ASP.NET Core EF - 上传文件时出错

Question

我正在开发一个使用 ASP.NET Core、EF Core 的系统，我的数据库是 MySQL，我使用 MySQL Connector.NET 作为适配器。

我的系统中有一个地方供用户选择文件并上传。 我的问题是，当我尝试上传超过 1000 KB 的文件时，出现以下错误：

已建立的连接被主机中的软件中止

该文件的数据库字段是LONGBLOB类型，模态类型是byte[] 。 该错误直接在dbcontext.SaveChanges()方法中抛出，这就是为什么很难调试和确定原因的原因。

我将在下面发布完整的堆栈跟踪：

   at MySqlConnector.Protocol.Serialization.SocketByteHandler.WriteBytesAsync(ArraySegment`1 data, IOBehavior ioBehavior) in C:\projects\mysqlconnector\src\MySqlConnector\Protocol\Serialization\SocketByteHandler.cs:line 90
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MySqlConnector.Utilities.ValueTaskExtensions.<ContinueWith>d__0`2.MoveNext() in C:\projects\mysqlconnector\src\MySqlConnector\Utilities\ValueTaskExtensions.cs:line 8
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MySqlConnector.Core.ServerSession.TryAsyncContinuation(Task`1 task) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ServerSession.cs:line 1225
   at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MySqlConnector.Core.TextCommandExecutor.<ExecuteReaderAsync>d__1.MoveNext() in C:\projects\mysqlconnector\src\MySqlConnector\Core\TextCommandExecutor.cs:line 36
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MySql.Data.MySqlClient.MySqlCommand.<ExecuteNonQueryAsync>d__60.MoveNext() in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlCommand.cs:line 261
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery() in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlCommand.cs:line 62
   at MySql.Data.MySqlClient.MySqlTransaction.Dispose(Boolean disposing) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlTransaction.cs:line 81
   at Microsoft.EntityFrameworkCore.Storage.RelationalTransaction.Dispose()
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(DbContext _, ValueTuple`2 parameters)
   at Pomelo.EntityFrameworkCore.MySql.Storage.Internal.MySqlExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(IEnumerable`1 commandBatches, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(IReadOnlyList`1 entriesToSave)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Zoneberry.Repository.ZONContext.SaveChanges() in path\ZONContext.cs:line 157
   at path.Commit() in project\UnitOfWork.cs:line 419
   at project.Controller.UploadFileFor(List`1 files, Int32 leadId, Int32 totalCount) in project\Controllers\LeadController.cs:line 220
   at lambda_method(Closure , Object , Object[] )
   at Microsoft.Extensions.Internal.ObjectMethodExecutor.Execute(Object target, Object[] parameters)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeActionMethodAsync>d__12.MoveNext()

当我上传小于 1MB 的文件时，系统工作正常。

Answer 1

可能您在MySql方面有限制。 尝试在MySql服务器上执行此命令：

SHOW VARIABLES LIKE 'max_allowed_packet';

如果结果接近1 million字节，那么您需要通过运行以下命令来增加该值（例如几乎 2 MB）：

SET GLOBAL max_allowed_packet=2000000;

但此设置将在服务器重新启动后重置。 要永久更改设置，您需要在[mysqld]部分下的my.ini或~/.my.cnf更改它：

max_allowed_packet=2M