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https://issues.apache.org/jira/browse/SPARK-21703?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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neoremind updated SPARK-21703:
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Description:
After seeing the details of how spark leverage netty, I found one question,
typically RPC message wire format would have a header+payload structure, and
netty uses a TransportFrameDecoder to deal with how to determine a complete
message from remote peer. But after using Wireshark sniffing tool, I found that
the message are sent separately with header and then followed by body, although
this works fine, but for underlying TCP there would be ACK segments sent back
to acknowledge, there might be a little bit redundancy since we can sent them
together and the header are usually very small.
The main reason can be found in MessageWithHeader class, since transferTo
method write tow times for header and body.
Could someone help me understand the background story on how to implement in
such way? Thanks!
was:
After seeing the details of how spark leverage netty, I found one question,
typically RPC message wire format would have a header+payload structure, and
netty uses a TransportFrameDecoder to deal with how to determine a complete
message from remote peer. But after using Wireshark sniffing tool, I found that
the message are sent separately with header and then followed by body, although
this works fine, but for underlying TCP there would be ACK segments sent back
to acknowledge, there might be a little bit redundancy since we can sent them
together and the header are usually very small.
The main reason can be found in MessageWithHeader class, since transferTo
method write tow times for header and body.
Could some one help me understand the background story on how to implement in
such way? Thanks!
> Why RPC message are transferred with header and body separately in TCP frame
> ----------------------------------------------------------------------------
>
> Key: SPARK-21703
> URL: https://issues.apache.org/jira/browse/SPARK-21703
> Project: Spark
> Issue Type: Question
> Components: Spark Core
> Affects Versions: 1.6.0
> Reporter: neoremind
> Priority: Trivial
> Labels: RPC
>
> After seeing the details of how spark leverage netty, I found one question,
> typically RPC message wire format would have a header+payload structure, and
> netty uses a TransportFrameDecoder to deal with how to determine a complete
> message from remote peer. But after using Wireshark sniffing tool, I found
> that the message are sent separately with header and then followed by body,
> although this works fine, but for underlying TCP there would be ACK segments
> sent back to acknowledge, there might be a little bit redundancy since we can
> sent them together and the header are usually very small.
> The main reason can be found in MessageWithHeader class, since transferTo
> method write tow times for header and body.
> Could someone help me understand the background story on how to implement in
> such way? Thanks!
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