Re: [Fab-user] Different roledefs per task

[Francisco José Marques Vieira]

Wow, this actually worked! And looks better than I ever hoped!

Now my fab_settings.py file looks like this:

--------------------------------------
from fabric.api import env

if env.get('group') == 'staging':
    ROLEDEFS = {
        'master': [
            'staging.host.01',
        ],
        'slaves': [
            'staging.host.02',
            'staging.host.03',
        ],
    }
elif env.get('group') == 'production':
    ROLEDEFS = {
        'master': [
            'production.host.01',
        ],
        'slaves': [
            'production.host.02',
            'production.host.03',
        ],
    }
else:
    ROLEDEFS = {} # This is required to avoid breaking the fabfile and 
thus breaking every fab command like fab -l
--------------------------------------


Then in my fabfile.py I have this:

--------------------------------------
from fab_settings import ROLEDEFS

env.roledefs = ROLEDEFS

@task
@roles('master')
def task1():
        ...

@task
@roles('slaves')
def task2():
        ...
--------------------------------------

And I can call the tasks like this:

--------------------------------------
fab task1 --set group=staging
--------------------------------------

So, the settings file became even simpler, and I can now have tasks for 
different roles in the same file while still being able to run them only 
in staging or production. And the only downside is that I have to use 
"--set group=staging" instead of just "-R staging"! xD

Thanks a lot, to you and to Fabric developers!
Francisco Vieira





On 12/18/2012 07:05 PM, Todd DeLuca wrote:
> This *might* answer your question.  I recommend providing more example
> code or output when posting to reduce ambiguity.
>
>
> The following fabfile.py allows you to define some tasks to run on
> "master" hosts and some on "slave" hosts.  You can then vary which hosts
> apply to these roles by using "prod" or "stage" to define env.roledefs
> when fabfile.py is imported.  Below I demonstrate using different
> command line syntaxes to accomplish the same thing, either `-R <role>`
> or `--set de=<role>` or using a task `<role>`.  I've used all 3 of these
> syntaxes in various fabfiles, depending on my mood the day I wrote them.
>   Personally I would avoid using `-R` to define `env.roledefs`, since
> they already have a different semantic association.
>
> The demo fabfile.py:
>
> from fabric.api import *
>
> # Using -R to set roledefs
> if 'prod' in env.roles:
>      env.roledefs = {'master': ['host1'], 'slave': ['host2', 'host3']}
> elif 'stage' in env.roles:
>      env.roledefs = {'master': ['host4'], 'slave': ['host5', 'host6']}
>
>
> # Using --set to set roledefs
> if env.get('de') == 'prod':
>      env.roledefs = {'master': ['host1'], 'slave': ['host2', 'host3']}
> elif env.get('de') == 'stage':
>      env.roledefs = {'master': ['host4'], 'slave': ['host5', 'host6']}
>
>
> # Using tasks to set roledefs
> @task
> def prod():
>      env.roledefs = {'master': ['host1'], 'slave': ['host2', 'host3']}
>
>
> @task
> def stage():
>      env.roledefs = {'master': ['host4'], 'slave': ['host5', 'host6']}
>
>
> # Roles to be executed on different sets of hosts
> @roles('master')
> @task
> def do_master():
>      print env.host_string
>
> @roles('slave')
> @task
> def do_slave():
>      print env.host_string
>
>
>
> Here you can see that the effect is the same no matter which command
> line syntax you use (though your edge cases might vary):
>
> $ fab --set de=prod do_master do_slave
> [host1] Executing task 'do_master'
> host1
> [host2] Executing task 'do_slave'
> host2
> [host3] Executing task 'do_slave'
> host3
>
> Done.
> $ fab --set de=stage do_master do_slave
> [host4] Executing task 'do_master'
> host4
> [host5] Executing task 'do_slave'
> host5
> [host6] Executing task 'do_slave'
> host6
>
> Done.
> $ fab -R prod do_master do_slave
> [host1] Executing task 'do_master'
> host1
> [host2] Executing task 'do_slave'
> host2
> [host3] Executing task 'do_slave'
> host3
>
> Done.
> $ fab -R stage do_master do_slave
> [host4] Executing task 'do_master'
> host4
> [host5] Executing task 'do_slave'
> host5
> [host6] Executing task 'do_slave'
> host6
>
> Done.
> $ fab prod do_master do_slave
> [host1] Executing task 'do_master'
> host1
> [host2] Executing task 'do_slave'
> host2
> [host3] Executing task 'do_slave'
> host3
>
> Done.
> $ fab stage do_master do_slave
> [host4] Executing task 'do_master'
> host4
> [host5] Executing task 'do_slave'
> host5
> [host6] Executing task 'do_slave'
> host6
>
> Done.
>
> Hope that helps,
> Todd
>
>
> On Tue, Dec 18, 2012 at 11:50 AM, Francisco José Marques Vieira
> <address@hidden <mailto:address@hidden>>
> wrote:
>
>     Hi everyone! This is my first post on this mailing list, so please
>     excuse me if I don't follow some rule or convention of yours.
>     My name is Francisco and I started using Fabric a couple weeks ago,
>     and so far I'm happy with what I've seen.
>     Nevertheless, there always comes a time when even the best tool
>     fails to accomplish some task, and that's why I'm here.
>
>     The thing is, I have two different ways to group my hosts: one is by
>     role (master or slave), the other is by staging or production, i.e.
>     there is a master and many slaves in staging, and another master and
>     many slaves in production.
>     I have tasks that I need to run only on the master and others to run
>     in the slaves. Also, I want to be able to run tasks only on staging
>     or only on production.
>
>     The way I've been handling this is by having two different roledefs,
>     one for master hosts and another for slaves. Each roledef has two
>     roles, staging and production, meaning I can do something like "fab
>     deploy -R staging" and this makes sure I won't be installing things
>     into production by mistake.
>     These roledefs are defined in a settings file and each fabfile of
>     mine imports one of them and sets env.roledefs to it.
>
>     This works as long as all the tasks in each file are to be executed
>     in hosts with the same role, either master or slaves. And so far
>     that's what happened naturally.
>     Now I have a fabfile which has some tasks that should run in the
>     master host and another task that should run in the slaves, but I
>     have no way of saying to fabric "please use a different roledef for
>     this task", since by the time my code inside the task starts to
>     execute, the roledefs have already been processed.
>     Is there any way around this which does not require me to separate
>     the tasks in two different files?
>
>     Francisco Vieira
>
>
>     P.S: Sorry for the such a big post for such a trivial matter...
>
>     _________________________________________________
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>
>
>
>
> --
> Todd DeLuca
> http://todddeluca.com
> http://wall.hms.harvard.edu/