在WCF服务返回DataTable时需要帮助解决错误：OutOfMemoryException

Question

我有一个WCF服务正在尝试返回DataTable。服务方法使用SqlDataReader，然后使用DataTable.Load()将数据输入它打算返回的DataTable。

问题：当服务方法返回一个大表时（我稍后会定义它），我在调试输出中得到这些异常（它们不会削弱服务）：

SMDiagnostics.dll中出现类型为“System.OutOfMemoryException”的第一次机会异常

SMDiagnostics.dll中发生了'System.InsufficientMemoryException'类型的第一次机会异常

“大”的定义：我测试中返回的记录集包含286760条记录，当该表导出为文本时，大小约为800MB。我知道这都是相对的，所以这可能都是毫无意义的。大多数情况下，我指出这一点，因为对于我来说，抛出内存异常似乎相当小，特别是考虑到我正在测试的开发机器有8GB内存。同样，它是相对的，也许是无关紧要的，但我正在努力提供足够的信息。

这是我的连接代码：

NetTcpBinding netBind = new NetTcpBinding();
netBind.Security.Mode = SecurityMode.Transport;
netBind.Security.Transport.ClientCredentialType = TcpClientCredentialType.Windows;
netBind.MaxReceivedMessageSize = Int32.MaxValue;
netBind.MaxBufferSize = Int32.MaxValue;
netBind.MaxBufferPoolSize = 0;
netBind.MaxConnections = 300;
netBind.ListenBacklog = 300;
netBind.ReaderQuotas = XmlDictionaryReaderQuotas.Max;
netBind.PortSharingEnabled = true;
netBind.OpenTimeout = new TimeSpan(0, 0, RegistryValues.DatabaseTimeout);
netBind.CloseTimeout = new TimeSpan(0, 0, RegistryValues.DatabaseTimeout);
netBind.ReceiveTimeout = new TimeSpan(0, 5, 0);
netBind.SendTimeout = new TimeSpan(0, 5, 0);
netBind.ReliableSession.InactivityTimeout = new TimeSpan(long.MaxValue);
netBind.TransferMode = TransferMode.Buffered;
uriBuilder = new UriBuilder("net.tcp", connServer, (connPort == -1 ? RegistryValues.ServerPort : connPort), "Data");
epAddress = new EndpointAddress(uriBuilder.Uri);
ChannelFactory<IData> iChannel = new ChannelFactory<IData>(netBind, epAddress);
iChannel.Credentials.Windows.AllowedImpersonationLevel = TokenImpersonationLevel.Identification;
IData svcCon = iChannel.CreateChannel();
((IClientChannel)svcCon).OperationTimeout = new TimeSpan(long.MaxValue);

请注意，我们正在使用Buffered传输模式。我正在考虑使用Streamed替代方案，但这会对代码的其余部分进行彻底的结构更改...如果在当前模型中有解决方案，那么我不想做什么。我回想一下这样一个事实：我不认为我在推动过多的数据。

此连接是作为创建Sql类对象（我的类）的一部分而建立的。当调用iChannel方法时，svcCon和Sql.Dispose()对象被一起处理（因为我们用Sql块创建这些using对象）。

这是我的Sql.Dispose()块应该触发的using方法（如果它很重要）：

public void Dispose()
{
    if (this != null && this.connection.State == ConnectionState.Open)
        ClearConnectionPool();

    try
    {
        if (iChannel.State != CommunicationState.Faulted)
            iChannel.Close();
    }
    catch { iChannel.Abort(); }

    try
    {
        if (((IClientChannel)svcCon).State != CommunicationState.Faulted)
            ((IClientChannel)svcCon).Close();
    }
    catch { ((IClientChannel)svcCon).Abort(); }
}

总之，我正在创建一个WCF通信通道，它反过来创建一个SqlConnection。使用它，我们启动SQL调用。然后尽快处理所有这些。我们不会挂起这些连接超过执行所需数据库操作所需的时间。并且在极少数情况下，这些东西不是在using区块内创建的，这意味着我很确定我们正在正确清理。当然，除非有人看到我的Dispose()方法有问题。

任何建议表示赞赏。我可以按要求提供更多代码。

一些附加信息：这是我在调试客户端时收到的堆栈跟踪，并进入服务器代码以查看当它尝试返回DataTable时会发生什么：

A first chance exception of type 'System.OutOfMemoryException' occurred in SMDiagnostics.dll
A first chance exception of type 'System.InsufficientMemoryException' occurred in SMDiagnostics.dll
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
Step into: Stepping over method without symbols 'System.ServiceModel.Dispatcher.MessageRpc.Process'
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
Step into: Stepping over method without symbols 'System.ServiceModel.Dispatcher.ChannelHandler.DispatchAndReleasePump'
A first chance exception of type 'System.IO.IOException' occurred in System.dll
Step into: Stepping over method without symbols 'System.ServiceModel.Dispatcher.ChannelHandler.HandleRequest'
Step into: Stepping over method without symbols 'System.ServiceModel.Dispatcher.ChannelHandler.AsyncMessagePump'
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in System.ServiceModel.dll
Step into: Stepping over method without symbols 'System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame'
Step into: Stepping over method without symbols 'System.ServiceModel.AsyncResult.Complete'
A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in mscorlib.dll
Step into: Stepping over method without symbols 'System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame'
Step into: Stepping over method without symbols 'System.ServiceModel.AsyncResult.Complete'
A first chance exception of type 'System.ServiceModel.CommunicationObjectFaultedException' occurred in System.ServiceModel.dll
Step into: Stepping over method without symbols 'System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame'
Step into: Stepping over method without symbols 'System.Net.LazyAsyncResult.Complete'
A first chance exception of type 'System.ServiceModel.CommunicationObjectFaultedException' occurred in mscorlib.dll
Step into: Stepping over method without symbols 'System.Net.Security.NegotiateStream.ProcessFrameBody'
A first chance exception of type 'System.ServiceModel.CommunicationObjectFaultedException' occurred in System.ServiceModel.dll
Step into: Stepping over method without symbols 'System.Net.Security.NegotiateStream.ReadCallback'
Step into: Stepping over method without symbols 'System.Net.FixedSizeReader.CheckCompletionBeforeNextRead'
Step into: Stepping over method without symbols 'System.Net.FixedSizeReader.ReadCallback'
Step into: Stepping over method without symbols 'System.ServiceModel.AsyncResult.Complete'
Step into: Stepping over method without symbols 'System.ServiceModel.Diagnostics.Utility.IOCompletionThunk.UnhandledExceptionFrame'
Step into: Stepping over method without symbols 'System.Threading._IOCompletionCallback.PerformIOCompletionCallback'

Answer 1

请验证behavior行为部分下的dataContractSerializer属性，并将值增加到更大的值。

还要检查readerQuotas部分以及maxBufferPoolSize，maxBufferSize和maxReceivedMessageSize属性。

Answer 2

将您的transfermode更改为流式传输web配置和其他配置...除非您在IIS中部署它，否则无法更改Web配置传输模式