ansible中任务执行控制

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: 172.25.0.254
  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: 172.25.0.254
 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

---

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: 172.25.0.254
 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

#example

---
- name: apache change port
 hosts: 172.25.0.254
 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

---
- name: apache change port
 hosts: 172.25.0.254
 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

#当符合条件时强制任务失败

---
- name: test
 hosts: 172.25.0.254
 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

---