feat(subscription): 有界队列执行维护并改进鉴权解析

backend/internal/service/subscription_maintenance_queue.go

@@ -0,0 +1,75 @@
+package service
+
+import (
+	"fmt"
+	"log"
+	"sync"
+)
+
+// SubscriptionMaintenanceQueue 提供“有界队列 + 固定 worker”的后台执行器。
+// 用于从请求热路径触发维护动作时，避免无限 goroutine 膨胀。
+type SubscriptionMaintenanceQueue struct {
+	queue chan func()
+	wg    sync.WaitGroup
+	stop  sync.Once
+}
+
+func NewSubscriptionMaintenanceQueue(workerCount, queueSize int) *SubscriptionMaintenanceQueue {
+	if workerCount <= 0 {
+		workerCount = 1
+	}
+	if queueSize <= 0 {
+		queueSize = 1
+	}
+
+	q := &SubscriptionMaintenanceQueue{
+		queue: make(chan func(), queueSize),
+	}
+
+	q.wg.Add(workerCount)
+	for i := 0; i < workerCount; i++ {
+		go func(workerID int) {
+			defer q.wg.Done()
+			for fn := range q.queue {
+				func() {
+					defer func() {
+						if r := recover(); r != nil {
+							log.Printf("SubscriptionMaintenance worker panic: %v", r)
+						}
+					}()
+					fn()
+				}()
+			}
+		}(i)
+	}
+
+	return q
+}
+
+// TryEnqueue 尝试将任务入队。
+// 当队列已满时返回 error（调用方应该选择跳过并记录告警/限频日志）。
+func (q *SubscriptionMaintenanceQueue) TryEnqueue(task func()) error {
+	if q == nil {
+		return fmt.Errorf("maintenance queue is nil")
+	}
+	if task == nil {
+		return fmt.Errorf("maintenance task is nil")
+	}
+
+	select {
+	case q.queue <- task:
+		return nil
+	default:
+		return fmt.Errorf("maintenance queue full")
+	}
+}
+
+func (q *SubscriptionMaintenanceQueue) Stop() {
+	if q == nil {
+		return
+	}
+	q.stop.Do(func() {
+		close(q.queue)
+		q.wg.Wait()
+	})
+}