Hi,

I believe that not much that kind of studies about load balancing WMS servers 
have been done. If there is high load then people very soon place some tile 
cache into front line and use WMS only for seeding the cache. Sharing load 
between tile servers is rather simple because each tile is about as expensive 
to serve. But users do want more different styles, possibility to select just 
some layer, wider support for coordinate systems etc. that may mean more demand 
for traditional WMS because caching all alternatives gets unpractical.

-Jukka Rahkonen-

Lähettäjä: mapserver-users <[email protected]> Puolesta 
Andreas Neumann
Lähetetty: perjantai 23. huhtikuuta 2021 18.21
Vastaanottaja: [email protected]
Aihe: [mapserver-users] Mapserver installation in cloud environments 
(kubernetes)

Hi,

For a small project as part of the Swiss National Geodata Infrastructure (grant 
project) several people worked on a study document called "Cloud-optimized OGC 
WMS Server" where we analyzed problems that can arise when you install an OGC 
web server in the cloud (e.g. docker image deployed via Kubernetes, OpenShift 
or the likes). This work had a focus on QGIS Server with it's own set of 
problems - but some of the issues studied in this document also matter for 
other OGC WMS servers, such as UMN Mapserver or Geoserver, such as the load 
balancing problem, how to share resources, etc.

Here is the link to the document (not in final form yet, but close to being 
final): 
https://docs.google.com/document/d/1cOUWgzalRx7CHWTFgHz6-uyScsCcoaEmYC0VBHdZShQ/edit#heading=h.c7gq4lie7ys2

I wonder if any similar work has been done specifically around problems, 
challenges and solutions when you deploy UMN Mapserver in cloud environments? 
Do you know of any work?

One major problem that probably all installations of an OGC WMS server have is 
how to deploy a more intelligent load balancing system? Often, the default load 
balancer is some kind of round robin load balancer system, but often this leads 
to inferior results where "cheap and short" requests (such as a simple 
GetFeatureInfo or GetLegendGraphics request) can be queued behind a 
long-running GetMap request (potentially with many layers, many features and a 
high-dpi, such as 600dpi, where the request can take several seconds to process.

In our production system we are currently separating the requests to dedicated 
instances for short requests and potentially long requests, to avoid the above 
mentioned scenario, but we are not so satisfied with the solution, as it is  a 
bit inflexible and also a bit harder to maintain. Ideally, we would like to 
have a more intelligent load balancer with incoming queue that holds back 
requests as long as all WMS server instances are busy. This would avoid the 
situation where a "less intelligent" load balancer would simply forward the 
requests to instances based on Round-Robin principle.

Do you know of any work in the UMN Mapserver community regarding cloud 
deployment, cloud optimization, load balancing and resource sharing?

In our study document I'd like to also include the perspective of other WMS 
servers besides QGIS server, so any input would be welcome.

Thanks,
Andreas

--
Andreas Neumann
QGIS.ORG<http://QGIS.ORG> board member (treasurer)
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