Ansible编写循环和条件任务

一、利用循环迭代任务

1️⃣: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

1、简单循环

1️⃣:简单循环对一组项目迭代任务。loop关键字添加到任务中,将应对其迭代任务的项目列表取为值。循环变量item保存每个迭代过程中使用的值

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: create user
      user:
        name: "{{ item }}"
        state: present
      loop:
        - zhangsan
        - lisi

 //测试执行play
[root@localhost project]# ansible-playbook playbook.yaml -C

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [create user] ********************************************************************************************************************************************************
changed: [client.example.com] => (item=zhangsan)
changed: [client.example.com] => (item=lisi)

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

2️⃣:此外、还可以通过变量给loop提供所使用的的列表

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  vars:
    users:
      - zhangsan
      - lisi
      - wangwu
  tasks:
    - name: create user
      user:
        name: "{{ item }}"
        state: present
      loop: "{{ users }}"

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml -C

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [create user] ********************************************************************************************************************************************************
changed: [client.example.com] => (item=zhangsan)
changed: [client.example.com] => (item=lisi)
changed: [client.example.com] => (item=wangwu)

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

2、循环散列或字典列表

1️⃣: loop列表不需要是简单值列表

  • 演示实例:item标识一个循环的项目(任务),item.name和item.group表示item的两个键值(键值可自定义,但必须与loop中的项目匹配)
//查看playbook文件
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: create user
      user:
        name: "{{ item.name }}"
        group: "{{ item.group}}"
        state: present
      loop:
        - name: zhangsan
          group: zhangsan
        - name: lisi
          group: lisi

 //测试是否可play
[root@localhost project]# ansible-playbook playbook.yaml -C

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [create user] ********************************************************************************************************************************************************
changed: [client.example.com] => (item={'name': 'zhangsan', 'group': 'zhangsan'})
changed: [client.example.com] => (item={'name': 'lisi', 'group': 'lisi'})

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

3、将Register变量于Loop一起使用

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: show some user
      shell: 'echo this user is {{ item }}'
      loop:
        - zhangsan
        - lisi
        - wangwu
      register: result

    - name: show these user
      debug:
        var: result

 //测试是否执行play
[root@localhost project]# ansible-playbook playbook.yaml -C

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [show some user] *****************************************************************************************************************************************************
skipping: [client.example.com] => (item=zhangsan) 
skipping: [client.example.com] => (item=lisi) 
skipping: [client.example.com] => (item=wangwu) 

TASK [show these user] 
............
"item": "zhangsan",
                "msg": "skipped, running in check mode",
                "skipped": true
............
"item": "lisi",
                "msg": "skipped, running in check mode",
                "skipped": true
.............
"item": "wangwu",
                "msg": "skipped, running in check mode",
                "skipped": true
.............

1️⃣: 在上面的例子中,results键包含一个列表。在下面,修改了playbook,使第二个任务迭代此列表

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: show some user
      shell: 'echo this user is {{ item }}'
      loop:
        - zhangsan
        - lisi
        - wangwu
      register: magic

    - name: show these user
      debug:
        msg: "{{ item.stdout }}"
      loop: "{{ magic['results'] }}"

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [show some user] *****************************************************************************************************************************************************
changed: [client.example.com] => (item=zhangsan)
changed: [client.example.com] => (item=lisi)
changed: [client.example.com] => (item=wangwu)

