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https://issues.apache.org/jira/browse/HADOOP-4096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12628822#action_12628822
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George Porter commented on HADOOP-4096:
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Yes, I meant the Datanode transfer protocol described in
DataNode.java, lines 916- 995. Sorry for the confusion.
Thanks,
George
> Support for options within the Datanode Transfer protocol
> ---------------------------------------------------------
>
> Key: HADOOP-4096
> URL: https://issues.apache.org/jira/browse/HADOOP-4096
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs
> Reporter: George Porter
>
> This proposal is to extend the DataNode Transfer protocol (described in
> DataNode.java lines 916 - 995) to support "options", in the spirit of IP or
> TCP options. This should make this protocol more extensible, allowing the
> client to include metadata along with commands. This would support efforts
> to include end-to-end and causal tracing into Hadoop, and hopefully other
> efforts as well.
> Options should have a type, and be of variable length. It should be possible
> to include multiple options along with each datanode command. The option
> should apply to both the command and any data that is part of the command.
> If the datanode does not understand a given option, it should ignore it.
> Options should be sent end-to-end through intermediate datanodes, if
> necessary. For example, if an OP_WRITE_BLOCK command is pipelined through
> several machines, the options should be sent along the pipeline. Nodes along
> the pipeline may modify the options.
> BTW, If HADOOP-4005 (concrete datanode protocol) is implemented, then it
> should solve this problem by simply letting the user add state to the
> concrete protocol class.
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