The Difference between Ansible Tasks and Handlers.

 

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 The difference between tasks and handlers with reference to Ansible playbook

In Ansible playbooks, tasks and handlers serve distinct purposes:

1. Tasks:

   • Tasks are the basic units of work in an Ansible playbook. They define the actions that should be executed on the managed nodes.
   • Each task specifies a module (e.g., apt, yum, copy, file, etc.) and the parameters required for that module to perform the desired operation.
   • Tasks run sequentially, and they are always executed when the playbook is run, unless conditions such as when statements or changed_when are used to control execution.

   Example:

   # yaml
   
   - name: Install a package
     apt:
       name: vim
       state: present
   

2. Handlers:

   • Handlers are special types of tasks that are only executed when notified by other tasks.
   • A handler is typically used for tasks that should only run if something has changed, such as restarting a service after a configuration file has been modified.
   • Handlers are defined in the handlers section of a playbook and are triggered by other tasks using the notify directive.

   Example:

   # yaml
   
   - name: Restart nginx
     service:
       name: nginx
       state: restarted
     when: nginx_config_changed
   
   handlers:
     - name: Restart nginx
       service:
         name: nginx
         state: restarted
   

Key Differences:

• Execution: Tasks always run when the playbook is executed, 
• whereas, handlers run only when they are notified by other tasks.
• Purpose: Tasks define the main actions to be performed (e.g., install software), 
• Meanwhile, handlers typically perform actions triggered by changes (e.g., restart a service after a configuration change).