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handlers 触发器
0. 场景引入
我们在 lineinfile 文件内容修改模块 模块中曾经向 nginx 配置文件最后写入了三行无意义的备注信息：
[root@node1 ~]# tail -n 3 /etc/nginx/nginx.conf # Orange # Apple # Banana [root@node1 ~]#
本节我们尝试将三行无意义的备注信息去掉，然后再重启 Nginx 服务，编写 ansible 剧本 handlers.yml 如下：
- hosts: node1 tasks: - name: Delete multiple lines ansible.builtin.lineinfile: path: /etc/nginx/nginx.conf line: "{{ item }}" backup: yes state: absent validate: /usr/sbin/nginx -t -c %s with_items: - '# Orange' - '# Apple' - '# Banana' become: yes - name: Restart Nginx server ansible.builtin.service: name: nginx state: restarted become: yes
运行一次剧本文件：
[ansible@master ~]$ cd ansible_playbooks/ [ansible@master ansible_playbooks]$ ansible-lint handlers.yml [ansible@master ansible_playbooks]$ ansible-playbook handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Delete multiple lines] ******************************************************************************************* changed: [node1] => (item=# Orange) changed: [node1] => (item=# Apple) changed: [node1] => (item=# Banana) TASK [Restart Nginx server] ******************************************************************************************** changed: [node1] PLAY RECAP ************************************************************************************************************* node1 : ok=3 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
此时，在 node1 节点查看配置文件以及 nginx 状态信息：
[root@node1 ~]# tail -n 3 /etc/nginx/nginx.conf } [root@node1 ~]# systemctl status nginx ● nginx.service - The nginx HTTP and reverse proxy server Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled) Active: active (running) since Sat 2023-07-08 22:16:43 CST; 12min ago Process: 22826 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS) Process: 22822 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS) Process: 22820 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS) Main PID: 22828 (nginx) Tasks: 3 Memory: 2.0M CGroup: /system.slice/nginx.service ├─22828 nginx: master process /usr/sbin/nginx ├─22829 nginx: worker process └─22830 nginx: worker process Jul 08 22:16:43 node1 systemd[1]: Starting The nginx HTTP and reverse proxy server... Jul 08 22:16:43 node1 nginx[22822]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok Jul 08 22:16:43 node1 nginx[22822]: nginx: configuration file /etc/nginx/nginx.conf test is successful Jul 08 22:16:43 node1 systemd[1]: Started The nginx HTTP and reverse proxy server. [root@node1 ~]#
可以看到，配置文件已经修改了，最后三行的注释已经没有了，然后 nginx 服务也在 22:16:43 重启了。
我们再次执行一次剧本：
[ansible@master ansible_playbooks]$ ansible-playbook handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Delete multiple lines] ******************************************************************************************* ok: [node1] => (item=# Orange) ok: [node1] => (item=# Apple) ok: [node1] => (item=# Banana) TASK [Restart Nginx server] ******************************************************************************************** changed: [node1] PLAY RECAP ************************************************************************************************************* node1 : ok=3 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
此时，再在节点 node1 查看配置文件信息和 nginx 服务信息：
