Cloud Native OGC APIs server, written in Go.

This server implements modern OGC APIs such as Common, Tiles, Styles. The goal of this server is to keep a narrow focus and not implement every aspect of these APIs, for complex logic this application will delegate to other implementations. For example vector tiles hosting is delegated to a vector tile engine or object storage, raster map hosting may be delegated to a WMS server, etc.

This application is deliberately not multi-tenant, it exposes an OGC API for one dataset.

• OGC API Common serves landing page and conformance declaration. Also serves OpenAPI specification and interactive Swagger UI.
  • Comes with default OGC OpenAPI specs out-of-the box with option to overwrite with your own custom spec.
• OGC API Tiles serves HTML, JSON and TileJSON metadata. Act as a proxy in front of a vector tiles engine of your choosing. Currently 3 projections (RD, ETRS89 and WebMercator) are supported.
• OGC API Styles serves HTML and JSON representation of supported styles.
• OGC API 3D GeoVolumes serves HTML and JSON metadata and functions as a proxy in front of a 3D Tiles server of your choosing.
• OGC API Processes act as a passthrough proxy to an OGC API Processes implementation of your choosing, but enables the use of OGC API Common functionality.
• OGC API Features in development.

docker build -t pdok/gokoala .

NAME:
   GoKoala - Cloud Native OGC APIs server, written in Go

USAGE:
   GoKoala [global options] command [command options] [arguments...]

COMMANDS:
   help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --host value            bind host for OGC server (default: "0.0.0.0") [$HOST]
   --port value            bind port for OGC server (default: 8080) [$PORT]
   --debug-port value      bind port for debug server (disabled by default), do not expose this port publicly (default: -1) [$DEBUG_PORT]
   --shutdown-delay value  delay (in seconds) before initiating graceful shutdown (e.g. useful in k8s to allow ingress controller to update their endpoints list) (default: 0) [$SHUTDOWN_DELAY]
   --config-file value     reference to YAML configuration file [$CONFIG_FILE]
   --openapi-file value    reference to a (customized) OGC OpenAPI spec for the dynamic parts of your OGC API [$OPENAPI_FILE]
   --allow-trailing-slash  support API calls to URLs with a trailing slash (default: false) [$ALLOW_TRAILING_SLASH]
   --help, -h              show help

Example (config-file is mandatory):

docker run -v `pwd`/examples:/examples -p 8080:8080 -it pdok/gokoala --config-file /examples/config_vectortiles.yaml

Now open http://localhost:8080. See examples for more details.

The configuration file consists of a general section and a section per OGC API building block (tiles, styles, etc). See example configuration files for details. You can reference environment variables in the configuration file. For example to use the MY_SERVER env var:

ogcApi:
  tiles:
    title: My Dataset
    tileServer: https://${MY_SERVER}/foo/bar

GoKoala ships with OGC OpenAPI support out of the box, see OpenAPI specs for details. You can overwrite or extend the defaults by providing your own spec using the openapi-file CLI flag.

Health endpoint is available on /health.

Besides the main OGC server GoKoala can also start a debug server. This server binds to localhost and a different port which you must specify using the --debug-port flag. You shouldn't expose this port publicly but only access it through a tunnel/port-forward. The debug server exposes /debug for use by pprof. For example with --debug-port 9001:

• Create a tunnel to the debug server e.g. in k8s: kubectl port-forward gokoala-75f59d57f4-4nd6q 9001:9001
• Create CPU profile: go tool pprof http://localhost:9001/debug/pprof/profile?seconds=20
• Start pprof visualization go tool pprof -http=":8000" pprofbin <path to pb.gz file>
• Open http://localhost:8000 to explore CPU flamegraphs and such.

A similar flow can be used to profile memory issues.

Set LOG_SQL=true to enable query logging stdout for debug purposes. Only applies to OGC API Features.

Design principles:

• Performance and scalability are key!
• Be opinionated when you can, only make stuff configurable when you must.
• The ogc package contains logic per specific OGC API building block.
• The engine package should contain general logic. ogc may reference engine.

  ⚠️ The other way around is not allowed!

• Geospatial related configuration is done through the config file, technical configuration (host/port/etc) is done through CLI flags/env variables.
• Fail fast, fail hard: do as much pre-processing/validation on startup instead of during request handling.
• Assets/templates/etc should be explicitly included in the Docker image, see COPY commands in Dockerfile.
• Document your changes to OGC OpenAPI example specs.

Install golangci-lint and run golangci-lint run from the root.

GoKoala includes a vector tile viewer which is available as a Web Component for embedding in HTML pages. To use the vector tile viewer locally when running GoKoala outside Docker execute: hack/build-local-viewer.sh. This will build the viewer and add it to the GoKoala assets.

Note this is only required for local development. When running GoKoala as a container this is already being taken care of when building the Docker container image.

• Install the Go Template plugin
• Open Preferences > Editor > File Types select Go Template files and add the following file patterns:
  • "*.go.html"
  • "*.go.json"
  • "*.go.tilejson"
• Now add template language support by running the setup-jetbrains-gotemplates.sh script.
• Now you'll have full IDE support in the GoKoala templates.

Also:

• Set import order in Preferences > Editor > Code Style > Go > Imports to goimports to align with VSCode and goimports usage in golangci-lint.

• Install the Go Template extension
• Open Extension Settings and add the following file patterns:
  • "*.go.html"
  • "*.go.json"
  • "*.go.tilejson"
• Also add html and json to the list of Go template languages.
• Now you'll have IDE support in the GoKoala templates.

Use the OGC TEAM Engine to validate compliance when available. In the case of OGC API Features follow these steps:

• Run docker run -p 8081:8080 ogccite/ets-ogcapi-features10
• Open http://localhost:8081/teamengine/
• Start GoKoala.
  • When running Docker in a VM (like on macOS) make sure to start GoKoala with base url: http://host.docker.internal:8080.
• Start a new test session in the TEAM Engine against http://localhost:8080 (or http://host.docker.internal:8080).
  • More details in the features conformance test suite.
• Publish test results HTML report in docs and list below.
  • Test results on 27-09-2023

Make a pull request...

Contacting the maintainers can be done through the issue tracker.