标签：python 循环语句 自动化运维 ansible playbooks
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playbooks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。
with_items是playbooks中最基本也是最常用的循环语句。
- name: add several users
user: name={{ item }} state=present groups=wheel
with_items:
- testuser1
- testuser2上边例子表示，添加两个用户分别为testuser1,testuser2。
也可以将用户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，也可以是一个可以迭代的较为复杂的数据结构，如字典类型：
- name: add several users
user: name={{ item.name }} state=present groups={{ item.groups }}
with_items:
- { name: ‘testuser1‘, groups: ‘wheel‘ }
- { name: ‘testuser2‘, groups: ‘root‘ }嵌套循环
- name: give users access to multiple databases
mysql_user: name={{ item[0] }} priv={{ item[1] }}.*:ALL append_privs=yes password=foo
with_nested:
- [ ‘alice‘, ‘bob‘ ]
- [ ‘clientdb‘, ‘employeedb‘, ‘providerdb‘ ]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。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：
- name: here, ‘users‘ contains the above list of employees
mysql_user: name={{ item[0] }} priv={{ item[1] }}.*:ALL append_privs=yes password=foo
with_nested:
- "{{users}}"
- [ ‘clientdb‘, ‘employeedb‘, ‘providerdb‘ ]with_dict可以遍历更复杂的数据结构：
如，有以下变量内容：
--- 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 }}"文件匹配遍历
with_fileglob匹配单个目录下所有文件
---
- hosts: all
tasks:
# first ensure our target directory exists
- file: dest=/etc/fooapp state=directory
# copy each file over that matches the given pattern
- copy: src={{ item }} dest=/etc/fooapp/ owner=root mode=600
with_fileglob:
- /playbooks/files/fooapp/*注：在角色中以相对路径使用with_fileglob,ansible会将路径解析为role/<rolename>/files。
遍历数据并行集合
[root@web1 ~]# cat /etc/ansible/loop.yml
---
- 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 }}"
[root@web1 ~]# ansible-playbook /etc/ansible/loop.yml
PLAY [webservers] *************************************************************
GATHERING FACTS ***************************************************************
ok: [192.168.1.65]
TASK: [debug msg="{{ item.0 }} and {{ item.1 }}"] *****************************
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"
}
PLAY RECAP ********************************************************************
192.168.1.65 : ok=2 changed=0 unreachable=0 failed=0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"
playbooks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.user }} password={{ item.0.mysql.password }} host={{ item.1 }} priv={{ item.0.mysql.privs | join(‘/‘) }}
with_subelements:
- users
- mysql.hosts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%02x
# 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
# a simpler way to use the sequence plugin
# create 4 groups
- group: name=group{{ item }} state=present
with_sequence: count=4随机选择
with_random_choice可以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"Do-Until 循环
- action: shell /usr/bin/foo
register: result
until: result.stdout.find("all systems go") != -1
retries: 5
delay: 10上边的例子重复执行shell模块，当shell模块执行的命令输出内容中包含"all systems go"的时候停止执行。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。
循环注册变量
在循环中使用register时，索保存的结果中包含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}}"示例：
[root@web1 ~]# cat /etc/ansible/reloop.yml
---
- hosts: webservers
remote_user: root
tasks:
- shell: echo "{{ item }}"
with_items:
- one
- two
register: echo
- debug: msg="{{ echo }}"
- name: Fail if return code is not 0
fail: msg=" The command {{ item.cmd }} has a 0 return code"
when: item.rc != 0
with_items: "{{ echo.results }}"
[root@web1 ~]# ansible-playbook /etc/ansible/reloop.yml
PLAY [webservers] *************************************************************
GATHERING FACTS ***************************************************************
ok: [192.168.1.65]
TASK: [shell echo "{{ item }}"] ***********************************************
changed: [192.168.1.65] => (item=one)
changed: [192.168.1.65] => (item=two)
TASK: [debug msg="{{ echo }}"] ************************************************
ok: [192.168.1.65] => {
"msg": "{‘msg‘: ‘All items completed‘, ‘changed‘: True, ‘results‘: [{u‘stdout‘: u‘one‘, u‘changed‘: True, u‘end‘: u‘2015-08-05 11:30:42.560652‘, u‘start‘: u‘2015-08-05 11:30:42.549056‘, u‘cmd‘: u‘echo \"one\"‘, u‘rc‘: 0, ‘item‘: ‘one‘, u‘stderr‘: u‘‘, u‘delta‘: u‘0:00:00.011596‘, ‘invocation‘: {‘module_name‘: u‘shell‘, ‘module_args‘: u‘echo \"one\"‘}, ‘stdout_lines‘: [u‘one‘], u‘warnings‘: []}, {u‘stdout‘: u‘two‘, u‘changed‘: True, u‘end‘: u‘2015-08-05 11:30:44.105387‘, u‘start‘: u‘2015-08-05 11:30:44.093500‘, u‘cmd‘: u‘echo \"two\"‘, u‘rc‘: 0, ‘item‘: ‘two‘, u‘stderr‘: u‘‘, u‘delta‘: u‘0:00:00.011887‘, ‘invocation‘: {‘module_name‘: u‘shell‘, ‘module_args‘: u‘echo \"two\"‘}, ‘stdout_lines‘: [u‘two‘], u‘warnings‘: []}]}"
}
TASK: [Fail if return code is not 0] ******************************************
skipping: [192.168.1.65] => (item={u‘cmd‘: u‘echo "one"‘, u‘end‘: u‘2015-08-05 11:30:42.560652‘, u‘stderr‘: u‘‘, u‘stdout‘: u‘one‘, u‘changed‘: True, u‘rc‘: 0, ‘item‘: ‘one‘, u‘warnings‘: [], u‘delta‘: u‘0:00:00.011596‘, ‘invocation‘: {‘module_name‘: u‘shell‘, ‘module_args‘: u‘echo "one"‘}, ‘stdout_lines‘: [u‘one‘], u‘start‘: u‘2015-08-05 11:30:42.549056‘})
skipping: [192.168.1.65] => (item={u‘cmd‘: u‘echo "two"‘, u‘end‘: u‘2015-08-05 11:30:44.105387‘, u‘stderr‘: u‘‘, u‘stdout‘: u‘two‘, u‘changed‘: True, u‘rc‘: 0, ‘item‘: ‘two‘, u‘warnings‘: [], u‘delta‘: u‘0:00:00.011887‘, ‘invocation‘: {‘module_name‘: u‘shell‘, ‘module_args‘: u‘echo "two"‘}, ‘stdout_lines‘: [u‘two‘], u‘start‘: u‘2015-08-05 11:30:44.093500‘})
PLAY RECAP ********************************************************************
192.168.1.65 : ok=4 changed=1 unreachable=0 failed=0本文出自 “diannaowa” 博客，请务必保留此出处http://diannaowa.blog.51cto.com/3219919/1682061
标签：python 循环语句 自动化运维 ansible playbooks
原文地址：http://diannaowa.blog.51cto.com/3219919/1682061
