Ansible:如果主机无法访问，则中止执行 [英] Ansible: Abort Execution if a host is unreachable

问题描述

摘要:一种更好的方法，可以在主机无法访问时立即中止可播放的剧本.

Summary: A better way for aborting ansible playbook immediately if any host is unreachable.

如果主机中的任何一个无法访问，是否可以中止Ansible剧本.我发现，如果无法连接到主机，它将继续运行并执行剧本中的所有剧本/任务.

Is there a way to abort Ansible playbook if any one of the host is unreachable. What I find that if it cannot reach a host it will still continue on and execute all the plays/tasks in the playbook.

我所有的剧本都将max_fail_percentage指定为0，但是在这种情况下，ansible不会抱怨，因为所有可访问的主机都可以执行所有剧本.

All my playbooks I specify the max_fail_percentage of 0, but in this case ansible does not complain since all the hosts that are reachable can execute all the plays.

目前，我有一个简单但棘手的解决方案，但看看是否有更好的答案.

Currently I have a simple but hacky solution, but seeing if there is a better answer.

由于第一步是运行剧本的一部分，因此ansible会收集所有主机的事实.并且在主机无法访问的情况下，它将无法访问.我在剧本的开头就写了一个简单的剧本，它将使用事实.并且如果主机不可访问，则该任务将失败，并显示未定义的变量错误".该任务只是一个虚拟任务，如果所有主机均可访问，它将始终通过.

Since the first step as part of running the playbooks, ansible gathers facts for all the hosts. And in case where a host is not reachable it will not be able to. I write a simple play at the very beginning of my playbook which will use a fact. And in case a host is unreachable that task will fail with "Undefined variable error". The task is just a dummy and will always pass if all hosts are reachable.

请参见下面的示例:

- name: Check Ansible connectivity to all hosts
  hosts: host_all
  user: "{{ remote_user }}"
  sudo: "{{ sudo_required }}"
  sudo_user: root
  connection: ssh # or paramiko
  max_fail_percentage: 0
  tasks:
    - name: check connectivity to hosts (Dummy task)
      shell: echo " {{ hostvars[item]['ansible_hostname'] }}"
      with_items: groups['host_all']
      register: cmd_output

    - name: debug ...
      debug: var=cmd_output

如果主机不可达，您将收到以下错误消息:

In case a host is unreachable you will get an error as below:

TASK: [c.. ***************************************************** 
fatal: [172.22.191.160] => One or more undefined variables: 'dict object'    has no attribute 'ansible_hostname' 
fatal: [172.22.191.162] => One or more undefined variables: 'dict object' has no attribute 'ansible_hostname'

FATAL: all hosts have already failed -- aborting

推荐答案

或者，这看起来更简单，更富有表现力

alternatively, this looks simplier and more expressive

- hosts: myservers
  become: true

  pre_tasks:
    - name: Check ALL hosts are reacheable before doing the release
      assert:
        that:
          - ansible_play_hosts == groups.myservers
        fail_msg: 1 or more host is UNREACHABLE
        success_msg: ALL hosts are REACHABLE, go on
      run_once: yes

  roles:
    - deploy

https://github.com/ansible/ansible/issues/18782 #issuecomment-319409529

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