循环语句

循环语句

简介

我们在编写playbook的时候，不可避免的要执行一些重复性操作，比如指安装软件包，批量创建用户，操作某个目录下的所有文件等。正如我们所说，ansible一门简单的自动化语言，所以流程控制、循环语句这些编程语言的基本元素它同样都具备。

下面我们简单的说一说Playbook中循环语句。

loop关键字说明

在playbook中使用循环，直接使用loop关键字即可。

如下示例，启动httpd和postfilx服务：

tasks:

  - name: postfix and httpd are running

    service:

      name: "{{ item }}"

      state: started

    loop:

      - postfix

      - httpd

也可以将loop循环的列表提前赋值给一个变量，然后在循环语句中调用：

#cat test_services.yml

test_services:

  - postfix

  - httpd

# cat install_pkgs.yml

- name: start services

  hosts: test

  vars_files:

    - test_services.yml

  tasks:

    - name: postfix and httpd are running

      service:

        name: "{{ item }}"

        state: started

      loop: "{{ test_services }}"

下面是一个循环更复杂类型数据的示例：

# cat test_loop.yml

- name: test loop

  hosts: test

  tasks:

  - name: add www group

    group:

      name: www

  - name: add several users

    user:

      name: "{{ item.name }}"

      state: present

      groups: "{{ item.groups }}"

    loop:

      - { name: 'testuser1', groups: 'wheel' }

      - { name: 'testuser2', groups: 'www' }

在循环语句中注册变量

下面是一个register的变量在循环中使用的例子：

# cat register_loop.yml

- name: registered variable usage as a loop list

  hosts: test

  tasks:

      - name: ensure /mnt/bkspool exists

        file:

          path: /mnt/bkspool

          state: directory

      - name: retrieve the list of home directories

        command: ls /home

        register: home_dirs

      - name: Show home_dirs results

        debug:

          var: home_dirs.stdout_lines

      - name: add home dirs to the backup spooler

        file:

          path: /mnt/bkspool/{{ item }}

          src: /home/{{ item }}

          state: link

          force: yes

        loop: "{{ home_dirs.stdout_lines }}"

在循环语句中注册变量：

- name: Loop Register test

  gather_facts: no

  hosts: test

  tasks:

    - name: Looping Echo Task

      shell: "echo this is my item: {{ item }}"

      loop:

        - one

        - two

      register: echo_results

    - name: Show echo_results variable

      debug:

        var: echo_results

执行语句，可以看到变量的返回结果为一个字典列表：

ok: [10.1.61.187] => {

    "echo_results": {

        "changed": true,

        "msg": "All items completed",

        "results": [

            {

                "ansible_loop_var": "item",

                "changed": true,

                "cmd": "echo this is my item: one",

                "delta": "0:00:00.004905",

                "end": "2019-06-10 00:23:51.814151",

                "failed": false,

                "invocation": {

                    "module_args": {

                        "_raw_params": "echo this is my item: one",

                        "_uses_shell": true,

                        "argv": null,

                        "chdir": null,

                        "creates": null,

                        "executable": null,

                        "removes": null,

                        "stdin": null,

                        "stdin_add_newline": true,

                        "strip_empty_ends": true,

                        "warn": true

                    }

                },

                "item": "one",

                "rc": 0,

                "start": "2019-06-10 00:23:51.809246",

                "stderr": "",

                "stderr_lines": [],

                "stdout": "this is my item: one",

                "stdout_lines": [

                    "this is my item: one"

                ]

            },

            {

                "ansible_loop_var": "item",

                "changed": true,

                "cmd": "echo this is my item: two",

                "delta": "0:00:00.004736",

                "end": "2019-06-10 00:23:52.008981",

                "failed": false,

                "invocation": {

                    "module_args": {

                        "_raw_params": "echo this is my item: two",

                        "_uses_shell": true,

                        "argv": null,

                        "chdir": null,

                        "creates": null,

                        "executable": null,

                        "removes": null,

                        "stdin": null,

                        "stdin_add_newline": true,

                        "strip_empty_ends": true,

                        "warn": true

                    }

                },

                "item": "two",

                "rc": 0,

                "start": "2019-06-10 00:23:52.004245",

                "stderr": "",

                "stderr_lines": [],

                "stdout": "this is my item: two",

                "stdout_lines": [

                    "this is my item: two"

                ]

            }

        ]

