Ansible变量 - 技术栈

1、Ansible 变量介绍

在 PlayBook中，将 PlayBook 类比成了 linux 中的shell。那么它作为一门 ansible 特殊的语言，肯定要涉及到变量定义、控制结构的使用等特性。

2、变量命名规则

变量的名字由字母、下划线和数字组成，必须以字母开头
保留关键字不能作为变量名称

3、变量类型

根据变量的作用范围大体的将变量分为：

全局变量
剧本变量
资产变量
Facts 变量
注册变量

3.1、全局变量

全局变量，是我们使用ansible 或使用 ansible-playbook 时，手动通过 -e 参数传递给 ansible 的变量。

通过 ansible 或者 ansible-playbook 的 help 帮助，可以获取具体格式使用方式：

cpp 复制代码

[root@master1 ~]# ansible -h |grep var -e EXTRA_VARS,--extra-vars=EXTRA_VARS set additional variables as key=value or YAML/JSON
[root@master1 ~]# ansible-playbook -h |grep var -e EXTRA_VARS,--extra-vars=EXTRA_VARS set additional variables as key=value or YAML/JSON

案例

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[root@master1 ~]# ansible all -i localhost,  -m debug -a "msg='my key is {{key}}'" -e "key=value"

#传递一个YAML/JSON 的形式（注意不管YAML 还是 JSON，它们的最终格式一定要是一个字典）、



[root@master1 ~]# cat test.json
{"name": "guan", "type": "people"}

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[root@master1 ~]# ansible all -i localhost,  -m debug -a "msg='name is {{name}},type is {{type}}'" -e @test.json
[WARNING]: Found variable using reserved name: name
localhost | SUCCESS => {
    "msg": "name is guan,type is people"
}

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[root@master1 ~]# cat abc.yml
---
name: guan
type: student
...
[root@master1 ~]# ansible all -i localhost,  -m debug -a "msg='name is {{name}},type is {{type}}'" -e @
abc.yml
[WARNING]: Found variable using reserved name: name
localhost | SUCCESS => {
    "msg": "name is guan,type is student"
}

3.2、剧本变量

这种变量和playbook 有关，定义在 playbook 中的，它的定义方式有多种。这里介绍两种最常见的定义方式。

通过 Playbook 属性 vars 定义

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---
- name: test play vars
  hosts: all
  vars:
    user: zhangsan
    home: /home/zhangsan
...

通过 Play 属性 vars_files 定义

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#当通过vars属性定义的变量很多时，这个 Play 就会感觉特别臃肿，此时我们可将变量单独从play中抽离出来
#形成单独的 yaml 文件
---
- name: test play vars
  hosts: all
  vars_files:
    - vars/users.yml
...

cpp 复制代码

#cat vars/users.yml
---
user: zhangsan
home: /home/zhangsan

如何在 playbook 中使用这些变量

在playbook中使用变量时，使用 {{ 变量名 }} 来使用变量

cpp 复制代码

---
- name: test play vars
  hosts: all
  vars:
    user: zhangsan
    home: /home/zhangsan
  tasks:
    - name: create the user {{ user}}
      user:
        name: "{{ user }}"
        home: "{{ home }}"
...

cpp 复制代码

[root@master1 ~]# vim test_play_vars.yml
[root@master1 ~]# ansible-playbook -i localhost,  test_play_vars.yml -C

PLAY [test play vars] *********************************************************************************

TASK [Gathering Facts] ********************************************************************************
The authenticity of host 'localhost (::1)' can't be established.
ECDSA key fingerprint is SHA256:ygT6h9ejxNmaemQtyIzVYHEbRko0BaG4PstS2LTavDM.
ECDSA key fingerprint is MD5:88:1f:c4:d2:fe:73:b9:1f:7f:26:cd:2c:ba:ad:5c:b5.
Are you sure you want to continue connecting (yes/no)? yes
fatal: [localhost]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.\r\nPermission denied (publickey,gssapi-keyex,gssapi-with-mic,password).", "unreachable": true}

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

[root@master1 ~]# ssh-copy-id root@192.168.115.181
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host '192.168.115.181 (192.168.115.181)' can't be established.
ECDSA key fingerprint is SHA256:ygT6h9ejxNmaemQtyIzVYHEbRko0BaG4PstS2LTavDM.
ECDSA key fingerprint is MD5:88:1f:c4:d2:fe:73:b9:1f:7f:26:cd:2c:ba:ad:5c:b5.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.115.181's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@192.168.115.181'"
and check to make sure that only the key(s) you wanted were added.

