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From Johnny Miller <johnny.p.mil...@gmail.com>
Subject Re: query tracing
Date Mon, 10 Nov 2014 14:52:41 GMT
Be cautious enabling query tracing. Great tool for dev/testing/diagnosing etc.. - but it does
persist data to the system_traces keyspace with a TTL of 24 hours and will, as a consequence,
consume resources.

http://www.datastax.com/dev/blog/advanced-request-tracing-in-cassandra-1-2 <http://www.datastax.com/dev/blog/advanced-request-tracing-in-cassandra-1-2>


> On 7 Nov 2014, at 20:20, Jonathan Haddad <jon@jonhaddad.com> wrote:
> 
> Personally I've found that using query timing + log aggregation on the client side is
more effective than trying to mess with tracing probability in order to find a single query
which has recently become a problem.  I recommend wrapping your session with something that
can automatically log the statement on a slow query, then use tracing to identify exactly
what happened.  This way finding your problem is not a matter of chance.
> 
> 
> 
> On Fri Nov 07 2014 at 9:41:38 AM Chris Lohfink <clohfink85@gmail.com <mailto:clohfink85@gmail.com>>
wrote:
> It saves a lot of information for each request thats traced so there is significant overhead.
 If you start at a low probability and move it up based on the load impact it will provide
a lot of insight and you can control the cost.
> 
> ---
> Chris Lohfink
> 
> On Fri, Nov 7, 2014 at 11:35 AM, Jimmy Lin <y2klyf+work@gmail.com <mailto:y2klyf+work@gmail.com>>
wrote:
> is there any significant  performance penalty if one turn on Cassandra query tracing,
through DataStax java driver (say, per every query request of some trouble query)?
> 
> More sampling seems better but then doing so may also slow down the system in some other
ways?
> 
> thanks
> 
> 
> 


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