[root@node1 ~]# tail -n 3 /etc/nginx/nginx.conf } [root@node1 ~]# systemctl status nginx ● nginx.service - The nginx HTTP and reverse proxy server Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled) Active: active (running) since Sat 2023-07-08 22:30:57 CST; 34s ago Process: 26713 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS) Process: 26709 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS) Process: 26707 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS) Main PID: 26715 (nginx) Tasks: 3 Memory: 2.0M CGroup: /system.slice/nginx.service ├─26715 nginx: master process /usr/sbin/nginx ├─26716 nginx: worker process └─26717 nginx: worker process Jul 08 22:30:57 node1 systemd[1]: Starting The nginx HTTP and reverse proxy server... Jul 08 22:30:57 node1 nginx[26709]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok Jul 08 22:30:57 node1 nginx[26709]: nginx: configuration file /etc/nginx/nginx.conf test is successful Jul 08 22:30:57 node1 systemd[1]: Started The nginx HTTP and reverse proxy server. [root@node1 ~]#
此时可以看到，配置文件没有变化，但 nginx 服务在 22:30:57 重启了。此时就有个问题，无论 Delete multiple lines 任务是否修改了 nginx 的配置文件，后面的 Restart Nginx server 任务都会执行。
我们期望的是当配置文件发生变化时，我们才执行后面的重启 nginx 服务任务。如果配置文件没有发生变化，则不用执行 nginx 重启任务。
这个时候 handlers 触发器就派上用场了！！
1. handlers 简介
- 在 Ansible 中，handlers 是一种特殊类型的任务，用于在 Playbook 的最后执行一些特定的操作。Handlers 通常用于响应其他任务的事件或变化，例如服务重启或配置文件更改。有点像代码中的条件语句，只有满足某条件后才执行！
handlers和tasks很类似，但是只能被tasks通知时才会触发运行！handlers只会在任务执行完成后执行，即使被通知了很多次，也只会执行一次！只有当任务真正changed时，才能触发后面的handlers里面的任务的执行。- 官方文档请参考 Handlers: running operations on change
2. 官方示例
--- - name: Verify apache installation hosts: webservers vars: http_port: 80 max_clients: 200 remote_user: root tasks: - name: Ensure apache is at the latest version ansible.builtin.yum: name: httpd state: latest - name: Write the apache config file ansible.builtin.template: src: /srv/httpd.j2 dest: /etc/httpd.conf notify: - Restart apache - name: Ensure apache is running ansible.builtin.service: name: httpd state: started handlers: - name: Restart apache ansible.builtin.service: name: httpd state: restarted
在该示例中，当 httpd 升级到最新版本，并修改配置文件后，才通知重启 httpd 服务。
3. handlers 触发器的使用
3.1 未配置 notify 通知参数
为了使用 handlers 触发器，我们将 nginx 配置文件最后一行写入# Orange：
[root@node1 ~]# echo '# Orange' >> /etc/nginx/nginx.conf [root@node1 ~]# tail /etc/nginx/nginx.conf # } # # error_page 500 502 503 504 /50x.html; # location = /50x.html { # } # } } # Orange [root@node1 ~]# ll /etc/nginx/nginx.conf -rw-r--r-- 1 root root 2473 Jul 8 22:58 /etc/nginx/nginx.conf [root@node1 ~]#
我们修改一下 handlers.yml 文件，只删除文件最后一行内容：
- hosts: node1 tasks: - name: Delete multiple lines ansible.builtin.lineinfile: path: /etc/nginx/nginx.conf line: "{{ item }}" state: absent with_items: - '# Orange' become: yes handlers: - name: Restart Nginx server ansible.builtin.service: name: nginx state: restarted become: yes
执行剧本：
[ansible@master ansible_playbooks]$ ansible-lint handlers.yml [ansible@master ansible_playbooks]$ ansible-playbook handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Delete multiple lines] ******************************************************************************************* changed: [node1] => (item=# Orange) PLAY RECAP ************************************************************************************************************* node1 : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
此时，可以看到 Restart Nginx server 任务并没有被执行！
查看一下 node1 节点上的配置文件和时间信息：
[root@node1 ~]# tail /etc/nginx/nginx.conf # location = /40x.html { # } # # error_page 500 502 503 504 /50x.html; # location = /50x.html { # } # } } [root@node1 ~]# ll /etc/nginx/nginx.conf -rw-r--r-- 1 root root 2464 Jul 8 23:01 /etc/nginx/nginx.conf [root@node1 ~]#
可以看到，最后一行被执行，文件时间发生了变化。
- 当没有配置
notify通知参数时，虽然设置了handlers触发器，但触发器中的任务并不会被执行！
3.2 使用 notify 通知参数
再次将 node1 节点上的配置还原，并查看文件时间和 nginx 服务状态：
