[MapProxy] fast 0 byte responses in stead of tiles

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[MapProxy] fast 0 byte responses in stead of tiles

Steven Ottens
Hi,

I've been asked to investigate why a MapProxy setup sometimes fails to
deliver tiles. It is mapproxy 1.9 on a VMware server with windows server
2012 and network attached storage. It is (obviously) not my setup, nor
well documented :( but what I can see it is running as a windows service
using cherrypy and python2.7

All the layers are mbtile-caches looking at Geoserver WMS (which runs
fine) and they are usually fast and I don't see any heavy server load,
nor is it running out of memory.

However every now and then mapproxy stops delivering the actual tiles,
but instead delivers within ~20ms an empty tile of 0 bytes. The logs
seem to be fine, but I'm not entirely sure where I should be looking.
Once I restart mapproxy all is fine again.

So the question is what might cause mapproxy to deliver empty tiles for
valid requests, in stead of error messages/log messages?

Cheers,

Steven

BTW. I understand upgrading to a newer version should be a first step,
but apart from the fact that I don't know (yet) how to upgrade a windows
service, I don't like to blindly upgrade the software without
understanding the root cause of the problem

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Re: [MapProxy] fast 0 byte responses in stead of tiles

Travis Kirstine
Hard to say what the issue is,  I would test the service using the mapproxy-util serve-develop tool in debug mode and watch for errors.

mapproxy-util serve-develop -b myserver.com:8585 mapproxy.yaml --debug

Go to the demo site myserver.com:8585 and turn on the browsers developer tools and try to generate errors

My guess is either it failed to get the image from the WMS or failed to write it to the mbtiles cache due to sqllite table locking.



On Wed, 23 Oct 2019 at 06:01, Steven Ottens <[hidden email]> wrote:
Hi,

I've been asked to investigate why a MapProxy setup sometimes fails to
deliver tiles. It is mapproxy 1.9 on a VMware server with windows server
2012 and network attached storage. It is (obviously) not my setup, nor
well documented :( but what I can see it is running as a windows service
using cherrypy and python2.7

All the layers are mbtile-caches looking at Geoserver WMS (which runs
fine) and they are usually fast and I don't see any heavy server load,
nor is it running out of memory.

However every now and then mapproxy stops delivering the actual tiles,
but instead delivers within ~20ms an empty tile of 0 bytes. The logs
seem to be fine, but I'm not entirely sure where I should be looking.
Once I restart mapproxy all is fine again.

So the question is what might cause mapproxy to deliver empty tiles for
valid requests, in stead of error messages/log messages?

Cheers,

Steven

BTW. I understand upgrading to a newer version should be a first step,
but apart from the fact that I don't know (yet) how to upgrade a windows
service, I don't like to blindly upgrade the software without
understanding the root cause of the problem

_______________________________________________
MapProxy mailing list
[hidden email]
https://lists.osgeo.org/mailman/listinfo/mapproxy

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[hidden email]
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Re: [MapProxy] fast 0 byte responses in stead of tiles

Steven Ottens

Thanks, will try that. 

But the problem is not that certain requests fail, but that after a certain point all requests fail; the ones that I'm a 100% sure are valid and cached in the sqlite, also all the layers fail at that point.

So something trigger Mapproxy to deliver empty tiles to all the requests, but since I don't know what causes the failure it is also hard to trigger it.


On 23-10-19 22:06, Travis Kirstine wrote:
Hard to say what the issue is,  I would test the service using the mapproxy-util serve-develop tool in debug mode and watch for errors.

mapproxy-util serve-develop -b myserver.com:8585 mapproxy.yaml --debug

Go to the demo site myserver.com:8585 and turn on the browsers developer tools and try to generate errors

My guess is either it failed to get the image from the WMS or failed to write it to the mbtiles cache due to sqllite table locking.



On Wed, 23 Oct 2019 at 06:01, Steven Ottens <[hidden email]> wrote:
Hi,

I've been asked to investigate why a MapProxy setup sometimes fails to
deliver tiles. It is mapproxy 1.9 on a VMware server with windows server
2012 and network attached storage. It is (obviously) not my setup, nor
well documented :( but what I can see it is running as a windows service
using cherrypy and python2.7

All the layers are mbtile-caches looking at Geoserver WMS (which runs
fine) and they are usually fast and I don't see any heavy server load,
nor is it running out of memory.

However every now and then mapproxy stops delivering the actual tiles,
but instead delivers within ~20ms an empty tile of 0 bytes. The logs
seem to be fine, but I'm not entirely sure where I should be looking.
Once I restart mapproxy all is fine again.

So the question is what might cause mapproxy to deliver empty tiles for
valid requests, in stead of error messages/log messages?

Cheers,

Steven

BTW. I understand upgrading to a newer version should be a first step,
but apart from the fact that I don't know (yet) how to upgrade a windows
service, I don't like to blindly upgrade the software without
understanding the root cause of the problem

_______________________________________________
MapProxy mailing list
[hidden email]
https://lists.osgeo.org/mailman/listinfo/mapproxy

_______________________________________________
MapProxy mailing list
[hidden email]
https://lists.osgeo.org/mailman/listinfo/mapproxy