[MapProxy] "Stuck" requests and Apache
penorman at mac.com
Mon Nov 11 11:28:33 PST 2013
I recently deployed mapproxy 1.6.0 with two layers and set up a demo
page showing those two layers at http://tile.paulnorman.ca/kelowna.html.
Last night I was having issues with apache becoming nonresponsive, so I
switched to the prefork MPM as suggested in the mapproxy documentation,
then put out a mailing list announcement.
This morning I woke up and checked /server-status on the machine. I see
there are 91 requests in the "sending reply" stage, all which have been
for at least 1 hour, and all on the overlay layer.
Two typical lines are
Srv PID Acc M CPU SS Req Conn Child Slot Client VHost
122-0 28898 0/17/17 W 0.32 5948 0 0.0 0.56 0.56 xxx
tile.paulnorman.ca GET /kelowna_overlay/20/176471/356076.
128-0 29331 0/0/0 W 0.00 5940 0 0.0 0.00 0.00 yyy
tile.paulnorman.ca GET /kelowna_overlay/18/44117/89020.pn
My config has two layers, an imagery layer and an overlay layer. The
relevant source definitions are
The imagery layer is handled by mapserver with the source data coming
from an ECW and appears to be working without problems. The overlay layer
is rendered by mapnik with the data coming from postgresql 9.3 + postgis
Mapproxy is deployed with Apache/2.2.22 (Ubuntu) mod_wsgi/3.3 Python/2.7.3
The machine is currently idle with a load average <0.1, CPU usage <0.5%
and no measurable IO.
`ps aux' shows 102 processes, all <0.5% CPU, 0.5% memory, assorted start
The machine has 8GB RAM and an i3 processor with 4 threads and 2 cores.
The only differences I can see between the two layers are
- mapnik vs mapserver
- png8 vs 32-bit PNGA
I'm going to try adjusting concurrent_requests and see if that helps
matters, but otherwise I'm out of ideas.
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