Switchboard

Switchboard

A small reverse proxy + load balancer I built in Go to understand how this stuff actually works (instead of just using NGINX blindly).

what it does

• listens on localhost:8080
• forwards requests to multiple backend servers
• rotates between them (round robin)
• skips a backend if it goes down

basically:

client → switchboard → backend(s)

nothing fancy, just the core idea working.

how to run

1. start a few backend servers

you’ll need 2–3 simple servers running on different ports.

example:

package main import ( "fmt" "net/http" ) func main() { port := "9001" http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { fmt.Fprintf(w, "hello from %s\n", port) }) http.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(200) }) http.ListenAndServe(":"+port, nil) }

run this on:

• 9001
• 9002
• 9003

2. start switchboard

go run main.go

3. test it

curl localhost:8080

hit it multiple times — you should see responses switch between servers.

health checks

switchboard periodically calls:

/health

if a backend:

• stops responding
• or returns non-200

it gets marked as dead and skipped automatically.

why i made this

mostly to understand:

• how reverse proxies actually forward requests
• how load balancing works under the hood
• how to handle shared state safely (mutex, etc.)

also just wanted to build something a bit closer to “real infra” instead of another CRUD app.

tech

• Go (net/http, httputil)
• goroutines
• mutex for safe routing

things i might add later

• better balancing (least connections)
• retry logic if a backend fails
• config file instead of hardcoding servers
• CLI (switchboard start etc.)

quick run

start backends

go run backend1.go go run backend2.go go run backend3.go

start proxy

go run main.go

test

curl localhost:8080

that’s it — simple, but it works