任务控制

编写循环和条件任务

利用循环迭代任务

通过利用循环，我们无需编写多个使用同一模块的任务。例如，他们不必编写五个任务来确保存在五个用户，而是只需编写一个任务来对含有五个用户的列表迭代，从而确保它们都存在。

Ansible支持使用loop关键字对一组项目迭代任务。可以配置循环以利用列表中的各个项目、列表中各个文件的内容、生成的数字序列或更为复杂的结构来重复任务

---
- hosts: 192.168.194.138
  tasks:
   - name: install
     yum:
      name: "{{ item }}"
      state: present
     loop:
       - httpd        

[root@localhost ~]# ansible-playbook  wh.yml

PLAY [192.168.194.138] *********************************************************

TASK [Gathering Facts] *********************************************************
ok: [192.168.194.138]

TASK [install] *****************************************************************
changed: [192.168.194.138] => (item=httpd)

PLAY RECAP *********************************************************************
192.168.194.138            : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

[root@localhost ~]# ansible-playbook  wh.yml

PLAY [192.168.194.138] *********************************************************

TASK [Gathering Facts] *********************************************************
ok: [192.168.194.138]

TASK [install] *****************************************************************
ok: [192.168.194.138] => (item=httpd)

PLAY RECAP *********************************************************************
192.168.194.138            : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

在守管主机上查看
[root@localhost ~]# rpm -qa| grep httpd
httpd-2.4.6-93.el7.centos.x86_64
httpd-tools-2.4.6-93.el7.centos.x86_64

当使用循环变量item编写：

---
- hosts: all
  tasks:
    - name: ssthdcjs
      service:
         name: "{{ item }}"
         state: started
      loop:
         - postfix
         - crond
[root@localhost ~]# ansible-playbook ww.yml 

PLAY [192.168.194.139] *********************************************************

TASK [Gathering Facts] *********************************************************
ok: [192.168.194.139]

TASK [ssthdcjs] ****************************************************************
ok: [192.168.194.139] => (item=postfix)
ok: [192.168.194.139] => (item=crond)

PLAY RECAP *********************************************************************
192.168.194.139            : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

可以测试的一个最简单条件是某一布尔变量是True还是False。以下示例中的when语句导致任务仅在run_my_task为True时运行

使用布尔值测试

---
- hosts: all
  vars:
    my_condition: True
  tasks:
    - name: Ensyre the httpd is installed
      yum:
        name: httpd
        statee: present
      when: my_condition

操作	示例
等于（值为字符串）	ansible_machine == “x86_64”
等于（值为数字）	max_memory == 512
小于	min_memory < 128
大于	min_memory > 256
小于等于	min_memory <= 256
大于等于	min_memory >= 512
不等于	min_memory != 512
变量存在	min_memory is defined
变量不存在	min_memory is not defined
布尔变量是True。1、True或yes的求值为True	memory_available
布尔变量是False。0、False或no的求值为False	not memory_available
第一个变量的值存在，作为第二个变量的列表中的值	ansible_distribution in supported_distros

测试多个条件

一个when语句可用于评估多个条件。使用and和or关键字组合条件，并使用括号分组条件
使用or语句时则任意一个条件为真时，则执行相应任务

[root@localhost ~]# vim jjj.yml
---
- hosts: 192.168.194.139
  vars:
    my_arch:
      - RedHat
      - CentOS
  tasks:
     - name: jdgvuid
       yum:
        name: httpd
        state: present
       when: ansible_facts['distribution'] in  my_arc
[root@localhost ~]#  ansible-playbook  jjj.yml 

PLAY [192.168.194.139] *********************************************************

TASK [Gathering Facts] *********************************************************
ok: [192.168.194.139]

TASK [jdgvuid] *****************************************************************
ok: [192.168.194.139]

PLAY RECAP *********************************************************************
192.168.194.139            : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 

[root@localhost ~]# ansible-playbook --syntax-check id.yml 

playbook: id.yml

---
- hosts: 192.168.194.138
  tasks:
      - name: hudjkh
        yum:
          name: httpd
          state: prsent
        when: ansible_facts['distrbution'] 'RedHat' and ansible_facts['distribution_version'] == '7.5'

---
- hosts: all
  tasks:
      - name: hudjkh
        yum:
          name: httpd
          state: absent
        when:
         -  ansible_facts['distrbution'] 'RedHat'
         - ansible_facts['distrbution_version']== '7.4'     

2.组合循环和有条件任务

循环和条件可以组合使用

[root@localhost ~]# vim i.yml
---
- hosts: 192.168.194.139
  tasks:
    - name: hjkdf
      yum:
        name: httpd
        state: absent
      loop: "{{ ansible_facts['mounts'] }}" 
      when:
        - item.mount == '/'
        - item.size_available >  92760410
~                                         
[root@localhost ~]# ansible-playbook  i.yml 

PLAY [192.168.194.139] *********************************************************

TASK [Gathering Facts] *********************************************************
ok: [192.168.194.139]

TASK [hjkdf] *******************************************************************
skipping: [192.168.194.139] => (item={'block_used': 33118, 'uuid': '04dd9450-994d-46e3-97d0-4e8dc836e571', 'size_total': 1063256064, 'block_total': 259584, 'mount': '/boot', 'block_available': 226466, 'size_available': 927604736, 'fstype': 'xfs', 'inode_total': 524288, 'options': 'rw,seclabel,relatime,attr2,inode64,noquota', 'device': '/dev/sda1', 'inode_used': 326, 'block_size': 4096, 'inode_available': 523962}) 
ok: [192.168.194.139] => (item={'block_used': 279995, 'uuid': '6e8789eb-cce5-4dfc-b585-f60a17a5e0f5', 'size_total': 18238930944, 'block_total': 4452864, 'mount': '/', 'block_available': 4172869, 'size_available': 17092071424, 'fstype': 'xfs', 'inode_total': 8910848, 'options': 'rw,seclabel,relatime,attr2,inode64,noquota', 'device': '/dev/mapper/centos-root', 'inode_used': 27062, 'block_size': 4096, 'inode_available': 8883786})

PLAY RECAP *********************************************************************
192.168.194.139            : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

ansible处理程序

Ansible模块设计为具有幂等性。这表示，在正确编写的playbook中，playbook及其任务可以运行多次而不会改变受管主机，除非需要进行更改使受管主机进入所需的状态

[root@localhost ~]# vim bu.yml

    - name: provides config
      template:
          src: files/httpd.conf
          dest: /etc/httpd/conf/httpd.conf
      notify:
          - restart apache

    - name: start service
      service:
           name: httpd

           state: started
  handlers:
    - name: restart apche
      service:
         name: httpd
         state: restarted

[root@localhost ~]# ansible-playbook --syntax-check bu.yml 

playbook: bu.yml
[root@localhost ~]# ansible-playbook bu.yml 

PLAY [192.168.194.139] *********************************************************

TASK [Gathering Facts] *********************************************************
ok: [192.168.194.139]

TASK [installed httpd] *********************************************************
changed: [192.168.194.139]

TASK [provides config] *********************************************************
fatal: [192.168.194.139]: FAILED! => {"changed": false, "msg": "Could not find or access 'files/httpd.conf'\nSearched in:\n\t/root/templates/files/httpd.conf\n\t/root/files/httpd.conf\n\t/root/templates/files/httpd.conf\n\t/root/files/httpd.conf on the Ansible Controller.\nIf you are using a module and expect the file to exist on the remote, see the remote_src option"}