5

WMS allows to set query constraints, for image size and for maximum number of layers in one request (see. OpenGIS® Web Map Server Implementation Specification - Version 1.3.0 - 7.2.4.3).

Is it possible to configure this values? If it is possible, how?

5

GeoServer works with memory limits, which are a more accurate and predictable way to control memory usage.

The image size per se is not very meaningful, depending on bit depth it can be very small, like with packed black and white images storing 8 pixels in one byte, or large, with up to 4 bytes per image (assuming 8 bit outputs). Also, image size it's too dependent on aspect ratio (a certain output can fit the total amount of pixels but fail the check because its aspect ratio is not the same as the limits one).

The downside of memory limits is that they cannot be advertised in the capabilities document. The beauty of open source is that you can push for GeoServer to implement that feature, follow this guide if you are interested: https://github.com/geoserver/geoserver/wiki/Successfully-requesting-and-integrating-new-features-and-improvements-in-GeoServer

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GeoServer does not support those constraints. What it does support is setting the maxRequestMemory and maxRenderingTime with the standard WMS settings http://docs.geoserver.org/stable/en/user/services/wms/configuration.html

An additional Control flow module gives some more tools for throttling and preventing overload http://docs.geoserver.org/stable/en/user/extensions/controlflow/

As a comparison, with MapServer the maximum size can be set with the MAXSIZE option http://mapserver.org/mapfile/map.html. The value of the setting that defaults to 4096 is also included in WMS 1.3.0 GetCapabilities as

<MaxWidth>4096</MaxWidth> 
<MaxHeight>4096</MaxHeight>

In addition MapServer supports the layer limit which can be set with WMS_LAYERLIMIT in the MAP > WEB > METADATA and is advertised as:

<LayerLimit>8</LayerLimit>

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