ansible handerls

Ansible handlers are a type of task that is triggered only when a task that precedes it in the playbook has made a change. They are used to perform additional actions that are dependent on the success or failure of a task. Handlers are defined separately from tasks and are only executed if the task they are associated with makes a change to the system.

Handlers are useful for tasks that require a change to be made only once, such as restarting a service or updating a configuration file. They can also be used to trigger actions on multiple hosts in a playbook.

To define a handler, use the "handlers" section in an Ansible playbook. Here is an example:

handlers:
  - name: restart apache
    service:
      name: apache
      state: restarted

In this example, the handler is named "restart apache" and it uses the Ansible service module to restart the Apache service. The handler will only be triggered if a task preceding it in the playbook makes a change to the Apache service.

Handlers can also be called explicitly using the "notify" keyword in a task. Here is an example:

tasks:
  - name: update configuration file
    template:
      src: config.j2
      dest: /etc/myapp.conf
    notify: restart apache

In this example, the "update configuration file" task will trigger the "restart apache" handler if it makes a change to the configuration file.

Overall, handlers are a powerful feature of Ansible that allow for more precise control over playbook execution and can help prevent unnecessary actions on systems.