[root@node1 ~]# echo '# Orange' >> /etc/nginx/nginx.conf [root@node1 ~]# tail /etc/nginx/nginx.conf # } # # error_page 500 502 503 504 /50x.html; # location = /50x.html { # } # } } # Orange [root@node1 ~]# ll /etc/nginx/nginx.conf -rw-r--r-- 1 root root 2473 Jul 8 23:09 /etc/nginx/nginx.conf [root@node1 ~]# systemctl status nginx ● nginx.service - The nginx HTTP and reverse proxy server Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled) Active: active (running) since Sat 2023-07-08 22:30:57 CST; 39min ago Process: 26713 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS) Process: 26709 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS) Process: 26707 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS) Main PID: 26715 (nginx) Tasks: 3 Memory: 2.1M CGroup: /system.slice/nginx.service ├─26715 nginx: master process /usr/sbin/nginx ├─26716 nginx: worker process └─26717 nginx: worker process Jul 08 22:30:57 node1 systemd[1]: Starting The nginx HTTP and reverse proxy server... Jul 08 22:30:57 node1 nginx[26709]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok Jul 08 22:30:57 node1 nginx[26709]: nginx: configuration file /etc/nginx/nginx.conf test is successful Jul 08 22:30:57 node1 systemd[1]: Started The nginx HTTP and reverse proxy server. [root@node1 ~]#
然后，修改 handlers.yml 剧本文件：
- hosts: node1 tasks: - name: Delete multiple lines ansible.builtin.lineinfile: path: /etc/nginx/nginx.conf line: "{{ item }}" state: absent with_items: - '# Orange' become: yes notify: - Restart Nginx server handlers: - name: Restart Nginx server ansible.builtin.service: name: nginx state: restarted become: yes
此时第一次执行剧本：
[ansible@master ansible_playbooks]$ ansible-lint handlers.yml [ansible@master ansible_playbooks]$ ansible-playbook handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Delete multiple lines] ******************************************************************************************* changed: [node1] => (item=# Orange) RUNNING HANDLER [Restart Nginx server] ********************************************************************************* changed: [node1] PLAY RECAP ************************************************************************************************************* node1 : ok=3 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
可以看到 TASK [Delete multiple lines] 的状态是 changed，即做了实际的改变，此时触发器执行了任务 Restart Nginx server, 即重启了 nginx 服务。
我们去节点 node1 上检查一下：
[root@node1 ~]# tail /etc/nginx/nginx.conf # location = /40x.html { # } # # error_page 500 502 503 504 /50x.html; # location = /50x.html { # } # } } [root@node1 ~]# ll /etc/nginx/nginx.conf -rw-r--r-- 1 root root 2464 Jul 8 23:12 /etc/nginx/nginx.conf [root@node1 ~]# systemctl status nginx ● nginx.service - The nginx HTTP and reverse proxy server Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled) Active: active (running) since Sat 2023-07-08 23:12:19 CST; 2min 44s ago Process: 4463 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS) Process: 4459 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS) Process: 4457 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS) Main PID: 4465 (nginx) Tasks: 3 Memory: 2.0M CGroup: /system.slice/nginx.service ├─4465 nginx: master process /usr/sbin/nginx ├─4466 nginx: worker process └─4467 nginx: worker process Jul 08 23:12:19 node1 systemd[1]: Starting The nginx HTTP and reverse proxy server... Jul 08 23:12:19 node1 nginx[4459]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok Jul 08 23:12:19 node1 nginx[4459]: nginx: configuration file /etc/nginx/nginx.conf test is successful Jul 08 23:12:19 node1 systemd[1]: Started The nginx HTTP and reverse proxy server. [root@node1 ~]#
可以看到，nginx 配置文件是最后一行的# Orange 被删除了，nginx 服务也被重启了！
我们再次执行一次剧本文件，看看效果是什么：
