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https://issues.apache.org/jira/browse/HADOOP-4386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12639097#action_12639097
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Doug Cutting commented on HADOOP-4386:
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> Isn't it enough to require that an asyncRPC is more like a sendMsg, in the
> sense that it sends a message without expecting any response?
If you send an async request to read some data, you want the data, but you
don't want to block. For example, during the shuffle, a tasktracker might send
requests to many other tasktrackers to read map outputs, but does not want to
block waiting for that data to be returned. Rather it could send requests in
one thread and receive response data in another.
For writes, the client typically wants an ack response that data was
successfully written.
Sends w/o response might be useful for status updates, where an error would be
ignored, but in most other cases I think we do care about the response.
> RPC support for large data transfers.
> -------------------------------------
>
> Key: HADOOP-4386
> URL: https://issues.apache.org/jira/browse/HADOOP-4386
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs, ipc
> Reporter: Raghu Angadi
>
> Currently HDFS has a socket level protocol for serving HDFS data to clients.
> Clients do not use RPCs to read or write data. Fundamentally there is no
> reason why this data transfer can not use RPCs.
> This jira is place holder for any porting Datanode transfers to RPC. This
> topic has been discussed in varying detail many times, the latest being in
> the context of HADOOP-3856. There are quite a few issues to be resolved both
> at API level and at implementation level.
> We should probably copy some of the comments from HADOOP-3856 to here.
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