rails applications with docker
TRANSCRIPT
Building Rails Applications with
DockerLaura Frank @rhein_wein
Software Engineer @codeship
Today’s Agenda
• An introduction to containers: what are they, and what makes them different from virtual machines?
• The Docker ecosystem
• Working with Docker on a Rails project
2
An Introduction to Containerization
Docker != containers
Docker manages containers
• Builds images to run as containers
• Can manage entire applications with docker-compose
• Provision machines with docker-machine
6
A container is a virtualization layer — sort of like a VM — but with some fundamental differences
Containers
• Run in a self-contained execution environment
• Share the kernel of host system
• Are isolated from other containers
• Have fast boot times & low overhead
8
infrastructure
host OS
hypervisor
$ guest OS
libraries
service 0
$ guest OS $ guest OS
libraries
service 2
libraries
service 1
libraries librarieslibraries
infrastructure
host OS
service 0 service 2service 1
host OS
libraries librarieslibraries
infrastructure
container runtime engine
service 0 service 2service 1
Getting started with containers may initially seem more complex…
…But they greatly reduce the amount of time and space needed
to run your application
Spend less time provisioning, rebooting, and fighting with
dependencies, and more time building what you want.
TL;DR
The Docker Ecosystem
Build Ship Run
Docker Images
Are images containers?No… an image is like a class, and a container is an
instance of that class
The Docker Hub
19
• ~15,000 images that you can pull down and use in your own projects
• Also includes additional features like webhooks, build triggers, authentication, and private repositories
• Use either the web GUI or the CLI — familiar workflow of login, push, pull, search, etc.
The Docker Hub
Different Types of Images
• Service: self-contained images that provide a self-contained service out-of-the-box. Postgres, MySQL.
• Project Base: intended to serve as a base for your own project; do not directly provide a service. Ruby, golang.
• Official Images: maintained by the organization/company themselves (i.e. the official Rails image)
• Build them yourself by creating a Dockerfile
• docker build -‐t image_name . \ # don’t forget the dot!
• run docker images to see all of the images you’ve downloaded or built
Your Own Docker Images
A Rails DockerfileFROM rails:4.2.4 MAINTAINER Laura Frank <[email protected]> RUN mkdir -p /var/app COPY . /var/app WORKDIR /var/app RUN bundle install CMD rails s -b 0.0.0.0
set versions here
Use the Docker Hub to find and store images to use in your project.
Use Docker Compose to build it.
Docker Compose
25
Building Your First Rails App with Docker
Installing Docker• The old way: boot2docker
• The new way: Docker Toolbox
• Docker Client, Machine, Engine, Compose (on a Mac), Kitematic, and Virtual Box
• You can migrate your boot2docker VM to a Docker Machine machine — check the docs
Development Goals
Run a Rails app in a container, so that a developer can:
• view the app running in the browser • edit files in a local environment and see the changes • run rake tasks like migrations • see log output
Remember This?FROM rails:4.2.4 MAINTAINER Laura Frank <[email protected]> RUN mkdir -p /var/app COPY Gemfile /var/app/Gemfile WORKDIR /var/app RUN bundle install CMD rails s -b 0.0.0.0
🚉 🐘
A Multi-‐Container Rails App
Rails App Postgres❤
How can I get containerized services to communicate with one another?container linking, environment variables…
and of course, a little config sugar
Docker Compose makes this easy.
db: image: postgres web: build: . command: bundle exec rails s -‐p 3000 -‐b '0.0.0.0' volumes: -‐ .:/var/app ports: -‐ '3333:3000' links: -‐ db
docker-‐compose.yml
development: &default adapter: postgresql encoding: unicode database: postgres pool: 5 username: postgres password: host: db
config/database.yml
Ship It
A simple CI/CD workflow would include
• running tests • building a new Docker image • pushing that image to a registry • firing up containers with the new image
#alwayskeepshipping
thanks!