Problem : Nginx Server is buffring the Server sent events(SSE).
Setup : Node v12.13.1, Nginx 1.16.1, Chrome v80
Scenario:
I tried to turn off buffering with proxy_buffering off; and even added "X-Accel-Buffering": "no" in server resonse header however nginx is still buffering all SSE. if I close node server or restart nginx server then all the SSE message are delivered to client in bulk. I tried alot but dont know that I'm missing.
Nginx Config file :
events {
worker_connections 1024;
}
http {
include mime.types;
sendfile on;
keepalive_timeout 65;
server {
listen 4200;
server_name localhost;
location / {
proxy_set_header Connection '';
proxy_http_version 1.1;
chunked_transfer_encoding off;
proxy_buffering off;
proxy_cache off;
proxy_pass http://localhost:8700;
}
}
}
Node Server :
var express = require('express');
var app = express();
var template =
`<!DOCTYPE html> <html> <body>
<script type="text/javascript">
var source = new EventSource("/events/");
source.onmessage = function(e) {
document.body.innerHTML += e.data + "<br>";
};
</script>
</body> </html>`;
app.get('/', function (req, res) {
res.send(template); // <- Return the static template above
});
var clientId = 0;
var clients = {}; // <- Keep a map of attached clients
// Called once for each new client. Note, this response is left open!
app.get('/events/', function (req, res) {
req.socket.setTimeout(Number.MAX_VALUE);
res.writeHead(200, {
'Content-Type': 'text/event-stream', // <- Important headers
'Cache-Control': 'no-cache',
'Connection': 'keep-alive',
'X-Accel-Buffering': 'no'
});
res.write('\n');
(function (clientId) {
clients[clientId] = res; // <- Add this client to those we consider "attached"
req.on("close", function () {
delete clients[clientId]
}); // <- Remove this client when he disconnects
})(++clientId)
});
setInterval(function () {
var msg = Math.random();
console.log("Clients: " + Object.keys(clients) + " <- " + msg);
for (clientId in clients) {
clients[clientId].write("data: " + msg + "\n\n"); // <- Push a message to a single attached client
};
}, 2000);
app.listen(process.env.PORT || 8700);