/home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/connection/ruby.rb:152:in `getaddrinfo': getaddrinfo: Name or service not known (SocketError)

Question

I am using docker-compose to provide development environment for developers with the tech-stack ROR, postgres, redis, mongo. The docker-compose build is running successfully but when I ran docker-compose up following error was encountered.

web_1   | => Booting Thin
web_1   | => Rails 4.2.3 application starting in development on http://0.0.0.0:3000
web_1   | => Run `rails server -h` for more startup options
web_1   | => Ctrl-C to shutdown server
web_1   | Exiting
web_1   | /home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/connection/ruby.rb:152:in `getaddrinfo': getaddrinfo: Name or service not known (SocketError)
web_1   |   from /home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/connection/ruby.rb:152:in `connect'
web_1   |   from /home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/connection/ruby.rb:211:in `connect'
web_1   |   from /home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/client.rb:322:in `establish_connection'
web_1   |   from /home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/client.rb:94:in `block in connect'
web_1   |   from /home/web/.gem/ruby/2.2.0/gems/redis-3.2.1/lib/redis/client.rb:279:in `with_reconnect'

Following is the Dockerfile

# Base image.
FROM atlashealth/ruby:2.2.1

# System dependencies for gems.
#RUN apt-get update
#RUN apt-get install -y --no-install-recommends libmysqlclient-dev
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev 

# Add 'web' user which will run the application.
RUN adduser web --home /home/web --shell /bin/bash --disabled-password --gecos ""

# Add directory where all application code will live and own it by the web user.
RUN mkdir /app
RUN chown -R web:web /app

# Install gems separately here to take advantage of container caching of `bundle install`.
# Also, ensure that gems are installed as the web user and not system-wide so that we can run
# `fig web bundle install` and the web user will have permissions to update the shared Gemfile.lock.
ADD Gemfile /app/
ADD Gemfile.lock /app/
RUN chown -R web:web /app
USER web
ENV HOME /home/web
ENV PATH $PATH:/home/web/.gem/ruby/2.2.0/bin
ENV GEM_HOME /home/web/.gem/ruby/2.2.0
ENV GEM_PATH $GEM_HOME
RUN gem install --user-install bundler
WORKDIR /app/
RUN bundle install
USER root

# Add the whole application source to the image and own it all by web:web.
# Note: this is overwritten in development because fig mounts a shared volume at /app.
ADD . /app/
RUN chown -R web:web /app

# Clean up APT and /tmp when done.
RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

# Default command to run when this container is run.
USER web
WORKDIR /app/
CMD ["bundle", "exec", "rails", "server"]

docker-compose.yml

db:  
  image: postgres
  ports:
    - "5432"

redis:  
  image: redis
  ports:
    - "6379"

sidekiq:  
  build: .
  command: bundle exec sidekiq
  links:
    - db
    - redis

web:  
  build: .
  command: bundle exec rails s -b 0.0.0.0
  volumes:
    - .:/app
  ports:
    - "3000:3000"
  links:
    - db
    - redis

I have setup the environment variable for postgres and redis host and port according to the output of docker-compose run web env command.

output of command docker-compose run web cat /etc/hosts

Starting xyz_db_1...
Starting xyz_redis_1...
172.17.0.32 2b231a706e7b
127.0.0.1   localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.31 redis 799b65ac89cd xyz_redis_1
172.17.0.31 redis_1 799b65ac89cd xyz_redis_1
172.17.0.30 db 0bd898e19822 xyz_db_1
172.17.0.30 db_1 0bd898e19822 xyz_db_1
172.17.0.30 xyz_db_1 0bd898e19822
172.17.0.31 xyz_redis_1 799b65ac89cd

config/sidekiq.yml

concurrency: 25
pidfile: ./tmp/pids/sidekiq.pid
logfile: ./log/sidekiq.log
queues:
  - default
  - [priority, 2]
daemon: true

config/app-config.yml

default: &default
  redis_host: <%= ENV['XYZ_REDIS_1_PORT_6379_TCP_ADDR'] %>
  redis_port: <%= ENV ['XYZ_REDIS_1_PORT_6379_TCP_PORT'] %>
  redis_namespace: 'RAILS_CACHE'

development:
  <<: *default
  redis_host: <%= ENV['XYZ_REDIS_1_PORT_6379_TCP_ADDR'] %>
  redis_port: <%= ENV['XYZ_REDIS_1_PORT_6379_TCP_PORT'] %>

config/initializers/redis.rb

# global variable to access Redis cache
# Requirement: Redis server should be up and running
# at below specified host and port
$redis = Redis.new(
  :host => APP_CONFIG["redis_host"],
  :port => APP_CONFIG["redis_port"]
)

Answer 1

The REDIS_URL environment variable can be used to pass the Redis url to both Sidekiq and the Redis gem.

This environment variable can be set in the docker-compose.yml like this:

db:  
  image: postgres
  ports:
    - "5432"

redis:  
  image: redis
  ports:
    - "6379"

web:  
  build: .
  command: bundle exec rails s -b 0.0.0.0
  volumes:
    - .:/app
  ports:
    - "3000:3000"
  links:
    - db
    - redis
  environment:
    REDIS_URL: "redis://redis:6379"

As Sidekiq and Redis gems will use REDIS_URL by default, you also need to make sure that you are not overriding this default behavior in your config files. You don't need the file config/initializers/redis.rb anymore, and your config/app-config.yml should contain only your namespace:

default: &default
  redis_namespace: 'RAILS_CACHE'

development:
  <<: *default