Ansible - [09] 高级语法

error 处理机制

默认 ansible 在遇到 error 会立刻停止 playbook

[root@control ansible]# cat ~/ansible/error.yml
---
- hosts: test
  tasks:
    - name: start a service that does not exist.
      service:
        name: hehe
        state: started
    - name: touch a file
      file:
        path: tmp/service.txt
        state: touch

如果第一个任务不能成功执行，那么剧本就会中止，不会执行后续任务。

如果想要在第一个任务执行失败之后，继续执行后续任务，那么……

可以在剧本中添加：ignore_errors: true，可以忽略错误，继续后续的任务

[root@control ansible]# cat ~/ansible/error.yml
---
- hosts: test
  tasks:
    - name: start a service that does not exist.
      service:
        name: hehe
        state: started
      ignore_errors: true
    - name: touch a file.
      file:
        path: /tmp/service.txt
        state: touch

以上配置针对是某个任务，如果针对剧本全局忽略错误，可以进行如下配置.

[root@control ansible]# cat ~/ansible/error.yml
---
- hosts: test
  ignore_errors: true
  tasks:
    - name: start a service that does not exist.
      service:
        name: hehe
        state: started
    - name: touch a file.
      file:
        path: /tmp/service.txt
        state: touch

handlers

当某个任务需要依赖其他任务怎么办？

• 可以通过handlers定义一组任务
• 仅当某个任务触发（notify）handlers时才执行相应的任务
• 如果有多个notify触发执行handlers任务，也仅执行一次
• 仅当任务的执行状态为changed时，handlers任务才执行
• handlers任务在所有其他任务都执行后才执行

[root@control ansible]# cat ~/ansible/handlers.yml
---
- hosts: test
  tasks:
    - name: create directory.
      file:
        path: /tmp/parents/subdir/
        state: directory
      notify: touch file
  handlers:
    - name: touch file
      file:
        path: /tmp/parents/subdir/new.txt
        state: touch

多次执行playbook该任务状态不再是changed

notify后面名称必须和handlers中的任务名称一致

when 条件判断

• when可以定义判断条件，条件为真时才执行某个任务
• 常见条件操作符如：==、!=、>、>=、<、<=
• 多个条件可以使用and或or分割
• when表达式中调用变量不要使用{{ }}

1、远程主机剩余内存不足700M则关闭NetworkManager

[root@control ansible]# cat ~/ansible/when_1.yml
---
- hosts: test
  tasks:
    - name: check memory size.
      service:
        name: NetworkManager
        state: stopped
      when: ansible_memfree_mb < 700

2、判断操作系统是RedHat8则创建测试文件（支持多行输入，不保留换行符）

[root@control ansible]# cat ~/ansible/when_2.yml
---
- hosts: test
  tasks:
    - name: touch a file
      file:
        path: /tmp/when.txt
        state: touch
      when: >
        ansible_distribution == "RedHat"
            and
        ansible_distribution_major_version == "8"

block 任务块

使用block可以将多个任务合并为一个组

[root@control ansible]# cat ~/ansible/block_1.yml
---
- hosts: test
  tasks:
    - name: define a group of tasks.
      block:
        - name: install httpd
          yum:
            name: httpd
            state: present
        - name: start httpd
          service:
            name: httpd
            state: started
      when: ansible_distribution == "RedHat"

rescue 定义block任务执行失败时要执行的其他任务

always 定义无论block任务是否成功，都要执行的任务

[root@control ansible]# cat ~/ansible/block_2.yml
---
- hosts: test
  tasks:
    - block:
        - name: touch a file test1.txt
          file:
            path: /tmp/test1.txt
            state: touch
      rescue:
        - name: touch a file test2.txt
          file:
            path: /tmp/test2.txt
            state: touch
      always:
        - name: touch a file test3.txt
          file:
            path: /tmp/test3.txt
            state: touch

loop 循环

1、循环创建多个目录

[root@control ansible]# cat ~/ansible/simple_loop.yml
---
- hosts: test
  tasks:
    - name: mkdir multi directory.
      file:
        path: /tmp/{{ item }}
        state: directory
      loop:
        - School
        - Legend
        - Life

item是关键字

2、循环创建多个用户

[root@control ansible]# cat ~/ansible/complex_loop.yml
---
- hosts: test
  tasks:
    - name: create multi user.
      user:
        name: "{{ item.iname }}"
        password: "{{ item.ipass | password_hash('sha512') }}"
      loop:
        - { iname: 'term', ipass: '123456' }
        - { iname: 'amy', ipass: '654321' }