[root@master1 ~]# ansible-playbook -i localhost,  test_play_vars.yml -C

PLAY [test play vars] *********************************************************************************

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

TASK [create the user zhangsan] ***********************************************************************
changed: [localhost]

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

[root@master1 ~]# cat test_play_vars.yml
---
- name: test play vars
  hosts: all
  vars:
    user: zhangsan
    home: /home/zhangsan
  tasks:
    - name: create the user {{ user}}
      user:
        name: "{{ user }}"
        home: "{{ home }}"
...
[root@master1 ~]#

执行出现以下错误的原因是 {{ user }} 两端没有加双引号

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[root@master1 ~]# ansible-playbook -i localhost,  test_play_vars.yml -C
ERROR! We were unable to read either as JSON nor YAML, these are the errors we got from each:
JSON: No JSON object could be decoded

Syntax Error while loading YAML.
  found unacceptable key (unhashable type: 'AnsibleMapping')

The error appears to be in '/root/test_play_vars.yml': line 10, column 16, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

      user:
        name: {{ user }}
               ^ here
We could be wrong, but this one looks like it might be an issue with
missing quotes. Always quote template expression brackets when they
start a value. For instance:

    with_items:
      - {{ foo }}

Should be written as:

    with_items:
      - "{{ foo }}"
[root@master1 ~]#

这样错误的主要原因是playbook 是yaml的格式文件，当 ansible 分析 yaml 文件时，有可能会误认为是字典。
name： {{ user }} 是一个字典的开始。因此，加针对变量的使用，加上了双引号，避免 ansible 错误解析。

3.3、资产变量

资产变量分为主机变量和主机组变量，分别针对资产中的单个主机和主机组。

主机变量

以下资产中，定义了一个主机变量 lisi ，此变量只针对 192.168.115.183 这台服务器有效。

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[root@master1 ~]# vim hosts_vars
[root@master1 ~]# cat hosts_vars
[web_servers]
192.168.115.183 user=lisi port=3309
192.168.115.182

[root@master1 ~]#

验证

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[root@master1 ~]# ansible 192.168.115.183 -i hosts_vars  -m debug -a "msg='{{user}} {{port}}'"
192.168.115.183 | SUCCESS => {
    "msg": "lisi 3309"
}
[root@master1 ~]# 
//未获取到定义的变量值，因为 user 这个变量针对 192.168.115.182 主机无效
[root@master1 ~]# ansible 192.168.115.182 -i hosts_vars  -m debug -a "var=user"
192.168.115.182 | SUCCESS => {
    "user": "VARIABLE IS NOT DEFINED!"
}

主机组变量

以下资产中，定义了一个组变量home，此变量将针对 web_servers 这个主机组中的所有服务器有效

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[root@master1 ~]# cat hosts_groupvars
[web_servers]
192.168.115.183 user=lisi port=3309
192.168.115.182

[web_servers:vars]
home="/home/lisi"

验证

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[root@master1 ~]# ansible web_servers -i hosts_groupvars  -m debug -a "var=home"
192.168.115.182 | SUCCESS => {
    "home": "/home/lisi"
}
192.168.115.183 | SUCCESS => {
    "home": "/home/lisi"
}
[root@master1 ~]#

主机变量 vs 主机组变量

当主机变量和组变量在同一个资产中发生重名的情况，会有什么效果

cpp 复制代码

[root@master1 ~]# vim hosts_vs
[root@master1 ~]# cat hosts_vs
[web_servers]
192.168.115.183 user=lisi 
192.168.115.182

