Ansible之八：Playbook循环
在使用ansible做自动化运维的时候，免不了的要重复执行某些操作，如：添加几个用户，创建几个MySQL用户并为之赋予权限，操作某个目录下所有文件等等。好在playbook支持循环语句，可以使得某些需求很容易而且很规范的实现。1、with_itemswith_items是playbooks中最基本也是最常用的循环语句：tasks:- name:Secure config files
file: path=/etc/{{ item }} mode=0600 owner=root group=root
with_items:
- my.cnf
- shadow
- fstab上面例子表示，创建三个文件分别为my.cnf、shadow、fstab也可以将文件列表提前赋值给一个变量，然后在循环语句中调用： with_items: "{{ somelist }}"使用with_items迭代循环的变量可以是个单纯的列表，也可以是一个较为复杂 的数据结果，如字典类型：
tasks:
- name: add several users
user: name={{ item.name }} state=present groups={{ item.groups }}
with_items:
- { name: 'testuser1', groups: 'wheel' }
- { name: 'testuser2', groups: 'root' }
2、with_nested嵌套循环示例：tasks:- name: give users access to multiple databasesmysql_user: name={{ item }} priv={{ item }}.*:ALL append_privs=yes password=foowith_nested: - [ 'alice', 'bob' ] - [ 'clientdb', 'employeedb', 'providerdb' ]item是循环的第一个列表的值['alice','bob']。item是第二个列表的值。表示循环创建alice和bob两个用户，并且为其赋予在三个数据库上的所有权限。也可以将用户列表事先赋值给一个变量：tasks:- name: here, 'users' contains the above list of employeesmysql_user: name={{ item }} priv={{ item }}.*:ALL append_privs=yes password=foowith_nested: - "{{users}}" - [ 'clientdb', 'employeedb', 'providerdb' ]3、with_dictwith_dict可以遍历更复杂的数据结构：
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文件匹配遍历
可以指定一个目录，使用with_fileglob可以循环这个目录中的所有文件，示例如下：
tasks:
- name:Make key directory
file: path=/root/.sshkeys ensure=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:
- keys/*.pub
- name:Assemble keys into authorized_keys file
assemble: src=/root/.sshkeys dest=/root/.ssh/authorized_keysmode=0600 owner=root group=root 5、with_subelement遍历子元素
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：
- 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
6、with_sequence循环整数序列
with_sequence可以生成一个自增的整数序列，可以指定起始值和结束值，也可以指定增长步长。 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：
- 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
7、with_random_choice随机选择
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"
8、do-Util循环
示例：
- 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。
9、循环注册变量在循环中使用register时，保存的结果中包含results关键字，该关键字保存模块执行结果的列表
- shell: echo "{{ item }}"
with_items:
- one
- two
register: echo
变量echo内容如下：
{
"changed": true,
"msg": "All items completed",
"results": [
{
"changed": true,
"cmd": "echo \"one\" ",
"delta": "0:00:00.003110",
"end": "2013-12-19 12:00:05.187153",
"invocation": {
"module_args": "echo \"one\"",
"module_name": "shell"
},
"item": "one",
"rc": 0,
"start": "2013-12-19 12:00:05.184043",
"stderr": "",
"stdout": "one"
},
{
"changed": true,
"cmd": "echo \"two\" ",
"delta": "0:00:00.002920",
"end": "2013-12-19 12:00:05.245502",
"invocation": {
"module_args": "echo \"two\"",
"module_name": "shell"
},
"item": "two",
"rc": 0,
"start": "2013-12-19 12:00:05.242582",
"stderr": "",
"stdout": "two"
}
]
}
遍历注册变量的结果：
- name: Fail if return code is not 0
fail:
msg: "The command ({{ item.cmd }}) did not have a 0 return code"
when: item.rc != 0
with_items: "{{echo.results}}"
10、with_together遍历数据并行集合
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: => (item=['a', 1]) => {
"item": [
"a",
1
],
"msg": "a and 1"
}
ok: => (item=['b', 2]) => {
"item": [
"b",
2
],
"msg": "b and 2"
}
ok: => (item=['c', 3]) => {
"item": [
"c",
3
],
"msg": "c and 3"
}
ok: => (item=['d', 4]) => {
"item": [
"d",
4
],
"msg": "d and 4"
}
loop模块一般在下面的场景中使用
[*]类似的配置模块重复了多遍
[*]fact是一个列表
[*]创建多个文件,然后使用assemble聚合成一个大文件
[*]使用with_fileglob匹配特定的文件管理
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