PHP MapScript hangs or performance degradation

[Doug]

No ideas at all, anyone?

Doug wrote:
> We've got a PHP MapScript application that seems to regularly hang or at
> least
> start responding *very* slowly.
>
> We're now at MapServer/MapScript 4.2.5 (have tried several previous fix
> levels), with PHP 4.3.8 (cgi), PostgreSQL 7.4.3, PostGIS 0.8.2, Apache
> 2.0.51,
> Fedora Core 2 SMP (Dual CPU 2GHz P4).
>
> Our MapScript basically does a map->draw(), followed by a couple of
> queryByRect() on non-shown layers, manual point->draw()s with custom,
> numbered
> labels, then a map->save().  (Somebody else wrote the code, so I'm
> trying to
> summarize my understanding the best I can in his absence.)
>
> Most of the time, this code seems to work fine and respond decently,
> although
> never "fast" for the particular locations that have lots of individual
> points
> to be numbered.
>
> When things are "normal", I can see one or two active php processes at any
> given point in time, none of which are older than the current minute.
> According to the "top" command, each such process does seem to use 100% of
> (one of?) the CPU while it's running, but that doesn't seem to prevent the
> system from otherwise responding normally.
>
> But fairly regularly, the php processes, and their owning httpd processes,
> start stacking up and not finishing or going away.  When this happens,
> queries
> to the php scripts start timing out and writing errors to Apache's stderr:
>
> [Thu Oct 21 16:47:30 2004] [error] [client 32.83.226.185] PHP Fatal error:
> Maximum execution time of 30 seconds exceeded in
> /var/www/html/offender/map.php on line 87
>
> (Line 87 is the map->draw() call)
>
> When this happens, *sometimes* the problem seems to eventually fix itself
> where the scripts start responding normally again.  But often the only way
> we're able to fix the problem is by stopping and re-starting Apache.
>
> One other interesting symptom is that even when these errors start
> occurring,
> some queries, those that are faster, seem to still work, and at a normal
> speed.  The slower ones don't come back at all.
>
> It acts like there's a resource deadlock or bottleneck somewhere, but I
> can't
> imagine a place which would block some queries and not others.
>
> Oh - the layers that we let map->draw() handle are in shapefiles.  The
> layers
> that we queryByRect() are in PostgreS/PostGIS.
>
> So, first, has anyone seen these kinds of symptoms before?  Is there some
> obvious problem they indicate?  If not, is there some obvious problem in
> the
> flow/configuration/algorithm I've described?
>
> I appreciate any help the community can offer.  We're currently having to
> recycle Apache 3-5 times per day because of these problems.
>
> Doug
>
>