[web_servers:vars]
user=tongtong

验证

cpp 复制代码

#在资产中定义了主机变量和组变量 user，此时发现 192.168.115.183 这台服务器的主机变量 user 的优先级 高于 组变量user 使用。
[root@master1 ~]# ansible web_servers -i hosts_vs  -m debug -a "var=user"
192.168.115.183 | SUCCESS => {
    "user": "lisi"
}
192.168.115.182 | SUCCESS => {
    "user": "tongtong"
}

变量的继承

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[root@master1 ~]# cat hosts_v1
[web3_servers]
192.168.115.183  

[web2_servers]
192.168.115.182


[allservers]
[allservers:children]
web2_servers
web3_servers

[allservers:vars]
user=lisi
#在资产继承的同时，对应的变量也发生了继承
[root@master1 ~]# ansible allservers -i hosts_v1  -m debug -a "var=user"
192.168.115.183 | SUCCESS => {
    "user": "lisi"
}
192.168.115.182 | SUCCESS => {
    "user": "lisi"
}
[root@master1 ~]# 
[root@master1 ~]# ansible web2_servers -i hosts_v1  -m debug -a "var=user"
192.168.115.182 | SUCCESS => {
    "user": "lisi"
}
[root@master1 ~]# ansible web3_servers -i hosts_v1  -m debug -a "var=user"
192.168.115.183 | SUCCESS => {
    "user": "lisi"
}

3.4、Facts 变量

facts 变量不包含在之前介绍的全局变量、剧本变量及资产变量之内。

facts 变量不需要我们人为去声明变量名及赋值。它的声明和赋值完全有 ansible 中的 setup 模块帮助我们完成。

它收集了有关被管理服务器的操作系统版本、服务器IP地址、主机名，磁盘的使用情况、cpu个数、内存条大小等等有关被管理服务器的私有信息。

在每次playbook运行的时候都会发现在 Playbook 执行一个 Gathering Facts的过程。这个过程就是收集被管理服务器的facts信息过程。

手动收集 Facts 变量

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[root@master1 ~]# ansible all -i localhost, -c local  -m setup
localhost | SUCCESS => {
    "ansible_facts": {
        "ansible_all_ipv4_addresses": [
            "192.168.115.181", 
            "192.168.122.1"
        ], 
        "ansible_all_ipv6_addresses": [
            "fe80::8054:e8a7:a00d:e7f5", 
            "fe80::2e53:1e73:716d:c608", 
            "fe80::5d99:b781:21b8:139b"
        ], 
        "ansible_apparmor": {
            "status": "disabled"
        }, 
        "ansible_architecture": "x86_64", 
        "ansible_bios_date": "07/22/2020", 
        "ansible_bios_version": "6.00", 
        "ansible_cmdline": {
            "BOOT_IMAGE": "/vmlinuz-3.10.0-957.el7.x86_64", 
            "LANG": "zh_CN.UTF-8", 
            "crashkernel": "auto", 
            "quiet": true, 
            "rd.lvm.lv": "centos/swap", 
            "rhgb": true, 
            "ro": true, 
            "root": "/dev/mapper/centos-root"
        }, 
...
...
...

过滤 Facts

通过刚刚的手动收集 Facts，我们发现facts 信息量很大。因此，可以有针对性的显示我们想要的信息。

可以通过使用facts 模块中filter 参数去过滤我们想要的信息。

仅获取服务器的内存信息情况

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[root@master1 ~]# ansible all -i localhost, -c local  -m setup -a "filter=*memory*"
localhost | SUCCESS => {
    "ansible_facts": {
        "ansible_memory_mb": {
            "nocache": {
                "free": 1826, 
                "used": 1001
            }, 
            "real": {
                "free": 189, 
                "total": 2827, 
                "used": 2638
            }, 
            "swap": {
                "cached": 94, 
                "free": 1567, 
                "total": 2047, 
                "used": 480
            }
        }, 
        "discovered_interpreter_python": "/usr/bin/python"
    }, 
    "changed": false
}

