donovanmuller/docker-gen-docker-cloud repository overview

⁠docker-gen for Docker Cloud

• 0.7.3 (Dockerfile⁠)

This is an enhancment to the docker-gen⁠ image that adds support for Docker Cloud⁠.

This image is used in context of this⁠ post on using JrCs/docker-letsencrypt-nginx-proxy-companion⁠ to generate Let's Encrypt certificates for a Ghost specific stack.

⁠The problem

The usual way of using docker-gen in conjunction with docker-letsencrypt-nginx-proxy-companion using the separate container method, is as follows (as per the docs⁠):

$ docker run -d \
    --name nginx-gen \
    --volumes-from nginx \
    -v /path/to/nginx.tmpl:/etc/docker-gen/templates/nginx.tmpl:ro \
    -v /var/run/docker.sock:/tmp/docker.sock:ro \
    jwilder/docker-gen \
    -notify-sighup nginx -watch -only-exposed -wait 5s:30s /etc/docker-gen/templates/nginx.tmpl /etc/nginx/conf.d/default.conf

however, within a Docker Cloud based environment we cannot use -notify-sighup nginx due to the fact that the container names (on the actual nodes) do not match their Service⁠ names. The result is that the nginx container (Service) never get's reloaded to take advantage of the generated Nginx configuration.

⁠The solution

How we get around this is to add the Docker Cloud CLI⁠ to the docker-gen image and add a script (restart_service.sh) that uses the CLI to redeploy a Service. For example, the following configuration, using Docker Cloud Stack file⁠ format, would be used to achieve the desired affect:

nginx-gen:
  image: donovanmuller/docker-gen-docker-cloud:1
  volumes:
    - "/var/run/docker.sock:/tmp/docker.sock:ro"
  volumes_from:
    - nginx-proxy
    - ghost-nginx-proxy-config
  entrypoint: /usr/local/bin/docker-gen -notify-output -notify "./restart_service.sh" -watch -only-exposed -wait 10s:30s /etc/docker-gen/templates/nginx.tmpl /etc/nginx/conf.d/default.conf
  environment:
    - PROXY_SERVICE_ENV_VAR=nginx-proxy
  roles:
   - global

Note the use of the restart_service.sh script with -notify-output -notify "./restart_service.sh". Instead of using -notify-sighup the script is executed which uses the docker-cloud CLI to redeploy the Service indicated by the environment variable PROXY_SERVICE_ENV_VAR. This variable represents the Service name (nginx-proxy in the example above) to redeploy, not the container name.

We also need the global role⁠ so that Docker Cloud can inject the DOCKERCLOUD_AUTH details needed by docker-cloud CLI to authenticate⁠ against.