RH294 - ch04s04

Bookmark this page

Guided Exercise: Implementing Handlers

In this exercise, you implement handlers in playbooks.

Outcomes

You should be able to define handlers in playbooks and notify them to apply configuration changes.

As the student user on the workstation machine, use the lab command to prepare your system for this exercise.

This command prepares your environment and ensures that all required resources are available.

[student@workstation ~]$ lab start control-handlers

Procedure 4.2. Instructions

On the workstation machine, open a new terminal and change to the /home/student/control-handlers directory.
```
[student@workstation ~]$ cd ~/control-handlers
[student@workstation control-handlers]$
```

Edit the configure_webapp.yml playbook file. This playbook installs and configures a web application server. When the web application server configuration changes, the playbook triggers a restart of the appropriate service.

Review the configure_webapp.yml playbook. It begins with the initialization of some variables:

---
- name: Web application server is deployed
  hosts: webapp
  vars:
    packages: 
      - nginx
      - php-fpm
    web_service: nginx 
    app_service: php-fpm 
    resources_dir: /home/student/control-handlers/files 
    web_config_src: "{{ resources_dir }}/nginx.conf.standard" 
    web_config_dst: /etc/nginx/nginx.conf 
    app_config_src: "{{ resources_dir }}/php-fpm.conf.standard" 
    app_config_dst: /etc/php-fpm.conf 

  tasks:

	`packages` specifies the name of the packages to install for the web application services.
	`web_service` specifies the name of the web server service.
	`app_service` specifies the name of the application server service.
	`resources_dir` specifies the directory where configuration files are located.
	`web_config_src` specifies the location of the web server configuration file to install.
	`web_config_dst`: specifies the location of the installed web server configuration file on the managed hosts.
	`app_config_src` specifies the location of the application server configuration file to install.
	`web_config_dst`: specifies the location of the installed application server configuration file on the managed hosts.

In the configure_webapp.yml file, define a task that uses the ansible.builtin.dnf module to install the required packages as defined by the packages variable.
The task should read as follows:
```
  tasks:
    - name: "{{ packages }} packages are installed"
      ansible.builtin.dnf:
        name: "{{ packages }}"
        state: present
```

Add two tasks to start and enable the web and application server services. The tasks should read as follows:

    - name: Make sure the web service is running
      ansible.builtin.service:
        name: "{{ web_service }}"
        state: started
        enabled: true

    - name: Make sure the application service is running
      ansible.builtin.service:
        name: "{{ app_service }}"
        state: started
        enabled: true

Add a task to download nginx.conf.standard to /etc/nginx/nginx.conf on the managed host, using the ansible.builtin.copy module. Add a condition that notifies the restart web service handler to restart the web server service after a configuration file change. The task should read as follows:
```
    - name: The {{ web_config_dst }} file has been deployed
      ansible.builtin.copy:
        src: "{{ web_config_src }}"
        dest: "{{ web_config_dst }}"
        force: true
      notify:
        - restart web service
```
Add a task to download php-fpm.conf.standard to /etc/php-fpm.conf on the managed host, using the ansible.builtin.copy module. Add a condition that notifies the restart app service handler to restart the application server service after a configuration file change. The task should read as follows:
```
    - name: The {{ app_config_dst }} file has been deployed
      ansible.builtin.copy:
        src: "{{ app_config_src }}"
        dest: "{{ app_config_dst }}"
        force: true
      notify:
        - restart app service
```
Add the handlers keyword to define the start of the handler tasks. Define the first handler, restart web service, which restarts the nginx service. The handler should read as follows:
```
  handlers:
    - name: restart web service
      ansible.builtin.service:
        name: "{{ web_service }}"
        state: restarted
```

Define the second handler, restart app service, which restarts the php-fpm service. The handler should read as follows:

    - name: restart app service
      ansible.builtin.service:
        name: "{{ app_service }}"
        state: restarted

The completed playbook should consist of the following content:

---
- name: Web application server is deployed
  hosts: webapp
  vars:
    packages:
      - nginx
      - php-fpm
    web_service: nginx
    app_service: php-fpm
    resources_dir: /home/student/control-handlers/files
    web_config_src: "{{ resources_dir }}/nginx.conf.standard"
    web_config_dst: /etc/nginx/nginx.conf
    app_config_src: "{{ resources_dir }}/php-fpm.conf.standard"
    app_config_dst: /etc/php-fpm.conf

  tasks:
    - name: "{{ packages }} packages are installed"
      ansible.builtin.dnf:
        name: "{{ packages }}"
        state: present

    - name: Make sure the web service is running
      ansible.builtin.service:
        name: "{{ web_service }}"
        state: started
        enabled: true

    - name: Make sure the application service is running
      ansible.builtin.service:
        name: "{{ app_service }}"
        state: started
        enabled: true

    - name: The {{ web_config_dst }} file has been deployed
      ansible.builtin.copy:
        src: "{{ web_config_src }}"
        dest: "{{ web_config_dst }}"
        force: true
      notify:
        - restart web service

    - name: The {{ app_config_dst }} file has been deployed
      ansible.builtin.copy:
        src: "{{ app_config_src }}"
        dest: "{{ app_config_dst }}"
        force: true
      notify:
        - restart app service

  handlers:
    - name: restart web service
      ansible.builtin.service:
        name: "{{ web_service }}"
        state: restarted

    - name: restart app service
      ansible.builtin.service:
        name: "{{ app_service }}"
        state: restarted

Before running the playbook, verify that its syntax is correct by running ansible-navigator with the --syntax-check option. Correct any reported errors before moving to the next step. You should see output similar to the following:
```
[student@workstation control-handlers]$ ansible-navigator run \
> -m stdout configure_webapp.yml --syntax-check

playbook: /home/student/control-handlers/configure_webapp.yml
```

Run the configure_webapp.yml playbook. The output shows that the handlers are being executed.

