Sylvain Lebresne created CASSANDRA-4480:
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Summary: Binary protocol: adds events push
Key: CASSANDRA-4480
URL: https://issues.apache.org/jira/browse/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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