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From "Sylvain Lebresne (JIRA)" <>
Subject [jira] [Created] (CASSANDRA-4480) Binary protocol: adds events push
Date Wed, 01 Aug 2012 19:18:02 GMT
Sylvain Lebresne created CASSANDRA-4480:

             Summary: Binary protocol: adds events push 
                 Key: CASSANDRA-4480
             Project: Cassandra
          Issue Type: Improvement
            Reporter: Sylvain Lebresne
            Assignee: Sylvain Lebresne
            Priority: Minor
             Fix For: 1.2

Clients needs to know about a number of cluster changes (new/removed nodes typically) to function
properly. With the binary protocol we could start pushing such events to the clients directly.

The basic idea would be that a client would register to a number of events and would then
receive notifications when those happened. I could at least the following events be useful
to clients:
* Addition and removal of nodes
* Schema changes (otherwise clients would have to pull schema all the time to know that say
a new column has been added)
* node up/dow events (down events might not be too useful, but up events could be helpful).

The main problem I can see with that is that we want to make it clear that clients are supposed
to register for events on only one or two of their connections (total, not per-host), otherwise
it'll be just flooding. One solution to make it much more unlikely that this happen could
be to distinguish two kinds of connections: Data and Control (could just a simple flag with
the startup message for instance). Data connections would not allow registering to events
and Control ones would allow it but wouldn't allow queries. I.e. clients would have to dedicate
a connection to those events, but that's likely the only sane way to do it anyway.

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