Ansible, saving list of hosts into a variable - sql

Question

I have a playbook where I am first running a SQL statement to get a list of hosts from a database. I then save that list into a variable and want to run the next set of tasks over this list of hosts. But I am not sure how to do this or if it is even possible to dynamically define the hosts into an Ansible variable?
Below is a snippet of my code and what I am trying to do.
---
- hosts: all
gather_facts: no
tasks:
- name: Get list of hosts
command: sqlcmd -d testDB -q "SET NOCOUNT ON; SELECT DISTINCT HostName FROM Servers" -S "Central_Server" -h -1
register: sql_servers
- hosts: '{{ sql_servers.stdout_lines }}'
serial: 1
gather_facts: no
tasks:
........
other tasks
........
In the above code, I am trying to save the list of hosts into the sql_servers variables and want to run the 2nd set of my playbook over those hosts.

Answer 1

You're running the play with hosts: all. This implicates that there might be more hosts and, as a result, more lists of sql_servers too. Let's concatenate the lists. For example, whatever the source of the lists might be, given the inventory
shell> cat hosts
srv1 sql_servers='["a", "b"]'
srv2 sql_servers='["c", "a"]'
srv3 sql_servers='["e", "b"]'
the play
- hosts: all
tasks:
- set_fact:
srvs: "{{ ansible_play_hosts|
map('extract', hostvars, 'sql_servers')|
flatten|unique }}"
run_once: true
gives
srvs:
- a
- b
- c
- e
Now, use add_host and create group sql_servers
- add_host:
hostname: "{{ item }}"
groups: sql_servers
loop: "{{ srvs }}"
run_once: true
Use this group in the next play. The complete simplified playbook
- hosts: all
tasks:
- add_host:
hostname: "{{ item }}"
groups: sql_servers
loop: "{{ ansible_play_hosts|
map('extract', hostvars, 'sql_servers')|
flatten|unique }}"
run_once: true
- hosts: sql_servers
tasks:
- debug:
var: ansible_play_hosts_all
run_once: true
gives
ansible_play_hosts_all:
- a
- b
- c
- e
Fit the control flow to your needs.