On Tue, 10 Feb 2015 15:47 -0500, Josh Smift <[email protected]> wrote:
> http://docs.ansible.com/intro_patterns.html shows
>
> webservers:dbservers:&staging:!phoenix
>
> as an example of a combination of unions and intersections, and says that
> this means
>
> all machines in the groups `webservers' and `dbservers' are to be
> managed if they are in the group `staging' also, but the machines are
> not to be managed if they are in the group `phoenix'
>
> To simplify slightly, because I don't actualy need the negation in my
> example, it's saying that
>
> webservers:dbservers:&staging
>
> means
>
> (websevers UNION dbservers) INTERSECTION staging
>
> which is cool.
>
> But, I have a use case where I want to say
>
> webservers UNION (dbservers INTERSECTION staging)
>
> i.e. I want to manage with all webservers and only staging dbservers. I
> didn't see an obvious way to do that; all three of
>
> webservers:dbservers:&staging
> webservers:staging:&dbservers
> dbservers:&staging:webservers
> staging:&dbservers:webservers
>
> seem to be equivalent, and adding parentheses didn't seem to be supported
> (I got "ERROR: provided hosts list is empty").
>
> I particularly want to use it in a --limit argument, if that matters.
>
> Is there a way to do this, or does union always take precedence over
> intersection?
There magic happens in lib/ansible/inventory.get_hosts() [1].
# when applying the host selectors, run those without the "&" or "!"
# first, then the &s, then the !s.
patterns = pattern_regular + pattern_intersection + pattern_exclude
[...]
if p.startswith("!"):
hosts = [ h for h in hosts if h not in that ]
elif p.startswith("&"):
hosts = [ h for h in hosts if h in that ]
else:
to_append = [ h for h in that if h.name not in [ y.name for y in hosts
] ]
hosts.extend(to_append)
My brain can't find a way to define what you want using patterns alone.
Filled issue#10234 as a possible improvement [2].
[1] -
https://github.com/ansible/ansible/blob/devel/lib/ansible/inventory/__init__.py#L176
[2] - https://github.com/ansible/ansible/issues/10234
Giovanni
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