NGINX Optimization for Server-Sent Events (SSE)

Posted July 26, 2021 984 views
NginxNode.jsServer Optimization

I have developed a group chat app using Node.js and have load tested with Gatling. When I test from either my laptop or directly on my droplet, it can handle 382 connections. However, when I set Gatling in the droplet to bypass NGINX and connect directly to Node.js, it can handle more than 8,000 connections.

Any ideas why NGINX maxes out at precisely 382 connections?

Here is my sites-available:

server {

  listen 443 ssl http2;
  listen [::]:443 ssl http2;
  ssl_certificate /etc/letsencrypt/live/; # managed by Certbot
  ssl_certificate_key /etc/letsencrypt/live/; # managed by Certbot
  include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
  ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

  location / {


    proxy_pass http://localhost:3000;
    proxy_http_version 1.1;
    proxy_set_header Connection '';



server {

  if ($host = {
    return 301 https://$host$request_uri;
  } # managed by Certbot

  listen 80;
  return 404; # managed by Certbot


And the headers sent from Node.js:

res.writeHead(200, {
  'Content-Type': 'text/event-stream',
  'Connection': 'keep-alive',
  'Cache-Control': 'no-cache',
  'X-Accel-Buffering': 'no'
edited by MattIPv4

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Show answer This answer has been marked as resolved by WalterMonroe.