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https://issues.apache.org/jira/browse/CASSANDRA-197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713143#action_12713143
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Jonathan Ellis commented on CASSANDRA-197:
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The problem is "client" in a loose sense means "anything that can add data to
or request data from the system." So each cassandra node can be considered a
"client" of the others which is meaningless.
So to me when I say a "client level api" I strictly mean one we expose via
thrift to processes that are not expected to know anything about the Cassandra
internals. As soon as you say "we should expose this to the client, but it
will need to use (non-thrift) org.apache.cassandra classes and the server .xml
file" then we are in violation of this implicit contract.
So:
No, we should not expose any internals to thrift-based clients. Other "client"
processes based on the server internals can of course make use of those
internals as much as they want, and the best way to do this is to have them use
the existing apis as much as possible rather than adding hacks to shuttle some
of this state from one server process to another via thrift. Using the exising
APIs promotes clean design and avoids other "wheel re-invention" problems as I
described above. ("The server already has perfectly good connection pooling
code; it makes sense to use that instead of creating a separate pooling
mechanism. Nor does it make sense when you are building off the server jars to
go through the extra thrift serialization; make the calls directly via
MessagingService [i.e., storageproxy].")
So having thought things through it is clear to me that my earlier suggestion
("i could see maybe having a call "endpoint_for_key" that gives an ip/port pair
for primary node owning a key") is also a poor one, and I withdraw it.
> Expose ring map to client for more direct access
> ------------------------------------------------
>
> Key: CASSANDRA-197
> URL: https://issues.apache.org/jira/browse/CASSANDRA-197
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Jun Rao
> Assignee: Jun Rao
> Attachments: issue197.patchv1
>
>
> For certain applications, it would be nice if a read is sent to a node that
> owns the data locally. This saves an extra network hop. To do that, a client
> will need to cache the ring map and use it to figure out the nodes owning a
> row.
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