Hi Bas,


thank you so much for your quick reply.



Here are a few more details. The data source consists mostly of aerial images 
(compressed 100 GB for one Layer). I used map2img to compare the response time 
between Debian 12 - MapServer 8.0.0 and Debian 13 - MapServer 8.4.0 The 
response time was ~ identical. The raster data is embedded in the map file 
using a gdaltindex. This took about 200ms for both systems with default map2img 
BBOX. The database response time for the metadata layer was about 20ms. 
However, when the system is running in production with Apache as an FCGI 
process, the MapServer processes consume more and more RAM up to 2GB / normal 
was 300MB (MapServer 8.0). An FCGI process runs for 60 minutes by default. I 
then reduced this to 10 minutes so that the process would terminate before too 
many processes consumed the available memory. This means that FCGI caching 
isn't working optimally, so the average response time in Apache status isn't 
settling at around 225 ms (Fig. 1), but rather at over 400 ms. Under Debian 12, 
the FCGI MapServer processes didn't consume RAM to this extent.



[cid:[email protected]]

Figure 1: Apache Server Status – average 245.706 ms/request





In my opinion, the problem isn't with PostgreSQL/PostGIS. Furthermore, I 
installed MapServer 8.6 from the backports repository and encountered the same 
behavior. Perhaps the issue lies with the MapServer or Apache-FCGI or 
GDAL-Version?



As a result, Debian 13 with Apache FCGI and MapServer is currently not as 
performant as the previous version.



I could also try installing MapServer version 8.4.0 from the backports on 
Debian 12 to test how this variant behaves.



Best regards,

Steffen



Quelle:

MapServer

https://packages.debian.org/source/bookworm/mapserver (8.0.0)

https://packages.debian.org/source/trixie/mapserver (8.4.0)



Apache2

https://packages.debian.org/bookworm/apache2 (2.4.65-1~deb12u1)

https://packages.debian.org/trixie/apache2  (2.4.65-2)



FCGI

https://packages.debian.org/bookworm/libapache2-mod-fcgid (2.3.9)

https://packages.debian.org/trixie/libapache2-mod-fcgid (2.3.9)



GDAL

https://packages.debian.org/bookworm/gdal-bin (3.6.2+dfsg-1)

https://packages.debian.org/trixie/gdal-bin (3.10.3+dfsg-1)



Posgtres

https://packages.debian.org/bookworm/postgresql-15-postgis-3 (PG 15 – PostGIS 
3.3.2)

https://packages.debian.org/trixie/postgresql-17-postgis-3 ( PG 17 – PostGIS 
3.5.2)













-----Ursprüngliche Nachricht-----
Von: Sebastiaan Couwenberg <[email protected]>
Gesendet: Dienstag, 16. Dezember 2025 13:58
An: Neubauer, Steffen (VermKV) <[email protected]>; 
[email protected]
Betreff: Re: Debian 13 - Apache - FCGI - cgi-mapserver



On 12/16/25 1:15 PM, Neubauer, Steffen (VermKV) via Pkg-grass-devel wrote:

> this week I performed a server migration from Debian 12 to Debian 13 using 
> the Apache2 and MapServer packages.

> Unfortunately, the MapServer behavior wasn't identical in the same 
> configuration.



You upgraded from 8.0.0 to 8.4.0, that's not unexpected.



Nothing on the migration guide springs out, though:



  https://mapserver.org/MIGRATION_GUIDE.html#mapserver-8-0-to-8-2-migration

  https://mapserver.org/MIGRATION_GUIDE.html#mapserver-8-2-to-8-4-migration



> The single MapServer FCGI processes

> were using 15% of the RAM instead of the previous 1.5%. This caused

> the VM's RAM to overflow. Even changing the Apache FCGI parameters

> didn't improve the situation. Additionally, the response time of the WMS 
> request was about 200ms slower because the FCGI performance couldn't be 
> achieved.



I'm using MapServer via MapScript and the system in question has plenty of RAM, 
so I don't have any relevant experience.



The response time can be influenced by changes other than MapServer, prime 
suspect is the data source.



PostGIS and PostgreSQL had many changes between bookworm and trixie as well, 
the PostGIS selectivity has a regression in 3.5 for example:



  https://lists.osgeo.org/pipermail/postgis-users/2025-September/046864.html

  https://trac.osgeo.org/postgis/ticket/5984



> Is there a known memory leak in the Debian 13 Apache2-FCGI-MapServer 
> configuration?



Nothing in the Debian BTS, you'll have better luck asking other MapServer users:



  https://mapserver.org/community/lists.html#mapserver-users



Kind Regards,



Bas



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