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# Copyright (c) 2017 Ansible Project
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
from __future__ import annotations
DOCUMENTATION = """
name: constructed
version_added: "2.4"
short_description: Uses Jinja2 to construct vars and groups based on existing inventory.
description:
- Uses a YAML configuration file with a valid YAML or C(.config) extension to define var expressions and group conditionals
- The Jinja2 conditionals that qualify a host for membership.
- The Jinja2 expressions are calculated and assigned to the variables
- Only variables already available from previous inventories or the fact cache can be used for templating.
- When O(strict) is False, failed expressions will be ignored (assumes vars were missing).
options:
plugin:
description: token that ensures this is a source file for the 'constructed' plugin.
required: True
choices: ['ansible.builtin.constructed', 'constructed']
use_vars_plugins:
description:
- Normally, for performance reasons, vars plugins get executed after the inventory sources complete the base inventory,
this option allows for getting vars related to hosts/groups from those plugins.
- The host_group_vars (enabled by default) 'vars plugin' is the one responsible for reading host_vars/ and group_vars/ directories.
- This will execute all vars plugins, even those that are not supposed to execute at the 'inventory' stage.
See vars plugins docs for details on 'stage'.
- Implicit groups, such as 'all' or 'ungrouped', need to be explicitly defined in any previous inventory to apply the
corresponding group_vars
required: false
default: false
type: boolean
version_added: '2.11'
extends_documentation_fragment:
- constructed
"""
EXAMPLES = r"""
# inventory.config file in YAML format
plugin: ansible.builtin.constructed
strict: False
compose:
var_sum: var1 + var2
# this variable will only be set if I have a persistent fact cache enabled (and have non expired facts)
# `strict: False` will skip this instead of producing an error if it is missing facts.
server_type: "ansible_hostname | regex_replace ('(.{6})(.{2}).*', '\\2')"
groups:
# simple name matching
webservers: inventory_hostname.startswith('web')
# using ec2 'tags' (assumes aws inventory)
development: "'devel' in (ec2_tags|list)"
# using other host properties populated in inventory
private_only: not (public_dns_name is defined or ip_address is defined)
# complex group membership
multi_group: (group_names | intersect(['alpha', 'beta', 'omega'])) | length >= 2
keyed_groups:
# this creates a group per distro (distro_CentOS, distro_Debian) and assigns the hosts that have matching values to it,
# using the default separator "_"
- prefix: distro
key: ansible_distribution
# the following examples assume the first inventory is from the `aws_ec2` plugin
# this creates a group per ec2 architecture and assign hosts to the matching ones (arch_x86_64, arch_sparc, etc)
- prefix: arch
key: architecture
# this creates a group per ec2 region like "us_west_1"
- prefix: ""
separator: ""
key: placement.region
# this creates a common parent group for all ec2 availability zones
- key: placement.availability_zone
parent_group: all_ec2_zones
"""
import os
from ansible import constants as C
from ansible.errors import AnsibleParserError
from ansible.inventory.helpers import get_group_vars
from ansible.plugins.inventory import BaseInventoryPlugin, Constructable
from ansible.plugins.loader import cache_loader
from ansible.utils.vars import combine_vars
from ansible.vars.plugins import get_vars_from_inventory_sources
class InventoryModule(BaseInventoryPlugin, Constructable):
""" constructs groups and vars using Jinja2 template expressions """
NAME = 'constructed'
# implicit trust behavior is already added by the YAML parser invoked by the loader
def verify_file(self, path):
valid = False
if super(InventoryModule, self).verify_file(path):
file_name, ext = os.path.splitext(path)
if not ext or ext in ['.config'] + C.YAML_FILENAME_EXTENSIONS:
valid = True
return valid
def get_all_host_vars(self, host, loader, sources):
""" requires host object """
return combine_vars(self.host_groupvars(host, loader, sources), self.host_vars(host, loader, sources))
def host_groupvars(self, host, loader, sources):
""" requires host object """
gvars = get_group_vars(host.get_groups())
if self.get_option('use_vars_plugins'):
gvars = combine_vars(gvars, get_vars_from_inventory_sources(loader, sources, host.get_groups(), 'all'))
return gvars
def host_vars(self, host, loader, sources):
""" requires host object """
hvars = host.get_vars()
if self.get_option('use_vars_plugins'):
hvars = combine_vars(hvars, get_vars_from_inventory_sources(loader, sources, [host], 'all'))
return hvars
def parse(self, inventory, loader, path, cache=False):
""" parses the inventory file """
super(InventoryModule, self).parse(inventory, loader, path, cache=cache)
self._read_config_data(path)
sources = []
try:
sources = inventory.processed_sources
except AttributeError:
if self.get_option('use_vars_plugins'):
raise
strict = self.get_option('strict')
cache = cache_loader.get(C.CACHE_PLUGIN)
try:
# Go over hosts (less var copies)
for host in inventory.hosts:
# get available variables to templar
hostvars = self.get_all_host_vars(inventory.hosts[host], loader, sources)
if cache.contains(host): # adds facts if cache is active
hostvars = combine_vars(hostvars, cache.get(host))
# create composite vars
self._set_composite_vars(self.get_option('compose'), hostvars, host, strict=strict)
# refetch host vars in case new ones have been created above
hostvars = self.get_all_host_vars(inventory.hosts[host], loader, sources)
if cache.contains(host): # adds facts if cache is active
hostvars = combine_vars(hostvars, cache.get(host))
# constructed groups based on conditionals
self._add_host_to_composed_groups(self.get_option('groups'), hostvars, host, strict=strict, fetch_hostvars=False)
# constructed groups based variable values
self._add_host_to_keyed_groups(self.get_option('keyed_groups'), hostvars, host, strict=strict, fetch_hostvars=False)
except Exception as ex:
raise AnsibleParserError(f"Failed to parse {path!r}.") from ex
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