDFS-12943.003.patch, HDFS-12976-HDFS-12943.004.patch,
> HDFS-12976.WIP.patch
>
>
> {{StandbyReadProxyProvider}} should implement {{FailoverProxyProvider}}
> interface and be able to submit read requests to ANN and SBN(s).
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