For everyone else's benefit, let me step back a little and provide some
background info.
(A)
Ansible has a directory called "host_vars/" where you can store variables
that are host specific
(B)
"hostvars" refers to an datastructure that can be used for getting
variables from other hosts.
For instance, if I want the OS family of a server named "foo.example.com"
when accessed from a template about *another* host:
{{ hostvars["foo.example.com"]["ansible_os_family"] }}
This is usually unneccessary as if you want the variable for your current
host it's just
{{ ansible_os_family }}
So the question is not, "how does the code work", but what problem are you
trying to solve that you are having trouble with?
(C)
Your question was "some of my plays on hosts need dynamic information from
other hosts so I am trying to understand when/which variable in the
playbooks become available in hostvars."
If you need to get a "fact" (some information discovered about a remote
system that is not explicitly set as a variable, but derived from talking
to it), you need to talk to that system in an earlier play.
For instance if the DB servers need the IP addresses of all the webservers,
this is common:
- hosts: webservers
tasks: []
- hosts: dbservers
tasks:
- # things go here
Talking to the webservers before will get their fact information.
Variables set otherwise are already availble, and do not require talking to
the hosts.
Sometime in 1.5 timeframe, we'll also be implementing a way to store facts
from previous runs, so you don't have to talk to nodes within the same play.
On Mon, Nov 25, 2013 at 5:59 AM, Jerome Wagner <[email protected]> wrote:
> Hello,
>
> some of my plays on hosts need dynamic information from other hosts so I
> am trying to understand when/which variable in the playbooks become
> available in hostvars.
>
> I undestand that :
> - a variable defined via gather_facts is available via hostvars[host]
> - a variable defined in host_vars is available via hostvars[host]
> - a variable defined in group_vars/group is available via hostvars[host]
> if the host belong to the group
> - a variable set on a host during a play via the register: syntax is
> available via hostvars[host]
> - a call to set_fact: on a host makes the variable available via
> hostvars[host]
>
> but a variable defined
> - at the play/vars: level
> - at the play/vars_files: level
> - at the role/vars level
> - role/default level
> are not made available to hostvars[host]
>
> Is this right ? is there a documentation explaining this along this angle
> that I could read ?
>
> on a vocabulary perspective, is it correct to say that
>
> - hostvars[host] contains all facts currently know about a host at a
> given step in the playbook execution
> - all facts known about a given host at a given step in the playbook
> execution are available in hostvars[host]
>
> Is there a simple way to express which variables become host facts ?
>
> Thank you
> Jerome
>
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--
Michael DeHaan <[email protected]>
CTO, AnsibleWorks, Inc.
http://www.ansibleworks.com/
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