在 WCF 中读取流并将其写入 Microsoft SQL Server 数据库表时设置缓冲区大小

Question

当在WCF中接收Stream并将其写入数据库表时，将数据写入数据库表时使用的缓冲区大小是多少，如何更改？

我使用的是.NET Framework 4.6和Microsoft SQL Server。

服务器

[ServiceContract(Name = "IUploadFileService")]
public interface IUploadFileService
{
[OperationContract]
void UploadFile(UploadFileMessage uploadFileMessage);
}
[MessageContract]
public class UploadFileMessage
{
[MessageBodyMember]
public Stream FileContents { get; set; }
}
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Multiple)]
public class UploadFileService : IUploadFileService
{
public void UploadFile(UploadFileMessage uploadFileMessage)
{
using (MyDbContext context = new MyDbContext())
{
DbConnection conn = context.Database.Connection;
ConnectionState initialState = conn.State;
try
{
if (initialState != ConnectionState.Open)
{
conn.Open();
}
using (DbCommand cmd = conn.CreateCommand())
{
// the FileContents field is a `varbinary(max)` data type
cmd.CommandText = "INSERT INTO [Files] (FileContents) VALUES (@FileContents)";
cmd.CommandTimeout = 0;
DbParameter parameter = cmd.CreateParameter();
parameter.ParameterName = "@FileContents";
parameter.DbType = DbType.Binary;
parameter.Size = -1;
parameter.Value = uploadFileMessage.FileContents; // what buffer size is used to read this Stream and write it to the database?
cmd.Parameters.Add(parameter);
cmd.ExecuteNonQuery();
}
}
finally
{
if (initialState != ConnectionState.Open)
{
conn.Close();
}
}
}
}
}

服务器配置

<?xml version="1.0" encoding="utf-8" ?>
<bindings>
<netTcpBinding>
<binding name="NetTcpBinding_IFileUploadService" closeTimeout="00:01:00" receiveTimeout="24.20:31:23.6470000" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647" transferMode="Streamed">
<readerQuotas maxArrayLength="32505856" maxStringContentLength="32505856" />
<security mode="None">
<transport clientCredentialType="None" protectionLevel="None" />
<message clientCredentialType="None" />
</security>
</binding>
</netTcpBinding>
</bindings>

客户

private static void UploadFile()
{
EndpointAddress endpointAddress = new EndpointAddress("net.tcp://localhost:4502/FileUploadService");
NetTcpBinding binding = new NetTcpBinding(SecurityMode.None)
{
TransferMode = TransferMode.Streamed,
MaxBufferSize = int.MaxValue,
MaxReceivedMessageSize = int.MaxValue,
SendTimeout = TimeSpan.MaxValue
};
FileUploadServiceClient fileUploadServiceClient = new FileUploadServiceClient(binding, endpointAddress);
using (FileStream fileStream = new FileStream(@"c:test.bin", FileMode.Open)) // read buffer size is 4096 bytes by default
{
fileUploadServiceClient.UploadFile(fileStream);
}
}

是这些吗？

• 在用于在客户端上打开文件的FileStream中指定的默认值
• 客户端上的NetTcpBinding.MaxBufferSize
• WCF 服务器配置中的maxBufferSize
• DbParameter.Size，这是int.MaxValue，因为它设置为-1和可以在varbinary(max)数据库字段中输入的最大字节数
• Network Packet SizeSQL Server 数据库中的配置设置
• 网络上MTU值
• 以上所有值的最小值

谢谢。

Answer 1

Windows Communication Foundation (WCF( 传输支持两种传输消息的模式：

1.缓冲传输将整个消息保存在内存缓冲区中，直到传输完成。必须先完全传递缓冲消息，然后接收方才能读取它。

2.流传输将消息公开为流。接收方在消息完全传递之前开始处理消息。

我看到您使用第二种传输模式，流式处理，它可以通过消除对大内存缓冲区的需求来提高服务的可伸缩性。

为了防止拒绝服务攻击，WCF 公开了 MaxReceivedMessageSize 属性来限制传入消息的大小属性，因此它还限制处理消息时访问的最大内存量。单位以字节为单位设置，默认值为 65,536 字节。

有关流式消息传输的更多信息，请参阅以下链接：

https://learn.microsoft.com/en-us/dotnet/framework/wcf/feature-details/streaming-message-transfer