Solving Docker Containers from Hostname

DPS can assign a hostname to your docker containers to solve it’s IPs by the :

  • HOSTNAMES env
  • Container Hostname
  • Container Name
  • Docker Compose Service Name

These are indivual forms of set a hostname to a container to query it, so you only need to use one of them.

Hostnames Env

Creating a test container

$ docker run -e HOSTNAMES="nginx1.dev,nginx1.docker" nginx

Solving from HOSTNAMES env

$ dig nginx1.dev @127.0.0.1 +noall +answer
nginx1.dev.		30	IN	A	172.17.0.2

$ dig nginx1.docker @127.0.0.1 +noall +answer
nginx1.docker.		30	IN	A	172.17.0.2

Container Hostname

DPS will register the ${Container Hostname} + '.' ${Domain Name} when Domain Name is set, if not set only the Hostname will be used.

Creating a test container (way 1)

$ docker run --rm  --hostname nginx1 --domainname app nginx

Creating a test container (way 2)

$ docker run --rm  --hostname nginx1.app nginx

Testing hostname

$ dig nginx1.app @127.0.0.1 +noall +answer
nginx1.app.		30	IN	A	172.17.0.2

Container Name

You can solve by the container name, this feature is disabled by default, so you need to enable it using MG_REGISTER_CONTAINER_NAMES=1 env, see a complete tutorial about this feature for more details.

Creating a test container

$ docker run --rm --name nginx1 nginx

Testing

$ dig nginx1.docker @127.0.0.1 +noall +answer
nginx1.docker.		30	IN	A	172.17.0.2

You can customize the .docker domain, with the MG_DOMAIN env, see the docs for more details.

Docker Compose Service Name

Works like Container Name feature, but in this case you can solve by the service name used at the container docker-compose.yml file.

docker-compose.yml

services:
  nginx:
    image: nginx

$ dig nginx.docker @127.0.0.1 +noall +answer
nginx.docker.		30	IN	A	172.23.0.3

Important

Be aware, when using docker-compose, specially with different docker-compose files you may have to lead with different docker networks limitations.