if和else在Ansible Playbook中使用寄存器变量stdout

Question

团队

我的目标是在fqdn上运行dig命令并获取其IP地址。然后根据IP返回或不打印消息。有点像如果，否则。这种方法是正确的，因为第一次出错，第二次运行有效。

-
  name: Test connectivity to target servers
  hosts: all
  vars_files:
           - vars.yaml
  tasks:
      - name: Ping test
        ping:

      - name: DNS test
        command: "dig +short {{ target_dns_host }} a"
        register: dns_result

      - name: "Validate DNS server"
        debug:
          msg: "Could not resolve DNS server '{{ target_dns_host }}' "
        when: dns_result.stdout == ""

      - name: "Validate DNS server"
        debug:
          msg: "Resolved DNS server '{{ target_dns_host }}' '{{ dns_result.stdout }}' "
        when: dns_result.stdout != ""

下面第一次运行的输出

ansible-playbook playbook-ping-dns-test.yaml -i inventory.txt 

PLAY [Test connectivity to target servers] ********************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************
ok: [target1]

TASK [Ping test] **********************************************************************************************************************************************
ok: [target1]

TASK [DNS test] ***********************************************************************************************************************************************

fatal: [target1]: FAILED! => {"changed": true, "cmd": ["dig", "+short", "www.google.com", "a"], "delta": "0:00:15.011879", "end": "2019-09-25 16:25:23.808746", "msg": "non-zero return code", "rc": 9, "start": "2019-09-25 16:25:08.796867", "stderr": "", "stderr_lines": [], "stdout": ";; connection timed out; no servers could be reached", "stdout_lines": [";; connection timed out; no servers could be reached"]}
    to retry, use: --limit @/home/osboxes/ansible-validate-maglev/playbook-ping-dns-test.retry

PLAY RECAP ****************************************************************************************************************************************************
target1                    : ok=2    changed=0    unreachable=0    failed=1 

第二次以下运行的输出

PLAY [Test connectivity to target servers] ********************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************
ok: [target1]

TASK [Ping test] **********************************************************************************************************************************************
ok: [target1]

TASK [DNS test] ***********************************************************************************************************************************************
changed: [target1]

TASK [Validate DNS server] ************************************************************************************************************************************
skipping: [target1]

TASK [Validate DNS server] ************************************************************************************************************************************
ok: [target1] => {
    "msg": "Resolved DNS server 'www.google.com' '172.217.11.164' "
}

PLAY RECAP ****************************************************************************************************************************************************
target1                    : ok=4    changed=1    unreachable=0    failed=0