ansible条件判断
在工作中，我们在执行playbook时，需要对某些条件进行判断，只有当满足条件才执行相应的tasks;
1.when条件判断：只条满足when的条件时才执行对应的tasks
注：when关键字后面跟着的是python的表达式,在表达式中你能够使用任何的变量或者facts
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#注：当需要用远程主机的一些信息时，gather_facts必须要开启，默认是开启状态
[root@nfs-server playbook]
# cat when.yml
---
- hosts: webservers
remote_user: root
#gather_facts: False
tasks:
- name: Host 192.168.1.101 run this task
debug:
'msg=" {{ ansible_default_ipv4.address }}"'
when: ansible_default_ipv4.address ==
"192.168.2.101"
- name: memtotal < 500M and processor_cores == 2 run this task
debug:
'msg="{{ ansible_fqdn }}"'
when: ansible_memtotal_mb < 500 and ansible_processor_cores == 2
- name: all host run this task
shell:
hostname
register: info
- name: Hostname is lamp1 Machie run this task
debug:
'msg="{{ ansible_fqdn }}"'
when: info[
'stdout'
] ==
"lamp1"
- name: Hostname is startswith l run this task
debug:
'msg="{{ ansible_fqdn }}"'
when: info[
'stdout'
].startswith(
'l'
)
[root@nfs-server playbook]
# ansible-playbook when.yml
PLAY [webservers] **************************************************************************************************************************************
TASK [Gathering Facts] *********************************************************************************************************************************
ok: [192.168.2.101]
ok: [192.168.2.111]
TASK [Host 192.168.1.101 run this task] ****************************************************************************************************************
ok: [192.168.2.101] => {
"msg"
:
" 192.168.2.101"
}
skipping: [192.168.2.111]
TASK [memtotal < 500M and processor_cores == 2 run this task] ******************************************************************************************
skipping: [192.168.2.101]
skipping: [192.168.2.111]
TASK [all host run this task] **************************************************************************************************************************
changed: [192.168.2.101]
changed: [192.168.2.111]
TASK [Hostname is lamp1 Machie run this task] **********************************************************************************************************
ok: [192.168.2.101] => {
"msg"
:
"lamp1"
}
skipping: [192.168.2.111]
TASK [Hostname is startswith l run this task] **********************************************************************************************************
ok: [192.168.2.101] => {
"msg"
:
"lamp1"
}
ok: [192.168.2.111] => {
"msg"
:
"lamp2"
}
PLAY RECAP *********************************************************************************************************************************************
192.168.2.101 : ok=5 changed=1 unreachable=0 failed=0
192.168.2.111 : ok=3 changed=1 unreachable=0 failed=0
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2.changed_when：先执行task,并对task返回的值进行判断，当满足changed_when指定的条件时说明是执行成功的
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#注：默认情况下执行了命令的主机状态都为changed，本例对输出进行判断，包含是某个指定字符才能为changed;
[root@nfs-server playbook]
# cat when_1.yml
---
- hosts: webservers
remote_user: root
#gather_facts: False
tasks:
- name: all host run this task
shell:
hostname
register: info
changed_when:
'"lamp1" in info.stdout'
[root@nfs-server playbook]
# ansible-playbook when_1.yml
PLAY [webservers] **************************************************************************************************************************************
TASK [Gathering Facts] *********************************************************************************************************************************
ok: [192.168.2.101]
ok: [192.168.2.111]
TASK [all host run this task] **************************************************************************************************************************
ok: [192.168.2.111]
changed: [192.168.2.101]
PLAY RECAP *********************************************************************************************************************************************
192.168.2.101 : ok=2 changed=1 unreachable=0 failed=0
192.168.2.111 : ok=2 changed=0 unreachable=0 failed=0
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3.failed_when:当执行失败后，会将信息存在register的stderr中，通过判断指定的字符是否在stderr中来确定是否真的失败；
暂时没有合适的例子，等有了再补~
本文转自激情燃烧的岁月博客51CTO博客，原文链接http://blog.51cto.com/liuzhengwei521/1962382如需转载请自行联系原作者
weilovepan520
