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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4480) Binary protocol: adds events push
Date Mon, 03 Sep 2012 18:12:07 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13447375#comment-13447375
] 

Sylvain Lebresne commented on CASSANDRA-4480:
---------------------------------------------

bq. optional unless you want push features?

That one.

bq. a driver which, for whatever reason, only needs a single connection at a time to the cluster

That's not a bad argument. Though I don't know if such tools will really care about push events.

I don't know, I do like the idea of making it harder to do the wrong thing, but maybe in that
case it's not worth it and good documentation would be good enough. Jonathan, an opinion on
the matter to have an odd number of opinions?

bq. The main downside I see to making the change is that it would use up more of your time

That's obviously a big big downside, but I'm willing to not take it into account as long as
we reach what we collectively decide is the best option.
                
> 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: 1.2.0
>
>         Attachments: 4480.txt
>
>
> 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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