Deployment

Learning Objectives

• Define 'deployment', and contrast different methods of deploying an application
• Describe the difference between development, test, and production environments
• Deploy a rails application using Heroku
• Run migrations on Heroku
• Debug errors on Heroku (using logs)
• Describe the major points of a 12-factor application as applied to deployment
• Use environment variables to keep sensitive data out of code
• List common pitfalls and their solutions when deploying to Heroku
• Describe the role of the asset pipeline in rails

Framing

Deployment is the act of putting an app up on one or more internet-connected servers that allow users to access and use the app.

About Deployment

What is deployment? What changes in an application when it is deployed?

Requirements for Deploying

There are generally a few things we need for an app to be properly deployed:

• server - the server(s) must be on and connected to the internet
• services - the server must be running the correct services (web, database, email, etc)
• dependencies - the server(s) must have the proper dependencies installed (e.g. ruby, our gems, postgres, etc)
• executable code - we must get our code onto the server and be able to run it
• configuration - we must configure our running app with respect to its deployment environment

Deployment Approaches

There are lots of ways to do each of these steps. For example, we can get our code onto a server by...

• Using FTP to transfer the files onto the server
• Adding a git remote and using git push to transmit files (like with GH pages)
• Putting the files on a flash drive, fastening it to a homing pigeon's leg, then having an operator receive the pigeon and copy the files over to the server

Heroku

Today, we'll be using a service called Heroku to deploy our apps, because it makes all the above steps easy. For example, Heroku automatically does the following...

• starts up a new server when we run heroku create, and installs all the necessary services
• adds a new remote to our git repo, so we can just run git push heroku master to copy our code over
• detects our database
• detects the language our program is written in and chooses a buildpack
• automatically uses bundle install to install our app's dependancies, and starts our app
• easily change configuration information using heroku config

You Do: Read through Rails Environments

Start by reading about environments. We've been using the development environment by default, now we'll look at other environments, particularly production.

You Do: Deploying to Heroku

We'll use Heroku to deploy our app, since it has a "free" pricing tier, and a ton of nice features that simplify and expedite deployment.

Quick References

• Common Errors

  Common Errors in Rails Deployments on Heroku

• Deployment Cheat Sheet

  Quick reference for deploying a Rails App to Heroku

Resources

• Rails Asset Pipeline
• Getting Started Deploying Rails on Heroku
• The Twelve-Factor App

Deployment Screencasts

• WDI7
  • Part 1
  • Part 2
  • Part 3
• WDI8
  • Part 1
  • Part 2
  • Part 3