Assigning the hosts attribute dynamically in Ansible from Python

Question

I am integrating Ansible with Python and MySQL DB. A part of my use case is that given a group name to Ansible, send that group name to python which does a db read and returns a list of IPs corresponding to that group name. For a test I want to ping the returned IPs.

Here is my playbook for achieving the same:

name: run a cmd
hosts: localhost
connection: local
tasks:
  name: runs a python script with a parameter
      shell: python /pythonScripts/AnsibleDBRead.py <someGroupName>
      register: py_ret
    - set_fact:
       ip_list: "{{py_ret.stdout}}"
   - debug: var=hostvars['localhost']['ip_list']  # option to set messages here as well but not both together


name: png the hosts returned 
hosts: hostvars['localhost']['ip_list'] #this does not work
#hosts: [ "127.0.0.1", "54.147.177.9"] #this works same value but hardcoded
tasks: 
    - debug: var=hostvars['localhost']['ip_list']  # able to print the value

I am trying to set the values stored in ip_list as the hosts: for second play but without any success. The error I get is no hosts matched. Here is the output whe n run with hardcoded part commented. Ignore the formatting of the script.

PLAY [run a cmd] ***************************************************************

TASK [setup] *******************************************************************
ok: [localhost]

TASK [runs a python script with a parameter] ***********************************
changed: [localhost]

TASK [set_fact] ****************************************************************
ok: [localhost]

TASK [debug] *******************************************************************
ok: [localhost] => {
    "hostvars['localhost']['ip_list']": [
        "127.0.0.1", 
        "54.147.177.9"
    ]
}

PLAY [png the hosts returned] **************************************************
skipping: no hosts matched

PLAY RECAP *********************************************************************
localhost                  : ok=4    changed=1    unreachable=0    failed=0

from what I have read I should be able to access the variable declared in one play in another play using hostvars. Any help is appreciated.

techraf · Accepted Answer · 2016-12-14 13:10:17Z

1

After some trial-and-error testing, I think this should work for you:

- name: ping the hosts returned 
  hosts: "{{ hostvars['localhost']['ip_list'] | join(',') }}"
  tasks: 
    - debug:

And it seems it's a known issue: pass array as "hosts" in playbook #16051 and workaround.

edited Dec 14, 2016 at 13:10

answered Dec 14, 2016 at 12:56

techraf

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2 Comments

shshnk Over a year ago

Thanks! it worked for me. Can you please explain the significance of "join" as the value returned from python was already comma separated ?

techraf Over a year ago

ip_list input was comma a separated string, but it got converted to a list object, so ip_list is a list object, ip_list | join(',') converts it to a string.

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