Ansible Plugin implementing the include_defaults action.

include_defaults.py

"""
Ansible Plugin implementing the include_defaults action.

Like include_vars, but the included defaults can be overridden by the
inventory or by group vars. Can be used to read the defaults from another role.

Usage: drop it into a directory called ``action_plugins`` in your playbook
directory. Then you can use it with::

    - name: get the defaults from the web server role
      action: include_defaults roles/web/defaults/main.yml

Proposed for inclusion in <https://github.com/ansible/ansible/pull/8808>.

"""
# (c) 2014 Daniele Varrazzo <daniele.varrazzo@gmail.com>

import os
from ansible.utils import template
from ansible import utils
from ansible import errors
from ansible.runner.return_data import ReturnData

class ActionModule(object):

    TRANSFERS_FILES = False

    def __init__(self, runner):
        self.runner = runner

    def run(self, conn, tmp, module_name, module_args, inject, complex_args=None, **kwargs):

        if not module_args:
            result = dict(failed=True, msg="No source file given")
            return ReturnData(conn=conn, comm_ok=True, result=result)

        source = module_args
        source = template.template(self.runner.basedir, source, inject)

        if '_original_file' in inject:
            source = utils.path_dwim_relative(inject['_original_file'], 'defaults', source, self.runner.basedir)
        else:
            source = utils.path_dwim(self.runner.basedir, source)

        if os.path.exists(source):
            data = utils.parse_yaml_from_file(source, vault_password=self.runner.vault_pass)
            if data and type(data) != dict:
                raise errors.AnsibleError("%s must be stored as a dictionary/hash" % source)
            elif data is None:
                data = {}
            inject['defaults'].update(data)
            return ReturnData(conn=conn, comm_ok=True, result={})
        else:
            result = dict(failed=True, msg="Source file not found.", file=source)
            return ReturnData(conn=conn, comm_ok=True, result=result)

Warning! unfortunately this implementation of include_defaults has an issue: because it changes some data structures in-place it doesn't work when ansible runs in parallel on many hosts, because the process forks and the modified variables get lost.

In my case, I have solved the issue by adding a vars_files list to the group_vars files: the list usually contains the name of the file in vars_files itself but it can contain further customization (can create configurations "inheriting" from a base one and tweaking a few things). I've then converted every task file where I was using include_defaults into include_vars, with a final include of vars_files too, in order to have the values specified in vars_files to override the "defaults" (which become too powerful otherwise). E.g. if a web client should know the port of the web server, you can have:

• file roles/web_server/defaults/main.yml:

http_port: 80

• file group_files/testsite:

http_port: 8080
vars_files:
  - group_files/testsite

• file roles/web_client/tasks/main.yml:

- include_vars: "{{item}}"
  with_items:
    - roles/web_server/defaults/main.yml
    - {{vars_files}}