fix(limiter): recover redis script after flush (#6486)

- Retry the Lua rate limiter with EVAL when Redis returns NOSCRIPT
- Add regression coverage for Redis script cache flush recovery

common/limiter/limiter.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	_ "embed"
 	"fmt"
+	"strings"
 	"sync"
 
 	"github.com/QuantumNous/new-api/common"
@@ -63,6 +64,20 @@ func (rl *RedisLimiter) Allow(ctx context.Context, key string, opts ...Option) (
 	).Int()
 
 	if err != nil {
+		if strings.HasPrefix(err.Error(), "NOSCRIPT ") {
+			result, err := rl.client.Eval(
+				ctx,
+				rateLimitScript,
+				[]string{key},
+				config.Requested,
+				config.Rate,
+				config.Capacity,
+			).Int()
+			if err != nil {
+				return false, fmt.Errorf("rate limit failed: %w", err)
+			}
+			return result == 1, nil
+		}
 		return false, fmt.Errorf("rate limit failed: %w", err)
 	}
 	return result == 1, nil

common/limiter/limiter_test.go

@@ -0,0 +1,80 @@
+package limiter
+
+import (
+	"context"
+	"sync"
+	"testing"
+
+	"github.com/alicebob/miniredis/v2"
+	"github.com/go-redis/redis/v8"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func useLimiterMiniRedis(t *testing.T) (*miniredis.Miniredis, *redis.Client) {
+	t.Helper()
+
+	previousInstance := instance
+
+	redisServer := miniredis.RunT(t)
+	redisClient := redis.NewClient(&redis.Options{Addr: redisServer.Addr()})
+	require.NoError(t, redisClient.Ping(context.Background()).Err())
+
+	instance = nil
+	once = sync.Once{}
+
+	t.Cleanup(func() {
+		_ = redisClient.Close()
+		instance = previousInstance
+		once = sync.Once{}
+		if previousInstance != nil {
+			once.Do(func() {})
+		}
+	})
+
+	return redisServer, redisClient
+}
+
+func TestAllowFallsBackToEvalAfterScriptFlush(t *testing.T) {
+	ctx := context.Background()
+	_, redisClient := useLimiterMiniRedis(t)
+
+	redisLimiter := New(ctx, redisClient)
+
+	allowed, err := redisLimiter.Allow(
+		ctx,
+		"rateLimit:test-before-flush",
+		WithCapacity(60),
+		WithRate(60),
+		WithRequested(60),
+	)
+	require.NoError(t, err)
+	assert.True(t, allowed)
+
+	exists, err := redisClient.ScriptExists(ctx, redisLimiter.limitScriptSHA).Result()
+	require.NoError(t, err)
+	require.Len(t, exists, 1)
+	assert.True(t, exists[0])
+
+	require.NoError(t, redisClient.ScriptFlush(ctx).Err())
+
+	exists, err = redisClient.ScriptExists(ctx, redisLimiter.limitScriptSHA).Result()
+	require.NoError(t, err)
+	require.Len(t, exists, 1)
+	assert.False(t, exists[0])
+
+	allowed, err = redisLimiter.Allow(
+		ctx,
+		"rateLimit:test-after-flush",
+		WithCapacity(60),
+		WithRate(60),
+		WithRequested(60),
+	)
+	require.NoError(t, err)
+	assert.True(t, allowed)
+
+	exists, err = redisClient.ScriptExists(ctx, redisLimiter.limitScriptSHA).Result()
+	require.NoError(t, err)
+	require.Len(t, exists, 1)
+	assert.True(t, exists[0])
+}