Handlers are helpful when you need to perform a task that relies on a specific task’s success or failure. For example, you can set a handler to send Apache logs if the service goes down.
This article will help you understand how to define and use the Ansible handler in playbooks.
Basic Usage
To illustrate how to use the Ansible handler, let us a simple example. The playbook below will install the Apache http server and use a handler to start the service.
- hosts: all
become: true
gather_facts: no
tasks:
- name: "install apache"
package:
name: apache2
state: present
notify:
startapache
handlers:
- name: startapache
service:
name: apache2
state: started
In the example playbook above, we start by installing the apache2 server using the package module. We then use a notify module to set a notify action.
The final step is to configure a handler to run after the server is installed. The name of the notification should be the same as the name used in the handler module. Otherwise, the specified handler will fail.
Save and run the above playbook:
How to Configure Ansible Notify Handler For Alert Message
You can also configure an ansible handler to display a message instead of taking actions such as restarting services.
For example, the playbook below restarts the apache service and displays a message to the user.
- hosts: all
become: true
tasks:
- name: "restart apache"
service:
name: apache2
state: restarted
notify:
apacherestarted
handlers:
- name: apacherestarted
debug:
msg: "The Apache service restarted successfully"
In the example above, we register a simple handler that shows a successful message when the apache service is restarted.
Below is an example output:
**********************
changed: [192.168.0.111]
RUNNING HANDLER [apache restarted]
************************************
ok: [192.168.0.111] => {
"msg": "The Apache service restarted successfully."
}
How to Configure Ansible Notify Handler For Multiple Handlers
Suppose you want to update the system and restart two services after the update. As shown in the playbook below, you can define two handlers to perform as actions:
- hosts: all
become: true
tasks:
- name: "update the system"
apt:
update_cache: yes
upgrade: dist
notify:
-apache
-mysql
handlers:
- name: apache
service:
name: apache2
state: restarted
- name: mysql
service:
name: mysqld
state: restarted
In this example playbook, we update the system using the apt module. Next, we use the notify modules to define two tasks.
Using handlers, we define actions for each notify task. In our example, we restarted both Apache and MySQL services.
Conclusion
This tutorial has shown you how to define and use the Ansible notify and handlers module to perform an action where a task is complete.
