服务器操作系统：Ubuntu 18.04.5
该问题随机发生，没有明显原因。
Nginx 停止接收 https 请求。
对服务器的任何 https 请求都会收到“连接超时”响应。
我的所有 SSL 证书均有效且未过期。
运行systemctl restart nginx有帮助，但显然无法解决问题。几天后，这种情况再次发生。
我检查过的内容：
systemctl status nginx
服务处于活动状态，
nginx 日志中没有错误
nmap <server-ip>
PORT STATE SERVICE
80/tcp open http
443/tcp filtered https
journalctl
没有错误
dmesg
没有错误
ufw status
不活跃
iptables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
我如何才能找到问题的原因？任何帮助都将不胜感激。
更新。
在我的 nginx.conf 中：
worker_processes 1;
...
worker_connections 1024;
当问题发生时，我不知道 ngx_http_stub_status_module。但现在一切正常时，输出如下所示：
Active connections: 37
server accepts handled requests
107208 107208 629578
Reading: 0 Writing: 1 Waiting: 36
systemctl status nginx
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/nginx.service.d
└─override.conf
Active: active (running) since Sun 2021-05-23 11:09:41 MSK; 1 day 6h ago
Docs: man:nginx(8)
Main PID: 12699 (nginx)
Tasks: 2 (limit: 1107)
CGroup: /system.slice/nginx.service
├─ 603 nginx: worker process
└─12699 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
更新 11.07.21
问题再次发生，我运行了一些额外的命令：
ss -plnt
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 16 128 127.0.0.1:7141 0.0.0.0:*
LISTEN 38 128 0.0.0.0:80 0.0.0.0:*
LISTEN 0 128 127.0.0.53%lo:53 0.0.0.0:*
LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
LISTEN 129 128 0.0.0.0:443 0.0.0.0:*
LISTEN 0 128 [::]:80 [::]:*
LISTEN 0 100 [::1]:8761 [::]:*
LISTEN 0 50 [::1]:8762 [::]:*
LISTEN 75 128 [::]:443 [::]:*
ss -atn sport == 443
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 129 128 0.0.0.0:443 0.0.0.0:*
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.14:50752
CLOSE-WAIT 62 0 <my-server-ip>:443 190.88.157.209:53692
CLOSE-WAIT 174 0 <my-server-ip>:443 188.120.116.128:9068
CLOSE-WAIT 414 0 <my-server-ip>:443 51.89.155.27:20400
CLOSE-WAIT 370 0 <my-server-ip>:443 63.143.42.242:35772
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63490
CLOSE-WAIT 518 0 <my-server-ip>:443 103.76.44.243:58496
CLOSE-WAIT 414 0 <my-server-ip>:443 51.89.155.27:21866
CLOSE-WAIT 518 0 <my-server-ip>:443 140.238.83.181:44782
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.14:64912
CLOSE-WAIT 304 0 <my-server-ip>:443 185.191.171.18:11146
CLOSE-WAIT 279 0 <my-server-ip>:443 68.4.27.246:63404
CLOSE-WAIT 518 0 <my-server-ip>:443 152.169.229.115:57877
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63481
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:27109
CLOSE-WAIT 218 0 <my-server-ip>:443 207.38.88.75:12518
CLOSE-WAIT 518 0 <my-server-ip>:443 124.240.214.92:32336
CLOSE-WAIT 373 0 <my-server-ip>:443 128.199.195.156:38372
CLOSE-WAIT 304 0 <my-server-ip>:443 185.191.171.26:23620
CLOSE-WAIT 518 0 <my-server-ip>:443 103.76.44.243:58500
CLOSE-WAIT 518 0 <my-server-ip>:443 174.2.25.50:48538
CLOSE-WAIT 377 0 <my-server-ip>:443 63.143.42.246:54248
CLOSE-WAIT 295 0 <my-server-ip>:443 54.156.8.33:20089
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:14355
CLOSE-WAIT 518 0 <my-server-ip>:443 124.240.214.92:32337
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.41:6010
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:55117
CLOSE-WAIT 518 0 <my-server-ip>:443 50.24.7.102:45514
CLOSE-WAIT 518 0 <my-server-ip>:443 66.102.8.216:35146
CLOSE-WAIT 518 0 <my-server-ip>:443 174.2.25.50:48552
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63510
CLOSE-WAIT 518 0 <my-server-ip>:443 103.76.44.243:58498
CLOSE-WAIT 518 0 <my-server-ip>:443 105.245.106.245:57395
CLOSE-WAIT 295 0 <my-server-ip>:443 54.156.8.33:2177
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63500
CLOSE-WAIT 373 0 <my-server-ip>:443 63.143.42.242:37358
CLOSE-WAIT 174 0 <my-server-ip>:443 188.120.116.128:9097
CLOSE-WAIT 518 0 <my-server-ip>:443 66.102.8.216:58832
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.41:18880
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63482