仅获取服务器的磁盘挂在情况

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[root@master1 ~]# ansible all -i localhost, -c local  -m setup -a "filter=*mount*"
localhost | SUCCESS => {
    "ansible_facts": {
        "ansible_mounts": [
            {
                "block_available": 213906, 
                "block_size": 4096, 
                "block_total": 259584, 
                "block_used": 45678, 
                "device": "/dev/sda1", 
                "fstype": "xfs", 
                "inode_available": 523947, 
                "inode_total": 524288, 
                "inode_used": 341, 
                "mount": "/boot", 
                "options": "rw,relatime,attr2,inode64,noquota", 
                "size_available": 876158976, 
                "size_total": 1063256064, 
                "uuid": "1bb90732-6784-4a0f-b4f7-71c74e55e7b5"
            }, 
            {
                "block_available": 0, 
                "block_size": 0, 
                "block_total": 0, 
                "block_used": 0, 
                "device": "/dev/fuse", 
                "fstype": "fuse", 
                "inode_available": 0, 
                "inode_total": 0, 
                "inode_used": 0, 
                "mount": "/run/user/1001/doc", 
                "options": "rw,nosuid,nodev,relatime,user_id=1001,group_id=1008", 
                "size_available": 0, 
                "size_total": 0, 
                "uuid": "N/A"
            }, 
            {
                "block_available": 2042537, 
                "block_size": 4096, 
                "block_total": 4452864, 
                "block_used": 2410327, 
                "device": "/dev/mapper/centos-root", 
                "fstype": "xfs", 
                "inode_available": 8670224, 
                "inode_total": 8910848, 
                "inode_used": 240624, 
                "mount": "/", 
                "options": "rw,relatime,attr2,inode64,noquota", 
                "size_available": 8366231552, 
                "size_total": 18238930944, 
                "uuid": "c26721c5-0deb-42fe-949d-3779b2bd4276"
            }
        ], 
        "discovered_interpreter_python": "/usr/bin/python"
    }, 
    "changed": false
}
[root@master1 ~]#

在 Playbook 中去使用Facts 变量

默认情况下，在执行Playbook的时候，它会去自动的获取每台被管理服务器的facts信息。

cpp 复制代码

[root@master1 ~]# vim facts.yml
[root@master1 ~]# ansible-playbook -i localhost, facts.yml

PLAY [print facts variable] ***************************************************************************

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

TASK [print facts variable] ***************************************************************************
ok: [localhost] => {
    "msg": "The default IPV4 address is [u'0', u'AuthenticAMD', u'AMD Ryzen 7 5700U with Radeon Graphics', u'1', u'AuthenticAMD', u'AMD Ryzen 7 5700U with Radeon Graphics']"
}

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

[root@master1 ~]# cat facts.yml
---
- name: print facts variable
  hosts: all
  tasks:
    - name: print facts variable
      debug: 
            msg: "The default IPV4 address is {{ ansible_default_ipv4.address }}"
...

[root@master1 ~]# 

[root@master1 ~]# ansible-playbook -i localhost, facts.yml

PLAY [print facts variable] ***************************************************************************

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

TASK [print facts variable] ***************************************************************************
ok: [localhost] => {
    "msg": "/usr/bin/python"
}

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

[root@master1 ~]# cat facts.yml
---
- name: print facts variable
  hosts: all
  tasks:
    - name: print facts variable
      debug: 
        msg: "{{ ansible_python.executable }}"  #如果是字典就通过键获取对应的值
...

[root@master1 ~]#

在Playbook 中去关闭 Facts 变量的获取

若在整个 Playbook 的执行过程中，完全未使用过 Facts 变量，此时我们可以将其关闭，以加速 playbook 的执行速度。

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---
- name: the first play example
  hosts: web_servers
  gather_facts: no  #关闭 facts 变量收集功能
  remote_user: root
  tasks:
    - name: install nginx package
      yum: name=nginx state=present
    - name: copy nginx.conf to remote server
      copy: src=nginx.conf dest=/etc/nginx/nginx.conf
    - name: start nginx server
      service:
        name: nginx
        enabled:true
        state: started
...

