all

Author: Shatwik7

.gitignore

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+# Ignore bin folder
+bin/

README.md

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+# Redis-Compatible Cache Server (Reverse Engineered)
+
+This project is a lightweight, reverse-engineered implementation of a Redis-compatible server. It supports basic caching operations such as `SET` and `GET`, and is designed to be compact and efficient. The server is compatible with the official Redis client, making it easy to integrate into existing systems that rely on Redis for caching.
+
+## Features
+
+- **Redis Protocol Compatibility**: The server implements a subset of the Redis protocol (RESP - REdis Serialization Protocol), allowing it to work seamlessly with the official Redis client.
+- **Basic Caching Operations**:
+  - `SET key value`: Stores a key-value pair in the cache.
+  - `GET key`: Retrieves the value associated with a key.
+- **Lightweight and Efficient**: The server is designed to be minimalistic, focusing only on the essential caching functionality.
+- **Concurrency Support**: The server uses a thread-safe key-value store, ensuring safe concurrent access to the cache.
+
+## How It Works
+
+The server listens for incoming connections on a specified port (default: `:2345`). When a client connects, it processes commands sent in the Redis protocol format. The server supports the following commands:
+
+1. **SET**: Stores a key-value pair in the cache.
+   - Example: `SET mykey myvalue`
+2. **GET**: Retrieves the value associated with a key.
+   - Example: `GET mykey`
+3. **HELLO**: A custom command that responds with server information.
+   - Example: `HELLO world`
+4. **CLIENT**: A placeholder command for future client-related functionality.
+
+The server uses a simple in-memory key-value store (`KeyVal`) to manage the cache. It ensures thread safety using a read-write mutex (`sync.RWMutex`).
+
+## Compatibility with Redis Client
+
+This server is designed to be compatible with the official Redis client. You can use any Redis client library or the `redis-cli` tool to interact with this server. For example:
+
+```bash
+# Using redis-cli
+$ redis-cli -p 2345
+127.0.0.1:2345> SET mykey myvalue
+OK
+127.0.0.1:2345> GET mykey
+"myvalue"

Taskfile.yaml

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+version: '3'
+
+tasks:
+  build:
+    cmds:
+      - go build -o bin/
+
+  run:
+    deps: [build]
+    cmds:
+      - ./bin/lightweightCacheServer.exe
+
+  test:
+    cmds:
+      - go test -v ./...

go.mod

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+module github.com/shatwik7/lightweightCacheServer
+
+go 1.23.5
+
+require github.com/gofiber/fiber/v2 v2.52.6
+
+require (
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
+	github.com/redis/go-redis/v9 v9.7.0 // indirect
+	github.com/tidwall/resp v0.1.1 // indirect
+	github.com/valyala/bytebufferpool v1.0.0 // indirect
+)

go.sum

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+github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
+github.com/gofiber/fiber/v2 v2.52.6 h1:Rfp+ILPiYSvvVuIPvxrBns+HJp8qGLDnLJawAu27XVI=
+github.com/gofiber/fiber/v2 v2.52.6/go.mod h1:YEcBbO/FB+5M1IZNBP9FO3J9281zgPAreiI1oqg8nDw=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/redis/go-redis/v9 v9.7.0 h1:HhLSs+B6O021gwzl+locl0zEDnyNkxMtf/Z3NNBMa9E=
+github.com/redis/go-redis/v9 v9.7.0/go.mod h1:f6zhXITC7JUJIlPEiBOTXxJgPLdZcA93GewI7inzyWw=
+github.com/tidwall/resp v0.1.1 h1:Ly20wkhqKTmDUPlyM1S7pWo5kk0tDu8OoC/vFArXmwE=
+github.com/tidwall/resp v0.1.1/go.mod h1:3/FrruOBAxPTPtundW0VXgmsQ4ZBA0Aw714lVYgwFa0=
+github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
+github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=

keyVal.go

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+package main
+
+import "sync"
+
+type KeyVal struct {
+	mu   sync.RWMutex
+	data map[string][]byte
+}
+
+func NewKeyVal() *KeyVal {
+	return &KeyVal{
+		data: map[string][]byte{},
+	}
+}
+
+func (KeyVal *KeyVal) Set(key, val []byte) error {
+	KeyVal.mu.Lock()
+	defer KeyVal.mu.Unlock()
+	KeyVal.data[string(key)] = []byte(val)
+	return nil
+}
+
+func (KeyVal *KeyVal) Get(key []byte) ([]byte, bool) {
+	KeyVal.mu.RLock()
+	defer KeyVal.mu.RUnlock()
+	val, ok := KeyVal.data[string(key)]
+	return val, ok
+}

keyVal_test.go

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+package main
+
+import (
+	"testing"
+)
+
+func TestKeyVal(t *testing.T) {
+	KeyVal := NewKeyVal()
+	key := "mykey"
+	val := "myval"
+	err := KeyVal.Set([]byte(key), []byte(val))
+	if err != nil {
+		t.Fatal(err)
+	}
+	val2, ok := KeyVal.Get([]byte(key))
+	if !ok {
+		t.Fatal(err)
+	}
+	if string(val2) != val {
+		t.Fatal(err)
+	}
+}