CLOSE-WAIT 518 0 <my-server-ip>:443 66.249.70.51:38665
CLOSE-WAIT 149 0 <my-server-ip>:443 190.88.157.209:53691
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:29591
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.41:40028
CLOSE-WAIT 1 0 <my-server-ip>:443 66.249.64.22:58748
CLOSE-WAIT 304 0 <my-server-ip>:443 185.191.171.18:43156
CLOSE-WAIT 211 0 <my-server-ip>:443 207.38.88.75:12734
CLOSE-WAIT 518 0 <my-server-ip>:443 151.82.77.142:14303
CLOSE-WAIT 1 0 <my-server-ip>:443 5.255.231.155:55850
CLOSE-WAIT 1 0 <my-server-ip>:443 66.249.64.24:51073
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63512
CLOSE-WAIT 373 0 <my-server-ip>:443 63.143.42.251:37356
CLOSE-WAIT 518 0 <my-server-ip>:443 50.24.7.102:45516
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.34:50266
CLOSE-WAIT 518 0 <my-server-ip>:443 105.245.106.245:57397
ESTAB 406 0 <my-server-ip>:443 95.91.75.32:3099
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.14:26910
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:31917
CLOSE-WAIT 518 0 <my-server-ip>:443 36.90.163.47:53848
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:16593
CLOSE-WAIT 414 0 <my-server-ip>:443 51.89.155.27:22292
CLOSE-WAIT 316 0 <my-server-ip>:443 5.255.231.155:47018
CLOSE-WAIT 518 0 <my-server-ip>:443 174.2.25.50:48546
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.14:2850
CLOSE-WAIT 304 0 <my-server-ip>:443 185.191.171.18:38278
CLOSE-WAIT 217 0 <my-server-ip>:443 93.158.90.56:49885
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63508
CLOSE-WAIT 518 0 <my-server-ip>:443 66.249.70.49:50315
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63483
ESTAB 0 0 <my-server-ip>:443 78.10.205.246:47113
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63509
CLOSE-WAIT 1 0 <my-server-ip>:443 85.52.243.124:46299
CLOSE-WAIT 525 0 <my-server-ip>:443 68.4.27.246:63485
CLOSE-WAIT 518 0 <my-server-ip>:443 66.102.8.216:45559
CLOSE-WAIT 294 0 <my-server-ip>:443 3.238.138.173:57324
CLOSE-WAIT 307 0 <my-server-ip>:443 185.191.171.41:4624
CLOSE-WAIT 304 0 <my-server-ip>:443 185.191.171.26:60256
CLOSE-WAIT 373 0 <my-server-ip>:443 63.143.42.242:57958
ESTAB 184 0 <my-server-ip>:443 95.91.75.32:34140
CLOSE-WAIT 1 0 <my-server-ip>:443 186.179.166.137:51668
...
ss -p | grep nginx | grep -i estab | wc -l
0
笔记：通常ss -plnt输出如下所示：
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 0.0.0.0:80 0.0.0.0:*
LISTEN 0 128 127.0.0.53%lo:53 0.0.0.0:*
LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
LISTEN 0 128 0.0.0.0:443 0.0.0.0:*
LISTEN 0 128 127.0.0.1:7141 0.0.0.0:*
LISTEN 0 128 [::]:80 [::]:*
LISTEN 0 100 [::1]:8761 [::]:*
LISTEN 0 50 [::1]:8762 [::]:*
LISTEN 0 128 [::]:443 [::]:*
输出ss -atn sport == 443通常如下所示：
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 0.0.0.0:443 0.0.0.0:*
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.79:49070
ESTAB 0 0 <my-server-ip>:443 66.249.70.53:54557
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.41:30578
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.79:38618
TIME-WAIT 0 0 <my-server-ip>:443 66.249.64.22:38639
ESTAB 0 0 <my-server-ip>:443 17.121.113.26:64778
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.79:42886
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.67:47202
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.79:15380
ESTAB 0 0 <my-server-ip>:443 223.236.100.52:39478
ESTAB 0 0 <my-server-ip>:443 41.186.78.109:26127
TIME-WAIT 0 0 <my-server-ip>:443 3.235.40.235:33774
ESTAB 0 0 <my-server-ip>:443 66.249.64.23:55669
ESTAB 0 0 <my-server-ip>:443 37.210.126.179:48524
TIME-WAIT 0 0 <my-server-ip>:443 52.71.251.5:55276
ESTAB 0 0 <my-server-ip>:443 201.230.235.12:51712
ESTAB 0 0 <my-server-ip>:443 197.158.235.224:44578
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.79:26606
TIME-WAIT 0 0 <my-server-ip>:443 54.36.148.79:60100
...