[ansible@master ansible_playbooks]$ ansible-playbook handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Delete multiple lines] ******************************************************************************************* ok: [node1] => (item=# Orange) PLAY RECAP ************************************************************************************************************* node1 : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
此时，可以看到 TASK [Delete multiple lines] 任务的状态是 ok，并没有真正的发生 changed 改变，所以此时没有触发任务 Restart Nginx server 的执行。
此时，再去查看 node1 节点上的配置文件时间信息以及 nginx 服务的时间信息，发现都没有发生变化！
这就说明了，当 nginx 配置发生变化时，才执行 nginx 服务的重启；当 nginx 配置未发生变化时，不执行 nginx 服务的重启任务，这就是 handlers 触发器的作用！
4. handler 触发器其他说明
4.1 notify 机制
tasks任务可以通过使用notify关键字来设置一个或多个handlers触发器程序。- 当任务真正发生改变时 (状态是
changed) 时触发器就会触发对应的任务执行。 notify关键字接受handlers名称列表或者handlers名称字符串。handler执行的顺序与handler在 playbook 中定义的顺序是相同的，与”handler 被 notify” 的顺序无关。- 如果相同的
handler被通知多次时，最终只执行一次。例如，如果多个任务更新配置文件并通知重启Apache服务，Ansible 只会重启一次Apache服务，避免没必要的多次重启服务。
以下示例是配置文件发生变化后，通知重启 memcached 和 httpd 服务：
tasks: - name: Template configuration file ansible.builtin.template: src: template.j2 dest: /etc/foo.conf notify: - Restart apache - Restart memcached handlers: - name: Restart memcached ansible.builtin.service: name: memcached state: restarted - name: Restart apache ansible.builtin.service: name: apache state: restarted
为了测试通知机制，我们在节点 node1 上面安装一下 memcached 包并启动服务：
[root@node1 ~]# yum install -y memcached [root@node1 ~]# systemctl start memcached [root@node1 ~]# systemctl status memcached|grep Active Active: active (running) since Sun 2023-07-09 09:22:34 CST; 16min ago
可以看到 memcached 服务在 09:22:34 启动了！
查看一下 nginx 服务状态：
[root@node1 ~]# systemctl status nginx|grep Active Active: active (running) since Sun 2023-07-09 09:34:36 CST; 4min 7s ago [root@node1 ~]#
可以看到 nginx 服务是 2023-07-09 09:34:36 启动的。
我们修改一下官方示例，得到以下剧本文件 notify_handlers.yml:
- hosts: node1 tasks: - name: Template configuration file 1 ansible.builtin.template: src: handlers_template.j2 dest: /etc/handlers_1.conf # notify接受触发器任务名称列表 notify: - Restart nginx - Restart memcached become: yes - name: Template configuration file 2 ansible.builtin.template: src: handlers_template.j2 dest: /etc/handlers_2.conf # notify接受触发器任务名称字符串 notify: Restart nginx become: yes handlers: - name: Restart memcached ansible.builtin.service: name: memcached state: restarted become: yes - name: Restart nginx ansible.builtin.service: name: nginx state: restarted become: yes
创建模板文件：
[ansible@master ansible_playbooks]$ echo "test notify handlers" > templates/handlers_template.j2 [ansible@master ansible_playbooks]$ cat templates/handlers_template.j2 test notify handlers [ansible@master ansible_playbooks]$
此时运行剧本：
[ansible@master ansible_playbooks]$ ansible-lint notify_handlers.yml [ansible@master ansible_playbooks]$ ansible-playbook notify_handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Template configuration file 1] *********************************************************************************** changed: [node1] TASK [Template configuration file 2] *********************************************************************************** changed: [node1] RUNNING HANDLER [Restart memcached] ************************************************************************************ changed: [node1] RUNNING HANDLER [Restart nginx] **************************************************************************************** changed: [node1] PLAY RECAP ************************************************************************************************************* node1 : ok=5 changed=4 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
通过本次剧本的执行，可以验证以下几点：
notify接受触发器任务名称列表，如notify: - Restart nginx这样，notify也接受触发器任务名称字符串，如notify: Restart nginx这样。- 在任务
