04.大项目管理

roles改造

一个标准项目由多个role组成目录如下：

roles/
│   └── webserver/
│       ├── tasks/
│       ├── templates/
│       ├── handlers/
│       ├── vars/
│       └── defaults/
│
└── playbook.yml

执行命令一次性创建成功

mkdir -p {roles/,roles/webserver/,roles/webserver/tasks/,roles/webserver/templates/,roles/webserver/handlers/,roles/webserver/vars/,roles/webserver/defaults/}

tasks

开始改造 roles/webserver/tasks/main.yml

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

- name: Ensure httpd is enabled and running
  service:
    name: httpd
    enabled: true
    state: started

- name: Deploy template
  template:
    src: index.html.j2
    dest: "/var/www/html/index.html"

设置变量

在 roles/webserver/defaults/main.yml 中定义默认变量。这里可以设置 my_custom_variable：

---
# roles/webserver/defaults/main.yml

my_custom_variable: "Some value"

设置template

将 index.html.j2 文件放在 roles/webserver/templates/ 目录下。

创建 Handlers

如果您需要重启 httpd 服务或执行其他 idempotent 操作，可以在 roles/webserver/handlers/main.yml 中定义 handlers：

---
- name: restart httpd
  service:
    name: httpd
    state: restarted

编写 Playbook

最后，在 playbook.yml 中引用这个 role：

---
- name: Deploy web server
  hosts: webservers
  become: true
  roles:
    - webserver

运行 Playbook

运行 playbook：

ansible-playbook playbook.yml

幂等改造

我们要求每次执行都使最终效果一致。修改roles/webserver/tasks/main.yml文件

---
- name: Check if httpd is installed
  command: rpm -q httpd
  register: httpd_installed
  failed_when: false
  changed_when: false
  check_mode: no

- name: Install httpd
  yum:
    name: httpd
    state: present
  when: httpd_installed.rc != 0

- name: Ensure httpd is enabled and running
  service:
    name: httpd
    enabled: true
    state: started

- name: Deploy template
  template:
    src: index.html.j2
    dest: "/var/www/html/index.html"

1. 我们首先使用 rpm -q httpd 命令检查 httpd 是否已安装，并将结果注册到变量 httpd_installed 中。
2. 在 "Install httpd" 任务中，我们通过 when 条件来判断 httpd 是否已安装。只有当 httpd 未安装（httpd_installed.rc != 0）时，才会执行安装。
3. "Ensure httpd is enabled and running" 任务会确保 httpd 服务启用并运行，这个任务本身就是幂等的。

• failed_when: false 和 changed_when: false 确保检查命令不会错误地标记任务为失败或改变状态。
• check_mode: no 确保即使在 check 模式下，这个检查也会被执行。

使用这种方法， playbook 在执行时将只有在必要时才会安装和配置 httpd，从而确保了幂等性。

添加卸载任务

继续在roles/webserver/tasks/main.yml后面追加下面的内容：

---
- name: Stop httpd service
  service:
    name: httpd
    state: stopped
  become: true
  when: cleanup | default(false)

- name: Remove httpd package
  yum:
    name: httpd
    state: absent
  become: true
  when: cleanup | default(false)

- name: Remove HTML files from /var/www/html/
  file:
    path: "/var/www/html/{{ item }}"
    state: absent
  with_items:
    - index.html
  become: true
  when: cleanup | default(false)

ansible-playbook playbook.yml -e "cleanup=true"

使用tag区分安装和卸载

---
# roles/webserver/tasks/main.yml

- name: Install httpd
  yum:
    name: httpd
    state: present
  tags: install

- name: Ensure httpd is enabled and running
  service:
    name: httpd
    enabled: true
    state: started
  tags: install

- name: Deploy template
  template:
    src: index.html.j2
    dest: "/var/www/html/index.html"
  tags: install

- name: Stop httpd service
  service:
    name: httpd
    state: stopped
  tags: cleanup

- name: Remove httpd package
  yum:
    name: httpd
    state: absent
  tags: cleanup

- name: Remove HTML files from /var/www/html/
  file:
    path: "/var/www/html/{{ item }}"
    state: absent
  with_items:
    - index.html
  tags: cleanup

分别执行命令体会

ansible-playbook playbook.yml --tags "install"
ansible-playbook playbook.yml --tags "cleanup"

思考：main太臃肿了，可拆分成多个文件，用include，你知道怎么做吗？