README.md

Linking Docker Containers

Developers might want to run the backend and Couper both in containers on their computer. Be aware that localhost in a Docker container is not the same thing as localhost on your host computer.

Use docker run --link parameter to allow Couper to reach the backend in your other container. In this case you can simply make up a hostname. But as the containers are then talking directly to each other, you have to use the internal service ports.

Let's start a local instance of httpbin in a container. It needs a name to be linkable:

docker run --rm --name httpbin kennethreitz/httpbin

Note, that we don't need to exported a port (-p) here.

Now this command starts Couper linked to our local httpbin container:

docker run --rm \
-p 8080:8080 \
-v "$(pwd)":/conf \
--link httpbin:httpbin \
-e BACKEND_ORIGIN=http://httpbin:80 \
coupergateway/couper

Docker automatically sets some environment variables for linked containers. With that in mind we could omit defining our own environment variable (BACKEND_ORIGIN) and rely on Docker's instead:

…
  endpoint "/example/**" {
    proxy {
      backend {
        origin = "http://${env.HTTPBIN_PORT_80_TCP_ADDR}:80"
      }
    }
  }
…

This is also an example for the handy variable substitutions in strings. We can use variables enclosed in curly brackets to insert dynamic data into a string.

Linking containers with docker-compose

Please have a look at the docker-compose example to see how you can link containers with docker-compose.