refactor(background): 使用线程替代BackgroundTasks执行异步任务

重构异步任务执行机制，将FastAPI的BackgroundTasks替换为独立的线程执行。修改了async_meeting_service，添加run_task_in_background方法创建守护线程，并在会议总结生成和音频上传后的自动总结监控中调用。这消除了对API层BackgroundTasks参数的依赖，使服务层更独立且便于测试。

backend/app/api/endpoints/meetings.py

@@ -1105,7 +1105,7 @@ def generate_meeting_summary_async(meeting_id: int, request: GenerateSummaryRequ
             })
         # 传递 prompt_id 和 model_code 参数给服务层
         task_id = async_meeting_service.start_summary_generation(meeting_id, request.user_prompt, request.prompt_id, request.model_code)
-        background_tasks.add_task(async_meeting_service._process_task, task_id)
+        async_meeting_service.run_task_in_background(async_meeting_service._process_task, task_id)
         return create_api_response(code="200", message="Summary generation task has been accepted.", data={
             "task_id": task_id, "status": "pending", "meeting_id": meeting_id
         })

backend/app/services/async_meeting_service.py

@@ -6,6 +6,7 @@ import uuid
 import time
 import os
 import re
+import threading
 from datetime import datetime
 from typing import Optional, Dict, Any, List
 from pathlib import Path
@@ -26,9 +27,14 @@ class AsyncMeetingService:
         self.redis_client = redis.Redis(**REDIS_CONFIG)
         self.llm_service = LLMService()  # 复用现有的同步LLM服务
 
+    def run_task_in_background(self, target, *args):
+        thread = threading.Thread(target=target, args=args, daemon=True)
+        thread.start()
+        return thread
+
     def start_summary_generation(self, meeting_id: int, user_prompt: str = "", prompt_id: Optional[int] = None, model_code: Optional[str] = None) -> str:
         """
-        创建异步总结任务，任务的执行将由外部（如API层的BackgroundTasks）触发。
+        创建异步总结任务。
 
         Args:
             meeting_id: 会议ID
@@ -70,7 +76,7 @@ class AsyncMeetingService:
 
     def _process_task(self, task_id: str):
         """
-        处理单个异步任务的函数，设计为由BackgroundTasks调用。
+        处理单个异步任务的函数。
         """
         print(f"Background task started for meeting summary task: {task_id}")
         try:
@@ -137,7 +143,7 @@ class AsyncMeetingService:
     ):
         """
         监控转录任务，完成后自动生成总结
-        此方法设计为由BackgroundTasks调用，在后台运行
+        此方法在独立后台线程中运行
 
         Args:
             meeting_id: 会议ID
@@ -194,8 +200,7 @@ class AsyncMeetingService:
                                 )
                                 print(f"[Monitor] Summary task {summary_task_id} started for meeting {meeting_id}")
 
-                                # 在后台执行总结任务
-                                self._process_task(summary_task_id)
+                                self.run_task_in_background(self._process_task, summary_task_id)
 
                             except Exception as e:
                                 error_msg = f"Failed to start summary generation: {e}"

backend/app/services/audio_service.py

@@ -141,16 +141,16 @@ def handle_audio_upload(
             transcription_task_id = transcription_service.start_transcription(meeting_id, file_path)
             print(f"Transcription task {transcription_task_id} started for meeting {meeting_id}")
 
-            # 5. 如果启用自动总结且提供了 background_tasks，添加监控任务
-            if auto_summarize and transcription_task_id and background_tasks:
-                background_tasks.add_task(
+            # 5. 如果启用自动总结，启动后台监控任务
+            if auto_summarize and transcription_task_id:
+                async_meeting_service.run_task_in_background(
                     async_meeting_service.monitor_and_auto_summarize,
                     meeting_id,
                     transcription_task_id,
                     prompt_id,
                     model_code
                 )
-                print(f"[audio_service] Auto-summarize enabled, monitor task added for meeting {meeting_id}, prompt_id: {prompt_id}, model_code: {model_code}")
+                print(f"[audio_service] Auto-summarize enabled, monitor task started for meeting {meeting_id}, prompt_id: {prompt_id}, model_code: {model_code}")
 
         except Exception as e:
             print(f"Failed to start transcription: {e}")