NGINX 服务器间歇性不响应新连接

Question

我设置了一个 Web 服务器，它通常响应速度极快（<100ms），即使将 keepalive_timeout 设置为 0，重复连接也不会出现连接问题。但是，偶尔在连接到站点时，浏览器会永远停滞，Wireshark 会显示多个未响应的 TCP 重传数据包。NGINX 在访问日志中没有显示任何问题。

/etc/nginx/nginx.conf：

user www-data;
worker_processes 4;
thread_pool default threads=32 max_queue=65536;
pid /run/nginx.pid;
worker_rlimit_nofile 8192;


events {
        worker_connections 512;
        multi_accept on;
}

http {

        ##
        # Basic Settings
        ##

        sendfile                        off;
        tcp_nopush                      off;
        tcp_nodelay                     on;
        #keepalive_timeout              10;
        keepalive_timeout               0;
        #types_hash_max_size            2048;

        #client_body_buffer_size        128k;
        client_max_body_size            10G;
        #client_header_buffer_size      1k;
        #large_client_header_buffers    4 4k;
        #output_buffers                 2 32k;
        postpone_output                 0;

        #server_names_hash_bucket_size 128; # this seems to be required for some vhosts

        access_log                      on;

        log_format upstream_time '$remote_addr - $remote_user [$time_local] '
                                 '"$request" $status $body_bytes_sent '
                                 '"$http_referer" "$http_user_agent"'
                                 'rt=$request_time uct="$upstream_connect_time" uht="$upstream_header_time" urt="$upstream_response_time"';

        include                         /etc/nginx/mime.types;
        default_type                    application/octet-stream;

        ##
        # SSL Settings
        ##

        ssl_protocols                   TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
        ssl_prefer_server_ciphers       on;
        ssl_certificate                 /etc/letsencrypt/live/www.baldeonline.com/fullchain.pem;
        ssl_certificate_key             /etc/letsencrypt/live/www.baldeonline.com/privkey.pem;
        ssl_session_cache shared:SSL:50m;
        ssl_session_timeout 1d;
        ssl_session_tickets off;
        ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:!DSS';
        ssl_dhparam /etc/nginx/ssl/dhparam.pem;
        ssl_ecdh_curve secp384r1;

        resolver 1.1.1.1 8.8.8.8 8.8.4.4;
        ssl_stapling on;
        ssl_stapling_verify on;
        ssl_trusted_certificate /etc/letsencrypt/live/www.baldeonline.com/chain.pem;

        ##
        # Logging Settings
        ##

        access_log                      /var/log/nginx/access.log upstream_time;
        error_log                       /var/log/nginx/error.log;

        ##
        # Gzip Settings
        ##

        gzip                            on;
        gzip_disable                    "msie6";
        gzip_min_length 32;
        gzip_comp_level 6;
        gzip_buffers 16 8k;
        gzip_http_version 1.1;
        gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

        ##
        # Virtual Host Configs
        ##

        include /etc/nginx/sites-enabled/*;
}

/etc/nginx/sites-enabled/www.baldeonline.com：

server {
        server_name www.baldeonline.com;
        listen 443 ssl http2 default_server;
        listen [::]:443 ssl http2 default_server;
        ssl    on;
        root "/http/www.baldeonline.com";
        include /etc/nginx/generalSubdomainHandler;
        location /phpmyadmin/ {
                allow 192.168.1.0/24;
                allow 10.8.0.0/24;
                deny all;
        }
        location /phppgadmin/ {
                allow 192.168.1.0/24;
                allow 10.8.0.0/24;
                deny all;
        }
}
server {
        listen 80 default_server;
        listen [::]:80 default_server;
        server_name $host;
        return 301 https://$host$request_uri;
}