Re: Load testing across 2 machines

On Sun, 09 Apr 2006 17:00:14 +0100
Simon Riggs <simon@2ndquadrant.com> wrote:

> On Sat, 2006-04-08 at 15:10 +0100, Gavin Hamill wrote:
>
> > SELECTS go to *both* live and test, but only the answers from live
> > are sent back to clients - the answers from test are discarded...
>
> Put log_min_duration_statement = 0 so all SELECTs go to the log.
>
> Sniff the live log for SELECT statements (plus their live durations),
> then route those same statements to the dev box and get a timing from
> there also. That way you'll be able to do this without any C coding,
> plus you'll have both the live and test elapsed times as a comparison.

Ah, having eaten and had my brain finally switch on, I've realised that
there's an unfortunate flaw in the plan; only a single process will be
executing the SELECT-log which pretty much defeats the purpose of the
experiment to simulate identical load patterns on both machines.

I might be wrong, but if I just end up grepping for 'SELECT' then
feeding the results into psql, then only a single connection will be
made to the test server, and all queries will be processed serially on
a single CPU, no?

Cheers,
Gavin.