Dockerizing a Ruby on Rails Application

Ref: Dockerizing a Ruby on Rails Application

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Brief version

• Install docker
• Install docker-compose
• Create postgres and redis volumes
• Create and migrate db using rake commands with docker-compose
• Run docker-compose up

Linux setup

Ubuntu

Ref: https://docs.docker.com/engine/installation/linux/ubuntulinux/

• Clone the project:

    git clone https://github.com/FullStackPE/drkiq.git
    cd drkiq
  

• Check your Ubuntu version. It has to be 64-bit. Additionally, your kernel must be 3.10 at minimum:

    uname -r
  

• Ensure that CA certificates are installed, and add the new GPG key

    sudo apt-get install apt-transport-https ca-certificates
    sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
  

• Add the following line to /etc/apt/sources.list.d/docker.list. The last part of the command depends on your Ubuntu version:

    deb https://apt.dockerproject.org/repo ubuntu-trusty main
  

• Update and verify that APT is pulling from the right repository:

    sudo apt-get update
    apt-cache policy docker-engine
  

• Install Docker Compose (reference 1, reference 2):

    sudo -i
    curl -L https://github.com/docker/compose/releases/download/1.8.0/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose
    chmod +x /usr/local/bin/docker-compose
    sudo apt-get update
    sudo apt-get install docker-engine
  

• Try to start docker. It's supposed to fail (almost always), so don't panic:

    service docker start
  

  If the last command failed, use sudo in front of it (reference):

  sudo service docker start
  

• Create postgres and redis volumes:

    sudo docker volume create --name drkiq-postgres
    sudo docker volume create --name drkiq-redis
  

• Let's try to run everything. Spoiler: it will fail!

    sudo docker-compose up
  

  Since the last command probably failed, please check the "Errors" section below. Once you solved the problem, run sudo docker-compose up again.

• You should now notice a few errors related to the db. That's because we still didn't create it. So let's stop everything (CTRL C) and set up the db:

    sudo docker-compose run --user "$(id -u):$(id -g)" drkiq rake db:reset
    sudo docker-compose run --user "$(id -u):$(id -g)" drkiq rake db:migrate
  

• In your browser, you should find everything at http://localhost:8000.

Errors

• You might get some error related to open ports:

  ERROR: for postgres Cannot start service postgres: driver failed programming external connectivity on endpoint drkiq_postgres_1 (39c02de08efcf3c9b4670ba0158f3f5bbc81324fb969d2043e77a2cf7ba90b6e): Error starting userland proxy: listen tcp 0.0.0.0:5432: bind: address already in use ERROR: Encountered errors while bringing up the project.

  Find out which process is using that door:

  sudo lsof -i :5432
  

  So we'll find out that postgres is using that port. Just shut down postgres:

  sudo /etc/init.d/postgresql stop
  

  Same for the other errors. For example, with redis:

  sudo lsof -i :6379
  # Guess what: it's redis-server!
  sudo /etc/init.d/redis-server stop
  

  Then we can give again:

  sudo docker-compose up
  

Mac OS X setup

Donwload and install the stable version of docker for mac as described here:

https://docs.docker.com/docker-for-mac

• Clone the project:

  git clone https://github.com/FullStackPE/drkiq.git

  cd drkiq

• Start the containers

  docker-compose up

• You may need to create and migrate the db

  docker-compose run drkiq rake db:reset

  docker-compose run drkiq rake db:migrate

Errors

To solve problems related to stopping local services that bind to the same ports used by Postgres and Redis (that run inside the container).

ERROR: for postgres  Cannot start service postgres: driver failed programming external connectivity on endpoint drkiq_postgres_1 (cb77f86584efd7f70c799b8f835fd9eb2ef257a7773d1bdd746375ad6a7e4798): Error starting userland proxy: Bind for 0.0.0.0:5432: unexpected error Uwt.Uwt_error(Uwt.EADDRINUSE, "listen", "")
ERROR: Encountered errors while bringing up the project.

Identify the service who bind to 5432 port

lsof -i :5432

COMMAND  PID USER  FD   TYPE DEVICE SIZE/OFF NODE NAME
postgres 99 johnny 5u   IPv6 0x29      0t0   TCP  localhost:postgresql (LISTEN)

brew services stop postgres

The same applies to Redis service

Some useful Docker commands

• Show docker images installed on your computer (images command ref.)

  docker images

• Show docker running images (ps command ref.)

  docker ps -a -q

• Delete a container (rm command ref.)

  docker rm CONTAINER_NAME

• Delete all containers (rm command ref.)

  docker rm $(docker ps -a -q)

• Delete all images (rmi command ref.)

  docker rmi $(docker images -q)