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From "David Erickson (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (CASSANDRA-1311) Support (asynchronous) triggers
Date Mon, 27 Dec 2010 19:01:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12975311#action_12975311
] 

David Erickson edited comment on CASSANDRA-1311 at 12/27/10 2:00 PM:
---------------------------------------------------------------------

I haven't dug into this implementation of triggers, but a use case could be using Cassandra
as a shared communication bus amongst distributed nodes.  If node 1 makes a change to its
Cassandra instance, the data then propagates to the other Cassandra instances, and the triggers
alert other nodes that a change has been made and they need to do some processing, which is
better than polling for the same changes.  Alternatively the nodes would have to have their
own protocol to alert each other outside of the database layer that changes have been made.

      was (Author: derickso):
    I haven't dug into this implementation of triggers, but the use case we had in mind is
using the database as a shared communication bus amongst distributed nodes.  If node 1 makes
a change to its Cassandra instance, once the data propagates to the other Cassandra instances
the triggers can alert other nodes that a change has been made and they need to do some processing.
 This is much better than polling for changes.  Alternatively the nodes would have to have
their own protocol to alert each other outside of the database layer that changes have been
made.
  
> Support (asynchronous) triggers
> -------------------------------
>
>                 Key: CASSANDRA-1311
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1311
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Contrib
>            Reporter: Maxim Grinev
>             Fix For: 0.8
>
>         Attachments: HOWTO-PatchAndRunTriggerExample-update1.txt, HOWTO-PatchAndRunTriggerExample.txt,
ImplementationDetails-update1.pdf, ImplementationDetails.pdf, trunk-967053.txt, trunk-984391-update1.txt,
trunk-984391-update2.txt
>
>
> Asynchronous triggers is a basic mechanism to implement various use cases of asynchronous
execution of application code at database side. For example to support indexes and materialized
views, online analytics, push-based data propagation.
> Please find the motivation, triggers description and list of applications:
> http://maxgrinev.com/2010/07/23/extending-cassandra-with-asynchronous-triggers/
> An example of using triggers for indexing:
> http://maxgrinev.com/2010/07/23/managing-indexes-in-cassandra-using-async-triggers/
> Implementation details are attached.

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