    }

}

旧循环语句

在Ansible 2.5以前，playbook通过不同的循环语句以实现不同的循环，这些语句使用with_作为前缀。这些语法目前仍然兼容，但在未来的某个时间点，会逐步废弃。

循环语句关键字	描述
with_items	简单的列表循环
with_nested	嵌套循环
with_dict	循环字典
with_fileglob	循环指定目录中的所有文件
with_lines	循环一个文件中的所有行
with_sequence	生成一个自增的整数序列，可以指定起始值和结束值以及步长。参数以key=value的形式指定，format指定输出的格式。数字可以是十进制、十六进制、八进制
with_subelement	遍历子元素
with_together	遍历数据并行集合

1. with_items

- hosts: test

  vars:

    data:

      - user0

      - user1

      - user2

  tasks:

    - name: "with_items"

      debug:

        msg: "{{ item }}"

      with_items: "{{ data }}"

2. with_nested

tasks:

  - name: debug loops

    debug: msg="name is {{ item[0] }}  vaule is {{ item[1] }} num is {{ item[2] }}"

    with_nested:

      - ['alice','bob']

      - ['a','b','c']

      - ['1','2','3']

item[0]是循环的第一个列表的值['alice','bob']。item[1]是第二个列表的值；item[2]则是第三个列表的值，以上的执行输出如下：

# ansible-playbook with_nested_ex.yml 

PLAY [with_nested test] ******************************************************************************************

TASK [Gathering Facts] *******************************************************************************************

ok: [10.1.61.187]

TASK [debug loops] ***********************************************************************************************

ok: [10.1.61.187] => (item=['alice', 'a', '1']) => {

    "msg": "name is alice  vaule is a num is 1"

}

ok: [10.1.61.187] => (item=['alice', 'a', '2']) => {

    "msg": "name is alice  vaule is a num is 2"

}

ok: [10.1.61.187] => (item=['alice', 'a', '3']) => {

    "msg": "name is alice  vaule is a num is 3"

}

ok: [10.1.61.187] => (item=['alice', 'b', '1']) => {

    "msg": "name is alice  vaule is b num is 1"

}

ok: [10.1.61.187] => (item=['alice', 'b', '2']) => {

    "msg": "name is alice  vaule is b num is 2"

}

ok: [10.1.61.187] => (item=['alice', 'b', '3']) => {

    "msg": "name is alice  vaule is b num is 3"

}

ok: [10.1.61.187] => (item=['alice', 'c', '1']) => {

    "msg": "name is alice  vaule is c num is 1"

}

ok: [10.1.61.187] => (item=['alice', 'c', '2']) => {

    "msg": "name is alice  vaule is c num is 2"

}

ok: [10.1.61.187] => (item=['alice', 'c', '3']) => {

    "msg": "name is alice  vaule is c num is 3"

}

ok: [10.1.61.187] => (item=['bob', 'a', '1']) => {

    "msg": "name is bob  vaule is a num is 1"

}

ok: [10.1.61.187] => (item=['bob', 'a', '2']) => {

    "msg": "name is bob  vaule is a num is 2"

}

ok: [10.1.61.187] => (item=['bob', 'a', '3']) => {

    "msg": "name is bob  vaule is a num is 3"

}

ok: [10.1.61.187] => (item=['bob', 'b', '1']) => {

    "msg": "name is bob  vaule is b num is 1"

}

ok: [10.1.61.187] => (item=['bob', 'b', '2']) => {

    "msg": "name is bob  vaule is b num is 2"

}

ok: [10.1.61.187] => (item=['bob', 'b', '3']) => {

    "msg": "name is bob  vaule is b num is 3"

}

ok: [10.1.61.187] => (item=['bob', 'c', '1']) => {

    "msg": "name is bob  vaule is c num is 1"

}

ok: [10.1.61.187] => (item=['bob', 'c', '2']) => {

    "msg": "name is bob  vaule is c num is 2"

}

ok: [10.1.61.187] => (item=['bob', 'c', '3']) => {

    "msg": "name is bob  vaule is c num is 3"

}

PLAY RECAP *******************************************************************************************************

10.1.61.187

3. with_dict

# 假如有如下变量内容：

users:

  alice:

    name: Alice Appleworth

    telephone: 123-456-7890

  bob:

    name: Bob Bananarama

    telephone: 987-654-3210

# 现在需要输出每个用户的用户名和手机号：

tasks:

  - name: Print phone records

    debug: msg="User {{ item.key }} is {{ item.value.name }} ({{ item.value.telephone }})"

    with_dict: "{{ users }}"

