Using docker compose

Using docker-compose

With high demands on the services and lots of users connecting to a service, it is necessary to run more than one container of a service. While traditional approaches just launched more instances of one server at different ports (e.g. :80, :81, :82, …), modern approaches not only use some kind of virtualization but also some kind of automatic proxying or load balancing (e.g. automatically linking :80 to various ports within the virtualization framework) and scaling (having a certain number of containers depending on e.g. server load).

This can be achieved and automated with docker-compose and with writing 'docker-compose.yaml' files (see reference here).

This example demonstrates how to run three instances of GALAXY on a single node by using haproxy (a http-proxy with load balancing features).

In our case we use the demo found at: https://github.com/korseby/docker-galaxy

The file docker-compose.yaml contains rules for running more than one container of a service.

We are using haproxy for load balancing between the three different containers of GALAXY, thus the directory galaxy-haproxy contains rules and the configuration file for haproxy running in a separate docker container. The same functionality can be achieved with nginx and other http-load balancers.

All you need to do is run docker-compose in order to orchestrate three running containers of GALAXY:

docker-compose up -d

Docker-compose does everything for you. It pulls the official GALAXY-image from dockerhub, starts three GALAXY-containers and then build and starts galaxy-haproxy. Galaxy-haproxy already receives proper dns-entries from docker-compose to link to the three instances of the GALAXY-service. The docker-compose.yaml file includes all rules that are needed and it looks like this:

galaxy-a:
  image: bgruening/galaxy-stable
  expose:
    - 80
galaxy-b:
  image: bgruening/galaxy-stable
  expose:
    - 80
galaxy-c:
  image: bgruening/galaxy-stable
  expose:
    - 80
galaxy-haproxy:
  build: galaxy-haproxy
  volumes:
   - galaxy-haproxy:/haproxy-override
  links:
   - galaxy-a
   - galaxy-b
   - galaxy-c
  ports:
   - "9080:80"
   - "9070:70"
  expose:
   - "80"
   - "70”

In our case, GALAXY can be reached at http://127.0.0.1:9080. Docker-compose automatically switches between the three containers in a round-robin way based on the session-id of the connection.

Statistics of haproxy can be seen at http://127.0.0.1:9070.

Some information of running containers can be obtained with:

docker-compose ps
docker-compose logs        # press CTRL-C

Docker-compose can be shut down with the following command:

docker-compose down