Passing list of lists in a playbook to a single command (not with_items)

ansible

I two groups of hosts: dc1 and dc2. Also combined to a DC group.

I need to pass a list of IP addresses of hosts from a foreign DC to a command. with_items doesn't work here at all.

Should look like this:

somescript -H 10.10.10.3 -H 10.10.10.4

So there're 2 points:
1. Get list of hosts in group DC excluding ones from host primary group. Not sure if that's possible at all, so the dirty way is to set a remote_dc variable (or array).
2. Let's say we have a list of hosts from p.1: groups[remote_dc]. How to use it as a key fro hostvars[ key ]['ansible_eth1']['ipv4']['address'] and get result as a list?

For now I had to use a very dirty way: I've created a remote_addresses list for each DC group and iterated like this:

command: somescript -H {{ remote_addresses|join(' -H ') }}

So is there a proper way to implement p.1 and p.2 and omit manual creation of the ip addresses list?

Best Answer

The ansible documentation has this example:

A frequently used idiom is walking a group to find all IP addresses in that group:

{% for host in groups['app_servers'] %}
   {{ hostvars[host]['ansible_eth0']['ipv4']['address'] }}
{% endfor %}

It does approximately what you want. You can use it like this:

- name: Execute somescript
  command: >
    somescript {% for host in groups['app_servers'] %}
                  -H {{ hostvars[host]['ansible_eth0']['ipv4']['address'] }}
               {% endfor %}

Now, you also want to exclude the host itself from the list of ip addresses. You can do this by modifying the {% for %} like this:

{% for host in groups['app_servers'] if host != ansible_host %}

Instead of ansible_host, you might need to use ansible_fqdn or ansible_nodename. You must check what works for you.

Related Topic