目錄
循環語句
簡介
我們在編寫playbook的時候，不可避免的要執行一些重復性操作，比如指安裝軟件包，批量創建用戶，操作某個目錄下的所有文件等。正如我們所說，ansible一門簡單的自動化語言，所以流程控制、循環語句這些編程語言的基本元素它同樣都具備。
下面我們簡單的說一說Playbook中循環語句。
loop關鍵字說明
在playbook中使用循環，直接使用loop關鍵字即可。
如下示例，啟動httpd和postfilx服務：
tasks:
- name: postfix and httpd are running
service:
name: "{{ item }}"
state: started
loop:
- postfix
- httpd
也可以將loop循環的列表提前賦值給一個變量，然后在循環語句中調用：
#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 }}"
下面是一個循環更復雜類型數據的示例：
# 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' }
在循環語句中注冊變量
下面是一個register的變量在循環中使用的例子：
# 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 }}"
在循環語句中注冊變量：
- 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
執行語句，可以看到變量的返回結果為一個字典列表：
ok: [192.168.0.187] => {
"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"
]
}
]
}
}
舊循環語句
在Ansible 2.5以前，playbook通過不同的循環語句以實現不同的循環，這些語句使用with_作為前綴。這些語法目前仍然兼容，但在未來的某個時間點，會逐步廢棄。
| 循環語句關鍵字 | 描述 |
|---|---|
| with_items | 簡單的列表循環 |
| with_nested | 嵌套循環 |
| with_dict | 循環字典 |
| with_fileglob | 循環指定目錄中的所有文件 |
| with_lines | 循環一個文件中的所有行 |
| with_sequence | 生成一個自增的整數序列，可以指定起始值和結束值以及步長。參數以key=value的形式指定，format指定輸出的格式。數字可以是十進制、十六進制、八進制 |
| with_subelement | 遍歷子元素 |
| with_together | 遍歷數據並行集合 |
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]是循環的第一個列表的值['alice','bob']。item[1]是第二個列表的值；item[2]則是第三個列表的值，以上的執行輸出如下：
# ansible-playbook with_nested_ex.yml
PLAY [with_nested test] ******************************************************************************************
TASK [Gathering Facts] *******************************************************************************************
ok: [192.168.0.187]
TASK [debug loops] ***********************************************************************************************
ok: [192.168.0.187] => (item=['alice', 'a', '1']) => {
"msg": "name is alice vaule is a num is 1"
}
ok: [192.168.0.187] => (item=['alice', 'a', '2']) => {
"msg": "name is alice vaule is a num is 2"
}
ok: [192.168.0.187] => (item=['alice', 'a', '3']) => {
"msg": "name is alice vaule is a num is 3"
}
ok: [192.168.0.187] => (item=['alice', 'b', '1']) => {
"msg": "name is alice vaule is b num is 1"
}
ok: [192.168.0.187] => (item=['alice', 'b', '2']) => {
"msg": "name is alice vaule is b num is 2"
}
ok: [192.168.0.187] => (item=['alice', 'b', '3']) => {
"msg": "name is alice vaule is b num is 3"
}
ok: [192.168.0.187] => (item=['alice', 'c', '1']) => {
"msg": "name is alice vaule is c num is 1"
}
ok: [192.168.0.187] => (item=['alice', 'c', '2']) => {
"msg": "name is alice vaule is c num is 2"
}
ok: [192.168.0.187] => (item=['alice', 'c', '3']) => {
"msg": "name is alice vaule is c num is 3"
}
ok: [192.168.0.187] => (item=['bob', 'a', '1']) => {
"msg": "name is bob vaule is a num is 1"
}
ok: [192.168.0.187] => (item=['bob', 'a', '2']) => {
"msg": "name is bob vaule is a num is 2"
}
ok: [192.168.0.187] => (item=['bob', 'a', '3']) => {
"msg": "name is bob vaule is a num is 3"
}
ok: [192.168.0.187] => (item=['bob', 'b', '1']) => {
"msg": "name is bob vaule is b num is 1"
}
ok: [192.168.0.187] => (item=['bob', 'b', '2']) => {
"msg": "name is bob vaule is b num is 2"
}
ok: [192.168.0.187] => (item=['bob', 'b', '3']) => {
"msg": "name is bob vaule is b num is 3"
}
ok: [192.168.0.187] => (item=['bob', 'c', '1']) => {
"msg": "name is bob vaule is c num is 1"
}
ok: [192.168.0.187] => (item=['bob', 'c', '2']) => {
"msg": "name is bob vaule is c num is 2"
}
ok: [192.168.0.187] => (item=['bob', 'c', '3']) => {
"msg": "name is bob vaule is c num is 3"
}
PLAY RECAP *******************************************************************************************************
192.168.0.187
3. with_dict
# 假如有如下變量內容：
users:
alice:
name: Alice Appleworth
telephone: 123-456-7890
bob:
name: Bob Bananarama
telephone: 987-654-3210
# 現在需要輸出每個用戶的用戶名和手機號：
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循環結構會讓你在控制主機上執行任意命令，並對命令的輸出進行逐行迭代。假設我們有一個 文件test.txt包含如下行：
Breeze Yan
Bernie Yang
jerry Qing
我們可以通過如下方法進行逐行輸出：
- name: print all names
debug: msg="{{ item }}"
with_lines:
- cat test.txt
6. with_subelement
假如現在需要遍歷一個用戶列表，並創建每個用戶，而且還需要為每個用戶配置以特定的SSH key登錄。變量文件內容如下：
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中定義如下：
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
也可以遍歷嵌套的子列表：
- 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用於指定步長
# 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
從列表中隨機取一個值：
- debug: msg={{ item }}
with_random_choice:
- "go through the door"
- "drink from the goblet"
- "press the red button"
- "do nothing"
9. do-Util循環
- action: shell /usr/bin/foo
register: result
until: result.stdout.find("all systems go") != -1
retries: 5
delay: 10
重復執行shell模塊，當shell模塊執行的命令輸出內容包含"all systems go"的時候停止。重試5次，延遲時間10秒。retries默認值為3，delay默認值為5。任務的返回值為最后一次循環的返回結果。
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 }}"
# 輸出的結果為：
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"
}