ansible的脚本中我们可能会要启动某项服务并等待，直到服务启动起来，然后再进行下一步
这个非常重要，我们举例来实验一下：
- hosts: localhost
vars:
local__service: ssh
tasks:
- block:
- name: "Stop {{ local__service }} service"
systemd:
service: "{{ local__service }}"
state: stopped
- name: "Populate ansible_facts.services variable"
ansible.builtin.service_facts:
- name: "{{ local__service }} state will be stopped as expected"
assert:
that:
ansible_facts.services[local__service].state == 'stopped'
- name: "Start {{ local__service }} service"
systemd:
service: "{{ local__service }}"
state: started
- name: "Registered {{ local__service }} state will still be stopped as it was not refreshed"
assert:
that:
ansible_facts.services[local__service].state == 'stopped'
- name: "Refresh ansible_facts.services variable"
ansible.builtin.service_facts:
- name: "{{ local__service }} state will be running as expected"
assert:
that:
ansible_facts.services[local__service].state == 'running'
上面的 playbook 一共有7步：
1、停止 ssh 服务
2、获取 ansible_fact 变量
3、断言 ansible_facts 中的 ssh 服务是 stopped 状态
4、重新启动 ssh 服务
5、断言 ansible_facts 中的 ssh 服务仍然是 stopped 状态
6、重新获取 ansible_fact 变量
7、这时 ansible_facts 中的 ssh 服务状态刷新了，变成了 running
就是服务启动后，必须去不断刷新 ansible_facts，才能获得刷新后的状态，所以我们利用这一点，脚本如下：
- hosts: localhost
vars:
local__service: ssh
tasks:
- block:
- name: "Stop {{ local__service }} service"
systemd:
service: "{{ local__service }}"
state: stopped
- name: "Wait until {{ local__service }} service is stopped"
ansible.builtin.service_facts:
register: temp__service_facts
until: temp__service_facts.ansible_facts.services[local__service].state == 'stopped'
retries: 20
delay: 2
- name: "Start {{ local__service }} service"
systemd:
service: "{{ local__service }}"
state: started
- name: "Wait until {{ local__service }} service is running"
ansible.builtin.service_facts:
register: temp__service_facts
until: temp__service_facts.ansible_facts.services[local__service].state == 'running'
retries: 20
delay: 2
上面wait until的步骤就是，注册一个临时的变量，然后不断去测试，重试20次，每次的延时是2秒。这样就可以解决了。