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

Question

我有一个 WCF 服务正在运行，它试图返回 DataTable。服务方法使用SqlDataReader，然后使用DataTable.Load() 将该数据获取到它打算返回的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（它们确实不是削弱服务）：

在 SMDiagnostics.dll 中发生了“System.OutOfMemoryException”类型的第一次机会异常

在 SMDiagnostics.dll 中出现“System.InsufficientMemoryException”类型的第一次机会异常

“Large”的定义：我的测试返回的记录集包含286760条记录，当这个表导出为文本时，它的大小大约是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，我指出这一点是因为在我看来，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 内存的事实。同样，这都是相对的，也许是无关紧要的，但我试图提供足够的信息。

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，我们使用的是Buffered 传输模式。我正在考虑Streamed 替代方案，但这将对代码的其余部分进行彻底的结构更改……如果当前模型中有解决方案，我不想这样做。我再次指出，我只是不认为我在推送过多的数据。

此连接是作为Sql 类对象（我的类）创建的一部分而建立的。 iChannel 和 svcCon 对象在调用 Sql.Dispose() 方法时被一起处理（因为我们使用 using 块创建这些 Sql 对象）。

这是我的using 块应该触发的Sql.Dispose() 方法（以防万一）：

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，该通道又创建一个 SqlConnection。使用它，我们触发 SQL 调用。所有这些都会尽快处理掉。我们不会在这些连接上挂起超过执行所需数据库操作所需的时间。还有非常罕见的情况，这些东西不是在using 块中创建的，这意味着我很确定我们正在正确清理。当然，除非有人发现我的 Dispose() 方法有问题。

感谢任何建议。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并单步进入服务器代码时收到的堆栈跟踪，以观察当它尝试返回 @987654340 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

将您的传输模式更改为流式传输网络配置和其他配置... 除非您将其部署在 IIS 中，否则您无法更改 Web 配置传输模式