OSRM Profile Proxy

OSRM profile proxy is a router which proxies OSRM routing requests to different OSRM instances depending on the profile parameter. Additionally profiles can be proxied with different mechanisms, e.g. by calculating the aerial distance between start and end of the route.

How to configure proxies

This example will configure three profiles: rail, water and driving. rail and water are simple proxies (see How a simple proxy works) and driving is a limit proxy (see How a limit proxy works).

Notice that rail, water and driving are just names, you can change them to your needs and add or remove other profiles in the proxy categories (simple and limit). In case no proxy of a certain type is needed, omit that category.

In order to perform a health check over all OSRM instances, a routing request based on the coordinates under healthCoordinates is performed for each instance. For more details see Health check.

proxy:
  profiles:
    fallback: driving
    simple:
      rail:
        destination: http://localhost:50003
      water:
        destination: http://localhost:50004
      # define as many simple proxies as you need
    limit:
      driving:
        limitInMeters: 75000
        destinations:
          underLimit: http://localhost:50001
          overLimit: http://localhost:50002
          fallback: http://localhost:50001
      # define as many limit proxies as you need
  healthCoordinates:
    start: #Berlin
      latitude: 52.517037
      longitude: 13.388860
    end: #Karlsruhe
      latitude: 49.014068
      longitude: 8.404437

How a simple proxy works

This is an example OSRM routing request to an OSRM instance on port 8080 with profile rail: http://maps.example.com:8080/osrm/route/v1/rail/10.415039,50.148746;8.525391,52.829321?overview=false&alternatives=true&steps=true

Notice at the beginning of the url path there is /osrm, this is needed for the proxy to recognize requests for OSRM. This will be cut out when proxied.

Start an OSRM instance on port 5003. When the profile-parameter in the url matches the proxy-name (in this case rail), then the request will be proxied to the given destination (in this case http://localhost:50003).

How a limit proxy works

This is an example OSRM routing request to an OSRM instance on port 8080 with profile driving: http://maps.example.com:8080/osrm/route/v1/driving/10.415039,50.148746;8.525391,52.829321?overview=false&alternatives=true&steps=true

Notice at the beginning of the url path there is /osrm, this is needed for the proxy to recognize requests for OSRM. This will be cut out when proxied.

Start two OSRM instances on different ports e.g. 5001 and 5002. The coordinates will be extracted from the url and the aerial distance will be calculated. Depending on the result, the request will be proxied to the corresponding OSRM instance e.g. http://localhost:5001 or http://localhost:5002 (which can be configured with the properties profiles.proxy.limit.driving.destinations.underLimit and profiles.proxy.limit.driving.destinations.overLimit). The limit itself is configured with profiles.proxy.limit.driving.limitInMeters.

Requests which are not routing requests (e.g. table requests) will be proxied to a fallback destination which can be configured with the property profiles.proxy.limit.driving.destinations.fallback. This destination should be the same as one of the two OSRM instances. In case there was an error while processing the routing request (e.g. coordinates which this implementation can't read) the request will be proxied to the fallback destination.

In case of a multistop routing request (more than just two pairs of coordinates) the aerial distance of the first and the last coordinate pair will be used to decide which instance should be used.

Health check

The application provides a health check at /health. That check performs a routing with all OSRM instances which are used by the proxies.It will report UP if all OSRM instances routed successfully, and DOWN otherwise. The routing can be influenced with the start and end parameters under proxy.healthCoordinates.

Development

To project is built with maven:

Build

./mvnw clean verify

Run locally

./mvnw spring-boot:run

This will start the proxy locally on port 8080. When the application is started in dev-profile, a wiremock server will be started as well. You can test the functionality by accessing the server via browser with a URL for OSRM instances. e.g. aerial distance under the limit, aerial distance over the limit or not a route request for the driving profile with the limit proxy. Profile rail for the rail profile with the simple proxy.

The response will not look like a response from an OSRM instance, but it will provide some useful information.