修改后端获取gpu数据逻辑

Change-Id: I4069a1bf5a01155aed82f655fb374445e3158442
diff --git a/Merge/back_rhj/app/utils/gpuwriter.py b/Merge/back_rhj/app/utils/gpuwriter.py
index 1e521f3..6c589d6 100644
--- a/Merge/back_rhj/app/utils/gpuwriter.py
+++ b/Merge/back_rhj/app/utils/gpuwriter.py
@@ -46,18 +46,18 @@
         session = self.Session()
         try:
             records = session.query(GpuUsage)\
-                           .order_by(GpuUsage.timestamp.desc())\
+                           .order_by(GpuUsage.created_at.desc())\
                            .limit(limit)\
                            .all()
             
             result = []
             for record in records:
                 result.append({
-                    'id': record.id,
+                    'id': record.gpu_id,  # 使用gpu_id作为id
                     'gpu_id': record.gpu_id,
                     'gpu_usage': record.gpu_usage,
                     'gpu_memory_usage': record.gpu_memory_usage,
-                    'timestamp': record.timestamp.isoformat() if record.timestamp else None
+                    'timestamp': record.created_at.isoformat() if record.created_at else None
                 })
             
             return result