In Ansible, handlers are tasks that are executed only when notified by other tasks. They are typically used to perform actions such as restarting a service or reloading a configuration file after a change has been made.

Handlers are defined in the same way as tasks, using the "handlers" keyword, and they are named using a unique identifier. Here is an example:

In this example, the playbook includes a task to configure Nginx using a Jinja2 template. When this task is executed, it notifies the "Restart nginx" handler using the "notify" keyword. The handler then restarts the Nginx service using the "service" module.

Handlers are executed at the end of a playbook run, after all tasks have been executed. If multiple tasks notify the same handler, it will only be executed once. If a handler is not notified, it will not be executed.

Handlers are a powerful feature in Ansible that can help ensure that changes are applied correctly and services are restarted when necessary.

Handlers can also be used with conditions, just like tasks. This can be useful in situations where you only want to restart a service if a specific configuration file has been modified, for example. Here is an example:

In this example, the "Configure nginx" task is registered using the "register" keyword, which saves its output to a variable named "nginx_config". The "Restart nginx" handler is then only executed if the configuration file has changed, as indicated by the "nginx_config.changed" condition.

Handlers can also be used in roles, which are reusable sets of tasks and files that can be shared across different playbooks. In a role, handlers are defined in a separate "handlers" directory, with one handler per file. The handler file must be named using the handler's unique identifier.

Handlers in Ansible are tasks that are executed only when notified by other tasks. They are typically used to perform actions such as restarting a service or reloading a configuration file after a change has been made. Handlers are defined using the "handlers" keyword, and they are named using a unique identifier. Handlers are executed at the end of a playbook run, after all tasks have been executed. If multiple tasks notify the same handler, it will only be executed once. Handlers can be used with conditions and can also be defined in roles, which are reusable sets of tasks and files that can be shared across different playbooks. Using handlers in Ansible can make your playbooks more efficient, reliable, and easier to maintain over time.

Ansible Handlers are just like other tasks in a playbook, the difference being that they are triggered using the notify directive, and are only run when there is a change of state.

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