我的WCF之旅(13):创建基于MSMQ的Responsive Service

一、One-way MEP V.S. Responsible Service

我们知道MSMQ天生就具有异步的特性,它只能以One-way的MEP(Message Exchange Pattern)进行通信。Client和Service之间采用One-way MEP的话就意味着Client调用Service之后立即返回,它无法获得Service的执行结果,也无法捕捉Service运行的Exception。下图简单表述了基于MSMQ的WCF Service中Client和Service的交互。


但是在有些场景 中,这是无法容忍的。再拿我在上一篇文章的Order Delivery的例子来说。Client向Service提交了Order,却无法确认该Order是否被Service正确处理,这显然是不能接受的。我们今天就来讨论一下,如何创建一个Responsive Service来解决这个问题:Client不再是对Service的执行情况一无所知,它可以获知Order是否被Service正确处理了。

二、 Solution

虽然我们的目的很简单:当Client向Service递交了Order之后,能以某种方式获知Order的执行结果;对于Service端来说,在正确把Order从Message Queue中获取出来、并正确处理之后,能够向Order的递交者发送一个Acknowledge Message。为了简单起见,这个Acknowledge Message包含两组信息:

  • Order No.: 被处理的Order的一个能够为一标志它的ID。
  • Exception: 如果处理失败的Exception,如果成功处理为null。

要在WCF中实现这样的目的,对于Request/Reply MEP来说是简单而直接的:Client向Service递交Order,并等待Service的Response,Service在处理接收到Order之后直接将处理结果 返回给Client就可以了。但是我们说过MSMQ天生就是异步的,我们只有采取一种间接的方式实现“曲线救国”。

我们的解决方案是:在每个Client Domain也创建一个基于MSMQ的本地的WCF Service,用于接收来自Order处理端发送的Acknowledge Message。对于处理Order 的Service来说,在正确处理Order之后,想对应的Client发送Acknowledge Message。下图简单演示整个过程:


三、Implementation

了解了上面的Solution之后,我们来看看该Solution在真正实现过程中有什么样的困难。对于处理Order的Service来说,在向Client端发送Acknowledge Message的时候,它必须要知道该Order对应的Client的Response Service的MSMQ的Address以及其他和Operation相关的Context信息(在这里我们不需要,不过考虑到扩展性,我们把包括了address的Context的信息 封装到一个了Class中,在这里叫做:OrderResponseContext)。而这些Context却不能在Configuration中进行配置,因为他可以同时面临着很多个Client:比如每个Client用于接收Response 的Message Queue的address都不一样。所以这个OrderResponseContext必须通过对应的Client来提供。基于此,我们具有两面两种解决方式:

方式一、修改Service Contract,把OrderResponseContext当成是Operation的一个参数

这是我们最容易想到的,比如我们原来的Operation这样定义:

namespace Artech.ResponsiveQueuedService.Contract
{
    [ServiceContract]
    [ServiceKnownType(
typeof(Order))]
    
public interface IOrderProcessor
    
{
        [OperationContract(IsOneWay 
= true)]
        
void Submit(Order order);
    }

}

现在变成:

namespace Artech.ResponsiveQueuedService.Contract
{
    [ServiceContract]
    [ServiceKnownType(
typeof(Order))]
    
public interface IOrderProcessor
    
{
        [OperationContract(IsOneWay 
= true)]
        
void Submit(Order order, OrderResponseContext responseContext);
    }

}

虽然这种方式看起来不错,但是却不值得推荐。在一般情况下,我们的Contract需要是很稳定的,一经确定就不能轻易更改,因为Contract是被交互的多方共同支持的,牵一发动全身;此外,从Service Contract代表的是Service的一个Interface,他是对业务逻辑的抽象、和具体实现无关,而对于我们的例子来说,我们仅仅是定义一个递交Order的Operation,从业务逻辑来看,OrderResponseContext和抽象的业务逻辑毫无关系。基于此,我们需要寻求一种和Service Contract无关的解决方式:

