Dockerizing simple Sinatra app using docker and fig

Docker is new hotness in market , docker use kernel level namespace’s and cgroups to create isolated container environment . according to Wikipedia .

UPDATE : fig is now merged in docker and now its called : compose  


Docker is an open-source project that automates the deployment of applications inside software containers, by providing an additional layer of abstraction and automation of operating system–level virtualization on Linux.[Docker uses resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent “containers” to run within a single Linux instance, avoiding the overhead of starting virtual machines.

docker logo

If you know what is lxc and thinking what is difference between LXC and docker then give a look at this excellent post : .

Install Docker

lets first install docker , You can use official Documentation to get up running docker

$ sudo apt-get install curl
$ curl -sSL | sudo sh

and lets install fig

$ sudo apt-get install python-pip
$ sudo pip install fig

Lets test our installation

$ docker --version && fig --versions

# lets run simple hello world inside a ubuntu container
$ sudo docker run -i -t ubuntu /bin/echo "Hello from container "

Sample output

alok@ubuntu:~$ sudo docker run -i -t ubuntu /bin/echo "Hello from container "
Hello from container

give non root access for avoiding using sudo every time with docker command .

$ sudo groupadd docker
$ sudo gpasswd -a ${USER} docker
$ sudo service docker restart

okay so , I wrote this simplest sinatra app , its contains five files 2 of them related to gem file and app.rb is our app and fig.yml will be used as fig configuration file and Dockerfile will be used to build our image

alok@ubuntu:~/code/ruby/app$ tree

├── app.rb
├── Dockerfile
├── fig.yml
├── Gemfile
└── Gemfile.lock

# app.rb

require "sinatra "

get '/'
"Hello World !"

and created Gemfille

source ''

gem 'sinatra'

okay , now lets build ruby image , I build using dockerfile because its take too much to download 800MB file .
okay . you can clone all this from github .


FROM ubuntu
RUN apt-get update

RUN apt-get -y update
RUN apt-get -y install git git-core curl gawk g++ gcc make libc6-dev libreadline6-dev \
zlib1g-dev libssl-dev libyaml-dev libsqlite3-dev sqlite3 autoconf \
libgdbm-dev libncurses5-dev automake libtool bison pkg-config libffi-dev

RUN apt-get install -y postgresql postgresql-contrib postgresql-client libpq5 libpq-dev
RUN curl -sSL | gpg --import -

RUN curl -L | bash -s stable

ENV PATH /usr/local/rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

RUN rvm install ruby-2.1.5
RUN rvm reload
CMD source /etc/profile
CMD source /usr/local/rvm/scripts/rvm
RUN apt-get install -y nodejs npm
RUN ln -s /usr/bin/nodejs /usr/bin/node
RUN ["/bin/bash", "-l", "-c", "rvm use 2.1.5 --default" ]
RUN ["/bin/bash", "-l", "-c", "rvm requirements; gem install bundler --no-ri --no-rdoc"]
RUN ["/bin/bash", "-l", "-c", "gem list"]
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev
RUN mkdir /myapp
WORKDIR /myapp
ADD Gemfile /myapp/Gemfile
RUN ["/bin/bash", "-l", "-c", "bundle install "]

fig is small utility that’s provide functionality to set up quick development environment . all it require a file fig.yml . read more about fig on fig’s website :

# fig.yml
build: .
command: ["/bin/bash", "-l", "-c", "ruby app.rb"]
- .:/myapp
- "8000:4567"

just use this Dockerfile to build image . you can tag use tag this image to use this image for your next ruby project .

$ git clone
$ cd sinatra_container
$ docker build -t="ubuntu/sinatra" .
$ fig build
$ fig up

it will take some time to build , it will install ruby using rvm and sinatra app .

fig up sample output
sinatra docker

now open your browser and point it to : http://localhost:8000 .
you will hello world program .

sinatra docker

Thats all for now , thanks for reading .

Useful Links :
* Docker :
* fig :
* sinatra :
* my github repo :

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