Re: [Fab-user] Providing a fallback for roles at runtime

[Michael Gliwinski]

On Thursday 19 Dec 2013 08:44:15 Paul Walsh wrote:
...
> "execute this task on db if db is in roles, otherwise, execute on default."
> 
> So, to achieve that, I tried:
> 
> import utilities
> 
> @roles(utilities.get_role('db'))
> @task
> def drop():
>     utilities.alert(u'Dropping the database.')
>     run('dropdb {name}'.format(name=env.db_name))
> 
> 
> # utilities.py
> def get_role(target_role):
>     if target_role in env.roles:
>         return target_role
>     else:
>         return 'default'
> 
> 
> However, the task still attempts to run on roles['default']. I'm diving in
> but I'm also wondering if there is another way I could, in the fabfile
> itself, dynamically set the role for a task like this.

I'm not sure how you set env.roles, but note that utilities.get_role will be 
executed when your fabfile is loaded.

Roles can actually be callables, so you could do something like:

  def db_or_default():
      if ...: return ['5.6.7.8']
      return env.roledefs['default']

  env.roledefs = {'default': ['1.2.3.4'], 'db': db_or_default}


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