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From "David Alves (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1123) Allow tracing query details
Date Mon, 27 Aug 2012 23:38:08 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13442806#comment-13442806
] 

David Alves commented on CASSANDRA-1123:
----------------------------------------

bq. Hmm, can we do something clever like http://stackoverflow.com/questions/4046228/log4j-excluding-the-logging-of-some-classes
to just log o.a.c.tracing to stdout + R so we don't just error out silently when something
goes wrong w/ tracing?

We can, I'm taking care of that on the next patch along with nodetool. Although, just to be
clear, using a bare TPE is still the way to go because we still wouldn't want to propagate
tracing to tracing mutation threads.

nice job on the DTPE cleanup.
                
> 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: David Alves
>             Fix For: 1.2.0 beta 1
>
>         Attachments: 1123-3.patch.gz, 1123.patch, 1123.patch, 1123.patch, 1123.patch,
1123-v6.txt
>
>
> 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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