ansible：在对一组主机（多个托管主机）运行 playbook 时只执行一次 local_action

Question

在local_action针对一组主机运行 playbook 时，是否可以使任务仅运行一次？

这是问题所在：

hosts:
    - macbooks
    - localhost
tasks:

#...<some_remote_tasks>...#

    - local_action: command
        ssh-keygen -o -a 100 -t ed25519 -f {{ ssh_key }} -q -N ''
      become: yes

结果：

fatal: [laptop -> localhost]: FAILED! => {"changed": true, "cmd": ["ssh-keygen", "-o", "-a", "100", "-t", "ed25519", "-f", "/etc/ssh/id_ed25519-HostCA", "-q", "-N", "", "-C", "SSH Host Certificate Authority for cypherpunk.synology.me"], "delta": "0:00:00.014818", "end": "2018-06-01 17:02:41.599111", "msg": "non-zero return code", "rc": 1, "start": "2018-06-01 17:02:41.584293", "stderr": "", "stderr_lines": [], "stdout": "/etc/ssh/id_ed25519-HostCA already exists.\nOverwrite (y/n)? ", "stdout_lines": ["/etc/ssh/id_ed25519-HostCA already exists.", "Overwrite (y/n)? "]}
changed: [localhost -> localhost] 

这是有道理的，因为剧本中的任何任务都必须为每个托管主机运行。

但是因为它是一个本地操作，所以它会按预期在创建密钥文件时第一次运行。第二次该文件已经存在并且 ansible 收到错误："/etc/ssh/id_ed25519-HostCA already exists. Overwrite (y/n)?"使用return code 1. 所以实际上它必须只运行一次（至少在这种情况下）。

我可以做这样的事情：

- local_action: shell >
         [[ ! -f {{ ssh_key }} ]] && \
         ssh-keygen -o -a 100 -t ed25519 -f {{ ssh_key }} -q -N ''; \
         exit 0
      become: yes

但我想知道是否有 ansible-recommended 解决方案？大家会怎么解决这个问题？

Answer 1

也许你应该检查：run_once & delegate_to

- command: /opt/application/upgrade_db.py
  run_once: true
  delegate_to: web01.example.org

文档：https : //docs.ansible.com/ansible/latest/user_guide/playbooks_delegation.html

亲切的问候，

C