Randomly Connection Closed behind NGINX reverse proxy

[IgorZanellaDev]

Summary

Hi, I created a project in next, it's published behind a NGINX reverse proxy. Sometimes (like 1 out of 100) randomly, when I first load any pages, I get a 404 error (not the 404 page i created, but the default client error page), on Sentry I get the Connection Closed error in the node_modules/next/dist/compiled/react-server-dom-webpack/cjs/react-server-dom-webpack-client.browser.production.js in t at line 1672:1.

With the same proxy and a v13 of next there weren't problems like this one.

The default is port 80 because in that case there is an application load balancer in front, while for the other HTTPS configurations (not here below), the connection is direct. The problem happens both on the connections with load balancer and direct ones.

Do you have any ideas why it happens?

nginx.conf file:

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ecdh_curve X25519:prime256v1:secp384r1;
    ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;
    ssl_prefer_server_ciphers off;

    ssl_dhparam /etc/nginx/dhparam.pem;

    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains";

    server_names_hash_bucket_size 128;
    server_names_hash_max_size 1024;

    map "$arg_name$arg_email$arg_message" $contact_us_key {
        default $binary_remote_addr;
        ""      "";
    }

    limit_req_zone $binary_remote_addr zone=search_zone:10m rate=10r/m;
    limit_req_zone $contact_us_key zone=contact_us_zone:10m rate=1r/m;
    limit_req_status 429;

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

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    gzip  on;

    proxy_buffering off;
    proxy_request_buffering off;
    proxy_read_timeout 3600s;
    proxy_send_timeout 3600s;
    proxy_http_version 1.1;
    chunked_transfer_encoding on;
    proxy_cache off;

    proxy_set_header Accept-Language $http_accept_language;
    proxy_set_header Connection "";
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;

    server_tokens off;
    proxy_pass_header Server;
    proxy_hide_header X-Middleware-Rewrite;
    proxy_hide_header X-Nextjs-Cache;
    proxy_hide_header X-Nextjs-Prerender;
    proxy_hide_header X-Nextjs-Stale-Time;

    include /etc/nginx/conf.d/*.conf;
}

default.conf file:

server {
    listen 80 default_server;
    server_name  _;
  
    location = /contact-us {
        limit_req zone=contact_us_zone nodelay;
        error_page 429 = @error_many_requests;

        proxy_pass http://127.0.0.1:3000/contact-us?$args;
    }

    location ~ "^/[a-z]{2}/search($|/)" {
        limit_req zone=search_zone burst=5 nodelay;
        error_page 429 = @error_many_requests;

        proxy_pass http://127.0.0.1:3000$request_uri;
    }

    location @error_many_requests {
        set $args $args&rateLimit=1;
        proxy_pass http://127.0.0.1:3000$uri?$args;
    }

    location / {
        proxy_pass http://127.0.0.1:3000;
    }
}

server {
    listen 443 ssl default_server;
    server_name _;
    ssl_certificate /etc/nginx/ssl/nginx.crt;
    ssl_certificate_key /etc/nginx/ssl/nginx.key;
    return 404;
}

Additional information

nginx: 1.28.0

next: 15.4.6
eslint-config-next: 15.4.6
react: 19.1.1
react-dom: 19.1.1
typescript: 5.8.3

Example

No response