[student@workstation control-handlers]$ ansible-navigator run \
> -m stdout configure_webapp.yml

PLAY [Web application server is deployed] ************************************

TASK [Gathering Facts] *******************************************************
ok: [servera.lab.example.com]

TASK [['nginx', 'php-fpm'] packages are installed] ***************************
changed: [servera.lab.example.com]

TASK [Make sure the web service is running] **********************************
changed: [servera.lab.example.com]

TASK [Make sure the application service is running] **************************
changed: [servera.lab.example.com]

TASK [The /etc/nginx/nginx.conf file has been deployed] **********************
changed: [servera.lab.example.com]

TASK [The /etc/php-fpm.conf file has been deployed] **************************
changed: [servera.lab.example.com]

RUNNING HANDLER [restart web service] ****************************************
changed: [servera.lab.example.com]

RUNNING HANDLER [restart app service] ****************************************
changed: [servera.lab.example.com]

PLAY RECAP *******************************************************************
servera.lab.example.com    : ok=8    changed=7    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Run the playbook again.

[student@workstation control-handlers]$ ansible-navigator run \
> -m stdout configure_webapp.yml

PLAY [Web application server is deployed] ************************************

TASK [Gathering Facts] *******************************************************
ok: [servera.lab.example.com]

TASK [['nginx', 'php-fpm'] packages are installed] ***************************
changed: [servera.lab.example.com]

TASK [Make sure the web service is running] **********************************
changed: [servera.lab.example.com]

TASK [Make sure the application service is running] **************************
changed: [servera.lab.example.com]

TASK [The /etc/nginx/nginx.conf file has been deployed] **********************
changed: [servera.lab.example.com]

TASK [The /etc/php-fpm.conf file has been deployed] **************************
changed: [servera.lab.example.com]

PLAY RECAP *******************************************************************
servera.lab.example.com    : ok=6    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

This time the handlers are skipped. If the remote /etc/nginx/nginx.conf configuration file is changed in the future, executing the playbook would trigger the restart web service handler but not the restart app service handler.

Finish

On the workstation machine, change to the student user home directory and use the lab command to complete this exercise. This step is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish control-handlers

This concludes the section.

Discuss Red Hat Enterprise Linux Automation with Ansible

Go to community

Red Hat Linux Automation with Ansible (RH294)

Haley_Ruccio

24 lip 2023

Learn how to automate Linux system administration tasks with Red Hat Ansible Automation PlatformRed Hat Enterprise Linux Automation with Ansible (RH294) is designed for Linux administrators and developers who need to automate repeatable and error-prone steps for system provisioning, configuration, application deployment, and orchestration. This course is based on Red Hat® Enterprise Linux® 9 and Red Hat Ansible Automation Platform 2.2.Course content summaryInstall Red Hat Ansible Automation Platform on control nodes.Create and update inventories of managed hosts and manage connections to them.Automate administration tasks with Ansible Playbooks and ad hoc commands.Write effective playbooks at scale.Protect sensitive data used by Ansible Automation Platform with Ansible Vault.Reuse code and simplify playbook development with Ansible Roles and Ansible Content Collections.Audience for this courseThis course is geared toward Linux system administrators, DevOps engineers, infrastructure automation engineers, and systems design engineers who are responsible for these tasks:Automating configuration managementEnsuring consistent and repeatable application deploymentProvisioning and deployment of development, testing, and production serversIntegrating with DevOps continuous integration/continuous delivery workflowsPrerequisites for this coursePass the Red Hat Certified System Administrator (RHCSA) exam (EX200), or demonstrate equivalent Red Hat Enterprise Linux knowledge and experience.Take our free assessment to gauge whether this offering is the best fit for your skills.

980

curl finds no route to host?

TPeters

23 lip 2023

I am doing the self-paced course RH294 . With two exercises (Ch.3 final Lab and Ch.4 lab exercise 2) I ran into this problem:after installing and starting a web service, from the classroom web termicaI I cannot reach servera.lab.example.com with curl: "No route to host". This despite the fact that I can ping it, open a shell to it, and install the package on it with Ansible.Anyone else have the same problem?What might be the cause?

1702

Welcome to the Red Hat Linux Automation with Ansible (RH294) group in the Red Hat Learning Community

cschunke

18 lip 2023

We are excited to launch a space dedicated to the Red Hat Training course Red Hat Linux Automation with Ansible! To gain the most value from this group - click the "Join Group" button in the upper right hand corner.We encourage group members to collaborate in this group to discuss topics, ask questions, share best practices and tips, provide course feedback, and share their accomplishments as it relates to RH294.Read more about Red Hat Linux Automation with Ansible here.

351

Revision: rh294-9.0-c95c7de