Ansible中的一些特殊变量与执行控制

---

一、注册变量

register 把模块输出注册到指定字符串中，如下所示：
---
- name: test register
  hosts: 172.25.0.254
  tasks:
    - name: hostname command
      shell:
        hostname
      register: info

    - name: show messages
      shell:
        echo "{
    
    {info['stdout']}}"

二、事实变量

事实变量是ansible在受控主机中自动检测出的变量
事实变量中还有与主机相关的信息
当需要使用主机相关信息时不需要采集赋值，直接调用即可
因为变量信息为系统信息所以不能随意设定仅为采集信息，故被成为事实变量

---
- name: test register
  hosts: 172.25.0.254
  tasks:
    - name: show messages
      debug:
        msg: "{
    
    {ansible_facts['architecture']}}"

三、魔术变量

这些变量不能由用户直接设置;Ansible 将始终覆盖它们以反映内部状态。

hostvars:		       %ansible软件的内部信息
group_names:		   %当前受管主机所在组
groups:			       %列出清单中所有的组和主机
inventory_hostname:	   %包含清单中配置的当前授管主机的名称	

四、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

五、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"

六、block

block块实际上是对task任务的分组

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

举例如下：
---
- hosts: webserver
  tasks:
  - name: deploy apache
    block:
    - name: install httpd
      dnf:
        name: httpd
        state: present
  
    - name: create index.html
      copy:
        content: "{
    
    { ansible_hostname }}\n"
        dest: /var/www/html/index.html
    
    - name: config httpd
      template:
        src: httpd.conf.j2
        dest: /etc/httpd/conf/httpd.conf
      notify: restart httpd
  
    - name: start httpd
      service:
        name: httpd
        state: started
        enabled: yes
  
    - name: accept httpd
      firewalld:
        service: http
        permanent: yes
        immediate: yes
        state: enabled
    
    - name: accept 8080
      firewalld:
        port: 8080/tcp
        permanent: yes
        immediate: yes
        state: enabled
    when: ansible_default_ipv4.address in groups['webserver'] %其中书写方式要根据ansible版本来定
查看ansible版本：
[root@test2 ansible]# rpm -q ansible
ansible-2.9.16-1.el8.noarch

查看ansible中ip相关书写格式问题：
ansible test -m setup | less      %其中test是hosts文件中所写的一个组