Ansible Playbooks 基本功能介绍及示例代码

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一、基本结构

用于安装或升级 apache 服务的 playbook 完整示例：

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---
- hosts: webservers
  remote_user: root
  vars:
    http_port: 80
    max_clients: 200
  tasks:
  - name: ensure apache is at the latest version
    yum:
      name: httpd
      state: latest
  - name: write the apache config file
    template:
      src: /srv/httpd.j2
      dest: /etc/httpd.conf
    notify:
    - restart apache
  - name: ensure apache is running
    service:
      name: httpd
      state: started
  handlers:
    - name: restart apache
      service:
        name: httpd
        state: restarted

target

target 部分用于指定执行 playbook 任务时面向的目标主机和远程用户。

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---
- hosts: webservers
  remote_user: root

远程用户也可以在特定的 task 中额外进行定义：

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---
- hosts: webservers
  remote_user: root
  tasks:
    - name: test connection
      ping:
      remote_user: yourname

执行任务时允许远程用户通过 sudo 提升权限：

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---
- hosts: webservers
  remote_user: yourname
  become: yes
  become_method: sudo

执行任务时切换到其他用户身份：

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---
- hosts: webservers
  remote_user: yourname
  become: yes
  become_user: postgres

variable

variable 部分用于定义变量，作用域为当前 play。

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vars:
  http_port: 80
  max_clients: 200

通过 vars_files 定义变量：

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vars_files:
  conf/country-AU.yml
  conf/datacenter-SYD.yml
  conf/cluster-mysql.yml

交互式地从用户输入中获取变量的值。如将用户输入赋值给变量 https_passphrase：

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vars_prompt:
  - name: https_passphrase
    prompt: Key Passphrase
    private: yes

task

task 部分包含了一系列我们希望在目标机器上执行的动作。

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tasks:
- name: ensure apache is at the latest version
  yum:
    name: httpd
    state: latest

handler

handler 与 task 有着相同的语法和类似的功能。但是 handler 只可以在特定的条件下由 task 调用后执行。

如配置文件替换成功后触发重启服务的动作：

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tasks:
  - name: copy the DHCP config
    copy:
      src: dhcp/dhcpd.conf
      dest: /etc/dhcp/dhcpd.conf
    notify: restart dhcp

handlers:
- name: restart dhcp
  service:
    name: dhcpd
    state: restarted

可以在单个 task 中同时调用多个 handler：

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---
- hosts: qroud
  tasks:
  - name: checkout Qroud
    git:
      repo:git@github.com:smarthall/Qroud.git
      dest: /opt/apps/Qroud force=no
    notify:
      - migrate db
      - generate static
      - restart httpd

handlers:
- name: migrate db
  command: ./manage.py migrate –all
  args:
    chdir: /opt/apps/Qroud

- name: generate static
  command: ./manage.py collectstatic -c –noinput
  args:
    chdir: /opt/apps/Qroud

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

二、playbook 模块

template

template 模块一般用于定义配置文件的主体框架，并为 Ansible 中的变量预留好位置以便在需要时渲染。类似于 Flask 应用依据模板文件动态地生成 HTML 文档。
其模板功能由 Jinja2 提供，支持条件语句、for 循环和宏等高级语法。

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{% for ip in ansible_all_ipv4_addresses %}
  {{ ip }};
{% endfor %}

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tasks:
- name: write the apache config file
  template:
    src: /srv/httpd.j2
    dest: /etc/httpd.conf
pause

pause 模块会将执行中的 playbook 暂停一段时间。比如部署了一个新版本的 web 应用，需要用户手动确认一切正常才能继续执行后面的任务。

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---
- hosts: localhost
  tasks:
  - name: wait on user input
    pause:
      prompt: "Warning! Press ENTER to continue or CTRL-C to quit."
  - name: timed wait
    pause:
      seconds: 30

wait_for

等待某个特定的 TCP 端口可以被远程主机访问连通。

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---
- hosts: webapps
  tasks:
  - name: Install Tomcat
    yum:
      name: tomcat7
      state: latest

  - name: Start Tomcat
    service:
      name: tomcat7
      state: started

  - name: Wait for Tomcat to start
    wait_for:
      port: 8080
      state: started

group_by

group_by 模块可以在 task 中基于收集到的 facts 信息动态地对 hosts 进行分组。

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---
- name: Create operating system group
  hosts: all
  tasks:
    - group_by: key=os_{{ ansible_distribution }}

- name: Run on CentOS hosts only
  hosts: os_CentOS
  tasks:
    - name: Install Apache
      yum: name=httpd state=latest

- name: Run on Ubuntu hosts only
  hosts: os_Ubuntu
  tasks:
  - name: Install Apache
    apt: pkg=apache2 state=latest

