[Ansible] 블록 (Block)

✔️ 블록

Blocks — Ansible Documentation

블록 - 여러 작업을 묶어놓은 그룹

 

✔️ 블록의 기능

1. 여러 작업에 공통의 키워드를 부여할 수 있음 (ex. 조건문)

 tasks:
   - name: Install, configure, and start Apache
     block:       - name: Install httpd and memcached
         ansible.builtin.yum:
           name:
           - httpd
           - memcached
           state: present

       - name: Apply the foo config template
         ansible.builtin.template:
           src: templates/src.j2
           dest: /etc/foo.conf

       - name: Start service bar and enable it
         ansible.builtin.service:
           name: bar
           state: started
           enabled: True
     when: ansible_facts['distribution'] == 'CentOS'
     become: true
     become_user: root
     ignore_errors: yes

block에 keyword를 부여하면 block 내의 모든 task에 부여되므로 코드 라인을 줄일 수 있다.

 

2. block, rescue, always 블록을 이용해 오류 처리를 할 수 있다.

• block 블록은 항상 실행
• rescue는 block 블록의 오류가 있을 때만 실행
• always는 항상 실행

블록문에서 오류가 발생하면 rescue로 분기해 오류를 해결하기 위한 작업을 실행한다.

 tasks:
 - name: Handle the error
   block:     - name: Print a message
       ansible.builtin.debug:
         msg: 'I execute normally'

     - name: Force a failure # 일부러 오류를 발생시키는 작업 
       ansible.builtin.command: /bin/false

     - name: Never print this # 후속 작업은 실행하지 않는다. 
       ansible.builtin.debug: # 태스크가 실패하면 플레이를 중단하고 
         msg: 'I never execute, due to the above task failing, :-('
   rescue:     
     - name: Print when errors
       ansible.builtin.debug: # rescue에 있는 태스크가 실행된다. 
         msg: 'I caught an error, can do stuff here to fix it, :-)'

python에서의 try, except 구문, java에서의 try, catch 구문과 같다.

 

✔️ Block always

 - name: Always do X
   block:     
     - name: Print a message
       ansible.builtin.debug:
         msg: 'I execute normally'

     - name: Force a failure
       ansible.builtin.command: /bin/false

     - name: Never print this
       ansible.builtin.debug:
         msg: 'I never execute :-('

   always:     
    - name: Always do this
       ansible.builtin.debug:
         msg: "This always executes, :-)"

블록 내 태스크의 실패 유무와 상관없이 always에 있는 태스크는 항상 실행이 된다.

 

- name: Attempt and graceful roll back demo
  block:    
    - name: Print a message
      ansible.builtin.debug:
        msg: 'I execute normally'

    - name: Force a failure
      ansible.builtin.command: /bin/false

    - name: Never print this
      ansible.builtin.debug:
        msg: 'I never execute, due to the above task failing, :-('
  rescue:    
    - name: Print when errors
      ansible.builtin.debug:
        msg: 'I caught an error'

    - name: Force a failure in middle of recovery! >:-)
      ansible.builtin.command: /bin/false

    - name: Never print this
      ansible.builtin.debug:
        msg: 'I also never execute :-('

  always:    
    - name: Always do this
      ansible.builtin.debug:
        msg: "This always executes"

블록에서 오류가 발생하지 않으면 rescue는 실행되지 않고 always는 실행되며
블록에서 오류가 발생하면 rescue가 실행되며 always는 항상 실행된다.

 

예제

/usr/bin/false 의 명령은 항상 fail을 만든다.

- hosts: 192.168.100.11

  tasks:
    - block:
        - debug:
            msg: hello world
        - command: /usr/bin/false
        - debug:
            msg: hello world2
      ignore_errors: yes

      rescue:
        - debug:
            msg: It's rescue

      always:
        - debug:
            msg: It's Always

 

결과

[vagrant@controller 05_block]$ ansible-playbook test.yaml

PLAY [192.168.100.11] ***************************************************************************************************************

TASK [Gathering Facts] **************************************************************************************************************
ok: [192.168.100.11]

TASK [debug] ************************************************************************************************************************
ok: [192.168.100.11] => {
    "msg": "hello world"
}

TASK [command] **********************************************************************************************************************
fatal: [192.168.100.11]: FAILED! => {"changed": true, "cmd": ["/usr/bin/false"], "delta": "0:00:00.004213", "end": "2022-04-18 06:18:07.178442", "msg": "non-zero return code", "rc": 1, "start": "2022-04-18 06:18:07.174229", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}

TASK [debug] ************************************************************************************************************************
ok: [192.168.100.11] => {
    "msg": "It's rescue"
}

TASK [debug] ************************************************************************************************************************
ok: [192.168.100.11] => {
    "msg": "It's Always"
}

PLAY RECAP **************************************************************************************************************************
192.168.100.11             : ok=4    changed=0    unreachable=0    failed=0    skipped=0    rescued=1    ignored=0   

[vagrant@controller 05_block]$ ansible-playbook test.yaml

PLAY [192.168.100.11] ***************************************************************************************************************

TASK [Gathering Facts] **************************************************************************************************************
ok: [192.168.100.11]

TASK [debug] ************************************************************************************************************************
ok: [192.168.100.11] => {
    "msg": "hello world"
}

TASK [debug] ************************************************************************************************************************
ok: [192.168.100.11] => {
    "msg": "hello world2"
}

TASK [debug] ************************************************************************************************************************
ok: [192.168.100.11] => {
    "msg": "It's Always"
}

PLAY RECAP **************************************************************************************************************************
192.168.100.11             : ok=4    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0  

 

 

✔️ ignore_errors

task가 실패하면 더 이상 후속 작업을 할 수 없는데 ignore_errors를 사용하면 후속 작업을 진행할 수 있다.

- hosts: 192.168.100.11

  tasks:
    - block:
        - debug:
            msg: hello world
        - command: /usr/bin/false
          ignore_errors: yes
        - debug:
            msg: hello world2
      # ignore_errors: yes  # 여기에 작성해도 된다. 
      rescue:
        - debug:
            msg: It's rescue

      always:
        - debug:
            msg: It's Always

결과

[vagrant@controller 05_block]$ ansible-playbook test.yaml

PLAY [192.168.100.11] ***

TASK [Gathering Facts] **
ok: [192.168.100.11]

TASK [debug] ****
ok: [192.168.100.11] => {
"msg": "hello world"
}

TASK [command] **
fatal: [192.168.100.11]: FAILED! => {"changed": true, "cmd": ["/usr/bin/false"], "delta": "0:00:00.002252", "end": "2022-04-18 06:20:13.333369", "msg": "non-zero return code", "rc": 1, "start": "2022-04-18 06:20:13.331117", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}
...ignoring

TASK [debug] ****
ok: [192.168.100.11] => {
"msg": "hello world2"
}

TASK [debug] ****
ok: [192.168.100.11] => {
"msg": "It's Always"
}

PLAY RECAP **
192.168.100.11 : ok=5 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=1

[vagrant@controller 05_block]$