TASK [show these user] ****************************************************************************************************************************************************
ok: [client.example.com] => (item={'cmd': 'echo this user is zhangsan', 'stdout': 'this user is zhangsan', 'stderr': '', 'rc': 0, 'start': '2020-09-03 15:28:50.767109', 'end': '2020-09-03 15:28:50.774188', 'delta': '0:00:00.007079', 'changed': True, 'invocation': {'module_args': {'_raw_params': 'echo this user is zhangsan', '_uses_shell': True, 'warn': True, 'stdin_add_newline': True, 'strip_empty_ends': True, 'argv': None, 'chdir': None, 'executable': None, 'creates': None, 'removes': None, 'stdin': None}}, 'stdout_lines': ['this user is zhangsan'], 'stderr_lines': [], 'failed': False, 'item': 'zhangsan', 'ansible_loop_var': 'item'}) => {
    "msg": "this user is zhangsan"
}
ok: [client.example.com] => (item={'cmd': 'echo this user is lisi', 'stdout': 'this user is lisi', 'stderr': '', 'rc': 0, 'start': '2020-09-03 15:28:51.542241', 'end': '2020-09-03 15:28:51.547953', 'delta': '0:00:00.005712', 'changed': True, 'invocation': {'module_args': {'_raw_params': 'echo this user is lisi', '_uses_shell': True, 'warn': True, 'stdin_add_newline': True, 'strip_empty_ends': True, 'argv': None, 'chdir': None, 'executable': None, 'creates': None, 'removes': None, 'stdin': None}}, 'stdout_lines': ['this user is lisi'], 'stderr_lines': [], 'failed': False, 'item': 'lisi', 'ansible_loop_var': 'item'}) => {
    "msg": "this user is lisi"
}
ok: [client.example.com] => (item={'cmd': 'echo this user is wangwu', 'stdout': 'this user is wangwu', 'stderr': '', 'rc': 0, 'start': '2020-09-03 15:28:52.292883', 'end': '2020-09-03 15:28:52.298768', 'delta': '0:00:00.005885', 'changed': True, 'invocation': {'module_args': {'_raw_params': 'echo this user is wangwu', '_uses_shell': True, 'warn': True, 'stdin_add_newline': True, 'strip_empty_ends': True, 'argv': None, 'chdir': None, 'executable': None, 'creates': None, 'removes': None, 'stdin': None}}, 'stdout_lines': ['this user is wangwu'], 'stderr_lines': [], 'failed': False, 'item': 'wangwu', 'ansible_loop_var': 'item'}) => {
    "msg": "this user is wangwu"
}

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=3    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

二、有条件的运行任务

Ansible可使用conditionals在符合特定条件时执行任务或play。例如,可以利用一个条件在Ansible安装或配置服务前确定受管主机上的可用内存

条件任务语法

1️⃣:when语句用于有条件地运行任务;它取要测试的条件为值。如果条件满足,则运行任务。如果条件不满足,则跳过任务

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  vars:
    package: True
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: installed
      when: package

 //测试执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

2️⃣:处理条件时可使用的一些运算示例

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

  • 演示实例一:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  vars:
    package: httpd
  tasks:
    - name: install {{ package }}
      yum:
        name: "{{ package }}"
        state: present
      when: package is defined

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

 

  • 演示实例二:第一个变量的值存在(一般是事实),且作为第二个变量列表中的值
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  vars:
    version:
      - RedHat
      - CentOS
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when: ansible_facts['distribution'] in version     //ansible_facts['distribution']该变量的值与versionversion中的值匹配

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

 

  • 演示实例三:(判断大小)
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  vars:
    number: 800
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when: number >= 800

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

2、测试多个条件

1️⃣:一个when语句可用于评估多个条件:使用andor关键字组合条件,并使用括号分组条件

2️⃣:使用and语句运算时,两个条件必须为真,才能满足整个条件语句

  • 演示实例一:and 语句第一种写法
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when: ansible_facts['distribution_version'] == "8.1" and ansible_facts['distribution'] == "RedHat"

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

 

  • 演示实例二:and 语句第二种写法
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when:
        - ansible_facts['distribution_version'] == "8.1" 
        - ansible_facts['distribution'] == "RedHat"

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

 

  • 演示实例三:and 语句第三中写法
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when:
        ( ansible_facts['distribution_version'] == "8.1" )
        and
        ( ansible_facts['distribution'] == "RedHat" )

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

3️⃣:使用or语句时,其中任一条件为真时,就能满足条件语句

  • 演示实例一:or 语句第一种写法
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when: ansible_facts['distribution'] == "RedHat" or ansible_facts['distribution_version'] == "7.9"

