Introduction to Ansible roles

• Ansible roles are designed to organize Playbook hierarchically and structurally.
• roles is by placing variables, files, tasks, modules and processors in separate directories, and can easily include them.
• roles are commonly used in host-based service building scenarios, and are frequently used in complex business scenarios in enterprises.
• Organize tasks, variables, handlers, templates, files, etc. with a specific hierarchical directory structure; it is equivalent to the call of functions to cut each function into fragments for execution.

roles directory structure

role_name: Defined role name

• files: Functions that store calls from modules such as copy or script
• tasks: Define various task s, with main.yml and other files including calls
• Handlers: Define various handlers, with main.yml and other files including calls
• vars: Define variables, have main.yml, other files include calls
• templates: Store template text invoked by the template module
• meta: Define the specific settings and dependencies of the current role, with the main.yml file
• defaults: There must be a main.yml file for setting default variables

Create roles

• The path where role is stored is defined in the configuration file / etc/ansible/ansible.cfg: roles_path = etc / ansible / roles

Give an example

Use roles to install and open httpd services for the host, and add httpd to the firewall list

• Switch to ordinary user devops and create a new directory roles in the ansible directory under the user's home directory.

su - devops
cd ansible
mkdir roles

• Edit the ansible.cfg file to add roles

[devops@server1 ansible]$ vim ansible.cfg
[defaults]
inventory = ./inventory
roles_path = ./roles    #Current directory

[privilege_escalation]
become=True
become_method=sudo
become_user=root
become_ask_pass=False

• Create an apache template

[devops@server1 roles]$ ansible-galaxy init apache
[devops@server1 roles]$ cd apache/
[devops@server1 apache]$ ls
defaults  files  handlers  meta  README.md  tasks  templates  tests  vars
[devops@server1 apache]$ rm -fr README.md  tests     #You can delete these two file directories

[devops@server1 ansible]$ pwd
/home/devops/ansible
[devops@server1 ansible]$ ansible-galaxy list     #List all galaxies

• Edit several main.yml files to split the contents of previous playbook.yml files.
• Copy template files to apache's template directory

[devops@server1 apache]$ cp ~/ansible/templates/httpd.conf.j2 templates/
[devops@server1 apache]$ cd templates/
[devops@server1 templates]$ ls
httpd.conf.j2

• Edit the main.yml file of task tasks

[devops@server1 apache]$ \vi tasks/main.yml
---
 - name: install httpd
  yum:
    name: httpd
    state: present
 - name: copy httpd
  copy:
    content: "{{ ansible_facts['hostname'] }}"
    dest: /var/www/html/index.html

 - name: configure httpd
  template:
    src: httpd.conf.j2    #Pay attention to modifying the path
    dest: /etc/httpd/conf/httpd.conf
    owner: root
    group: root
    mode: 644
  notify: restart httpd

 - name: start httpd and firewalld
  service:
    name: "{{ item }}"
    state: started
  loop:
    - httpd
    - firewalld
 - name: configure firewalld
  firewalld:
    service: http
    permanent: yes
    immediate: yes
    state: enabled

• Edit the main.yml file of the trigger handles

[devops@server1 apache]$ \vi handlers/main.yml
---
 - name: restart httpd
  service:
    name: httpd
    state: restarted

• Edit the main.yml file of the variable

[devops@server1 ansible]$ vim roles/apache/vars/main.yml
---
http_host: "{{ ansible_facts['default_ipv4']['address'] }}"
http_port: 80

• New apache.yml file

[devops@server1 ansible]$ vim apache.yml
---
 - hosts: webserver
  roles:
    - apache

• Modify the inventory file to read as follows.

[devops@server1 ansible]$ vim inventory 
[test]
server2	

[prod]
server3	
server4

[webserver:children]
test
prod

• Inspection and execution

[devops@server1 ansible]$ ansible-playbook apache.yml -C		#Detection only, no modification
[devops@server1 ansible]$ ansible-playbook apache.yml

haproxy deployment (load balancing)

• Create a haproxy template

[devops@server1 roles]$ ansible-galaxy init haproxy
 - haproxy was created successfully
[devops@server1 roles]$ ls
apache  haproxy

• Edit the main.yml file of the trigger

[devops@server1 haproxy]$ \vi handlers/main.yml
---
 - name: restart haproxy
  service:
    name: haproxy
    state: restarted

• Copy template files to haproxy template directory

[devops@server1 haproxy]$ cp ~/ansible/templates/haproxy.cfg.j2 templates/
[devops@server1 haproxy]$ cd templates/
[devops@server1 templates]$ ls
haproxy.cfg.j2

• main.yml file for editing task

[devops@server1 haproxy]$ \vi tasks/main.ym
---
 - name: install haproxy
  yum:
    name: haproxy
    state: present

 - name: configure haproxy
  template:
    src: haproxy.cfg.j2    #Pay attention to modifying the path
    dest: /etc/haproxy/haproxy.cfg
  notify: restart haproxy

 - name: start haproxy
  service:
    name: haproxy
    state: started

• On the basis of the apache.yml file just now, edit it and add judgment conditions.

---
 - hosts: all
  tasks:
    - import_role:
        name: apache
      when: ansible_hostname in groups['webserver']
    - import_role:
        name: haproxy
      when: ansible_hostname in groups['lb']

• Edit inventory file

[devops@server1 ansible]$ vim inventory 
[lb]
server1     #Writing localhost prompts skipping

[test]
server2

[prod]
server3

[webserver:children]
test
prod

• Implementation:

[devops@server1 ansible]$ ansible-playbook apache.yml

• Check the haproxy service status and port after successful execution (port 80 is modified in our template file).

[devops@server1 ansible]$ systemctl status haproxy
[devops@server1 ansible]$ netstat -antlp

Implementation of keeping alive + haproxy high availability

In Blog https://blog.csdn.net/even160941/article/details/99128262 Medium.