First draft, it's working already

README.md

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+redis-sentinel-proxy
+====================
+
+Small command utility that:
+
+* Given a redis sentinel server listening on `SENTINEL_PORT`, keeps asking it for the address of a master named `NAME`
+
+* Proxies all tcp requests that it receives on `PORT` to that master
+
+
+Usage:
+
+`./redis-sentinel-proxy -listen IP:PORT -sentinel :SENTINEL_PORT -master NAME`

main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"strings"
+	"time"
+)
+
+var (
+	masterAddr *net.TCPAddr
+	raddr      *net.TCPAddr
+	saddr      *net.TCPAddr
+
+	localAddr    = flag.String("listen", ":9999", "local address")
+	sentinelAddr = flag.String("sentinel", ":26379", "remote address")
+	masterName   = flag.String("master", "mymaster", "name of the master redis node")
+)
+
+func main() {
+	flag.Parse()
+
+	laddr, err := net.ResolveTCPAddr("tcp", *localAddr)
+	if err != nil {
+		log.Fatal("Failed to resolve local address: %s", err)
+	}
+	saddr, err = net.ResolveTCPAddr("tcp", *sentinelAddr)
+	if err != nil {
+		log.Fatal("Failed to resolve sentinel address: %s", err)
+	}
+
+	go master()
+
+	listener, err := net.ListenTCP("tcp", laddr)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for {
+		conn, err := listener.AcceptTCP()
+		if err != nil {
+			log.Println(err)
+			continue
+		}
+
+		go proxy(conn, masterAddr)
+	}
+}
+
+func master() {
+	var err error
+	for {
+		masterAddr, err = getMasterAddr(saddr, *masterName)
+		if err != nil {
+			log.Fatal(err)
+		}
+		time.Sleep(1 * time.Second)
+	}
+}
+
+func pipe(r io.Reader, w io.WriteCloser) {
+	io.Copy(w, r)
+	w.Close()
+}
+
+func proxy(local io.ReadWriteCloser, remoteAddr *net.TCPAddr) {
+	remote, err := net.DialTCP("tcp", nil, remoteAddr)
+	if err != nil {
+		log.Println(err)
+		local.Close()
+		return
+	}
+	go pipe(local, remote)
+	go pipe(remote, local)
+}
+
+func getMasterAddr(sentinelAddress *net.TCPAddr, masterName string) (*net.TCPAddr, error) {
+	conn, err := net.DialTCP("tcp", nil, sentinelAddress)
+	if err != nil {
+		log.Fatal("Error connecting to sentinel: %s", err)
+	}
+
+	defer conn.Close()
+
+	conn.Write([]byte(fmt.Sprintf("sentinel get-master-addr-by-name %s\n", masterName)))
+
+	b := make([]byte, 256)
+	_, err = conn.Read(b)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	parts := strings.Split(string(b), "\r\n")
+
+	//getting the string address for the master node
+	stringaddr := fmt.Sprintf("%s:%s", parts[2], parts[4])
+	addr, err := net.ResolveTCPAddr("tcp", stringaddr)
+	return addr, err
+}