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.

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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.

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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.

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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.

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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.

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Lab 1.3: Conditional Notifications

Scenario:

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

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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.

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Optional Lab: Chain Multiple Handlers

Scenario:

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

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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."

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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.