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.

--
Daniel Morissette
http://www.mapgears.com/
Provider of Professional MapServer Support since 2000

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