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ansible学习之十：Error Handling In Playbooks
Jul 21, 2014 • ansible
当遇到一些重复的任务，比如通过yum模块安装多个包，为每个包写一个task就太无聊了，可以在playbook中使用循环来解决这类问题。
标准循环，最常用到的就是它，with_items可以用于迭代一个列表或字典，通过{{ item }}获取每次迭代的值，如通过一条task创建多个用户：
- name: add several users
user: name={{ item }} state=present groups=wheel #创建user1、user2、user3三个用户
with_items: #这里还可以直接写成with_items: ['user1', 'user2', 'user3']
- user1
- user2
- user3
迭代一个简单字典：
- name: add several users
user: name={{ item.name }} state=present groups={{ item.groups }}
with_items:
- { name: 'user1', groups: 'wheel' }
- { name: 'user2', 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', 'eve' ]
- ['clientdb', 'employeedb', 'providerdb']
上面例子不容易看懂，我们通过debug模块写另一个例子测试：
---
- hosts: 127.0.0.1
gather_facts: no
tasks:
- debug: msg="{{ item[0] }} - {{ item[1] }}"
with_nested:
- ['alice', 'bob']
- ['clientdb', 'employeedb', 'providerdb']
执行：
$ ansible-playbook test.yml
PLAY [127.0.0.1] **************************************************************
TASK: [debug msg="{{item[0]}} - {{item[1]}}"] *********************************
ok: [127.0.0.1] => (item=['alice', 'clientdb']) => {
"item": [ #每次循环item变量是一个双元素列表
"alice",
"clientdb"
],
"msg": "alice - clientdb"
}
ok: [127.0.0.1] => (item=['alice', 'employeedb']) => {
"item": [
"alice",
"employeedb"
],
"msg": "alice - employeedb"
}
ok: [127.0.0.1] => (item=['alice', 'providerdb']) => {
"item": [
"alice",
"providerdb"
],
"msg": "alice - providerdb"
}
ok: [127.0.0.1] => (item=['bob', 'clientdb']) => {
"item": [
"bob",
"clientdb"
],
"msg": "bob - clientdb"
}
ok: [127.0.0.1] => (item=['bob', 'employeedb']) => {
"item": [
"bob",
"employeedb"
],
"msg": "bob - employeedb"
}
ok: [127.0.0.1] => (item=['bob', 'providerdb']) => {
"item": [
"bob",
"providerdb"
],
"msg": "bob - providerdb"
}
PLAY RECAP ********************************************************************
127.0.0.1 : ok=1 changed=0 unreachable=0 failed=0
所以最开始例子其实相当于两个for循环：
for user in [ 'alice', 'bob', 'eve' ]:
for db in ['clientdb', 'employeedb', 'providerdb']:
mysql_user: name=user priv=db.*:ALL append_privs=yes password=foo
迭代字典，接受一个字典类型的值，{{ item.key }}是字典的键，{{ item.value }}是字典的值，字典值还可以是一个子字典
在变量文件定义一个复杂的字典变量：
---
users:
alice:
name: Alice Appleworth
telephone: 123-456-7890
bob:
name: Bob Bananarama
telephone: 987-654-3210
playbook文件test.yml内容：
---
- hosts: 127.0.0.1
gather_facts: no
tasks:
- name: Print phone records
debug: msg="User {{ item.key }} is {{ item.value.name }} ({{ item.value.telephone }})"
with_dict: users
执行：
$ ansible-playbook test.yml
TASK: [Print phone records] ***************************************************
ok: [127.0.0.1] => (item={'value': {'name': 'Bob Bananarama', 'telephone': '987-654-3210'}, 'key': 'bob'}) => {
"item": {
"key": "bob",
"value": {
"name": "Bob Bananarama",
"telephone": "987-654-3210"
}
},
"msg": "User bob is Bob Bananarama (987-654-3210)"
}
ok: [127.0.0.1] => (item={'value': {'name': 'Alice Appleworth', 'telephone': '123-456-7890'}, 'key': 'alice'}) => {
"item": {
"key": "alice",
"value": {
"name": "Alice Appleworth",
"telephone": "123-456-7890"
}
},
"msg": "User alice is Alice Appleworth (123-456-7890)"
}
匹配指定目录下的所有文件(非递归)，或指定目录下和pattern匹配的文件
---
- hosts: all
tasks:
- name: first ensure our target directory exists
file: dest=/etc/fooapp state=directory
- name: copy each file over that matches the given pattern
copy: src={{ item }} dest=/etc/fooapp/ owner=root mode=600
with_fileglob:
- /playbooks/files/fooapp/* #这里如果是"*.py"，就只会复制该目录下所有py文件
迭代并行数据集
---
- hosts: '192.168.12.238'
tasks:
- debug: msg="{{ item.0 }} and {{ item.1 }}"
with_together: #相当于: for item in [('a',1), ('b', 2), ('c', 3), ('d', 4)]
- ['a', 'b', 'c', 'd']
- [1, 2, 3, 4]
迭代子元素
---
- hosts: 127.0.0.1
