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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1311) Support (asynchronous) triggers
Date Fri, 31 Dec 2010 18:08:56 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12976313#action_12976313
] 

Jonathan Ellis commented on CASSANDRA-1311:
-------------------------------------------

bq. if the write has been acknowledged, the client can be sure the trigger will be executed
(at least once)

the problem is with the inverse scenario:

if a write *has not* been acknowledged, it may still have succeeded in the base columnfamily
(Table.apply) but not the trigger (TriggerSlave.storeDanglingTrigger).  So, because [from
my look at the code at least] trigger execution is not part of log replay, you can end up
with data that never had the trigger fire.

In this situation, the client will see a TimedOutException, which it is important to remember
is NOT the same as failure; it means instead "we don't know what happened."

> 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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