Unable to get remote target hostname when using delegate_to

[Shifa Shaikh]

Below playbook gets the disk usage percentage of '/tmp' from a list of remote_hosts [20 remote servers] and stores it locally (delegate_to) in a file {{ playbook_dir }}/tmpfiles/stats.yml

---
hosts: remote_hosts
  tasks:    
    - name: Generate JSON data
      lineinfile:
        path: "{{ playbook_dir }}/tmpfiles/stats.yml"
        line: "{{ inventory_hostname }}_{{ item.mount }}: {{ (100 * ((item.size_total - item.size_available) / item.size_total)) | round(1, 'common') }}"
        insertafter: EOF
      delegate_to: localhost
      when: item.mount == '/tmp'
      with_items: '{{ ansible_mounts }}'

I wish to get the target hostname_mountname in the stats.yml

Thus if the remote_hosts are

10.0.0.2
10.0.0.3
10.0.0.5

My stats.yml should have the below entries (Expected Output):

10.0.0.2_/tmp: 54
10.0.0.3_/tmp: 42
10.0.0.5_/tmp: 65

However, after using lineinfile and delegate_to it always prints localhost

localhost:/tmp: 54
localhost_/tmp: 42
localhost_/tmp: 65

I tried using {{ ansible_host }} instead of {{ inventory_hostname }} but it always prints localhost instead of the target from where it is fetching the disk usage information.

Note: if I remove delegate_to then it prints the remote IP fine but then I wish the file to be created locally and not on the remote host.

[Kai Stian Olstad]

Delegate to localhost does not change inventory_hostname, if it did it would break a lot of code out there.
And I can prove it with this code that mimic you codes behavior.

$ more test.yml
---
- hosts: a1,a2
gather_facts: no
become: no
vars:
myvar:
- value1
- value2
- value3
tasks:
- lineinfile:
path: /tmp/test
line: "{{ inventory_hostname }} {{ item }}"
insertafter: EOF
create: true
delegate_to: localhost
when: item == "value2"
with_items: "{{ myvar }}"

And by running it I get

$ ansible-playbook test.yml; echo "Content of /tmp/test:"; cat /tmp/test

PLAY [a1,a2] ***************************************************************

TASK [lineinfile] **********************************************************
skipping: [a1] => (item=value1)
skipping: [a2] => (item=value1)
changed: [a1 -> localhost] => (item=value2)
skipping: [a1] => (item=value3)
changed: [a2 -> localhost] => (item=value2)
skipping: [a2] => (item=value3)

PLAY RECAP *****************************************************************
a1 : ok=1 changed=1 unreachable=0 failed=0
a2 : ok=1 changed=1 unreachable=0 failed=0

Content of /tmp/test:
a1 value2
a2 value2


--
Kai Stian Olstad