Extract hostvar list

Question

I'm trying to get secondary ip addresses from hosts in a group and set them to a fact.

my hostvars contain

{
  "network_interfaces": [
    {
      "private_ip_address": "10.224.1.48",
      "private_ip_addresses": [
        {
          "primary": true,
          "private_dns_name": "ip-10-224-1-48.us-east-2.compute.internal",
          "private_ip_address": "10.224.1.48"
        },
        {
          "primary": false,
          "private_dns_name": "ip-10-224-1-66.us-east-2.compute.internal",
          "private_ip_address": "10.224.1.66"
        },
        {
          "primary": false,
          "private_dns_name": "ip-10-224-1-135.us-east-2.compute.internal",
          "private_ip_address": "10.224.1.135"
        }
      ],
      "source_dest_check": true,
      "status": "in-use",
      "subnet_id": "subnet-0cfc6e2da31b9cf50",
      "vpc_id": "vpc-123456"
    }
  ],
}

Something like

set_fact:
  private_ips: "{{ groups['database'] | map('extract', hostvars, ['network_interfaces[0]','private_ip_addresses[1]','private_ip_address']) | join(',')  }}"

which doesn't work.

set_fact: 
  private_ips: "{{ groups['database'] | map('extract', hostvars, ['network_interfaces']) | map(attribute='private_ip_addresses') }}"  

ends up with "private_ips": "[AnsibleUndefined, AnsibleUndefined]"

I'm looking for the result to be just a single IP out of private_ip_addresses from each host in the group

Answer 1

Create the list of IPs at each host

    - set_fact:
        my_ip: "{{ network_interfaces|json_query(_query) }}"
      vars:
        _query: '[].private_ip_addresses[].private_ip_address'

gives for the data from the example

  my_ip:
  - 10.224.1.48
  - 10.224.1.66
  - 10.224.1.135

Then, select the second item from the lists of all hosts in the group database

    - set_fact:
        private_ips: "{{ groups.database|
                         map('extract', hostvars, 'my_ip')|
                         map(attribute=1)|list }}"
      run_once: true