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Date: Tue, 4 Sep 2012 05:06:07 +1100 (NCT)
From: "paul cannon (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-4480) Binary protocol: adds events
 push
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    [ https://issues.apache.org/jira/browse/CASSANDRA-4480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13447372#comment-13447372 ] 

paul cannon commented on CASSANDRA-4480:
----------------------------------------

Just optional unless you want push features. But I think most clients will want push features.
                
> 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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