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https://issues.apache.org/jira/browse/CASSANDRA-1311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12975311#action_12975311
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David Erickson edited comment on CASSANDRA-1311 at 12/27/10 2:00 PM:
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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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