Docker + Rails + Puma + Postgres + Nginx

.dockerignore

.git
.gitignore
doc
.yardoc
coverage
jsdoc
tmp
log
README.md
public/uploads/
spec

docker-compose.yml

app:
  env_file: .env
  build: .
  entrypoint: bundle exec
  command: rails server -p 3000
  volumes:
    - .:/app
  ports:
    - "3000"
  links:
    - postgres
postgres:
  env_file: .env
  image: postgres:9.4
  ports:
    - "5432"
nginx:
  image: nginx
  links:
    - app
  volumes_from:
    - app
  volumes:
    - ./nginx.conf:/etc/nginx/conf.d/my_app.conf:ro
  ports:
    - "80:80"

Dockerfile

FROM ruby:2.3.1-slim

RUN apt-get update && apt-get install -qq -y build-essential

RUN apt-get install -y libpq-dev
RUN apt-get install -y --fix-missing libxml2-dev libxslt1-dev
RUN apt-get install -y nodejs

ENV INSTALL_PATH /app
ENV RAILS_ENV production
ENV RACK_ENV production

RUN mkdir $INSTALL_PATH

WORKDIR $INSTALL_PATH

COPY Gemfile* $INSTALL_PATH/

RUN bundle install --jobs 20 --retry 5 --without development test

COPY . $INSTALL_PATH

nginx.conf

# From http://chrisstump.online/2016/02/20/docker-existing-rails-application/

upstream puma {
  server app:3000;
}

server {
  # define your domain
  server_name my_app.com;

  # define the public application root
  root   /app/public;
  index  index.html;

  # define where Nginx should write its logs
  access_log /app/log/nginx.access.log;
  error_log /app/log/nginx.error.log;

  # deny requests for files that should never be accessed
  location ~ /\. {
    deny all;
  }

  location ~* ^.+\.(rb|log)$ {
    deny all;
  }

  # serve static (compiled) assets directly if they exist (for rails production)
  location ~ ^/(assets|images|javascripts|stylesheets|swfs|system)/ {
    try_files $uri @rails;

    access_log off;
    gzip_static on; # to serve pre-gzipped version

    expires max;
    add_header Cache-Control public;

    # Some browsers still send conditional-GET requests if there's a
    # Last-Modified header or an ETag header even if they haven't
    # reached the expiry date sent in the Expires header.
    add_header Last-Modified "";
    add_header ETag "";
    break;
  }

  # send non-static file requests to the app server
  location / {
    try_files $uri @rails;
  }

  location @rails {
    proxy_set_header  X-Real-IP  $remote_addr;
    proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;
    proxy_pass http://puma;
  }
}