并发优化

backend/app/services/summary_service.py

@@ -180,62 +180,76 @@ async def generate_unified_summaries():
     """Scheduled task: refresh summaries and topic tags for hot unified events."""
     print(f"[{utcnow()}] Start unified summary generation task...")
 
+    # 先提取需要处理的事件 ID，尽早释放 session，不长期占用 db session
     with SessionLocal() as db:
         recent_threshold = utcnow() - timedelta(days=3)
-
         events = db.query(UnifiedEvent).filter(
             UnifiedEvent.hot_score >= HOT_SCORE_THRESHOLD,
             UnifiedEvent.hot_score > UnifiedEvent.last_summarized_trends_count,
             UnifiedEvent.created_at >= recent_threshold,
         ).all()
-
+        
         if not events:
             print("No events require summary update in this round.")
             return
+            
+        # 复制出需要的信息，脱离 session
+        event_ids = [e.id for e in events]
+        event_hot_scores = {e.id: e.hot_score for e in events}
 
-        for event in events:
+    # 外层循环：针对每个 event_id 开启一个极短生命周期的 session 获取依赖数据
+    for event_id in event_ids:
+        platform_dict: dict[str, set[str]] = {}
+        with SessionLocal() as db:
             trends = (
                 db.query(TrendingEvent, InfoSource.source_name)
                 .join(InfoSource, TrendingEvent.source_id == InfoSource.id)
-                .filter(TrendingEvent.unified_event_id == event.id)
+                .filter(TrendingEvent.unified_event_id == event_id)
                 .all()
             )
 
             if not trends:
                 continue
 
-            platform_dict: dict[str, set[str]] = {}
             for trend_record, source_name in trends:
                 platform_dict.setdefault(source_name, set()).add(trend_record.current_headline)
 
-            prompt_lines = [
-                f"[{platform}] {', '.join(sorted(headlines))}"
-                for platform, headlines in platform_dict.items()
-            ]
-            platform_data_text = "\n".join(prompt_lines)
+        prompt_lines = [
+            f"[{platform}] {', '.join(sorted(headlines))}"
+            for platform, headlines in platform_dict.items()
+        ]
+        platform_data_text = "\n".join(prompt_lines)
 
-            try:
-                llm_result = await call_llm_for_summary(platform_data_text)
+        try:
+            # 大模型调用可能耗时几十秒，绝对不能把它包裹在数据库事务里
+            llm_result = await call_llm_for_summary(platform_data_text)
+            
+            # 调用完成后，再开启一个新的极短事务，进行数据回写
+            with SessionLocal() as write_db:
+                event = write_db.query(UnifiedEvent).get(event_id)
+                if not event:
+                    continue
 
                 if "unified_title" in llm_result and llm_result["unified_title"]:
                     event.unified_title = llm_result["unified_title"]
                 if "ai_comprehensive_summary" in llm_result and llm_result["ai_comprehensive_summary"]:
                     event.ai_comprehensive_summary = llm_result["ai_comprehensive_summary"]
 
-                if event.hot_score >= TOPIC_TAG_MIN_HOT_SCORE:
+                hot_score = event_hot_scores.get(event_id, event.hot_score)
+                if hot_score >= TOPIC_TAG_MIN_HOT_SCORE:
                     topic_candidates = parse_topic_keywords(llm_result)
                     normalized_topics = normalize_topic_keywords(topic_candidates)
                     if normalized_topics:
-                        replace_event_topics(db, event.id, normalized_topics)
+                        replace_event_topics(write_db, event.id, normalized_topics)
 
                 event.last_summarized_trends_count = event.hot_score
+                write_db.commit()
+                
                 print(
                     f"Updated event {event.id} summary"
                     f" (hot_score={event.hot_score})."
                 )
 
-            except Exception as exc:
-                print(f"Event {event.id} summary generation failed: {exc}")
-                continue
-
-        db.commit()
+        except Exception as exc:
+            print(f"Event {event_id} summary generation failed: {exc}")
+            continue