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From "David Alves (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1123) Allow tracing query details
Date Mon, 23 Jul 2012 01:59:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13420392#comment-13420392
] 

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

What should we do wrt to reads then? also store the complete results (what is returned to
the client) and the whole row (required to cover the examples you mentioned), or do we summarize
in that case? In this case not summarizing can be costly (lots of net traffic).


                
> 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
>
>         Attachments: 1123-3.patch.gz, 1123.patch
>
>
> 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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