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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1123) Allow tracing query details
Date Mon, 23 Jul 2012 01:40:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13420385#comment-13420385
] 

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

bq. I think we could get away with storing the number and size of both argument and results
in the "coordinator" node and store the actual size of the whole row (num and size of cols)
in the nodes that are performing the reads.

That would be adequate in this instance, but if we log the arguments we arm ourselves against
the scenarios we *didn't* think of ahead of time, as well as the ones we did.

I think it's straightforward what we should do here.  Implement parameter logging and if sometime
down the road someone comes along and says "I really want to trace my application but I can't
afford to log parameters" we (or he) can add some way to make it optional.  Until then YAGNI
applies.
                
> 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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