fab roles example

#!/usr/bin/env python

'''
This is a high level basic example of roles
'''

from fabric.api import *

@task
def load_hosts(region='region'):
    rack = CloudProviderAPI(region=region)
    env.roledefs = {
        'web': ['web-ip-address', 'web-hostname-2', 'web-ip-address-1'],
        'db': ['db-server-1', 'db-server-2'],
        'app': ['app-server-1', 'app-server-2', 'app-server-3']
    }

@parallel
def ship_code():
    put("/tmp/artifact.tar.gz", "/opt/code-location/")

@roles('web', 'app') # Only will run on web and app hosts
@parallel # Task will run in parallel
def restart_service_x():
    run("service service_x restart")

@roles('db') #This will ensure that task is only run on db hosts
@serial #This will ensure tasks are run on one host at a time
def do_database_stuff():
    run('echo "RUN DB COMMAND HERE ONLY ON DB SERVERS"')

@task
@roles('web', 'app', 'db')
def run():
    execute(ship_code)
    execute(do_database_stuff)
    execute(restart_service_x)

then to actually run the deploy, you would do this:

fab load_hosts run

OR you can do this:

fab -R web run << something like that, I need to test it but i'm too busy right now :-P