gather_facts: no
vars:
users: #定义一个字典变量
- name: alice
authorized: #列表
- /tmp/alice/onekey.pub
- /tmp/alice/twokey.pub
- name: bob
authorized:
- /tmp/bob/id_rsa.pub
tasks:
- debug: msg="{{ item.0.name }} - {{ item.1 }}"
with_nested:
- users
- authorized
执行：
$ ansible-playbook test.yml
PLAY [127.0.0.1] **************************************************************
TASK: [debug msg="{{item.0.name}} - {{item.1}}"] ******************************
ok: [127.0.0.1] => (item=[{'name': 'alice', 'authorized': ['/tmp/alice/onekey.pub', '/tmp/alice/twokey.pub']}, 'authorized']) => {
"item": [ #每次迭代item变量的结构
{
"authorized": [
"/tmp/alice/onekey.pub",
"/tmp/alice/twokey.pub"
],
"name": "alice"
},
"authorized"
],
"msg": "alice - authorized"
}
ok: [127.0.0.1] => (item=[{'name': 'bob', 'authorized': ['/tmp/bob/id_rsa.pub']}, 'authorized']) => {
"item": [
{
"authorized": [
"/tmp/bob/id_rsa.pub"
],
"name": "bob"
},
"authorized"
],
"msg": "bob - authorized"
}
PLAY RECAP ********************************************************************
127.0.0.1 : ok=1 changed=0 unreachable=0 failed=0
按照升序生成一个数字序列，可以指定开始(start)、结束(stop)和步长(stride)
---
- hosts: all
tasks:
- user: name={{ item }} state=present groups=evens
with_sequence: start=1 end=32 format=testuser%02d #创建用户testuser01、testuser02、...、testuser32
- file: dest=/var/stuff/{{ item }} state=directory
with_sequence: start=0 end=20 stride=5 #stride表示步长step，也就是间隔
# a simpler way to use the sequence plugin create 4 groups
- group: name=group{{ item }} state=present
with_sequence: count=4
从列表中随机选择一项
- debug: msg={{ item }}
with_random_choice: #每次都随机选择一项
- "go through the door"
- "drink from the goblet"
- "press the red button"
- "do nothing"
不停重试，直到某些条件完成
- shell: /usr/bin/foo
register: result #保存命令结果，和until搭配使用时，result还有个attempts属性，表示当前重试次数
until: result.stdout.find("all systems go") != -1
retries: 5
delay: 10
不停重新执行命令，直到命令输出中出现”all systems go”，或者重试次数达到5次间隔10秒，默认重试3次间隔5秒
查找并返回列表中第一个存在的文件
简略版：
- name: INTERFACES | Create Ansible header for /etc/network/interfaces
template: src={{ item }} dest=/etc/foo.conf
with_first_found: #第一个文件不存在，就去找第二个文件
- "{{ansible_virtualization_type}_foo.conf"
- "default_foo.conf"
高级版：
- name: some configuration template
template: src={{ item }} dest=/etc/file.cfg mode=0444 owner=root group=root
with_first_found:
- files:
- "{{inventory_hostname}}/etc/file.cfg"
paths:
- ../../../templates.overwrites
- ../../../templates
- files:
- etc/file.cfg
paths:
- templates
按行迭代命令输出
---
- hosts: "192.168.12.238"
tasks:
- debug: msg="stdout - {{ item }}"
with_lines: /bin/echo -e "111\n222\n333" #按行迭代echo命令的输出
通过之前学过的with_items也能达到同样的效果
---
- hosts: "192.168.12.238"
tasks:
- shell: /bin/echo -e "111\n222\n333"
register: results
- debug: msg="stdout - {{ item }}"
with_items: results.stdout_lines
迭代一个列表，获取每一项的索引和值，{{ item.0 }}是索引，{{ item.1 }}是值
- name: indexed loop demo
debug: msg="at array position {{ item.0 }} there is a value {{ item.1 }}"
with_indexed_items: ['a', 'b', 'c']
展开嵌套列表并循环，如[1, [2, [3]]]展开为[1, 2, 3]并循环这个列表
---
- hosts: "192.168.12.238"
vars:
packages_base:
- ['foo-package', 'bar-package']
packages_apps:
- [['one-package', 'two-package']]
- [['red-package'], ['blue-package']]
tasks:
- name: indexed loop demo
debug: msg="value - {{ item }}"
with_flattened:
- packages_base
- packages_apps
注册一个标量，用来保存命令task的输出。在循环中使用register，数据结构会变得不同，注册变量会包含一个results属性，该属性的值是一个列表，包含该模块本次循环的所有响应数据：
- shell: echo "{{ item }}"
with_items:
- one
- two
register: echo
此时echo变量的内容为：
{
"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"
}
]
}
在随后一个task中迭代echo.results这个列表：
- name: Fail if return code is not 0
debug: msg="The command ({{ item.cmd }}) did not have a 0 return code"
when: item.rc != 0
with_items: echo.results
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