To run multiple HTTP servers concurrently, use the reusePort option in Bun.serve(). It shares one port across multiple processes, and incoming requests are load balanced across them.
server.tsimport { serve } from "bun";
const id = Math.random().toString(36).slice(2);
serve({
port: process.env.PORT || 8080,
development: false,
// Share the same port across multiple processes
// This is the important part!
reusePort: true,
async fetch(request) {
return new Response("Hello from Bun #" + id + "!\n");
},
});
Linux only — Windows and macOS ignore the reusePort option. This is an operating system limitation with
SO_REUSEPORT.
reusePort uses the Linux SO_REUSEPORT and SO_REUSEADDR socket options to ensure fair load balancing across processes. Learn more about SO_REUSEPORT and SO_REUSEADDR
cluster.ts import { spawn } from "bun";
const cpus = navigator.hardwareConcurrency; // Number of CPU cores
const buns = new Array(cpus);
for (let i = 0; i < cpus; i++) {
buns[i] = spawn({
cmd: ["bun", "./server.ts"],
stdout: "inherit",
stderr: "inherit",
stdin: "inherit",
});
}
function kill() {
for (const bun of buns) {
bun.kill();
}
}
process.on("SIGINT", kill);
process.on("exit", kill);
Bun also implements the node:cluster module; reusePort is a faster but more limited alternative.