阶段2（上）：后端专题 Go/Gin/PostgreSQL/MySQL/Redis/MQ/gRPC 的课程、企业场景、面试题和可运行示例

topics/backend/redis/examples/stock-lock-ratelimit/ratelimit.go

@@ -0,0 +1,42 @@
+package stocklock
+
+import (
+	"context"
+	"fmt"
+	"sync/atomic"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// 滑动窗口：ZSET 里存每次请求的时间戳（毫秒），先删掉窗口外的，再数窗口内的
+var slidingScript = redis.NewScript(`
+local key, now, window, limit, member = KEYS[1], tonumber(ARGV[1]), tonumber(ARGV[2]), tonumber(ARGV[3]), ARGV[4]
+redis.call("ZREMRANGEBYSCORE", key, 0, now - window)
+if redis.call("ZCARD", key) >= limit then
+  return 0
+end
+redis.call("ZADD", key, now, member)
+redis.call("PEXPIRE", key, window)
+return 1`)
+
+type SlidingWindow struct {
+	rdb    *redis.Client
+	limit  int
+	window time.Duration
+	seq    func() string // 生成唯一成员，避免同一毫秒的请求互相覆盖
+}
+
+func NewSlidingWindow(rdb *redis.Client, limit int, window time.Duration) *SlidingWindow {
+	var n atomic.Uint64 // 并发安全的序号；多实例部署时成员里再加上实例标识或用 UUID
+	return &SlidingWindow{rdb: rdb, limit: limit, window: window, seq: func() string {
+		return fmt.Sprintf("%d-%d", time.Now().UnixNano(), n.Add(1))
+	}}
+}
+
+// Allow 判断 key（如 "rl:user:42"）在当前窗口内是否还能通过
+func (s *SlidingWindow) Allow(ctx context.Context, key string, now time.Time) (bool, error) {
+	n, err := slidingScript.Run(ctx, s.rdb, []string{key},
+		now.UnixMilli(), s.window.Milliseconds(), s.limit, s.seq()).Int()
+	return n == 1, err
+}