[mapserver-users] Errors when using SLDs under stress test

[Sebastián Cruz]

On Mon, 2011-11-28 at 23:20 -0500, Daniel Morissette wrote:
> On 11-11-28 10:04 PM, Sebastián Cruz wrote:
> >
> > AFAIK from my configuration, every client request triggers a Mapserver
> > process to "download" the SLD from the URL specified and that in turn
> > makes it "download" every image in the ExternalGraphic URL. When there
> > are up to 10 concurrent requests everything is working fine, but when
> > that goes up to 20 or 40 concurrent requests the errors appear. You can
> > see this in this reflected in JMeter's result table [5]. Consider that
> > the SLD file and the images are served through the same Apache that's
> > serving Mapserver as FastCGI, so the "downloading" of info necessary to
> > draw the map involves network connections to the same host.
> >
> > I'm guessing that maybe Mapserver and/or Apache are running out of file
> > descriptors? Or available sockets? Or just hitting some limit of that
> > kind that I'm not aware of. Am I trying to do this correctly?
> >
> 
> It may be that you are hitting Apache's MaxClients, and because of the 
> recursive downloads (MapServer initiating downloads to the same Apache 
> that called it) you eventually end up in a deadlock situation where all 
> your MapServer instances are holding Apache client connections while 
> they wait for more clients connections to be available to complete all 
> their own downloads.
> 
> If that's the case then you should see errors about MaxClients being 
> reached in your Apache error log.

I have no records about MaxClients on Apache's logs. I've also tried
upping the limits to reach 1500 clients but the behaviour is the same.

Anyway, the deadlock scenario you mention is what I suspect. Could it be
happening in some other form?

Thanks!

-- 
Sebastián Cruz
default50 at gmail.com
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