2-Day2-2-NotifyAndHandlers

Ansible Playbook: Notify and handlers in ansible

Objective

Let's update the playbook to include a feature that restarts the Apache service in case of any changes in the web content. We'll utilize the notification handlers to achieve this.

For this demonstration, we'll use Apache running on a CentOS server.

Instructions

Create the index.html File Locally:
- Open your terminal or command prompt.
- Type vi index.html and press ENTER.
- You'll enter the vi editor. Press i to enter insert mode.
- Copy and paste the following HTML content into the editor:
  <!DOCTYPE html> <html> <head> <title>Hello from Ansible on CentOS with Apache!</title> </head> <body> <h1>Welcome to my Ansible-powered website!</h1> <p>This is a sample webpage created using Ansible.</p> </body> </html>
- Press ESC to exit insert mode.
- Type :wq and press ENTER to save and exit.

Create the Ansible Playbook:

Create a new playbook file named nginx-playbook.yml:
```
nano nginx-playbook.yml
```

Add the following content to your nginx-playbook.yml file:

---
- hosts: centos_servers
  become: yes
  tasks:
    - name: Install apache on CentOS
      yum:
        name: httpd
        state: present

    - name: Copy HTML file to the server
      copy:
        src: /path/to/your/local/index.html
        dest: /var/www/html/index.html
      notify:
      - Restart Apache if content changes
    - name: Start apache service
      systemd:
        name: httpd
        enabled: yes
        state: started

  handlers:
    - name: Restart Apache if content changes
      systemd:
        name: httpd
        state: restarted
      listen: "content_changed"

Replace /path/to/your/local/index.html with the actual path to your locally created index.html file.
Save and close the file (if using nano, press CTRL+X, then Y, and ENTER).

Run the Playbook:
- Execute the playbook on the target CentOS servers:
  ansible-playbook -i inventory nginx-playbook.yml
- Verify that Nginx is installed, the HTML page is accessible, and the content matches what you created locally.

Notify and Handlers Explained

Notifies:
- In Ansible, a notify is a way to trigger a handler when a task changes something.
- When a task modifies a resource (e.g., installs a package, creates a file), it can notify a specific handler.
- Handlers are only executed if the task reports a change.
- Useful for services that need to be restarted after configuration changes (e.g., Nginx, Apache).
- Example:
  - name: Copy HTML file to the server copy: src: /path/to/your/local/index.html dest: /var/www/html/index.html notify: - Restart Apache if content changes
Handlers:
- Handlers are tasks that are only executed when notified by other tasks.
- They are defined separately from regular tasks.
- Handlers are typically used to restart services or perform other actions after configuration changes.
- Example:
  handlers: - name: Restart Apache if content changes systemd: name: httpd state: restarted listen: "content_changed"

For more details, explore additional Ansible concepts in the official Ansible documentation. .

Testing Notify and Handlers

Objective

In this lab, we'll modify the content of the index.html file, rerun the playbook, and observe how the notify and handlers work when the content changes.

Instructions

Create the index.html File Locally:

Open your terminal or command prompt.
Type vi index.html and press ENTER.
You'll enter the vi editor. Press i to enter insert mode.

Copy and paste the following HTML content into the editor:

<!DOCTYPE html>
<html>
<head>
    <title>Hello from Ansible on CentOS with Apache!</title>
</head>
<body>
    <h1>Welcome to my Ansible-powered website!</h1>
    <p>This is a sample webpage created using Ansible.</p>
    <p>Let us observe how the `notify` and `handlers` work when the content changes.</p>
</body>
</html>

Press ESC to exit insert mode.
Type :wq and press ENTER to save and exit.

Rerun the Ansible Playbook:
- Execute the playbook on the target CentOS servers (replace with your own inventory file and administrative user):
  ansible-playbook -i inventory nginx-playbook.yml
- Verify that httpd is still running and the updated content is displayed when you access the server via a web browser.
Observe the Handler in Action:
- Check the status of the Nginx service:
  systemctl status httpd
- If the content has changed, the handler will automatically restart Nginx.

Conclusion

You've successfully tested the notify and handlers mechanism in Ansible! The Nginx service should restart automatically when the content changes.

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Last updated 13 days ago