5.5_Ansible中的任务执行控制

##1.循环##

#循环迭代任务#

（1）简单循环

loop:
  - value1    ##赋值列表
  - 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

测试：

安装并开启vsftpd、apache、dns，并在火墙中允许这些服务访问。

##2.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

##3.触发器##

notify: 触发器当遇到更改时触发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

#4.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：

#控制任务报告它已进行更改

#实例
---
- 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#

挂载/dev/cdrom到/mnt/isodir里

如果/mnt/isodir不存在 -----> /mnt/isodir is not exist -----> create /mnt/isodir

如果/mnt/isodir存在 -----> 直接挂载