[mapserver-dev] Mapserver causes too many open files error

[Lime, Steve D (MNIT)]

The former is certainly simpler. How expensive is setting up and clearing out the cache? Probably should look at Thomas’ RFC on the topic.

From: mapserver-dev [mailto:mapserver-dev-bounces at lists.osgeo.org] On Behalf Of Tamas Szekeres
Sent: Sunday, November 26, 2017 2:01 PM
To: mapserver-dev at lists.osgeo.org
Subject: [mapserver-dev] Mapserver causes too many open files error

Hi Devs,

We experienced an issue with mapserver 7.x (comparing to 6.x) that it causes too many open file handles in a multi-threaded environment. Actually the process is using the ASP.NET<http://ASP.NET> backend where the web requests are served through the ASP.NET<http://ASP.NET> worker process by using a thread pool, and the process should be considered as a long running process, where msCleanup is not being called regularly.

By looking into the code the issue should probably be dedicated to the global font cache approach implemented in mapserver 7. Since freetype keeps the font files open, we get the number of fonts used in the mapfile multiplied with the thread pool size which may exceed the number of stdio open file handle limit as per https://msdn.microsoft.com/en-us/library/kdfaxaay(v=vs.140).aspx

With the former approach (ie. 6.x) the font cache was implemented in the renderers and the cache cleanup was happening on the renderer cleanup in msFreeOutputFormat/msFreeMap.

Do you have any suggestions about a proper workaround to this?

I might think that we should either bind the font cache to each map objects (like earlier) or use a single common font cache for the entire process. I would probably prefer the first one as soon as we want to clean up every resources what a rendering session allocates.

Thanks,

Tamas


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