Ansible switch between host targets with the same name

Question

In our playbook we have a host named: backupserver Lets assume we have a big list of inventories +- 100. Now we have a new backupserver, so we end up with 2 different hosts:

• backupserver-1
• backupserver-2

Per inventory we want to specify which one to use. e.g.

• inventory-1 should connect to backupserver-1
• inventory-2 should connect to backupserver-2
• inventory-3 should connect to backupserver-2
• inventory-4 should connect to backupserver-1

However they use the same playbook, in which we point to backupserver.

e.g.

delegate_to: backupserver

Our goal is to only setup the correct backupserver in the inventory files, we do not want to change the playbooks. Is it possible to make something like an alias to point to from the inventories? What I have in mind (The following is a group, so not a single delegate option and will not work)

in Inventory 1

hosts:
 backupserver:
    backupserver1 

Inventory 2

hosts:
 backupserver:
    backupserver2

Lets say we want to change the backupserver2's ip address, we do not want to update all the inventory files, but want to have 1 definintion of backupserver2 that is shared, so we can update it from 1 spot, for example with host_vars. What I have in mind visualized:

Or is there another way that makes sense, where we can have different targets in the inventory files but the same name in the playbook.

Answer 1

Lets say we want to change the backupserver2's ip address, we do not want to update all the inventory files, but want to have 1 definintion of backupserver2 that is shared, so we can update it from 1 spot, for example with host_vars.

If backupserver-1 and backupserver-2 are names, not ip addresses, the syntax you suggest is close but not correct; you would want tomsething like this in inventory 1:

all:
  hosts:
    backupserver:
      ansible_host: backupserver-1

And in inventory 2:

all:
  hosts:
    backupserver:
      ansible_host: backupserver-2

Etc.

If you are using an ip address (why are you doing that?), you can take advantage of the fact that your "inventory file" can actually be multiple files. Put the entry for the backup servers in separate files. That is, create backupserver1.yaml with:

all:
  hosts:
    backupserver:
      ansible_host: backupserver-1

Now you can run ansible like this:

ansible-playbook playbook.yaml -i inventory1.yaml -i backupserver1.yaml

Or if you're working with inventory 2 instead:

ansible-playbook playbook.yaml -i inventory2.yaml -i backupserver2.yaml

In either case, if the address of backupserver1 changes, you only need to update the value in one place, and similarly for your other servers.

---

Alternately, if your only interaction with the backup server is via delegation, then there is potentially a much simpler solution. Just put all the backup servers in one inventory file:

backupservers:
  hosts:
    backupserver1:
    backupserver2:

Set an inventory variable to identify the appropriate backup server for that inventory, e.g. in inventory1.yaml:

servers:
  hosts:
    node0:
    node1:
  vars:
    backupserver: backupserver1

In your playbook, using the variable in your delegate_to option:

- hosts: servers
  tasks:
  - name: mumble backup server mumble
    delegate_to: "{{ backupserver }}"
    command: date

And then always include your "target" inventory and your backupservers inventory:

ansible-playbook playbook.yaml -i inventory1.yaml -i backupservers.yaml