feat(wecom-aibot): enhance stream task management with StreamClosedAt and improved cleanup logic

pkg/channels/wecom/aibot.go

@@ -46,6 +46,7 @@ type streamTask struct {
 	CreatedTime    time.Time
 	Deadline       time.Time // ~30s, we close the stream here and switch to response_url
 	StreamClosed   bool      // stream returned finish:true; waiting for agent to reply via response_url
+	StreamClosedAt time.Time // set when StreamClosed becomes true; used for accelerated cleanup
 	Finished       bool      // fully done
 	mu             sync.Mutex
 	answerCh       chan string        // receives agent reply from Send()
@@ -781,6 +782,7 @@ func (c *WeComAIBotChannel) getStreamResponse(task *streamTask, timestamp, nonce
 		// Only mark stream as closed; keep in chatTasks for Send() to find.
 		task.mu.Lock()
 		task.StreamClosed = true
+		task.StreamClosedAt = time.Now()
 		task.mu.Unlock()
 		// Remove from streamTasks (no more stream polls expected).
 		c.taskMu.Lock()
@@ -1117,13 +1119,24 @@ func (c *WeComAIBotChannel) cleanupLoop() {
 	}
 }
 
-// cleanupOldTasks removes tasks that have been alive longer than 1 hour
+// cleanupOldTasks removes tasks that have exceeded their expected lifetime:
-// (response_url validity window), which is the absolute maximum lifetime of any task.
+//   - Active tasks (in streamTasks): cleaned up after 1 hour (response_url validity window).
+//   - StreamClosed tasks (in chatTasks only): cleaned up after streamClosedGracePeriod.
+//     These tasks are waiting for the agent to call Send() via response_url. If the agent
+//     crashes or times out without calling Send(), we must not let them accumulate indefinitely.
+//     The grace period is generous enough to cover typical LLM latency but far shorter than 1 hour,
+//     preventing chatTasks from filling up when many requests time out in quick succession.
+const (
+	streamClosedGracePeriod = 10 * time.Minute // max wait for agent after stream closes
+	taskMaxLifetime         = 1 * time.Hour    // absolute max (≈ response_url validity)
+)
+
 func (c *WeComAIBotChannel) cleanupOldTasks() {
 	c.taskMu.Lock()
 	defer c.taskMu.Unlock()
 
-	cutoff := time.Now().Add(-1 * time.Hour)
+	now := time.Now()
+	cutoff := now.Add(-taskMaxLifetime)
 	for id, task := range c.streamTasks {
 		if task.CreatedTime.Before(cutoff) {
 			delete(c.streamTasks, id)
@@ -1143,12 +1156,19 @@ func (c *WeComAIBotChannel) cleanupOldTasks() {
 			})
 		}
 	}
-	// Also clean up StreamClosed tasks from chatTasks that are older than 1 hour.
+	// Clean up StreamClosed tasks from chatTasks.
-	// These were removed from streamTasks earlier but kept alive for response_url delivery.
+	// Two expiry conditions are checked:
+	//  1. Absolute expiry: task was created more than taskMaxLifetime ago.
+	//  2. Grace expiry: stream closed more than streamClosedGracePeriod ago
+	//     (agent had enough time to reply; it is not coming back).
 	for chatID, queue := range c.chatTasks {
 		filtered := queue[:0]
 		for _, t := range queue {
-			if !t.Finished && t.CreatedTime.After(cutoff) {
+			absoluteExpired := t.CreatedTime.Before(cutoff)
+			graceExpired := t.StreamClosed &&
+				!t.StreamClosedAt.IsZero() &&
+				t.StreamClosedAt.Before(now.Add(-streamClosedGracePeriod))
+			if !t.Finished && !absoluteExpired && !graceExpired {
 				filtered = append(filtered, t)
 			} else if !t.Finished {
 				t.cancel() // cancel any lingering agent goroutine