About enable/disable by conditional values in ansible yaml manifest

I want a variable on Ansible to be active or passive depending on the condition.

I am using the role "davidwittman.redis". I'm setting up a redis cluster. I need to run a single yml file by deploying it to 3 servers at the same time. I can't distribute "yml" files separately.

I have a simple setup configuration below. Here, I want to activate the "redis_slaveof" value on all other servers, except the master server, depending on the condition.

In other words, I want the "redis_slaveof" value I selected to not be active on the master server, but to have this value active on the other 2 servers.

How can I do this, do you have any suggestions ?

my main ansible configuration;

> - name: Redis Replication Slave Installations   hosts: localhost
> 
>   pre_tasks:
>   - name: check redis server1
>     shell: "cat /etc/hosts |grep redis |awk '{print $2}' |sed -n 1p"
>     register: server01
> 
>   - name: check redis server2
>     shell: "cat /etc/hosts |grep redis |awk '{print $2}' |sed -n 2p"
>     register: server02
> 
>   - name: check redis server3
>     shell: "cat /etc/hosts |grep redis |awk '{print $2}' |sed -n 3p"
>     register: server03
> 
>   roles:
>     - role: davidwittman.redis
> 
>       vars:
>         - redis_version: 6.2.6
>         - redis_bind: 0.0.0.0
>         - redis_port: 6379
>         - redis_service_name: redis-service
>         - redis_protected_mode: "no"
>         - redis_config_file_name: "redis.conf"
> 
> #        - redis_slaveof: "{{ server01.stdout }} 6379"

I tried the following;

I added extra task and "import_role". I put a when condition in it. If my server01 value and server local hostname value are not the equal, enable this role. Thus, I thought that it would activate this value on other servers except the master server.But it didn't work, added it on all servers. I saw the following error in the logs. "[WARNING]: flush_handlers task does not support when conditional"

 tasks:
  - name: test
    import_role:
      name: davidwittman.redis
    vars:
      redis_slaveof: "{{ server01.stdout }} 6379"
    when: '"{{ (server01.stdout) }}" != "{{ ansible_hostname }}"'

I added the when condition to the main role as above and made it to two different roles in a single yml. This method also failed.

- role: davidwittman.redis
  when: '"{{ (server01.stdout) }}" != "{{ ansible_hostname }}"'

I defined the "if/else" condition as follows in the variable. But although it seems to have worked, it still gave the error "does not support when conditional". Added it to all servers as well.

redis_slaveof: "{%if '{{ (server01.stdout) }} != {{ ansible_hostname }}' %} {{ '{{ (server01.stdout) }} 6379' }} {% else %} {{ '' }} {% endif %}"

Solution

So you want to run a role differently, based on variables.

In your playbook do not use

roles:
  - role: davidwittman.redis

but rather do

tasks:
  - name: Pass variables to role
    include_role:
      name: myrole
    vars:
      rolevar1: value from task

This is executed after roles but now you can add when expressions:

tasks:
  - name: Pass variables to role
    include_role:
      name: myrole
    vars:
      rolevar1: value from task
    when: ansible_hostname = "server1"

  - name: Pass variables to role
    include_role:
      name: myrole
    vars:
      rolevar1: value from task
      additionalrolevar: whatever
    when: ansible_hostname != "server1"