Pythonic Deployment with Fabric 0.9

Corey OordtThe Washington Times

@coordtcoordt@washingtontimes.comhttp://opensource.washingtontimes.com/

Easy Deployment for Different Environments

Testing

Staging

Production

Easy Deployment to Multiple Computers

Production 1

Production 2

Production 3

Installation of Fabric

$ easy_install paramiko

$ easy_install pycrypto

$ easy_install http://git.fabfile.org/cgit.cgi/fabric/snapshot/fabric-0.9b1.tar.gz

Fabric is just a command and a python script

fab fabfile.py

The fabfile.py

from fabric.api import *

env.roledefs = {

'web': ['172.16.12.1', '172.16.12.2',],

'media': ['172.16.12.4',],

'staging': ['172.16.12.5',],

'testing': ['172.16.12.6',],

'database': ['172.16.12.7', '172.16.12.8',],

}

env.root_path = '/var/websites'

Define Tasks to Setup Environments

def testing():

env.hosts = env.roledefs['testing']

env.user = 'testuser'

def staging():

env.hosts = env.roledefs['staging']

env.user = 'staginguser'

def production():

env.hosts = env.roledefs['web']

env.user = 'produser'

Task Example

def clean(site=None):

"""Remove .pyc files from a site."""

from os import path

if not site:

site = prompt('Please specify which site(s) to

clean (a comma delimited list is accepted): ', validate=r'^[\w-.,]+$')

site_list = site.split(',')

for item in site_list:

path = path.join(env.root_path, item)

sudo("find %s -name '*.pyc' -depth -exec rm {} \;"

% path)

Fabric Commands

• require: Make sure that certain environment variables are available.

• prompt: Display a prompt to the user and store the input in the given variable. Validation is optional.

• put: Upload files to the remote host(s).

• get: Download a file from a remote host.

• run: Run a shell command on the remote host(s).

• sudo: Run a root privileged shell command command on the remote host(s).

• local: Run a command locally.

Fabric Contrib Commands

• rsync_project: Synchronize a remote directory with the current project directory via rsync.

• upload_project: Upload the current project to a remote system, tar-gzipping during the move.

• exists: Return True if given path exists.

• first: Given one or more file paths, returns first one found, or None.

• upload_template: Render and upload a template text file to a remote host.

• sed: Run a search-and-replace on filename with given regex patterns.

• comment/uncomment: Attempt to (un)comment out all lines in filename matching regex.

• contains: Return True if filename contains text.

• append: Append string (or list of strings) text to filename.

• confirm: Ask user a yes/no question and return their response as True /False.

Fabric Decorators

• hosts: Defines on which host or hosts to execute the wrapped function.

• roles: Defines a list of role names, used to look up host lists.

• runs_once: Prevents wrapped function from running more than once.

@hosts('user1@host1', 'host2', 'user2@host3')@runs_oncedef my_func(): pass

@roles('web')def my_other_func(): pass

Usage Example

$ fab testing clean:site=basenews

[172.16.12.6] sudo: find /var/websites/basenews -name '*.pyc' -depth -exec rm {} \;

Password for testuser@192.168.56.3:

Done.

Disconnecting from 172.16.12.6... done.

$

Example Uses

• Reload web server settings

• Clean .pyc files

• Check out new revision from a SCM repository

• Install packages on servers

• Apply patches

• Restart caching server

• Dump database and restore it locally

Let’s look at an example fabfile.py…

Thank YouCorey OordtThe Washington Times

@coordtcoordt@washingtontimes.comhttp://opensource.washingtontimes.com/