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From "Patrick McFadin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9193) Facility to write dynamic code to selectively trigger trace or log for queries
Date Wed, 15 Apr 2015 00:41:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14495451#comment-14495451
] 

Patrick McFadin commented on CASSANDRA-9193:
--------------------------------------------

I don't think this is too far away from CASSANDRA-7526 with addition of metadata. 

I have used something similar on F5 network appliances in a feature called iRules. It was
a feature to run a trigger based on a network event. My favorite part was how the user specified
actions. You assigned a rule to a network port and wrote a collection of actions on events.
If I were to translate that to a Cassandra use case, you would assign a rule set to a Table.
Inside the rule set would be actions on events. Something like this pseudo code:

{
   onRequest {
      if(consistencyLevel == ALL) {
         log.WARN ("Dude. Seriously?")
      }
   }

   onResponse {
      if (consistencyError) {
         ...do something...
      }

      if (data.size > 500000) {
         log.WARN ("Dude. Seriously?")
      }
   }
}

Not proposing syntax but you get the idea. Could be a very powerful tool for troubleshooting
and insight. 



> Facility to write dynamic code to selectively trigger trace or log for queries
> ------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-9193
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9193
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Matt Stump
>
> I want the equivalent of dtrace for Cassandra. I want the ability to intercept a query
with a dynamic script (assume JS) and based on logic in that script trigger the statement
for trace or logging. 
> Examples 
> - Trace only INSERT statements to a particular CF. 
> - Trace statements for a particular partition or consistency level.
> - Log statements that fail to reach the desired consistency for read or write.
> - Log If the request size for read or write exceeds some threshold
> At some point in the future it would be helpful to also do things such as log partitions
greater than X bytes or Z cells when performing compaction. Essentially be able to inject
custom code dynamically without a reboot to the different stages of C*. 
> The code should be executed synchronously as part of the monitored task, but we should
provide the ability to log or execute CQL asynchronously from the provided API.
> Further down the line we could use this functionality to modify/rewrite requests or tasks
dynamically.



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