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Date: Fri, 23 Mar 2012 16:17:28 +0000 (UTC)
From: "Jonathan Ellis (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-1123) Allow tracing query details
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    [ https://issues.apache.org/jira/browse/CASSANDRA-1123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13236728#comment-13236728 ] 

Jonathan Ellis commented on CASSANDRA-1123:
-------------------------------------------

That is a good idea, although I'd still like the ability to store results as well (which would let us do always-on sampling of the workload for instance)
                
> Allow tracing query details
> ---------------------------
>
>                 Key: CASSANDRA-1123
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1123
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Aaron Morton
>             Fix For: 1.2
>
>         Attachments: 1123-3.patch.gz
>
>
> In the spirit of CASSANDRA-511, it would be useful to tracing on queries to see where latency is coming from: how long did row cache lookup take?  key search in the index?  merging the data from the sstables?  etc.
> The main difference vs setting debug logging is that debug logging is too big of a hammer; by turning on the flood of logging for everyone, you actually distort the information you're looking for.  This would be something you could set per-query (or more likely per connection).
> We don't need to be as sophisticated as the techniques discussed in the following papers but they are interesting reading:
> http://research.google.com/pubs/pub36356.html
> http://www.usenix.org/events/osdi04/tech/full_papers/barham/barham_html/
> http://www.usenix.org/event/nsdi07/tech/fonseca.html

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