求知

用HttpWebRequest去Call别的Service，怎样才能提高并发量和性能?

因为建立一个TCP连接要三次握手，.Net 默认使用 keepAlive = Ture 去重用连接，避免重建Connection的开销，还有一些设置我们也要注意:

DefaultConnectionLimit

  description: Maximum number of concurrent connections to a single ServicePoint

  default: 2

  suggested: 12*N, N is the number of CPU
  
MaxServicePointIdleTime

  description: Maximum idle time of ServicePoint object, but in the testing, i found it's the maximum idle time of the TCP connection in connection pool, http://msdn.microsoft.com/en-US/library/system.net.servicepointmanager.maxservicepointidletime.aspx

  default: 100000ms

  suggested: 3600000ms, 1 hour, set a long time to keep the connection, avoid creating connection every call.
  

ConnectionLeaseTimeout

  description: A Int32 that specifies the number of milliseconds that an active ServicePoint connection remains open. The default is -1, which allows an active ServicePoint connection to stay connected indefinitely. Set this property to 0 to force ServicePoint connections to close after servicing a request.

  default: -1

  suggested: -1

MaxServicePoints

  description: Maximum number of concurrent ServicePoint objects

  default: 0, means no limited.

  suggested: 0

TcpKeepAliveTimeInMillis 

  description: after idle more than n ms, a keepalive tcp package will be send by client, to verify the connection is still available or not.

  default: 7200000ms, 2 hours

  suggested: 10000ms, 10s, recyle the bad connections in time, reduce the burden of the server.

TcpKeepAliveIntervalInMillis

  description: between when successive keep-alive packets are sent if no acknowledgement is received, until received a response, if 5 packages were sent, and no any response, this connection will be drop, http://msdn.microsoft.com/en-us/library/system.net.servicepointmanager.settcpkeepalive.aspx

  default: 1000ms

  suggested: 1000ms

ServicePointManager.Expect100Continue = false;
ServicePointManager.UseNagleAlgorithm = false;

MaxWorkerThreads    100
MaxIOThreads     100
MaxConnection     12*N
MinfreeThreads     88*N
MinLocalRequestfreeThreads   88*N
MinWorkerThreds     50  (MaxWorkerThreads/2)

参考资料:

http://support.microsoft.com/kb/821268
http://social.msdn.microsoft.com/Forums/en-US/windowsazuredata/thread/d84ba34b-b0e0-4961-a167-bbe7618beb83
http://blogs.msdn.com/b/jpsanders/archive/2009/05/20/understanding-maxservicepointidletime-and-defaultconnectionlimit.aspx
http://blogs.msdn.com/b/adarshk/archive/2005/01/02/345411.aspx

既然有了xs:integer,为什么还要有xs:int?

经过一番查找，真相浮出：

xs:integer 无小数的任意长度的整数, 如果要表示money, 或者会很大的数字，或者需要方便以后的扩展，这个会更合适

xs:int        无小数的32位长度的整数

以下实现的目标是:

localhost:6677/Services/China

localhost:6677/Services/USA

localhost:6677/Services/...

以上所有调用都走到Service方法中，因为支持的国家是未知的，不能写成方法，并且请求的schame已经确定，不能再做修改，所以就有了以下实现:

定义Service Interface，包含一个方法Service.

代码 比较简单，只是重写OperationSelector属性，返回所有请求到方法"Service"(大小区分)

public class RouteBehaviorExtension : BehaviorExtensionElement
{
public override Type BehaviorType
{
get { return typeof(RouteBehavior); }
}
protected override object CreateBehavior()
{
return new RouteBehavior();
}
}

public class RouteBehavior : Attribute, IEndpointBehavior
{
private _operationSelector;

public RouteBehavior()
{
_operationSelector = new Router();
}

public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
{
}

public void ApplyClientBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.ClientRuntime clientRuntime)
{
}

public void ApplyDispatchBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.EndpointDispatcher endpointDispatcher)
{
endpointDispatcher.DispatchRuntime.OperationSelector = _operationSelector;
}

public void Validate(ServiceEndpoint endpoint)
{
}
}

internal class Router : IDispatchOperationSelector
{
public string SelectOperation(ref Message message)
{
return "Service";
}
}

配置:

添加RouteBehaviorExtension,并加该Behavior到EndpointBehaviors(注意Behavior的顺序,从上而下依次执行的)

取第二个参数:

OperationContext.Current.IncomingMessageHeaders.To.Segments[2]

在windows services开发中，碰到一个奇怪的问题：

有时可以启动，有时启动超时，经过漫长的分析（有引用其它的组件），发现问题出在Performance counter的创建上，sometimes, the code will be hang here.

Link:

http://www.pcreview.co.uk/forums/strange-performance-counter-performance-problem-windows-service-application-t2781664.html

解决方法：

将Performance Counter操作放到OnStart方法中，不要放到ServiceBase.Run之前就可以.

.Net 的Bug也真是不少啊