Python 金甲2号'；{%set…%}'；ansible playbook中的处理

我不明白如何在ansible剧本中使用jinja2模板命令

我的理解是，在执行之前，playbook应该作为jinja2模板处理，但显然不能在文件解析为yaml之前处理，因为在文件顶部使用jinja2命令会产生语法错误，例如：

{% set test_var = "test_value" %}
- hosts: all
  remote_user: "my_user"
  tasks:
    - debug: var=test_var
    {% set another_var = "another_value" %}
    - debug: var=another_var

如果对JICAN2命令进行注释以避免该解析错误，则在顶部处理第一个命令，而不是在PooBooad中间的其他命令：

# {% set test_var = "test_value" %}
- hosts: all
  remote_user: "my_user"
  tasks:
    - debug: var=test_var # this works
    # {% set another_var = "another_value" %}
    - debug: var=another_var
    # ok: [localhost] => {
    #   "another_var": "VARIABLE IS NOT DEFINED!: 'another_var' is undefined"
    # }

我不明白ansible是如何处理剧本模板的。难道不应该有一个只处理jinja2语法的第一个过程，然后在删除jinja2语法的情况下输出yaml吗

$ ansible-playbook --version
ansible-playbook 2.9.1
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/me/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/me/.local/lib/python3.7/site-packages/ansible
  executable location = /home/me/.local/bin/ansible-playbook
  python version = 3.7.3 (default, Apr  3 2019, 19:16:38) [GCC 8.0.1 20180414 (experimental) [trunk revision 259383]]

---

谢谢

jinja2在ansible运行时处理的是yaml变量的内容，而不是yaml文件本身。这是在几个过程中完成的，如果你想确切地了解引擎盖下面是什么，请仔细阅读ansible代码

为了让你走上正轨，这是你在问题中尝试的可行方法

- hosts: all
  remote_user: "my_user"

  # These are playbook vars set at playbook level
  # Vars can also be in inventories, roles....
  # see https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html
  vars:
    test_var: test_value

  tasks:

    - name: debug my test_var
      debug:
        var: test_var

    - name: if you need to set var at run time you can use set_fact
      set_fact:
        # Jinja2 templating will be honored here
        another_var: "another_{{ test_var }}"

    - name: debug var we just valued
      debug:
        var: another_var

- hosts: all
  remote_user: "my_user"

  # These are playbook vars set at playbook level
  # Vars can also be in inventories, roles....
  # see https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html
  vars:
    test_var: test_value

  tasks:

    - name: debug my test_var
      debug:
        var: test_var

    - name: if you need to set var at run time you can use set_fact
      set_fact:
        # Jinja2 templating will be honored here
        another_var: "another_{{ test_var }}"

    - name: debug var we just valued
      debug:
        var: another_var