Fabric: A Capistrano Alternative

Fabric - A Lightweight Deployment Tool for Rubyists and Pythonists Alike
Mike Leone - Panoptic Development, Inc

Why Fabric?
Capistrano is elegant, powerful, extensible
but...
Too many features for small, simple projects
If you're using a DSL, the implementation language isn't so important
If you know Ruby, you already know enough Python for a simple fabric script!

Can you teach a Rubyist how Capistrano works in 3 minutes?
Probably not!
Makes assumptions about your version control system
Release directory structure
The way your server restarts
In typical Ruby fashion, there's lots of ”magic”

Fabric is two things
API for streamlining the use of SSH for app deployment or sys admin tasks
Command-line interface for calling Python methods

Example $ fab free_space

Write a deploy script in 3 minutes
We want a script that will:
test our code
deploy it to our server in the /mnt directory
restart the web server

Install Fabric
$ sudo apt-get install python-setuptools $ sudo easy_install fabric

Add Fabric to your Ruby App
$ cd my/awsome/rails_app $ touch fabfile.py

Three Lines of Boilerplate
from fabric.api import * env.hosts = ['myserver.com'] env.user = ”mike”

Run the tests
def test(): local('rake spec')
If tests fail, deployment will stop

Send your App Code Over
def pack_code(): local('tar czf /tmp/latest.tgz') def upload_code(): put('/tmp/latest.tgz', '/tmp/') with cd('/mnt/rails_app'): run('tar xzf /tmp/latest.tgz')

Restart the Web Server
def restart(): sudo('/etc/init.d/apache2 restart')

Put it all Together
def deploy(): test() pack_code() upload_code() restart()

Your new Deploy Script

Deploy!
$ fab deploy

Deploy your Release Branch
$ git checkout my-release-branch $ fab deploy

Advantages
Don't have to include branch, repository info
Use any release directory structure you want
Someone knowing nothing about deployment tools can look at your script and understand exactly what's going on

Further Reading
Fabric documentation:
http://docs.fabfile.org/0.9.1/
My Company Website and Blog:
http://panopticdev.com

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Fabric: A Capistrano Alternative

by Panoptic Development, Inc. on Jun 24, 2010

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