Ansible实践总结

Ansible playbook 根据条件动态设置变量

---

1. 首先新建 inventory，主机列表如下：

   node-01 ansible_host=192.168.64.30
   node-02 ansible_host=192.168.64.31
   
   [app]
   node-01
   
   [db]
   node-02

2. 然后新建一个 test.yml，新增如下内容：

   - hosts: db[0]:app[0]   # 支持索引取值
     vars:
       - Role: "{{ 'db' if 'app' in group_names else 'app' }}"   # 动态设置变量
       - Ports:
           app: 4503
           db: 4502
   
     pre_tasks:   # 默认tasks只能在roles执行完后才执行，而pre-tasks可以在roles之前执行
       - name: Debug
         debug:
           msg: This is a test message.
   
     roles:
       - testrole

3. 新建 roles/testrole/defaults/main.yml

   ---
   RESTLink: 'http://{{ inventory_hostname }}:{{ Ports[Role] }}'

4. 新建 roles/testrole/tasks/main.yml

   ---
   - debug:
       msg: "Final URL is {{ RESTLink }}"

5. 执行该 playbook

   ansible-playbook -i inventory test.yml

   输出结果是：

   
   PLAY [db[0]:app[0]] *******************************************************************************************************************************************
   
   TASK [Gathering Facts] ****************************************************************************************************************************************
   Tuesday 27 August 2019  18:22:30 +0800 (0:00:00.121)       0:00:00.121 ********
   ok: [node-01]
   ok: [node-02]
   
   TASK [debug] **************************************************************************************************************************************************
   Tuesday 27 August 2019  18:22:32 +0800 (0:00:02.242)       0:00:02.363 ********
   ok: [node-02] => {
       "msg": "This is a test message."
   }
   ok: [node-01] => {
       "msg": "This is a test message."
   }
   
   TASK [testrole : Debug] ***************************************************************************************************************************************
   Tuesday 27 August 2019  18:22:33 +0800 (0:00:00.255)       0:00:02.620 ********
   ok: [node-02] => {
       "msg": "Final URL is http://node-02:4503"
   }
   ok: [node-01] => {
       "msg": "Final URL is http://node-01:4502"
   }
   
   PLAY RECAP ****************************************************************************************************************************************************
   node-01                    : ok=3    changed=0    unreachable=0    Failed=0
   node-02                    : ok=3    changed=0    unreachable=0    Failed=0

总结：

1. When used in this manner, the order of execution for your playbook is as follows:

• Any pre_tasks defined in the play.
• Any handlers triggered so far will be run.
• Each role listed in roles will execute in turn. Any role dependencies defined in the roles Meta/main.yml will be run first, subject to tag filtering and conditionals.
• Any tasks defined in the play.
• Any handlers triggered so far will be run.
• Any post_tasks defined in the play.
• Any handlers triggered so far will be run.