Re: [Fab-user] Serial to parallel execution

[Jeff Forcier]

Hi Steven,

On Wed, Nov 16, 2011 at 5:36 PM, Hajducko, Steven
<address@hidden> wrote:

> Basic premise is, want to be able to compile ( once ), then parallel the 
> push/install.
> Also want to use roles to be able to selectively decide which environment to 
> push to at runtime.

Your posted code is acceptable for what you need to do, given how
things currently work. However, another possibly cleaner alternative
would be this:

    @task
    @parallel
    def push():
        ...

    @task
    @runs_once
    def package():
        ...

    @task
    def deploy(ver, rolename):
        <set env vars>
        execute(package) # runs only once like this anyway, but
keeping @runs_once doesn't hurt
        execute(push, role=rolename)

Unless there are bugs (!) you should be able to run this like so
(note: no global host/role arguments):

    $ fab deploy:1.73,prod

while as a bonus, retaining the ability to run push() or package() as
regular standalone tasks.

The trick is omitting any global connection params, and instead
leveraging execute()'s host/role kwargs.

The only downside is that Fab auto-interprets certain task args
("host", "roles" etc -- see execution docs) so you have to use some
name other than "role" or Fab will still end up running 'deploy' with
a host list.

FWIW, if this pattern becomes more prevalent I might add an option to
disable auto-interpretation so you can use more natural kwarg names.

> Also, is there a better way to test directory existence that I’m missing?

Try fabric.contrib.files.exists :) (It's in the 'contrib' API docs.)


Best,
Jeff

-- 
Jeff Forcier
Unix sysadmin; Python/Ruby engineer
http://bitprophet.org