Ansible实现仅启动停止状态服务失败求助

需求：实现仅当MariaDB服务处于停止状态时启动该服务。
编写的Playbook如下：

tasks:
   - name: Check the Service Status
     ansible.builtin.command: systemctl status mariadb.service
     register: service_status
     notify: Mariadb restart
     changed_when: service_status.rc != 0
     ignore_errors: true


  handlers:
    - name: Mariadb restart
      ansible.builtin.service:
         name: httpd
         state: restarted

运行时即使配置了ignore_errors: true，仍出现任务失败提示，运行日志：

TASK [Check the Service Status] ************************************************************************************************************************************************************
fatal: [192.168.1.102]: FAILED! => {"changed": true, "cmd": ["systemctl", "status", "mariadb.service"], "delta": "0:00:00.016680", "end": "2024-11-21 00:20:53.396153", "msg": "non-zero return code", "rc": 3, "start": "2024-11-21 00:20:53.379473", "stderr": "", "stderr_lines": [], "stdout": "○ mariadb.service - MariaDB 10.5 database server\n     Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; preset: disabled)\n     Active: inactive (dead) since Wed 2024-11-20 23:30:01 EST; 50min ago\n   Duration: 3min 52.893s\n       Docs: man:mariadbd(8)\n             https://mariadb.com/kb/en/library/systemd/\n    Process: 12935 ExecStartPre=/usr/libexec/mariadb-check-socket (code=exited, status=0/SUCCESS)\n    Process: 12957 ExecStartPre=/usr/libexec/mariadb-prepare-db-dir mariadb.service (code=exited, status=0/SUCCESS)\n    Process: 12992 ExecStart=/usr/libexec/mariadbd --basedir=/usr $MYSQLD_OPTS $_WSREP_NEW_CLUSTER (code=exited, status=0/SUCCESS)\n    Process: 13004 ExecStartPost=/usr/libexec/mariadb-check-upgrade (code=exited, status=0/SUCCESS)\n   Main PID: 12992 (code=exited, status=0/SUCCESS)\n     Status: \"MariaDB server is down\"\n        CPU: 526ms\n\nNov 20 23:26:08 RHEL-Node-2 systemd[1]: Starting MariaDB 10.5 database server...\nNov 20 23:26:08 RHEL-Node-2 mariadb-prepare-db-dir[12957]: Database MariaDB is probably initialized in /var/lib/mysql already, nothing is done.\nNov 20 23:26:08 RHEL-Node-2 mariadb-prepare-db-dir[12957]: If this is not the case, make sure the /var/lib/mysql is empty before running mariadb-prepare-db-dir.\nNov 20 23:26:08 RHEL-Node-2 systemd[1]: Started MariaDB 10.5 database server.\nNov 20 23:30:01 RHEL-Node-2 systemd[1]: Stopping MariaDB 10.5 database server...\nNov 20 23:30:01 RHEL-Node-2 systemd[1]: mariadb.service: Deactivated successfully.\nNov 20 23:30:01 RHEL-Node-2 systemd[1]: Stopped MariaDB 10.5 database server.", "stdout_lines": ["○ mariadb.service - MariaDB 10.5 database server", "     Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled; preset: disabled)", "     Active: inactive (dead) since Wed 2024-11-20 23:30:01 EST; 50min ago", "   Duration: 3min 52.893s", "       Docs: man:mariadbd(8)", "             https://mariadb.com/kb/en/library/systemd/", "    Process: 12935 ExecStartPre=/usr/libexec/mariadb-check-socket (code=exited, status=0/SUCCESS)", "    Process: 12957 ExecStartPre=/usr/libexec/mariadb-prepare-db-dir mariadb.service (code=exited, status=0/SUCCESS)", "    Process: 12992 ExecStart=/usr/libexec/mariadbd --basedir=/usr $MYSQLD_OPTS $_WSREP_NEW_CLUSTER (code=exited, status=0/SUCCESS)", "    Process: 13004 ExecStartPost=/usr/libexec/mariadb-check-upgrade (code=exited, status=0/SUCCESS)", "   Main PID: 12992 (code=exited, status=0/SUCCESS)", "     Status: \"MariaDB server is down\"", "        CPU: 526ms", "", "Nov 20 23:26:08 RHEL-Node-2 systemd[1]: Starting MariaDB 10.5 database server...", "Nov 20 23:26:08 RHEL-Node-2 mariadb-prepare-db-dir[12957]: Database MariaDB is probably initialized in /var/lib/mysql already, nothing is done.", "Nov 20 23:26:08 RHEL-Node-2 mariadb-prepare-db-dir[12957]: If this is not the case, make sure the /var/lib/mysql is empty before running mariadb-prepare-db-dir.", "Nov 20 23:26:08 RHEL-Node-2 systemd[1]: Started MariaDB 10.5 database server.", "Nov 20 23:30:01 RHEL-Node-2 systemd[1]: Stopping MariaDB 10.5 database server...", "Nov 20 23:30:01 RHEL-Node-2 systemd[1]: mariadb.service: Deactivated successfully.", "Nov 20 23:30:01 RHEL-Node-2 systemd[1]: Stopped MariaDB 10.5 database server."]}
...ignoring

PLAY RECAP *********************************************************************************************************************************************************************************
192.168.1.102              : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=1

1. 命令选择不当：systemctl status命令在服务停止时返回非0值，Ansible会默认标记任务失败，ignore_errors: true仅让Play继续执行，但无法消除任务失败的提示。
2. Handler配置错误：Handler中指定的服务名是httpd，与目标服务mariadb不符，即使触发也不会正确操作MariaDB。
3. 状态参数错误：使用state: restarted会强制重启服务，无论当前状态，不符合“仅启动停止服务”的需求，应使用state: started。

方案一：使用Ansible内置Service模块（推荐） #

Ansible的service模块会自动检测服务状态，仅当服务未运行时执行启动操作，无需额外判断，简洁且可靠：

- name: Ensure MariaDB is started when stopped
  hosts: 192.168.1.102
  tasks:
    - name: Start MariaDB if it's not running
      ansible.builtin.service:
        name: mariadb
        state: started

方案二：改进命令检测方式（不推荐，仅作参考） #

若必须通过命令判断状态，可使用systemctl is-active命令，该命令返回0表示服务活跃，3表示服务停止，通过failed_when控制任务失败条件：

- name: Ensure MariaDB is started when stopped
  hosts: 192.168.1.102
  tasks:
    - name: Check MariaDB service status
      ansible.builtin.command: systemctl is-active mariadb.service
      register: service_status
      # 仅当返回值不是0（活跃）或3（停止）时标记任务失败
      failed_when: service_status.rc not in [0, 3]
      # 仅当服务停止时标记任务为changed
      changed_when: service_status.rc == 3

    - name: Start MariaDB if stopped
      ansible.builtin.service:
        name: mariadb
        state: started
      # 仅当服务停止时执行该任务
      when: service_status.rc == 3

内容的提问来源于stack exchange，提问作者Linux4u