Linux自动化运维——5、Ansible中的任务执行控制

一.循环

循环迭代任务

1.简单循环

loop:		##赋值列表
  - value1
  - value2
  - ...


{{item}}	##迭代变量名称

实例

---
- name: create file
  hosts: all
  tasks:
    - name: file module
      file:
        name: /mnt/{{item}}
        state: present

      loop:
        - westos_file1
        - westos_file2

2.循环散列或字典列表

---
- name: create file
  hosts: all
  tasks:
    - name: file module
      service:
        name: "{{ item.name}}"
        state: "{{ item.state }}"
      loop:
        - name: httpd
          state: started
        - name: vsftpd
          state: stopped

二.条件

when:
  - 条件1
  - 条件2

条件判断

=			value == "字符串",value == 数字
<			value <  数字
>			value >  数字
<=			value <= 数字
>=			value >= 数字 
!=			value != 数字
is defined value	value is defined	变量存在
is not defined		value is not defined	变量不存在
in                      value is in value       变量为    
not in                  value is not in value   变量不为
bool变量 为true		value			value的值为true
bool变量 false		not value		value的值为false
			value in value2		value的值在value2列表中

多条条件组合

when：
  条件1 and 条件2
  - 条件1
  - 条件2

when:
  条件1 or 条件2

when: >
  条件1
  or
  条件2

测试题：

建立playbook  ~/ansibles/lvm.yml要求如下:
*建立大小为1500M名为exam_lvm的lvm 在westos组中
*如果westos不存在请输出:
 vg westos  is not exist
*如果westos大小不足1500M请输出：
 vg westos is less then 1500M
 并建立800M大小的lvm

---
- name: create lvm
  hosts: all
  tasks:
    - name: check /dev/vdb
      debug:
        msg: vg westos is not exist
      when: ansible_facts['lvm']['vgs']['westos'] is not defined

    - name: create 1500M lvm
      lvol:
        vg: westos
        lv: exam_lvm
        size: 1500m
      when: ansible_facts['lvm']['vgs']['westos'] is defined
      ignore_errors: yes
      register: LVState

    - name: create 800m
      lvol:
        vg: westos
        lv: exam_lvm
        size: 800m
      when:
        - ansible_facts['lvm']['vgs']['westos'] is defined
        - LVState['rc'] != 0

三.触发器

notify: 触发器当遇到更改是触发handlers

handlers： 触发器触发后执行的动作

实例

---
- name: create virtualhost for web server
  hosts: all
  vars_files:
    ./vhost_list.yml
  tasks:
    - name: create document
      file:
        path: "{{web2.document}}"
        state: directory
    - name: create vhost.conf
      copy:
        dest: /etc/httpd/conf.d/vhost.conf
        content:
          "<VirtualHost *:{{web1.port}}>\n\tServerName {{web1.name}}\n\tDocumentRoot {{web1.document}}\n\tCustomLog logs/{{web1.name}}.log combined\n</VirtualHost>\n\n<VirtualHost *:{{web2.port}}>\n\tServerName {{web2.name}}\n\tDocumentRoot {{web2.document}}\n\tCustomLog logs/{{web2.name}}.log combined\n</VirtualHost>"
      notify:
        restart apache

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

四.处理失败任务

1.ignore_errors
作用：当play遇到任务失败是会终止
ignore_errors: yes 将会忽略任务失败使下面的任务继续运行

实例

- name: test
  dnf:
    name: westos
    state: latest
  ignore_errors: yes
  
- name: create file
  file:
    path: /mnt/westos
    state: touch

2.force_handlers
作用：当任务失败后play被终止也会调用触发器进程

实例

---
- name: apache change port
  hosts: all
  force_handlers: yes
  vars:
    http_port: 80
  tasks:
    - name: configure apache conf file
      lineinfile:
        path: /etc/httpd/conf/httpd.conf
        regexp: "^Listen"
        line: "Listen {{ http_port }}"
      notify: restart apache

    - name: install error
      dnf:
        name: westos
        state: latest

  handlers:
    - name: restart apache
      service:
        name: httpd
        state: restarted
        enabled: yes

3.changed_when
作用：控制任务在何时报告它已进行更改

实例

---
- name: apache change port
  hosts: all
  force_handlers: yes
  vars:
    http_port: 8080
  tasks:
    - name: configure apache conf file
      lineinfile:
        path: /etc/httpd/conf/httpd.conf
        regexp: "^Listen"
        line: "Listen {{ http_port }}"
      changed_when: true
      notify: restart apache


  handlers:
    - name: restart apache
      service:
        name: httpd
        state: restarted
        enabled: yes

4.failed_when
作用：当符合条件时强制任务失败

---
- name: test
  hosts: all
  tasks:
    - name: shell
      shell: echo hello
      register: westos
      failed_when: "'hello' in westos.stdout"

5.block

block: 		##定义要运行的任务
rescue:		##定义当block句子中出现失败任务后运行的任务
always：	##定义最终独立运行的任务

测试练习

建立playbook  ~/westos.yml要求如下:
建立大小为1500M名为/dev/vdb1的设备
如果/dev/vdb不存在请输入:
     /dev/vdb  is not exist
如果/dev/vdb大小不足2G请输出：
     /dev/vdb is less then 2G
并建立800M大小的/dev/vdb1
此设备挂载到/westos上

---
- name: create lvm
  hosts: all
  tasks:
    - name: check /dev/vdb
      debug:
        msg: /dev/vdb is not exist
      when: ansible_facts['devices']['vdb'] is not defined

    - name: create /dev/vdb1
      block:
        - name: create 1500M
          parted:
            device: /dev/vdb
            number: 1
            state: present
            part_end: 1500MB
          when: ansible_facts['devices']['vdb'] is defined

      rescue:
        - name: create 800MB
          parted:
            device: /dev/vdb
            number: 1
            state: present
            part_end: 800MB
          when: ansible_facts['devices']['vdb'] is defined

      always:
        - name: mkfs.xfs /dev/vdb1
          filesystem:
            fstype: xfs
            dev: /dev/vdb1
        - name: mkdir /westos
          file:
            path: /westos
            state: directory
        - name: mount /dev/vdb1
          mount:
            path: /westos
            src: /dev/vdb1
            fstype: xfs
            state: mounted
          when: ansible_facts['devices']['vdb'] is defined