Ansible - Multiple/ Alternative hostnames for the same host

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Assume I have hosts with multiple (DNS) names/IPs, e.g. because they have multiple NICs and thus routes to reach them.

I want to play a playbook in case one of these routes fails. Since I do not know which one works, I would like ansible to try all of them and then play the book only once for this host. It would be easy to put all the host's names into the inventory and let it run, but then the playbook would be executed once for each name of the host.

Question: Is there a way to specify alternative host names or to tell ansible to run the playbook only on one host per group?

ansible
1 Answers

It can be implemented

to run the playbook only on one host per group

See example below.

- hosts: jails-01                                                                            
  strategy: linear                                                                           
  vars:                                                                                      
    lock_file: /var/lock/my_ansible_hostname.lock                                                 
  tasks:                                                                                     
    - name: delete lock_file                                                                 
      file:                                                                                  
        path: "{{ lock_file }}"                                                              
        state: absent                                                                        
      run_once: true                                                                         
      delegate_to: localhost                                                                 
    - name: select host                                                                      
      shell: "echo {{ ansible_hostname }}  > {{ lock_file }}"                                
      args:                                                                                  
        creates: "{{ lock_file }}"                                                           
      delegate_to: localhost                                                                 
    - name: winner takes it all                                                              
      fail:                                                                                  
        msg: "Too late. Other thread is running. End of play."                               
      when: lookup('file', lock_file) != ansible_hostname                                    
    - name: go ahead                                                                         
      debug:                                                                                 
        msg: "{{ ansible_hostname }} goes ahead ... "


# ansible-playbook playbook.yml | grep msg
fatal: [test_01]: FAILED! => {"changed": false, "msg": "Too late. Other thread is running. End of play."}
fatal: [test_03]: FAILED! => {"changed": false, "msg": "Too late. Other thread is running. End of play."}
    "msg": "test_02 goes ahead ... "
user_64825610
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