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https://issues.apache.org/jira/browse/CASSANDRA-197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12712293#action_12712293
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Jun Rao commented on CASSANDRA-197:
-----------------------------------
I am not sure if we should make client a member of the cluster and receive all
the gossiped messages. For request routing, the client only cares about the
event of adding/removing nodes, which is infrequent. Making client a member of
the cluster exposes it to way too many irrelevant messages. An out-of-date
cached ring map only affects performance, not correctness. In practice, it's
probably good enough for each client to simply refresh its cached ring map, say
once per hour.
As for that the client has to include the server code and config file, I don't
think it's a big deal. The server jar is already needed for java clients today
and a client has to be aware of the thrift port. Further, each client has to
explicitly maintain a list of cassandra servers to connect to (RingCache
obviates that).
It is a bit awkward to expose the getRIngMap api in thrift, since only the
client library really needs to see it, not the actual client code. However,
thrift seems to be the only simple way for a client to talk to the server.
MessageService is too heavy to use just for infrequent server calls. Could we
just document that the api is not intended for direct client usage?
> 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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