Template configuration file 1中需要通知Restart nginx和Restart memcached两个触发器任务，在Template configuration file 2中需要通知Restart nginx触发器任务，Restart nginx触发器任务被通知了多次，但最终执行效果中可以看到Restart nginx触发器任务只执行了一次！说明触发器任务最多只执行一次，不会执行多次！ - 在任务
Template configuration file 1中需要通知Restart nginx和Restart memcached两个触发器任务，Restart nginx触发器任务在前，Restart memcached触发器任务在后，但实际执行时，是先执行RUNNING HANDLER [Restart memcached], 后执行RUNNING HANDLER [Restart nginx]，即与notify中定义的顺序无关，而是与handlers中定义的任务顺序相同，即在handlers中先定义的任务先执行，后定义的任务后执行。
此时，在节点 node1 上面检查生成的配置文件以及服务情况：
[root@node1 ~]# ll /etc/handlers_* -rw-r--r-- 1 root root 21 Jul 9 09:40 /etc/handlers_1.conf -rw-r--r-- 1 root root 21 Jul 9 09:40 /etc/handlers_2.conf [root@node1 ~]# cat /etc/handlers_1.conf test notify handlers [root@node1 ~]# cat /etc/handlers_2.conf test notify handlers [root@node1 ~]# systemctl status memcached|grep Active Active: active (running) since Sun 2023-07-09 09:40:06 CST; 1min 8s ago [root@node1 ~]# systemctl status nginx|grep Active Active: active (running) since Sun 2023-07-09 09:40:06 CST; 1min 15s ago [root@node1 ~]#
可以看到，配置文件生成成功，并且 memcached 和 nginx 服务都在 2023-07-09 09:40:06 的时候启动了！说明触发器中的任务执行了。
再次执行一次剧本文件：
[ansible@master ansible_playbooks]$ ansible-playbook notify_handlers.yml PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Template configuration file 1] *********************************************************************************** ok: [node1] TASK [Template configuration file 2] *********************************************************************************** ok: [node1] PLAY RECAP ************************************************************************************************************* node1 : ok=3 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
由于上一次执行剧本时，已经生成了配置文件，这次不会重新生成，因此 TASK [Template configuration file 1] 和 TASK [Template configuration file 2] 任务的状态都是 ok，不是 changed，因此不会触发后面触发器任务。
4.2 命名触发器
handlers触发器任务必须设置全局唯一的名称，这样tasks任务就可以通过notify通知这些触发器任务。handlers触发器可以使用listen关键字来监听由多个触发器任务组成的组主题。- 通过使用
listen关键字，使得同时通知多个触发器任务变得更容易，无论这些触发器任务命名成什么都没有关系。
以下是在任务执行完成后，执行重启 web 服务的示例：
- hosts: node1 tasks: - name: Restart everything command: echo "this task will restart the web services" notify: "restart web services" become: yes # [301] Commands should not change things if nothing needs doing register: myoutput changed_when: myoutput.rc == 0 handlers: - name: Restart memcached ansible.builtin.service: name: memcached state: restarted listen: "restart web services" become: yes - name: Restart nginx ansible.builtin.service: name: nginx state: restarted listen: "restart web services" become: yes
在执行剧本前，在节点 node1 上面查看 nginx 和 memecached 服务的状态信息：
[root@node1 ~]# systemctl status memcached|grep Active Active: active (running) since Sun 2023-07-09 09:40:06 CST; 13h ago [root@node1 ~]# systemctl status nginx|grep Active Active: active (running) since Sun 2023-07-09 09:40:06 CST; 13h ago [root@node1 ~]#
然后执行剧本：
[ansible@master ansible_playbooks]$ ansible-playbook naming_handlers.yml -v Using /etc/ansible/ansible.cfg as config file PLAY [node1] *********************************************************************************************************** TASK [Gathering Facts] ************************************************************************************************* ok: [node1] TASK [Restart everything] ********************************************************************************************** changed: [node1] => {"changed": true, "cmd": ["echo", "this task will restart the web services"], "delta": "0:00:00.010154", "end": "2023-07-09 23:06:21.326729", "rc": 0, "start": "2023-07-09 23:06:21.316575", "stderr": "", "stderr_lines": [], "stdout": "this