Using Reuse Port for Multiple Kemal Processes

require "kemal"

# Define a simple route that returns a message
get "/" do
  "Reusing port 3000"
end

# Start Kemal with custom server configuration
Kemal.run do |config|
  # Get the server instance from the config
  server = config.server.not_nil!
  
  # Bind the server to port 3000 with reuse_port enabled
  # reuse_port: true allows multiple processes to listen on the same port
  # This is useful for load balancing across multiple worker processes
  server.bind_tcp "0.0.0.0", 3000, reuse_port: true
end

You can use the following script to spawn multiple Kemal processes according to your CPU cores.

#!/bin/bash

for i in $(seq 1 $(nproc --all)); do
  ./app
done

wait

Important: This is for demonstration purpose only. You should use a mature process manager / monitor for production.

Source Code