Ansible playbook循环实践总结<一>

1、标准Loops

标准loops可以直接减少task的次数，如下：

[root@zero01 playbook]# vi loops.yaml
---
- hosts: all
gather_facts: False
tasks:
- name: debug loops
debug: msg="name ------> {{ item }}"
with_items:
- one
- two

　　

运行 loops.yaml 如下：

[root@zero01 playbook]# ansible-playbook loops.yaml -l 192.168.79.129

PLAY [all] ***********************************************************************************************

TASK [debug loops] ***************************************************************************************
"changed": false, 
"item": "one", 
"msg": "name ------> one"
}
ok: [192.168.79.129] => (item=two) => {
"changed": false, 
"item": "two", 
"msg": "name ------> two"
}

PLAY RECAP ***********************************************************************************************
192.168.79.129 : ok=1 changed=0 unreachable=0 failed=0

　　

其中with_items的值是python list数据结构，每个task会循环读取list里面的值。with_items后也可以跟python字典，如下：

[root@zero01 playbook]# vi loops.yaml 
---
- hosts: all
gather_facts: False
tasks:
- name: debug loops
debug: msg="name ------> {{ item.key }}
value -----> {{ item.value }}"
with_items:
- {key: "one", value: "VALUE1"}
- {key: "one", value: "VALUE2"}

运行 loops.yaml 如下：

[root@zero01 playbook]# ansible-playbook loops.yaml -l 192.168.79.129

PLAY [all] ***********************************************************************************************

TASK [debug loops] ***************************************************************************************
ok: [192.168.79.129] => (item={u'key': u'one', u'value': u'VALUE1'}) => {
"changed": false, 
"item": {
"key": "one", 
"value": "VALUE1"
}, 
"msg": "name ------> one value -----> VALUE1"
}
ok: [192.168.79.129] => (item={u'key': u'one', u'value': u'VALUE2'}) => {
"changed": false, 
"item": {
"key": "one", 
"value": "VALUE2"
}, 
"msg": "name ------> one value -----> VALUE2"
}

PLAY RECAP ***********************************************************************************************
192.168.79.129 : ok=1 changed=0 unreachable=0 failed=0

2、嵌套 Loops

嵌套 Loops 也是常见的循环，主要实现一对多或者多对多的合并，如下：

[root@zero01 playbook]# vi loops.yaml 
---
- hosts: all
gather_facts: False
tasks:
- name: debug loops
debug: msg="name ------> {{ item[0] }}
value ------> {{ item[1] }}"
with_nested:
- ['A']
- ['a','b','c']

运行如下：

[root@zero01 playbook]# ansible-playbook loops.yaml -l 192.168.79.129

PLAY [all] ********************************************************************************

TASK [debug loops] ************************************************************************
ok: [192.168.79.129] => (item=[u'A', u'a']) => {
"changed": false, 
"item": [
"A", 
"a"
], 
"msg": "name ------> A value ------> a"
}
ok: [192.168.79.129] => (item=[u'A', u'b']) => {
"changed": false, 
"item": [
"A", 
"b"
], 
"msg": "name ------> A value ------> b"
}
ok: [192.168.79.129] => (item=[u'A', u'c']) => {
"changed": false, 
"item": [
"A", 
"c"
], 
"msg": "name ------> A value ------> c"
}

PLAY RECAP ********************************************************************************
192.168.79.129 : ok=1 changed=0 unreachable=0 failed=0

类似：

one=['A']

two=['a','b','c']

[i + y for i in one for y in two]

['Aa', 'Ab', 'Ac']