main.go

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+package main
+
+import (
+	"fmt"
+	"log/slog"
+	"net"
+
+	"github.com/gofiber/fiber/v2/log"
+	"github.com/tidwall/resp"
+)
+
+const defaultListenAddress = ":2345"
+
+type Message struct {
+	cmd  Command
+	peer *Peer
+}
+
+type Config struct {
+	ListenAddress string
+}
+
+type Server struct {
+	Config
+	peers     map[*Peer]bool
+	ln        net.Listener
+	addPeerCh chan *Peer
+	quitCh    chan struct{}
+	msgCh     chan Message
+	delPeerCh chan *Peer
+	KeyVal    *KeyVal
+}
+
+func NewServer(cfg Config) *Server {
+	if len(cfg.ListenAddress) == 0 {
+		cfg.ListenAddress = defaultListenAddress
+	}
+	return &Server{
+		Config:    cfg,
+		peers:     make(map[*Peer]bool),
+		addPeerCh: make(chan *Peer),
+		quitCh:    make(chan struct{}),
+		msgCh:     make(chan Message),
+		delPeerCh: make(chan *Peer),
+		KeyVal:    NewKeyVal(),
+	}
+}
+
+func (s *Server) Start() error {
+	ln, err := net.Listen("tcp", s.ListenAddress)
+	if err != nil {
+		return err
+	}
+	s.ln = ln
+	go s.loop()
+	log.Infof("Running on PORT : ", s.Config.ListenAddress)
+	return s.acceptLoop()
+}
+func (s *Server) loop() {
+	for {
+		select {
+		case msg := <-s.msgCh:
+			if err := s.handleMessage(msg); err != nil {
+				slog.Error("raw message eror", "err", err)
+			}
+		case <-s.quitCh:
+			return
+		case peer := <-s.addPeerCh:
+			slog.Info("peer connected", "remoteAddr", peer.conn.RemoteAddr())
+			s.peers[peer] = true
+		case peer := <-s.delPeerCh:
+			slog.Info("peer disconnected", "remoteAddr", peer.conn.RemoteAddr())
+			delete(s.peers, peer)
+		}
+	}
+}
+
+func (s *Server) acceptLoop() error {
+	for {
+		conn, err := s.ln.Accept()
+		if err != nil {
+			log.Error("Accept Error : Can not accept :", err)
+			continue
+		}
+		go s.handleConn(conn)
+	}
+}
+
+func (s *Server) handleMessage(msg Message) error {
+	switch v := msg.cmd.(type) {
+	case ClientCommand:
+		if err := resp.
+			NewWriter(msg.peer.conn).
+			WriteString("OK"); err != nil {
+			return err
+		}
+	case SetCommand:
+		if err := s.KeyVal.Set(v.key, v.val); err != nil {
+			return err
+		}
+		if err := resp.
+			NewWriter(msg.peer.conn).
+			WriteString("OK"); err != nil {
+			return err
+		}
+	case GetCommand:
+		val, ok := s.KeyVal.Get(v.key)
+		if !ok {
+			return fmt.Errorf("key not found")
+		}
+		if err := resp.
+			NewWriter(msg.peer.conn).
+			WriteString(string(val)); err != nil {
+			return err
+		}
+	case HelloCommand:
+		spec := map[string]string{
+			"server": "redis",
+		}
+		_, err := msg.peer.Send(respWriteMap(spec))
+		if err != nil {
+			return fmt.Errorf("peer send error: %s", err)
+		}
+	}
+	return nil
+}
+
+func (s *Server) handleConn(conn net.Conn) {
+	peer := NewPeer(conn, s.msgCh, s.delPeerCh)
+	s.addPeerCh <- peer
+	slog.Info("new peer connected", "remote Addr :", conn.RemoteAddr().String())
+	if err := peer.readLoop(); err != nil {
+		log.Error("Peer read error", err)
+	}
+}
+
+func main() {
+	server := NewServer(Config{})
+	log.Fatal(server.Start().Error())
+	fmt.Println("hi!")
+}

main_test.go

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+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"testing"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+func TestOfficialRedisClient(t *testing.T) {
+	listenAddr := ":5001"
+	server := NewServer(Config{
+		ListenAddress: listenAddr,
+	})
+	go func() {
+		log.Fatal(server.Start())
+	}()
+	time.Sleep(time.Millisecond * 400)
+
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     fmt.Sprintf("localhost%s", ":5001"),
+		Password: "",
+		DB:       0,
+	})
+
+	testCases := map[string]string{
+		"hello":   "world",
+		"creater": "god",
+		"god":     "me",
+		"me":      "shatwik",
+	}
+	for key, val := range testCases {
+		if err := rdb.Set(context.Background(), key, val, 0).Err(); err != nil {
+			t.Fatal(err)
+		}
+		newVal, err := rdb.Get(context.Background(), key).Result()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if newVal != val {
+			t.Fatalf("expected %s but got %s", val, newVal)
+		}
+	}
+}