feat: use Redis Lua script for atomic concurrency counting (fixes #9)

internals/Service/redisDB.go

@@ -2,70 +2,68 @@ package Service
 
 import (
 	"context"
+	_ "embed"
 	"log"
-	"sync"
 
 	config "Load-Pulse/Config"
 
 	redis "github.com/redis/go-redis/v9"
 )
 
-var client *redis.Client;
+var client *redis.Client
 
-var ctx = context.Background();
+var ctx = context.Background()
 
-var mu sync.Mutex;
+//go:embed scripts/increment.lua
+var kaimScript string
 
-func IncrementRequestCount() {
-	mu.Lock()
-	defer mu.Unlock()
+// Lua script to atomically check and increment
+var incrementScript = redis.NewScript(kaimScript)
+
+func TryIncrementRequestCount(limit int) (bool, error) {
 	cfg := config.GetConfig()
-	err := client.Incr(ctx, cfg.RedisKey).Err()
+	result, err := incrementScript.Run(ctx, client, []string{cfg.RedisKey}, limit).Int64()
 	if err != nil {
-		log.Fatal("[ERR]: Error in Incrementing Concurrent Request Count from Redis !!", err);
+		return false, err
 	}
+	// If result is -1, limit reached. Otherwise (new count), success.
+	return result != -1, nil
 }
 
 func DecrementRequestCount() {
-	mu.Lock()
-    defer mu.Unlock()
-	cfg := config.GetConfig();
-	err := client.Decr(ctx, cfg.RedisKey).Err();
+	cfg := config.GetConfig()
+	err := client.Decr(ctx, cfg.RedisKey).Err()
 	if err != nil {
-		log.Fatal("[ERR]: Error in Decrementing Concurrent Request Count from Redis !!", err);
+		log.Fatal("[ERR]: Error in Decrementing Concurrent Request Count from Redis !!", err)
 	}
 }
 
 func GetRequestCount() int64 {
-	mu.Lock()
-    defer mu.Unlock()
-	cfg := config.GetConfig();
-	currentCount, err := client.Get(ctx, cfg.RedisKey).Int64();
+	cfg := config.GetConfig()
+	currentCount, err := client.Get(ctx, cfg.RedisKey).Int64()
 	if err != nil {
-		log.Fatal("[ERR]: Error in Fetching Concurrent Requests Count from Redis !!", err);
-		return 0;
+		log.Fatal("[ERR]: Error in Fetching Concurrent Requests Count from Redis !!", err)
+		return 0
 	}
-	return currentCount;
+	return currentCount
 }
 
 func ResetRequestCount() {
-	mu.Lock()
-    defer mu.Unlock()
-	cfg := config.GetConfig();
-	err := client.Set(ctx, cfg.RedisKey, 0, 0).Err();
+	cfg := config.GetConfig()
+	err := client.Set(ctx, cfg.RedisKey, 0, 0).Err()
 	if err != nil {
-		log.Fatal("[ERR]: Error in Resetting Concurrent Requests Count in Redis !!", err);
+		log.Fatal("[ERR]: Error in Resetting Concurrent Requests Count in Redis !!", err)
 	}
-	LogServer("[LOG]: Concurrency Count Reset Done\n");
+	LogServer("[LOG]: Concurrency Count Reset Done\n")
 }
 
 func InitRedisClient() {
-	cfg := config.GetConfig();
+	cfg := config.GetConfig()
 	client = redis.NewClient(&redis.Options{
 		Addr:     cfg.RedisURL,
 		Password: cfg.RedisPassword,
 		DB:       0,
 		Protocol: 2,
 	})
-	LogServer("[LOG]: Redis Client Initialized\n");
-}
+	LogServer("[LOG]: Redis Client Initialized\n")
+}

internals/Service/scripts/increment.lua

@@ -0,0 +1,8 @@
+local key = KEYS[1]
+local limit = tonumber(ARGV[1])
+local current = tonumber(redis.call("GET", key) or "0")
+if current < limit then
+	return redis.call("INCR", key)
+else
+	return -1
+end