I would like to run a handler only once in an entire playbook.
I attempted using an include statement in the following in the playbook file, but this resulted in the handler being run multiple times, once for each play:
- name: Configure common config
hosts: all
become: true
vars:
OE: "{{ ansible_hostname[5] }}"
roles:
- { role: common }
handlers:
- include: handlers/main.yml
- name: Configure metadata config
hosts: metadata
become: true
vars:
OE: "{{ ansible_hostname[5] }}"
roles:
- { role: metadata }
handlers:
- include: handlers/main.yml
Here is the content of handlers/main.yml:
- name: restart autofs
service:
name: autofs.service
state: restarted
Here is an example of one of the tasks that notifies the handler:
- name: Configure automount - /opt/local/xxx in /etc/auto.direct
lineinfile:
dest: /etc/auto.direct
regexp: "^/opt/local/xxx"
line: "/opt/local/xxx -acdirmin=0,acdirmax=0,rdirplus,rw,hard,intr,bg,retry=2 nfs_server:/vol/xxx"
notify: restart autofs
How can I get the playbook to only execute the handler once for the entire playbook?
For such requirements where we need one tasks to run only once on a batch of hosts and we will be running that from Ansible controller node, we have feature parameter named run_once. When we have this parameter mentioned in a task, that task will run only once on first host it finds despite the host batch.
You can also limit the hosts you target on a particular run with the --limit flag. Negated limit. Note that single quotes MUST be used to prevent bash interpolation.
The easiest way to run only one task in Ansible Playbook is using the tags statement parameter of the “ansible-playbook” command. The default behavior is to execute all the tags in your Playbook with --tags all .
The answer
The literal answer to the question in the title is: no.
Playbook is a list of plays. Playbook has no namespace, no variables, no state. All the configuration, logic, and tasks are defined in plays.
Handler is a task with a different calling schedule (not sequential, but conditional, once at the end of a play, or triggered by the meta: flush_handlers
task).
A handler belongs to a play, not a playbook, and there is no way to trigger it outside of the play (i.e. at the end of the playbook).
Solution
The solution to the problem is possible without referring to handlers.
You can use group_by
module to create an ad-hoc group based on the result of the tasks at the bottom of each play.
Then you can define a separate play at the end of the playbook restarting the service on targets belonging to the above ad-hoc group.
Refer to the below stub for the idea:
- hosts: all
roles:
# roles declaration
tasks:
- # an example task modifying Nginx configuration
register: nginx_configuration
# ... other tasks ...
- name: the last task in the play
group_by:
key: hosts_to_restart_{{ 'nginx' if nginx_configuration is changed else '' }}
# ... other plays ...
- hosts: hosts_to_restart_nginx
gather_facts: no
tasks:
- service:
name: nginx
state: restarted
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