task will restart the web services", "stdout_lines": ["this task will restart the web services"]} RUNNING HANDLER [Restart memcached] ************************************************************************************ changed: [node1] => {"changed": true, "name": "memcached", "state": "started", "status": {"ActiveEnterTimestamp": "Sun 2023-07-09 09:40:06 CST", "ActiveEnterTimestampMonotonic": "9455685640456", "ActiveExitTimestamp": "Sun 2023-07-09 09:40:06 CST", "ActiveExitTimestampMonotonic": "9455685627167", "ActiveState": "active", "After": "system.slice network.target systemd-journald.socket basic.target", "AllowIsolate": "no", "AmbientCapabilities": "0", "AssertResult": "yes", "AssertTimestamp": "Sun 2023-07-09 09:40:06 CST", "AssertTimestampMonotonic": "9455685635489", "Before": "httpd.service shutdown.target", "BlockIOAccounting": "no", "BlockIOWeight": "18446744073709551615", "CPUAccounting": "no", "CPUQuotaPerSecUSec": "infinity", "CPUSchedulingPolicy": "0", "CPUSchedulingPriority": "0", "CPUSchedulingResetOnFork": "no", "CPUShares": "18446744073709551615", "CanIsolate": "no", "CanReload": "no", "CanStart": "yes", "CanStop": "yes", "CapabilityBoundingSet": "18446744073709551615", "CollectMode": "inactive", "ConditionResult": "yes", "ConditionTimestamp": "Sun 2023-07-09 09:40:06 CST", "ConditionTimestampMonotonic": "9455685635489", "Conflicts": "shutdown.target", "ControlGroup": "/system.slice/memcached.service", "ControlPID": "0", "DefaultDependencies": "yes", "Delegate": "no", "Description": "Memcached", "DevicePolicy": "auto", "EnvironmentFile": "/etc/sysconfig/memcached (ignore_errors=yes)", "ExecMainCode": "0", "ExecMainExitTimestampMonotonic": "0", "ExecMainPID": "21492", "ExecMainStartTimestamp": "Sun 2023-07-09 09:40:06 CST", "ExecMainStartTimestampMonotonic": "9455685640423", "ExecMainStatus": "0", "ExecStart": "{ path=/usr/bin/memcached ; argv[]=/usr/bin/memcached -u $USER -p $PORT -m $CACHESIZE -c $MAXCONN $OPTIONS ; ignore_errors=no ; start_time=[Sun 2023-07-09 09:40:06 CST] ; stop_time=[n/a] ; pid=21492 ; code=(null) ; status=0/0 }", "FailureAction": "none", "FileDescriptorStoreMax": "0", "FragmentPath": "/usr/lib/systemd/system/memcached.service", "GuessMainPID": "yes", "IOScheduling": "0", "Id": "memcached.service", "IgnoreOnIsolate": "no", "IgnoreOnSnapshot": "no", "IgnoreSIGPIPE": "yes", "InactiveEnterTimestamp": "Sun 2023-07-09 09:40:06 CST", "InactiveEnterTimestampMonotonic": "9455685627745", "InactiveExitTimestamp": "Sun 2023-07-09 09:40:06 CST", "InactiveExitTimestampMonotonic": "9455685640456", "JobTimeoutAction": "none", "JobTimeoutUSec": "0", "KillMode": "control-group", "KillSignal": "15", "LimitAS": "18446744073709551615", "LimitCORE": "18446744073709551615", "LimitCPU": "18446744073709551615", "LimitDATA": "18446744073709551615", "LimitFSIZE": "18446744073709551615", "LimitLOCKS": "18446744073709551615", "LimitMEMLOCK": "65536", "LimitMSGQUEUE": "819200", "LimitNICE": "0", "LimitNOFILE": "4096", "LimitNPROC": "15066", "LimitRSS": "18446744073709551615", "LimitRTPRIO": "0", "LimitRTTIME": "18446744073709551615", "LimitSIGPENDING": "15066", "LimitSTACK": "18446744073709551615", "LoadState": "loaded", "MainPID": "21492", "MemoryAccounting": "no", "MemoryCurrent": "790528", "MemoryLimit": "18446744073709551615", "MountFlags": "0", "Names": "memcached.service", "NeedDaemonReload": "no", "Nice": "0", "NoNewPrivileges": "no", "NonBlocking": "no", "NotifyAccess": "none", "OOMScoreAdjust": "0", "OnFailureJobMode": "replace", "PermissionsStartOnly": "no", "PrivateDevices": "no", "PrivateNetwork": "no", "PrivateTmp": "no", "ProtectHome": "no", "ProtectSystem": "no", "RefuseManualStart": "no", "RefuseManualStop": "no", "RemainAfterExit": "no", "Requires": "system.slice