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https://issues.apache.org/jira/browse/HDFS-13399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16459341#comment-16459341
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Konstantin Shvachko edited comment on HDFS-13399 at 5/1/18 12:49 AM:
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Spent a lot of time on this and finally realized what is the problem here.
You are trying to convert {{ConfiguredFailoverProxyProvider}} into an observer
proxy provider, which is not what we want. We want all existing proxy providers
to work exactly as they are without {{AlignmentContext}}.
And we want to create a new proxy provider, which has the
{{AlignmentContext}}. Such provider will probably use a new factory, and will
use new {{createProxy()}} methods, which will propagate {{AlignmentContext}}
into {{RPCEngine}}(s) etc. This is targeted in HDFS-12976. Until then we cannot
even build a test for that.
Here are some more thoughts:
# {{DFSClient}} should not be a holder of {{alignmentContext}} member. It
should be a part of the {{StandbyReadProxyProvider}}. Proxy providers are in
1-1 mapping with clients, so it is the same thing.
# {{alignmentContext}} in {{Invoker}} of RPC engine is probably unavoidable,
mostly because we cannot change signature of {{invoke()}} call.
# For {{ipc.Client}} it is better to move {{alignmentContext}} from {{Call}}
into {{Connection}}, and set it in {{sendRpcRequest(Call, AlignmentContext)}}
rather than in the constructor. I can send you a patch for that.
I don't know if 2 and 3 belong to this jira or to HDFS-12976. In any case
removing static {{AlignmentContext}} from {{Client}} still makes sense. Only
your tests will not work until {{StandbyReadProxyProvider}} is introduced. Hold
on to them until then.
was (Author: shv):
Spent a lot of time on this and finally realized what is the problem here.
You are trying to convert {{ConfiguredFailoverProxyProvider}} into an observer
proxy provider, which is not what we want. We want all existing proxy providers
to work exactly as they are without {{AlignmentContext}}.
And we want to create a new proxy provider, which has the {{AlignmentContext}}.
Such provider will probably use a new factory, and will use new
{{createProxy()}} methods, which will propagate {{AlignmentContext}} into
{{RPCEngine}}(s) etc. This is targeted in HDFS-12976. Until then we cannot even
build a test for that.
Here are some more thoughts:
# {{DFSClient}} should not be a holder of {{alignmentContext}} member. It
should be a part of the {{StandbyReadProxyProvider}}. Proxy providers are in
1-1 mapping with clients, so it is the same thing.
# {{alignmentContext}} in {{Invoker}} of RPC engine is probably unavoidable,
mostly because we cannot change signature of {{invoke()}} call.
# For {{ipc.Client}} it is better to move {{alignmentContext}} from {{Call}}
into {{Connection}}, and set it in sendRpcRequest(Call, AlignmentContext)}}
rather than in the constructor. I can send you a patch for that.
I don't know if 2 and 3 belong to this jira or to HDFS-12976. In any case
removing static {{AlignmentContext}} from {{Client}} still makes sense. Only
your tests will not work until {{StandbyReadProxyProvider}} is introduced. Hold
on to them until then.
> Make Client field AlignmentContext non-static.
> ----------------------------------------------
>
> Key: HDFS-13399
> URL: https://issues.apache.org/jira/browse/HDFS-13399
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: HDFS-12943
> Reporter: Plamen Jeliazkov
> Assignee: Plamen Jeliazkov
> Priority: Major
> Attachments: HDFS-13399-HDFS-12943.000.patch,
> HDFS-13399-HDFS-12943.001.patch, HDFS-13399-HDFS-12943.002.patch,
> HDFS-13399-HDFS-12943.003.patch, HDFS-13399-HDFS-12943.004.patch,
> HDFS-13399-HDFS-12943.005.patch
>
>
> In HDFS-12977, DFSClient's constructor was altered to make use of a new
> static method in Client that allowed one to set an AlignmentContext. This
> work is to remove that static field and make each DFSClient pass it's
> AlignmentContext down to the proxy Call level.
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