执行

cpp 复制代码

[root@master1 ~]# ansible-playbook   -i hosts my_playbook01.yml

3.5、注册变量

用于保存一个 task 任务的执行结果，以便于 debug 时使用，或者将此次 task 任务的结果作为条件，去判断是否执行其他 task 任务。

注册变量在playbook中通过 register 关键字去实现。

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[root@master1 ~]# vim  my_playbook02.yml
[root@master1 ~]# cat  my_playbook02.yml
---
- name: install a package and print the result
  hosts: web_servers
  remote_user: root
  tasks:
    - name: install nginx package
      yum: name=nginx state=present 
      register: install_result
    - name: print result
      debug: 
        msg: "{{ install_result }}"
...

执行

cpp 复制代码

[root@master1 ~]# ansible-playbook  -i hosts my_playbook02.yml

PLAY [install a package and print the result] *********************************************************

TASK [Gathering Facts] ********************************************************************************
ok: [192.168.115.183]

TASK [install nginx package] **************************************************************************
ok: [192.168.115.183]

TASK [print result] ***********************************************************************************
ok: [192.168.115.183] => {
    "install_result": {
        "changed": false, 
        "failed": false, 
        "msg": "", 
        "rc": 0, 
        "results": [
            "1:nginx-1.20.1-10.el7.x86_64 providing nginx is already installed"
        ]
    }
}

PLAY RECAP ********************************************************************************************
192.168.115.183            : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

[root@master1 ~]#

4、变量优先级

前面介绍了全局变量、剧本变量、资产变量、Facts 变量及注册变量，其中 facts 变量不需要人为去声明、赋值；注册变量只需通过关键字 register 去声明，而不需要赋值，而全局变量、剧本变量及资产变量则完全需要人为的去声明、赋值。

变量的优先权讨论，也将从这三类变量去分析。

假设在使用过程中，我们同时在全局变量、剧本变量及资产变量声明了同一个变量名，那么哪一个优先级最高呢？

下面通过实验去验证变量的优先级

环境准备

定义一份资产、且定义了资产变量 user

cpp 复制代码

[root@master1 ~]# vim  hosts_v1
[root@master1 ~]# cat hosts_v1
[web3_servers]
192.168.115.183  

[web2_servers]
192.168.115.182


[allservers]
[allservers:children]
web2_servers
web3_servers

[allservers:vars]
user=tomcat

[root@master1 ~]#

编写一份 playbook 、同样定义剧本变量 user

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[root@master1 ~]# vim  user_playbook.yml
[root@master1 ~]# cat  user_playbook.yml
---
- name: test variable priority
  hosts: all 
  remote_user: root
  vars:
    user: mysql
  tasks:
    - name: print the user value
      debug: msg='the user value is {{ user }}'
...
[root@master1 ~]#

验证测试

cpp 复制代码

[root@master1 ~]# ansible-playbook  -i hosts priority.yml

PLAY [test variable priority] *************************************************************************

TASK [Gathering Facts] ********************************************************************************
ok: [192.168.115.183]
ok: [192.168.115.182]

TASK [print the user value] ***************************************************************************
ok: [192.168.115.183] => {
    "msg": "the user value is mysql"
}
ok: [192.168.115.182] => {
    "msg": "the user value is mysql"
}

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

[root@master1 ~]# ansible-playbook  -i hosts priority.yml -e  "user=xiaobai"

PLAY [test variable priority] *************************************************************************

TASK [Gathering Facts] ********************************************************************************
ok: [192.168.115.183]
ok: [192.168.115.182]

TASK [print the user value] ***************************************************************************
ok: [192.168.115.183] => {
    "msg": "the user value is xiaobai"
}
ok: [192.168.115.182] => {
    "msg": "the user value is xiaobai"
}

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

[root@master1 ~]#