[ILUG] Slightly OT: Suggestions for performance testing PHP website

[Phil Bradley]

Hi all,

I have a site written in PHP/Apache/Postgres/Windows (I know, they're a 
non-profit and Windows is what they were given) which will be going live 
shortly. It will be reasonably high profile, and we expect at least a 
couple of thousand visitors on the first day and a sustained rate of 
maybe 1000 vistors per day (I'm stabbing in the dark a little on the 
numbers).

I've gone through sourceforge looking for something that will help me 
with characterising the performance of the system under load but I've 
had little success so far.

What I'd like to see is how the response time for a given sample page 
varies with the number of simultaneous users making requests. I envisage 
something like a HTTP client with "n" threads/processes, repeatedly 
fetching from the server under test (maybe with a random wait time 
between fetches to simulate human behaviour). They might be re-fetching 
the same content repeatedly or maybe drawing sequentially/randomly from 
a set of test URLs. So a system configured to simulate 10 users would 
consist of 10 threads repeatedly fetching from the server. This would 
then be repeated  for a range of values of "n".

If my mental model is correct, I would expect the response time to be 
invariant with respect to "n" initially. At some point, as the system 
encounters bottlenecks, requests would start to get queued and the 
response time would then be a linear function of "n". Obviously, 
there'll be a point at which the network/server is just saturated and 
the numbers will cease to be meaningful, reaching that point is also 
useful as it would indicate the level of traffic at which the site 
becomes useless.

So, my questions are:
1. Does this seem like a reasonable testing methodology
2. Is there a tool the can implement this type of methodology?

I've tried out OpenSTA, JMeter and WebLOAD but they don't quite seem to 
do this. When you eliminate alpha projects that haven't been updated 
since 2001 from sourceforge, there are too many left. I can probably 
script something in perl but if there's something pre-rolled, I'd like 
to avoid the overhead of having to code it myself.

Thanks,
  -Phil