9-Day4-1-NotifyHandlers

**Lab Exercise:- Notify Handlers for Event-Driven Actions

Objective:

Participants will learn to use notify and handlers to implement event-driven actions in Ansible. The labs will demonstrate triggering handlers based on task outcomes, including optional exercises for advanced learning.

Lab 1.1: Basic Notify and Handlers

Scenario:

You want to install Apache, start the service, and restart it only if the configuration file is updated.

Steps:

  1. Create the Playbook:

    • Save as ~/day4/notify_basic.yaml:

      - name: Notify Handlers Demo - Basic
  hosts: web_servers
  tasks:
    - name: Install Apache
      yum:
        name: httpd
        state: present

    - name: Update Apache Configuration
      copy:
        src: ~/day4/httpd.conf
        dest: /etc/httpd/conf/httpd.conf
      notify: Restart Apache

    - name: Start Apache
      service:
        name: httpd
        state: started

  handlers:
    - name: Restart Apache
      service:
        name: httpd
        state: restarted

  2. Create a Sample Config File:

    • Save httpd.conf in ~/day4/:

      # Basic Apache Config
ServerName localhost

  3. Run the Playbook:

    ansible-playbook ~/day4/notify_basic.yaml -i ~/day3/inventory.ini

  4. Expected Output:

    • Apache is installed.

    • If httpd.conf is updated, the "Restart Apache" handler is triggered.

Lab 1.2: Multiple Handlers

Scenario:

Expand the setup to include additional services like enabling the firewall and restarting Apache only after the firewall is configured.

Steps:

  1. Create the Playbook:

    • Save as ~/day4/multiple_handlers.yaml:

      - name: Notify Handlers Demo - Multiple Handlers
  hosts: web_servers
  tasks:
    - name: Install Apache
      yum:
        name: httpd
        state: present

    - name: Configure Firewall for HTTP
      firewalld:
        port: 80/tcp
        permanent: true
        state: enabled
      notify: Reload Firewall

    - name: Update Apache Configuration
      copy:
        src: ~/day4/httpd.conf
        dest: /etc/httpd/conf/httpd.conf
      notify:
        - Restart Apache
        - Log Apache Update

    - name: Start Apache
      service:
        name: httpd
        state: started

  handlers:
    - name: Restart Apache
      service:
        name: httpd
        state: restarted

    - name: Reload Firewall
      service:
        name: firewalld
        state: restarted

    - name: Log Apache Update
      debug:
        msg: "Apache configuration has been updated and restarted."

  2. Run the Playbook:

    ansible-playbook ~/day4/multiple_handlers.yaml -i ~/day3/inventory.ini

  3. Expected Output:

    • The firewall configuration is reloaded if HTTP is enabled.

    • Apache restarts only if its configuration file is updated.

Lab 1.3: Conditional Notifications

Scenario:

Add a conditional notification for restarting Apache only if the server has more than 1GB of free memory.

Steps:

  1. Create the Playbook:

    • Save as ~/day4/conditional_notify.yaml:

      - name: Notify Handlers Demo - Conditional Notifications
  hosts: web_servers
  tasks:
    - name: Check Free Memory
      shell: free -m | awk '/^Mem/ { print $4 }'
      register: free_memory

    - name: Install Apache
      yum:
        name: httpd
        state: present

    - name: Update Apache Configuration
      copy:
        src: ~/day4/httpd.conf
        dest: /etc/httpd/conf/httpd.conf
      notify: Restart Apache

    - name: Trigger Restart if Free Memory > 1024MB
      debug:
        msg: "Memory is sufficient. Triggering restart."
      when: free_memory.stdout | int > 1024
      notify: Restart Apache

  handlers:
    - name: Restart Apache
      service:
        name: httpd
        state: restarted

  2. Run the Playbook:

    ansible-playbook ~/day4/conditional_notify.yaml -i ~/day3/inventory.ini

  3. Expected Output:

    • Apache restarts only if there’s more than 1GB of free memory.

Optional Lab: Chain Multiple Handlers

Scenario:

Update a custom HTML file and restart Apache only if the update is successful.

  1. Create the Playbook:

    • Save as ~/day4/chain_handlers.yaml:

      - name: Chain Multiple Handlers Demo
  hosts: web_servers
  tasks:
    - name: Install Apache
      yum:
        name: httpd
        state: present

    - name: Update Website Content
      copy:
        src: ~/day4/index.html
        dest: /var/www/html/index.html
      notify: Verify Content Update

  handlers:
    - name: Verify Content Update
      shell: "grep 'Welcome' /var/www/html/index.html"
      register: content_check
      changed_when: content_check.rc == 0
      notify: Restart Apache

    - name: Restart Apache
      service:
        name: httpd
        state: restarted

  2. Create the index.html File:

    • Save in ~/day4/:

      <html>
<body>
  <h1>Welcome to Ansible Training!</h1>
</body>
</html>

  3. Run the Playbook:

    ansible-playbook ~/day4/chain_handlers.yaml -i ~/day3/inventory.ini

  4. Expected Output:

    • Apache restarts only if index.html contains "Welcome."

Key Learning Points:

  1. Notify and Handlers:

    • Trigger handlers based on task outcomes.

    • Chain multiple handlers for dependent actions.

  2. Conditional Notifications:

    • Use conditional logic to control when handlers are triggered.

  3. Optional Exercises:

    • Allow participants to explore chaining and advanced notifications.

This lab ensures a hands-on understanding of notify and handlers in Ansible with real-world scenarios and customization opportunities.

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