How to increment a value on hosts (Ansible)

Question

I have endless kafka servers to configure, their ids must be different from each other. Configuration must be done through jinja templating.

Their broker.id field should start from 0 to infinity if there are infinite number of servers.

# The id of the broker. This must be set to a unique integer for each broker.
broker.id={{ broker_id }}

Expected on the conf files:

server1

broker.id=0

server2

broker.id=1

serverN

broker.id=N-1

EDIT

main.yml

---

- include: install.yml
  tags:
    - kafka
    - install

- include: config.yml
  tags:
    - kafka
    - config

config.yml

---

- name: server properties
  template:
    src: server.properties
    dest: /opt/kafka/config/server.properties

- name: zookeeper properties
  template:
    src: zookeeper.properties
    dest: /opt/kafka/config/zookeeper.properties

defaults/main.yml

---
#server.properties
broker_id: 0

templates/server.properties

.
.
.

############################# Server Basics #############################

# The id of the broker. This must be set to a unique integer for each broker.
broker.id={{ broker_id }}

############################# Socket Server Settings #############################
.
.
.

Ansible is applying same configuration to multiple servers, as normal behavior. But while applying same configuration broker.id must be unique.

{{ 99999999 | random | to_uuid }}

This is working, still i'm curious if it's possible to assign 0 to broker.id and increment +1 on each server?

Answer 1

Add below

- name: Set Broker ID
  set_fact:
     broker_id: {{ groups['all'].index(inventory_hostname) }}

followed by other tasks.

Answer 2

It's possible to create the inventory dynamically in the first play and use it in the second play. For example the playbook below

- hosts: localhost
  vars:
    no_of_servers: 3
  tasks:
    - add_host:
        name: "srv-{{ item }}"
        groups: kafka
        id: "{{ my_idx }}"
      loop: "{{ range(0, no_of_servers)|list }}"
      loop_control:
        index_var: my_idx

- hosts: kafka
  tasks:
    - debug:
        msg: "{{ inventory_hostname }} id: {{ id }}"

gives

ok: [srv-0] => {
    "msg": "srv-0 id: 0"
}
ok: [srv-1] => {
    "msg": "srv-1 id: 1"
}
ok: [srv-2] => {
    "msg": "srv-2 id: 2"
}

Answer 3

Try this, I think it will solve

broker.id={{ (inventory_hostname.split('0')[-1] | int) }}