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https://issues.apache.org/jira/browse/CASSANDRA-9193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14514386#comment-14514386
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Sylvain Lebresne commented on CASSANDRA-9193:
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bq. The consumer of this facility would primarily be advanced users that are
attempting to gain visibility into Cassandra internals
I don't entirely disagree, but at the same time, the more easy this is to use,
the more likely this will be to people. In particular, tying this too much to
the internals will imo make it painful in practice because those can change a
lot and without warnings.
bq. I want to back port this to older versions of Cassandra \[...\] The reason
being is that the field needs this now and it's going to take a while before
whatever branch of 3.X this lands in becomes readily deployed.
While I understand the need, this is pretty much out of scope for anyting
pre-3.0. I also really think for anything user-facing like this, we should try
to make it as clean, generally useful and easy to maintain moving forward as
possible, and this even if this mean taking more time to deliver it.
> 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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