我正在进行定期更新表扫描
Using connect1 As New MySqlConnection(ConnectLocalhost.serverString)
connect1.Open()
Dim cmd = New MySqlCommand("set net_write_timeout=99999; set net_read_timeout=99999", connect1) ' // Setting tiimeout on mysqlServer
cmd.ExecuteNonQuery()
Dim BusinessReader = selectSomeQuery("Select * from tablebusiness limit 800,10000000", connect1)
Do While BusinessReader.Read 'random exception here
有时我收到此错误
MySql.Data.MySqlClient.MySqlException was unhandled
ErrorCode=-2147467259
Message=Fatal error encountered during data read.
Number=0
Source=MySql.Data
StackTrace:
at MySql.Data.MySqlClient.MySqlDataReader.Read()
at dreamhost.Business.InsertLocalhost() in \\work\c\business\fromwork\currentprojects\program\library\vb.net\badger.vb:line 1849
at dreamhost.Business.surFoursquare() in \\work\c\business\fromwork\currentprojects\program\library\vb.net\badger.vb:line 1939
at dreamhost.traverseweb._Lambda$__92() in \\work\c\business\fromwork\currentprojects\program\library\vb.net\traverseweb.vb:line 77
at dreamhost.buttonClicking.startAndStopClickingButton(Object sender, Action SomeSub) in \\work\c\business\fromwork\currentprojects\program\library\vb.net\buttonclicking.vb:line 45
at dreamhost.traverseweb.foursquare_Click(Object sender, EventArgs e) in \\work\c\business\fromwork\currentprojects\program\library\vb.net\traverseweb.vb:line 77
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(ApplicationContext context)
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
at dreamhost.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException: MySql.Data.MySqlClient.MySqlException
ErrorCode=-2147467259
Message=Reading from the stream has failed.
Number=0
Source=MySql.Data
StackTrace:
at MySql.Data.MySqlClient.MySqlStream.LoadPacket()
at MySql.Data.MySqlClient.MySqlStream.ReadPacket()
at MySql.Data.MySqlClient.NativeDriver.FetchDataRow(Int32 statementId, Int32 columns)
at MySql.Data.MySqlClient.Driver.FetchDataRow(Int32 statementId, Int32 columns)
at MySql.Data.MySqlClient.ResultSet.GetNextRow()
at MySql.Data.MySqlClient.ResultSet.NextRow(CommandBehavior behavior)
at MySql.Data.MySqlClient.MySqlDataReader.Read()
InnerException: System.IO.IOException
Message=Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
Source=MySql.Data
StackTrace:
at MyNetworkStream.HandleOrRethrowException(Exception e)
at MyNetworkStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at MySql.Data.MySqlClient.TimedStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at System.IO.BufferedStream.Read(Byte[] array, Int32 offset, Int32 count)
at MySql.Data.MySqlClient.MySqlStream.ReadFully(Stream stream, Byte[] buffer, Int32 offset, Int32 count)
at MySql.Data.MySqlClient.MySqlStream.LoadPacket()
InnerException: System.Net.Sockets.SocketException
ErrorCode=10054
Message=An existing connection was forcibly closed by the remote host
NativeErrorCode=10054
Source=System
StackTrace:
at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
InnerException:
我想要的只是当这件事发生时程序才“继续”。但这似乎是不可能的。所以我想我需要一种方法来确保不会发生这个错误。它随机发生了大约800个条目。
在我看来，远程主机强行关闭连接。在这种情况下，我只想继续前进并重新开始。
答案 0 :(得分：1)
连接断开可能有很多原因（服务器负载，网络问题等）。您的程序崩溃表明您的数据库代码不受try语句的保护。如果您这样做：
try
Using connect1 As New MySqlConnection(ConnectLocalhost.serverString)
connect1.Open()
Dim cmd = New MySqlCommand("set net_write_timeout=99999; _
set net_read_timeout=99999", connect1)
cmd.ExecuteNonQuery()
Dim BusinessReader = selectSomeQuery("Select *...", connect1)
Do While BusinessReader.Read
'random exception here'
'...more code'
Loop
End Using
Catch ex As Exception
' code breaks here on exception - recover from this point '
End Try
我不会进行关于异常处理的长篇论文，但如果你看一下，那里有很多资源。你如何处理它将取决于你的具体情况 - 是否记录异常，记录上次成功的操作，是否尝试从你所在的位置恢复或是否尝试重新做一遍，通知用户等等。