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https://issues.apache.org/jira/browse/CASSANDRA-8789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14512587#comment-14512587
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Benedict edited comment on CASSANDRA-8789 at 4/25/15 4:50 PM:
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bq. Gossip always contended with mutation *responses* and read responses.
I suspect there may be an issue with nomenclature here. These statements made
by Ariel are both true, but the internal nomenclature for both of these is
REQUEST_RESPONSE. But to further clarify, the distinction has never been
command/data, but between command/acknowledgement. Where acknowledgement in the
case of a read request includes the entire data for serving that read request.
was (Author: benedict):
bq. Gossip always contended with mutation *responses* and read responses.
I suspect there may be an issue with nomenclature here. These statements made
by Ariel are both true, but the internal nomenclature for both of these is
REQUEST_RESPONSE.
> OutboundTcpConnectionPool should route messages to sockets by size not type
> ---------------------------------------------------------------------------
>
> Key: CASSANDRA-8789
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8789
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Ariel Weisberg
> Assignee: Ariel Weisberg
> Fix For: 3.0
>
> Attachments: 8789.diff
>
>
> I was looking at this trying to understand what messages flow over which
> connection.
> For reads the request goes out over the command connection and the response
> comes back over the ack connection.
> For writes the request goes out over the command connection and the response
> comes back over the command connection.
> Reads get a dedicated socket for responses. Mutation commands and responses
> both travel over the same socket along with read requests.
> Sockets are used uni-directional so there are actually four sockets in play
> and four threads at each node (2 inbounded, 2 outbound).
> CASSANDRA-488 doesn't leave a record of what the impact of this change was.
> If someone remembers what situations were made better it would be good to
> know.
> I am not clear on when/how this is helpful. The consumer side shouldn't be
> blocking so the only head of line blocking issue is the time it takes to
> transfer data over the wire.
> If message size is the cause of blocking issues then the current design mixes
> small messages and large messages on the same connection retaining the head
> of line blocking.
> Read requests share the same connection as write requests (which are large),
> and write acknowledgments (which are small) share the same connections as
> write requests. The only winner is read acknowledgements.
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