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https://issues.apache.org/jira/browse/HDFS-12977?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16396403#comment-16396403
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Konstantin Shvachko commented on HDFS-12977:
--------------------------------------------
Was looking into this and realized the main problem here is that we still set
{{transactionId}} explicitly in {{ipc.Server.setupResponse()}}, which defeats
the purpose of abstracting the state context. Here is a suggestion
# May be a better name for the {{CallStateHandler}} interface would be
{{ServerStateContext}}
#- with abstract method
{code}void updateResponseState(RpcResponseHeaderProto.Builder
responseHeader);{code}
#- Then we should have a class {{NNStateIdContext}} in {{NameNodeRPCServer}},
with the {{namesystem}} as its member, and which sets txId into the header.
# {{ipc.Server}} has additional member {{serverStateContext}}. Then
{{ipc.Server.setupResponse()}} should make a call:
{code}
if(callStateHandler != null)
callStateHandler.updateResponseState(headerBuilder);
{code}
# This should eliminate other changes like adding {{Server.Call.transactionId}}
or changing {{ProtobufRPCEngine.call()}} method.
# We should use {{stateId}} consistently instead of {{transactionId}}.
LMK if it makes sense.
> Add stateId to RPC headers.
> ---------------------------
>
> Key: HDFS-12977
> URL: https://issues.apache.org/jira/browse/HDFS-12977
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ipc, namenode
> Reporter: Konstantin Shvachko
> Assignee: Plamen Jeliazkov
> Priority: Major
> Attachments: HDFS_12977.trunk.001.patch, HDFS_12977.trunk.002.patch,
> HDFS_12977.trunk.003.patch
>
>
> stateId is a new field in the RPC headers of NameNode proto calls.
> stateId is the journal transaction Id, which represents LastSeenId for the
> clients and LastWrittenId for NameNodes. See more in [reads from Standby
> design
> doc|https://issues.apache.org/jira/secure/attachment/12902925/ConsistentReadsFromStandbyNode.pdf].
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