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
 //我当前使用的是RHEL8.1版本

 

  • 演示实例二:or 语句第二种写法
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when: >               //这里可以加,也可以不加;>:是允许下面的变量可以换行写
        ( ansible_facts['distribution'] == "RedHat" )
        or 
        ( ansible_facts['distribution_version'] == "7.9 )"

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

 

  • 演示实例三:or 语句的第三种写法(与and语句嵌套使用)
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      when:
        ( ansible_facts['distribution'] == "RedHat" and ansible_facts['kernel'] == "4.18.0-147.el8.x86_64"  )
        or 
        ( ansible_facts['distribution_version'] == "7.9" and ansible_facts['distribution_major_version'] == "7" )

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

三、组合循环和有条件任务

使用Loop和When组合使用

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      loop: "{{ ansible_facts['mounts'] }}"
      when:
        - item.mount == "/"
        - item.size_available > 50000000000

 //执行paly
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com] => (item={'mount': '/', 'device': '/dev/mapper/rhel-root', 'fstype': 'xfs', 'options': 'rw,seclabel,relatime,attr2,inode64,noquota', 'size_total': 53660876800, 'size_available': 51805659136, 'block_size': 4096, 'block_total': 13100800, 'block_available': 12647866, 'block_used': 452934, 'inode_total': 26214400, 'inode_available': 26178405, 'inode_used': 35995, 'uuid': '6a525cf5-3f23-4639-81cb-04fcdb764eb6'})
skipping: [client.example.com] => (item={'mount': '/home', 'device': '/dev/mapper/rhel-home', 'fstype': 'xfs', 'options': 'rw,seclabel,relatime,attr2,inode64,noquota', 'size_total': 28922376192, 'size_available': 28686655488, 'block_size': 4096, 'block_total': 7061127, 'block_available': 7003578, 'block_used': 57549, 'inode_total': 14129152, 'inode_available': 14129137, 'inode_used': 15, 'uuid': '2840f839-89b2-4717-b1d0-c74c46d05019'}) 
skipping: [client.example.com] => (item={'mount': '/boot', 'device': '/dev/nvme0n1p1', 'fstype': 'xfs', 'options': 'rw,seclabel,relatime,attr2,inode64,noquota', 'size_total': 1063256064, 'size_available': 882565120, 'block_size': 4096, 'block_total': 259584, 'block_available': 215470, 'block_used': 44114, 'inode_total': 524288, 'inode_available': 523987, 'inode_used': 301, 'uuid': '234365dc-2262-452e-9cbb-a6acfde04385'}) 
skipping: [client.example.com] => (item={'mount': '/mnt', 'device': '/dev/sr0', 'fstype': 'iso9660', 'options': 'ro,relatime,nojoliet,check=s,map=n,blocksize=2048', 'size_total': 7851202560, 'size_available': 0, 'block_size': 2048, 'block_total': 3833595, 'block_available': 0, 'block_used': 3833595, 'inode_total': 0, 'inode_available': 0, 'inode_used': 0, 'uuid': '2019-10-15-13-34-03-00'}) 

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

 

2、使用Register和When组合使用

  • 演示实例:
//查看playbook
[root@localhost project]# cat playbook.yaml 
---
- hosts: all
  tasks:
    - name: install httpd
      yum:
        name: httpd
        state: present
      ignore_errors: yes       //在运行时,如果出现错误且命令失败,将不会停止,继续执行其他的命令
      register: result       //将安装成功后的结果注册到result变量中

    - name: start httpd
      service:
        name: httpd
        state: started
      when: result.rc == 0    //在该变量中匹配到返回值rc=0执行该命令

 //执行play
[root@localhost project]# ansible-playbook playbook.yaml 

PLAY [all] ****************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************
ok: [client.example.com]

TASK [install httpd] ******************************************************************************************************************************************************
changed: [client.example.com]

TASK [start httpd] ********************************************************************************************************************************************************
changed: [client.example.com]

PLAY RECAP ****************************************************************************************************************************************************************
client.example.com         : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0