wmts-kvp-to-restful

Purpose

WMTS-KVP-to-RESTful is a WMTS RESTful proxy that rewrites WMTS KVP requests to WMTS RESTful requests.

Template used: original-path/{layer}/{tilematrixset}/{tilematrix}/{tilecol}/{tilerow}.{translated format}

Example

/tiles/service/wmts?layer=brtachtergrondkaart&style=default&tilematrixset=EPSG:28992&Service=WMTS&Request=GetTile&Version=1.0.0&Format=image/png&TileMatrix=04&TileCol=7&TileRow=8

becomes

/tiles/service/wmts/brtachtergrondkaart/EPSG:28992/04/7/8.png

A request that cannot be rewriten is passed through unhandled.

Geowebcache issue

The WMTS-KVP-to-RESTful proxy will try to solve the issue with Geowebcache WMTS KVP generated requests. The issue is that the tilematrix values generated contain the tilematrixset as a prefix. This something that doesn't match well with a WMTS RESTful request. This is a issue that some are experiencing and that we ourself have experienced, especially when services are migrated from Geowebcache to a new WMTS server (like mapproxy).

An invalid WMTS RESTful path would generate, the WMTS KVP request:

/ws/raadpleegdiensten/wmts?SERVICE=WMTS&REQUEST=GetTile&VERSION=1.0.0&LAYER=grb_bsk_grijs&STYLE=&TILEMATRIXSET=BPL72VL&TILEMATRIX=BPL72VL:11&TILEROW=1072&TILECOL=730&FORMAT=image/png

becomes

/ws/raadpleegdiensten/wmts/grb_bsk_grijs/BPL72VL/BPL72VL:11/730/1072.png

With an incorrect tilematrix value of BPL72VL:11 instead of 11. Through a regex the prefix will be stripped from the tilematrix value.

WMTS Capabilities

WMTS requests come in 3 flavours: GetTile, GetCapabilities and GetFeatureInfo requests. While the main focus of the wmts-kvp-to-restful application is rewriting the GetTile request, the other two requesttypes still part of the WMTS KVP spec. So when starting the application there is the option in setting an template for the WMTS GetCapabilities request.

-t=./path/to/template/WMTSCapabilities.template.xml

An example of this template can be found in the example dir.

Logging

Logging is disabled by default and can be enabled by setting the parameter -l=true.

-l=true

The logging will log:

• HTTP Status Code
• Request duration in milliseconds
• The requestURI (path + querystring), and if proxied the new requestURI

Shutdown delay

Delay (in seconds) before initiating graceful shutdown (e.g. useful in k8s to allow ingress controller to update their endpoints list. The default is 0. Can be set with the parameter -d=15.

Tech

test

go test ./...

run

go run . -host=http://{target host} -t={WMTS Capabilities template} -l=true

build

go build .

docker

docker build -t pdok/wmts-kvp-to-restful .
docker run -v `pwd`/example/config:/config --name wmts-proxy -p 9001:9001 pdok/wmts-kvp-to-restful /wmts-kvp-to-restful -host=http://localhost -t=./config/WMTSCapabilities.template.xml -l=true
docker stop wmts-proxy
docker rm wmts-proxy

docker-compose

In the folder example there is a docker-compose which will start both the wmts-kvp-to-restful proxy and a mapproxy with a OSM wmts service.

docker-compose up
docker-compose down