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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Created: (CASSANDRA-1123) Allow tracing query details
Date Mon, 24 May 2010 21:54:25 GMT
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
             Fix For: 0.7


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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