4. with_fileglob

- hosts: test

  tasks:

    - name: Make key directory

      file:

        path: /root/.sshkeys

        state: directory

        mode: 0700

        owner: root

        group: root 

    - name: Upload public keys

      copy:

        src: "{{ item }}"

        dest: /root/.sshkeys

        mode: 0600

        owner: root

        group: root

      with_fileglob:

        - /root/.ssh/*.pub 

    - name: Assemble keys into authorized_keys file

      assemble:

        src: /root/.sshkeys

        dest: /root/.ssh/authorized_keys

        mode: 0600

        owner: root

        group: root

5. with_lines

with_lines循环结构会让你在控制主机上执行任意命令，并对命令的输出进行逐行迭代。假设我们有一个文件test.txt包含如下行：

Breeze Yan

Bernie Yang

jerry Qing

我们可以通过如下方法进行逐行输出：

- name: print all names

  debug: msg="{{ item }}"

  with_lines:

    - cat test.txt

6. with_subelement

假如现在需要遍历一个用户列表，并创建每个用户，而且还需要为每个用户配置以特定的SSH key登录。变量文件内容如下：

users:

  - name: alice

    authorized:

      - /tmp/alice/onekey.pub

      - /tmp/alice/twokey.pub

    mysql:

        password: mysql-password

        hosts:

          - "%"

          - "127.0.0.1"

          - "::1"

          - "localhost"

        privs:

          - "*.*:SELECT"

          - "DB1.*:ALL"

  - name: bob

    authorized:

      - /tmp/bob/id_rsa.pub

    mysql:

        password: other-mysql-password

        hosts:

          - "db1"

        privs:

          - "*.*:SELECT"

          - "DB2.*:ALL"

playbook中定义如下：

tasks:

  - user: name={{ item.name }} state=present generate_ssh_key=yes

    with_items: "{{users}}"

  - authorized_key: "user={{ item.0.name }} key='{{ lookup('file', item.1) }}'"

    with_subelements:

     - users

     - authorized

也可以遍历嵌套的子列表：

- name: Setup MySQL users

  mysql_user: name={{ item.0.name }} password={{ item.0.mysql.password }} host={{ item.1 }} priv={{ item.0.mysql.privs | join('/') }}

  with_subelements:

    - users

    - mysql.hosts

7. with_sequence

- hosts: all

  tasks:

    # create groups

    - group: name=evens state=present

    - group: name=odds state=present

    # create some test users

    - user: name={{ item }} state=present groups=evens

      with_sequence: start=0 end=32 format=testuser%02d

    # create a series of directories with even numbers for some reason

    - file: dest=/var/stuff/{{ item }} state=directory

      with_sequence: start=4 end=16 stride=2    # stride用于指定步长

    # a simpler way to use the sequence plugin

    # create 4 groups

    - group: name=group{{ item }} state=present

      with_sequence: count=4

8. with_random_choice

从列表中随机取一个值：

- debug: msg={{ item }}

  with_random_choice:

     - "go through the door"

     - "drink from the goblet"

     - "press the red button"

     - "do nothing"

9. do-Util循环

- action: shell /usr/bin/foo

  register: result

  until: result.stdout.find("all systems go") != -1

  retries: 5

  delay: 10

重复执行shell模块，当shell模块执行的命令输出内容包含"all systems go"的时候停止。重试5次，延迟时间10秒。retries默认值为3，delay默认值为5。任务的返回值为最后一次循环的返回结果。

10. with_together

示例：

- hosts: webservers

  remote_user: root

  vars:

    alpha: [ 'a','b','c','d']

    numbers: [ 1,2,3,4 ]

  tasks:

    - debug: msg="{{ item.0 }} and {{ item.1 }}"

      with_together:

         - "{{ alpha }}"

         - "{{ numbers }}"

# 输出的结果为：

ok: [192.168.1.65] => (item=['a', 1]) => {

    "item": [

        "a",

        1

    ],

    "msg": "a and 1"

}

ok: [192.168.1.65] => (item=['b', 2]) => {

    "item": [

        "b",

        2

    ],

    "msg": "b and 2"

}

ok: [192.168.1.65] => (item=['c', 3]) => {

    "item": [

        "c",

        3

    ],

    "msg": "c and 3"

}

ok: [192.168.1.65] => (item=['d', 4]) => {

    "item": [

        "d",

        4

    ],

    "msg": "d and 4"

}

巴特西

Ansible13：Playbook循环语句