basic.target", "Restart": "no", "RestartUSec": "100ms", "Result": "success", "RootDirectoryStartOnly": "no", "RuntimeDirectoryMode": "0755", "SameProcessGroup": "no", "SecureBits": "0", "SendSIGHUP": "no", "SendSIGKILL": "yes", "Slice": "system.slice", "StandardError": "inherit", "StandardInput": "null", "StandardOutput": "journal", "StartLimitAction": "none", "StartLimitBurst": "5", "StartLimitInterval": "10000000", "StartupBlockIOWeight": "18446744073709551615", "StartupCPUShares": "18446744073709551615", "StatusErrno": "0", "StopWhenUnneeded": "no", "SubState": "running", "SyslogLevelPrefix": "yes", "SyslogPriority": "30", "SystemCallErrorNumber": "0", "TTYReset": "no", "TTYVHangup": "no", "TTYVTDisallocate": "no", "TasksAccounting": "no", "TasksCurrent": "6", "TasksMax": "18446744073709551615", "TimeoutStartUSec": "1min 30s", "TimeoutStopUSec": "30s", "TimerSlackNSec": "50000", "Transient": "no", "Type": "simple", "UMask": "0022", "UnitFilePreset": "disabled", "UnitFileState": "disabled", "WatchdogTimestamp": "Sun 2023-07-09 09:40:06 CST", "WatchdogTimestampMonotonic": "9455685640445", "WatchdogUSec": "0"}} RUNNING HANDLER [Restart nginx] **************************************************************************************** changed: [node1] => {"changed": true, "name": "nginx", "state": "started", "status": {"ActiveEnterTimestamp": "Sun 2023-07-09 09:40:06 CST", "ActiveEnterTimestampMonotonic": "9455686083958", "ActiveExitTimestamp": "Sun 2023-07-09 09:40:06 CST", "ActiveExitTimestampMonotonic": "9455686040308", "ActiveState": "active", "After": "system.slice network-online.target -.mount remote-fs.target nss-lookup.target basic.target systemd-journald.socket tmp.mount", "AllowIsolate": "no", "AmbientCapabilities": "0", "AssertResult": "yes", "AssertTimestamp": "Sun 2023-07-09 09:40:06 CST", "AssertTimestampMonotonic": "9455686060529", "Before": "shutdown.target multi-user.target", "BlockIOAccounting": "no", "BlockIOWeight": "18446744073709551615", "CPUAccounting": "no", "CPUQuotaPerSecUSec": "infinity", "CPUSchedulingPolicy": "0", "CPUSchedulingPriority": "0", "CPUSchedulingResetOnFork": "no", "CPUShares": "18446744073709551615", "CanIsolate": "no", "CanReload": "yes", "CanStart": "yes", "CanStop": "yes", "CapabilityBoundingSet": "18446744073709551615", "CollectMode": "inactive", "ConditionResult": "yes", "ConditionTimestamp": "Sun 2023-07-09 09:40:06 CST", "ConditionTimestampMonotonic": "9455686060528", "Conflicts": "shutdown.target", "ControlGroup": "/system.slice/nginx.service", "ControlPID": "0", "DefaultDependencies": "yes", "Delegate": "no", "Description": "The nginx HTTP and reverse proxy server", "DevicePolicy": "auto", "ExecMainCode": "0", "ExecMainExitTimestampMonotonic": "0", "ExecMainPID": "21604", "ExecMainStartTimestamp": "Sun 2023-07-09 09:40:06 CST", "ExecMainStartTimestampMonotonic": "9455686083931", "ExecMainStatus": "0", "ExecReload": "{ path=/usr/sbin/nginx ; argv[]=/usr/sbin/nginx -s reload ; ignore_errors=no ; start_time=[n/a] ; stop_time=[n/a] ; pid=0 ; code=(null) ; status=0/0 }", "ExecStart": "{ path=/usr/sbin/nginx ; argv[]=/usr/sbin/nginx ; ignore_errors=no ; start_time=[Sun 2023-07-09 09:40:06 CST] ; stop_time=[Sun 2023-07-09 09:40:06 CST] ; pid=21602 ; code=exited ; status=0 }", "ExecStartPre": "{ path=/usr/sbin/nginx ; argv[]=/usr/sbin/nginx -t ; ignore_errors=no ; start_time=[Sun 2023-07-09 09:40:06 CST] ; stop_time=[Sun 2023-07-09 09:40:06 CST] ; pid=21598 ; code=exited ; status=0 }", "FailureAction": "none", "FileDescriptorStoreMax": "0", "FragmentPath": "/usr/lib/systemd/system/nginx.service", "GuessMainPID": "yes", "IOScheduling": "0", "Id": "nginx.service", "IgnoreOnIsolate": "no", "IgnoreOnSnapshot": "no", "IgnoreSIGPIPE": "yes", "InactiveEnterTimestamp": "Sun 2023-07-09 09:40:06 CST", "InactiveEnterTimestampMonotonic": "9455686053191", "InactiveExitTimestamp": "Sun 2023-07-09 09:40:06 CST", "InactiveExitTimestampMonotonic": "9455686064435", "JobTimeoutAction": "none", "JobTimeoutUSec": "0", "KillMode": "process", "KillSignal": "3", "LimitAS": "18446744073709551615", "LimitCORE": "18446744073709551615", "LimitCPU": "18446744073709551615", "LimitDATA": "18446744073709551615", "LimitFSIZE": "18446744073709551615", "LimitLOCKS": "18446744073709551615", "LimitMEMLOCK": "65536", "LimitMSGQUEUE": "819200", "LimitNICE": "0", "LimitNOFILE": "4096", "LimitNPROC": "15066", "LimitRSS": "18446744073709551615", "LimitRTPRIO": "0", "LimitRTTIME": "18446744073709551615", "LimitSIGPENDING": "15066", "LimitSTACK": "18446744073709551615", "LoadState": "loaded", "MainPID": "21604", "MemoryAccounting": "no", "MemoryCurrent": "2215936", "MemoryLimit": "18446744073709551615", "MountFlags": "0", "Names": "nginx.service", "NeedDaemonReload": "no", "Nice": "0", "NoNewPrivileges": "no", "NonBlocking": "no", "NotifyAccess": "none", "OOMScoreAdjust": "0", "OnFailureJobMode": "replace", "PIDFile": "/run/nginx.pid", "PermissionsStartOnly": "no", "PrivateDevices": "no", "PrivateNetwork": "no", "PrivateTmp": "yes", "ProtectHome": "no", "ProtectSystem": "no", "RefuseManualStart": "no", "RefuseManualStop": "no", "RemainAfterExit": "no", "Requires": "system.slice basic.target -.mount", "RequiresMountsFor": "/var/tmp", "Restart": "no", "RestartUSec": "100ms", "Result": "success", "RootDirectoryStartOnly": "no", "RuntimeDirectoryMode": "0755", "SameProcessGroup": "no", "SecureBits": "0", "SendSIGHUP": "no", "SendSIGKILL": "yes", "Slice": "system.slice", "StandardError": "inherit", "StandardInput": "null", "StandardOutput": "journal", "StartLimitAction": "none", "StartLimitBurst": "5", "StartLimitInterval": "10000000", "StartupBlockIOWeight": "18446744073709551615", "StartupCPUShares": "18446744073709551615", "StatusErrno": "0", "StopWhenUnneeded": "no", "SubState": "running", "SyslogLevelPrefix": "yes", "SyslogPriority": "30", "SystemCallErrorNumber": "0", "TTYReset": "no", "TTYVHangup": "no", "TTYVTDisallocate": "no", "TasksAccounting": "no", "TasksCurrent": "3", "TasksMax": "18446744073709551615", "TimeoutStartUSec": "1min 30s", "TimeoutStopUSec": "5s", "TimerSlackNSec": "50000", "Transient": "no", "Type": "forking", "UMask": "0022", "UnitFilePreset": "disabled", "UnitFileState": "enabled", "WantedBy": "multi-user.target", "Wants": "network-online.target", "WatchdogTimestamp": "Sun 2023-07-09 09:40:06 CST", "WatchdogTimestampMonotonic": "9455686083945", "WatchdogUSec": "0"}} PLAY RECAP ************************************************************************************************************* node1 : ok=4 changed=3 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 [ansible@master ansible_playbooks]$
此时，在节点 node1 上面查看服务状态信息：
[root@node1 ~]# systemctl status memcached|grep Active Active: active (running) since Sun 2023-07-09 23:06:22 CST; 2min 0s ago [root@node1 ~]# systemctl status nginx|grep Active Active: active (running) since Sun 2023-07-09 23:06:22 CST; 2min 2s ago
可以看到 memecached 和 nginx 服务都重启了。
由于 Restart memcached 和 Restart nginx 两个触发器任务的 listen: "restart web services" 监听相同，被认为是相同的组，因此在 Restart everything 任务中使用 notify: "restart web services" 通知触发器时，会通知触发器组下面的所有任务，也就是 Restart memcached 和 Restart nginx 两个触发器任务都会被触发执行。