三、Playbooks 进阶

Looping
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tasks:
- name: Secure config files file
  file:
    path: "/etc/{{ item }}"
    mode: 0600
    owner: root
    group: root
  with_items:
    - my.cnf
    - shadow
    - fstab
条件语句
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---
- name: Install VIM
  hosts: all
  tasks:
  - name: Install VIM via yum
    yum:
      name: vim-enhanced
      state: latest
    when: ansible_os_family == "RedHat"

  - name: Install VIM via apt
    apt:
      name: vim
      state: latest
    when: ansible_os_family == "Debian"

  - name: Unexpected OS family
    debug:
      msg: "OS Family {{ ansible_os_family }} is not supported"
      fail: yes
    when: ansible_os_family != "RedHat" and ansible_os_family != "Debian"
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# Copy a file to the remote server if the hosts file doesn't exist
tasks:
- stat: path=/etc/hosts
  register: hosts_file
- copy: src=path/to/local/file dest=/path/to/remote/file
  when: not hosts_file.stat.exists
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# Downgrade PHP version if the current version contains '7.0'.
tasks:
- shell: php --version
  register: php_version
- shell: yum -y downgrade php*
  when: "'7.0' in php_version.stdout"
注册变量
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- name: Using register
  hosts: ansibletest
  remote_user: root
  tasks:
  - name: Get /tmp info
    file:
      dest: /tmp
      state: directory
    register: tmp

  - name: Set mode on /tmp/subtmp
    file:
      dest: /tmp/subtmp
      mode: "{{ tmp.mode }}"
      state: directory

debug 查看变量的值：

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- name: capture output of id command
  command: id -un
  register: login
- debug: msg="Logged in as user {{ login.stdout }}"

filter

Jinja2 模板提供的 filter 功能可以将原始数据转换为用户需要的格式

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---
- name: Create user accounts
  hosts: all
  vars:
    users:
  tasks:
  - name: Create accounts
    user: name={{ item|lower }} state=present
    with_items:
      - Fred
      - John
      - DanielH

常用 filter：

  • min：参数为列表，返回列表中最小的项目
  • max：参数为列表，返回列表中最大的项目
  • random：参数为列表，随机返回列表中的某个值
  • default(x)：指定变量不存在时，以 x 为该变量的默认值
  • unique：参数为列表，返回该列表去除重复项后的版本
  • replace(x, y)：将字符串中出现的所有 x 替换为 y
  • join(x)：参数为列表，返回由 x 拼接所有列表项后形成的字符串

针对文件路径的常用 filter：

  • basename：返回路径中包含的文件名
  • dirname：返回文件所在的目录
  • expanduser：将路径中包含的 ~ 替换为 home 目录
  • realpath：文件的真实路径
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vars:
  homepage: /usr/share/nginx/html/index.html
tasks:
- name: copy home page
  copy: src=files/{{ homepage | basename }} dest={{ homepage }}
Lookup

lookups 允许 Ansible 从多种类型的源头（如文本文档、CSV 文件等）读取配置数据。

file：读取文本文件内容作为参数

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- name: Add my public key as an EC2 key
  ec2_key: name=mykey key_material="{{ lookup('file', '/Users/lorin/.ssh/id_rsa.pub') }}"

pipe：在远程机器上执行某个外部程序并关联其标准输出

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- name: get SHA of most recent commit
  debug: msg="{{ lookup('pipe', 'git rev-parse HEAD') }}"

env：获取远程机器上的某个环境变量

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- name: get the current shell
  debug: msg="{{ lookup('env', 'SHELL') }}"

password：生成随机密码，并将该密码写入指定文件

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- name: create deploy postgres user
  postgresql_user:
    name: deploy
    password: "{{ lookup('password', 'deploy-password.txt') }}"

redis-kv：获取 redis 服务器上某个 key 的值（需要在远程机器上安装 redis Python 库）

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- name: look up value in Redis
  debug: msg="{{ lookup('redis_kv', 'redis://localhost:6379,weather') }}"

复杂循环
名称 输入 循环规则
with_items 列表 遍历所有列表项
with_lines 命令 遍历命令输出的所有行
with_fileglob Glob 遍历文件（文件名可使用通配符）
with_first_found 路径列表 路径中检索到的第一个文件目标
with_dict 字典 遍历字典中的数据项
with_flattened 多层列表 遍历展开后的多层列表
with_inventory Host 模式 遍历匹配的主机

with_lines：

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# files/turing.txt
Leslie Lamport
Silvio Micali
Shafi Goldwasser
Judea Pearl

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- name: Send out a slack message
  slack:
    domain: example.slack.com
    token: "{{ slack_token }}"
    msg: "{{ item }} was in the list"
  with_lines:
    - cat files/turing.txt

with_fileglob：

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- name: add public keys to account
  authorized_key: user=deploy key="{{ lookup('file', item) }}"
  with_fileglob:
    - /var/keys/*.pub
    - keys/*.pub

with_dict：

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- name: iterate over ansible_eth0
  debug: msg={{ item.key }}={{ item.value }}
  with_dict: "{{ ansible_eth0.ipv4 }}"

参考资料

Ansible Configuration Management - Second Edition