How to pair hosts with variables in ansible - ansible

Question

I have an inventory like:
all:
children:
server_group1:
hosts:
host1:
server_group2:
children:
app1:
hosts:
host2:
host3:
app2:
hosts:
host4:
host5:
server_group3:
...
I have organized my server variables like so:
> cat group_vars/server_group2/app1
app1:
name1: value1
name2: value2
> cat group_vars/server_group2/app2
app2:
name1: value11
name2: value21
I am trying to name my dict after the group (thus making them unique) and access it in my playbook:
hosts: server_group2
tasks:
- name: check file
local_action: stat path=path/to/test/{{hostvars[0].name1}}
register: payld_txt
- name: conditional transfer
copy:
src: path/to/test/{{hostvars[0].name1}}
dest: /svr/path/{{hostvars[0].name2}}
when: payld_txt.stat.exists
I end up with this error:
The task includes an option with an undefined variable. The error was: 'name1' is undefined
Where am I going wrong?

Answer 1

Before you go any further, you need to fix your inventory which does not respect ansible's structure for yaml sources. A simple command as the following can give you some hints:
$ ansible -i inventories/test.yml all --list-hosts
[WARNING]: Skipping unexpected key (server_group1) in group (all), only "vars", "children" and "hosts" are valid
[WARNING]: Skipping unexpected key (server_group2) in group (all), only "vars", "children" and "hosts" are valid
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'
hosts (0):
The correct syntax is:
---
all:
children:
server_group1:
hosts:
host1:
server_group2:
children:
app1:
hosts:
host2:
host3:
app2:
hosts:
host4:
host5:
Which now gives:
$ ansible -i inventories/test.yml all --list-hosts
hosts (5):
host1
host2
host3
host4
host5

Answer 2

``hostvars[0].name1`` The error was: 'name1' is undefined
Q: "Where am I going wrong?"
A: The variable name1 is item of the dictionary app1 or app2. It must be referenced app1.name1 or app2.name1. In addition to this,
hostvars is a dictionary not an array. hostvars[0] does not exist. An item of a dictionary must be referenced by a key. For example the play below
- hosts: server_group2
tasks:
- set_fact:
my_keys: "{{ hostvars.keys()|list }}"
run_once: true
- debug:
var: my_keys
run_once: true
- debug:
msg: "{{ hostvars[item].app1.name1 }}"
loop: "{{ my_keys }}"
when: "item in groups['app1']"
run_once: true
- debug:
msg: "{{ hostvars[item].app2.name1 }}"
loop: "{{ my_keys }}"
when: "item in groups['app2']"
run_once: true
gives
ok: [host5] =>
my_keys:
- host5
- host4
- host3
- host2
- host1
ok: [host5] => (item=host3) =>
msg: value1
ok: [host5] => (item=host2) =>
msg: value1
ok: [host5] => (item=host5) =>
msg: value11
ok: [host5] => (item=host4) =>
msg: value11
Optionally use json_query to create the list of the keys
- set_fact:
my_keys: "{{ hostvars|dict2items|json_query('[].key') }}"
run_once: true
The simplified version of the playbook
- hosts: server_group2
tasks:
- debug:
msg: "{{ hostvars[inventory_hostname].app1.name1 }}"
when: "inventory_hostname in groups['app1']"
- debug:
msg: "{{ hostvars[inventory_hostname].app2.name1 }}"
when: "inventory_hostname in groups['app2']"
gives
skipping: [host5]
skipping: [host4]
ok: [host3] =>
msg: value1
ok: [host2] =>
msg: value1
ok: [host5] =>
msg: value11
ok: [host4] =>
msg: value11
skipping: [host3]
skipping: [host2]
In fact, addressing hostvars[inventory_hostname] is not necessary. The simplified tasks below give the same output.
- debug:
msg: "{{ app1.name1 }}"
when: "inventory_hostname in groups['app1']"
- debug:
msg: "{{ app2.name1 }}"
when: "inventory_hostname in groups['app2']"