Ansible lineinfile with list to set ntp servers - loops

Question

I want to add some lines to a file (they are ntp servers in /etc/ntp.conf). Unfortunately, I can't use a template for various reasons.
so I have a variable like so:
vars:
- dns:
- "{ 'region': 'syd', 'dns_servers': ['1.2.3.4', '2.3.4.5', '3.4.5.6' ] }"
- "{ 'region': 'lon', 'dns_servers': ['2.2.2.2', '3.3.3.3', '4.4.4.4' ] }"
- "{ 'region': 'ny', 'dns_servers': ['5.5.5.5', '6.6.6.6', '7.7.7.7' ] }"
- ntp:
- { 'region': 'syd', 'ntp_servers': ['syd1.pool.ntp.org','syd2.pool.ntp.org','syd2.pool.ntp.org'] }
- { 'region': 'lon', 'ntp_servers': ['lon1.pool.ntp.org','lon2.pool.ntp.org','lon2.pool.ntp.org'] }
- { 'region': 'ny', 'ntp_servers': ['ntp1.pool.ntp.org','ntp2.pool.ntp.org','ntp2.pool.ntp.org'] }
So there's 2 lists there; dns and ntp. Each list contains a dictionary of region -> server mappings.
I want to iterate over the (in this case the ntp list) list to add a line for each ntp server in turn. I've discovered the loop_control parameter to a loop construct, which allows me to set an offset into the ntp_servers list.
Here's one attempt I'm making to loop over the elements of the list in the dictionary:
- name: Replace ntp servers in /etc/ntp.conf
debug:
msg: "{{ item[loop_count] }}"
loop: "{{ ntp['region']['ntp_servers'] }}"
loop_control:
index_var: loop_count
when: item.region == region
(As an aside, how do you feel about using 'i' as the loop counter variable? )
I know this would be much easier with a template, and that lineinfile is an antipattern, but I am constrained by issues outside of my control.
The problem I have is that I want to loop over the items of the ntp_servers array, but my loop is looping over the ntp dictionary. I've tried various combinations, but suspect that I'm using the wrong data structure - can anyone advise, please?
Thanks

Answer 1

i see an issue with the vars structure. you should remove the hyphen from the ntp and dns variable declaration:
vars:
ntp:
.....
dns:
.....
Also, the double quotes in the dns list elements, are making the elements considered as strings, ntp look ok.
to get all 9 ntp servers of the ntp variable in a list, so you can process in a loop, you can use the expression (feel free to remove the sum(start=[]) and final list conversion, and then add them back to see why i used them):
"{{ ntp | map(attribute='ntp_servers') | list | sum(start=[]) | list }}"
example playbook:
- hosts: localhost
gather_facts: false
vars:
ntp:
- { 'region': 'syd', 'ntp_servers': ['syd1.pool.ntp.org','syd2.pool.ntp.org','syd2.pool.ntp.org'] }
- { 'region': 'lon', 'ntp_servers': ['lon1.pool.ntp.org','lon2.pool.ntp.org','lon2.pool.ntp.org'] }
- { 'region': 'ny', 'ntp_servers': ['ntp1.pool.ntp.org','ntp2.pool.ntp.org','ntp2.pool.ntp.org'] }
tasks:
- name: print
debug:
msg: "{{ item }}"
with_items:
- "{{ ntp | map(attribute='ntp_servers') | list | sum(start=[]) | list }}"
output:
TASK [print] ********************************************************************************************************************************************************************************************************
ok: [localhost] => (item=None) => {
"msg": "syd1.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "syd2.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "syd2.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "lon1.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "lon2.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "lon2.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "ntp1.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "ntp2.pool.ntp.org"
}
ok: [localhost] => (item=None) => {
"msg": "ntp2.pool.ntp.org"
}
PLAY RECAP