Can a Python Fabric task invoke other tasks and respect their hosts lists?

Question

I have a fabfile like the following:

@hosts('host1')
def host1_deploy():
    """Some logic that is specific to deploying to host1"""

@hosts('host2')
def host2_deploy():
    """Some logic that is specific to deploying to host2"""

def deploy():
    """"Deploy to both hosts, each using its own logic"""
    host1_deploy()
    host2_deploy()

I would like to do

fab deploy

and have it be equivalent to

fab host1_deploy host2_deploy

In other words, run each of the subtasks and for each one use the list of hosts that it specifies. However, this does not work. Instead, the deploy() task wants its own list of hosts that it will propogate to all of its subtasks.

Is there a way to update the deploy() task here so it will do what I want while leaving the subtasks alone so they can be run individually?

Answer 1

Since Fabric 1.3, the execute helper is now available to do just this. The documentation is available here: Intelligently executing tasks with execute.

Here is the example they use:

from fabric.api import run, roles, execute

env.roledefs = {
    'db': ['db1', 'db2'],
    'web': ['web1', 'web2', 'web3'],
}

@roles('db')
def migrate():
    # Database stuff here.
    pass

@roles('web')
def update():
    # Code updates here.
   pass

And then to run both migrate and web from another task deploy:

def deploy():
    execute(migrate)
    execute(update)

And this will respect the roles and hosts lists that those tasks have.