方式二、将OrderResponseContext放到Soap Message 的Header中

其实我们要解决的问题很简单,就是要把OrderResponseContext的信息置于Soap Message中发送到Service。而我们知道,Soap的Header具有极强的可伸缩性,原则上,我们可以把任何控制信息置于Header中。基于WCF的编程模式很容易地帮助我们实现对Soap Header的插入和获取:

我们可以通过下面的方式获得当前Operation Context的Incoming Message Headers和Outgoing Message Headers

OperationContext.Current.IncomingMessageHeaders
OperationContext.Current.OutgoingMessageHeaders

如果我们要把一个OrderResponseContext 对象插入到当前Operation Context的Outgoing Message Headers中,我们可以通过下面的代码来实现:

OrderResponseContext context = new OrderResponseContext();
MessageHeader
<OrderResponseContext> header = new MessageHeader<OrderResponseContext>( context);
OperationContext.Current.OutgoingMessageHeaders.Add(header.GetUntypedHeader(
"name""namespace"));

相应的,我们可以通过下面的代码从Outgoing Message Headers OrderResponseContext的数据获取的内容:

OrderResponseContext context = OperationContext.Current.IncomingMessageHeaders.GetHeader<OrderResponseContext>("name""namespace"));

四、Sample

我们照例给出一个完整的Sample,下面是整个Solution的结构:


除了一贯使用的4层结构(Contract-Service-Hosting-Client),还为ResponseService增加了下面两层:

  • Localservice: 作为Client Domain的ResponseService。
  • LocalHosting:Host Localservice。

1.Contract:  Artech.ResponsiveQueuedService.Contract

Service Contract: Artech.ResponsiveQueuedService.Contract. IOrderProcessor

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;

namespace Artech.ResponsiveQueuedService.Contract
{
    [ServiceContract]
    [ServiceKnownType(
typeof(Order))]
    
public interface IOrderProcessor
    
{
        [OperationContract(IsOneWay 
= true)]
        
void Submit(Order order);
    }

}

Service Contract: Artech.ResponsiveQueuedService.Contract.IOrderRessponse

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;

namespace Artech.ResponsiveQueuedService.Contract
{
    [ServiceContract]
    
public interface  IOrderRessponse
    
{
        [OperationContract(IsOneWay 
=true)]
        
void SubmitOrderResponse(Guid orderNo,FaultException exception);
    }

}

接收来自Order processing端的Response:Order No.和Exception。

Data Contract: Artech.ResponsiveQueuedService.Contract.Order

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.Serialization;

namespace Artech.ResponsiveQueuedService.Contract
{
    [DataContract]
    
public class Order
    
{
        
Private Fields

        
Constructors

        
Public Properties

        
Public Methods
    }

}

对Order的封装。

Data Contract:Artech.ResponsiveQueuedService.Contract. OrderResponseContext

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.Serialization;
using System.ServiceModel;

namespace Artech.ResponsiveQueuedService.Contract
{    
    [DataContract]
    
public class OrderResponseContext
    
{
        
private Uri _responseAddress;

        [DataMember]
        
public Uri ResponseAddress
        
{
            
get return _responseAddress; }
            
set { _responseAddress = value; }
        }


        
public static OrderResponseContext Current
        
{
            
get
            
{
                
if (OperationContext.Current == null)
                
{
                    
return null;
                }


                
return OperationContext.Current.IncomingMessageHeaders.GetHeader<OrderResponseContext>("OrderResponseContext""Artech.ResponsiveQueuedService.Contract");
            }

            
set
            
{
                MessageHeader
<OrderResponseContext> header = new MessageHeader<OrderResponseContext>(value);
                OperationContext.Current.OutgoingMessageHeaders.Add(header.GetUntypedHeader(
"OrderResponseContext""Artech.ResponsiveQueuedService.Contract"));
            }

        }

    }

}

ResponseAddress代表Host在Client Domain的Response Service的Address。同过Current把OrderResponseContext插入到Outgoing Message Headers中、以及从Ingoing Message Headers取出OrderResponseContext对象。

2.Order Processing Service:Artech.ResponsiveQueuedService.Service

using System;
using System.Collections.Generic;
using System.Text;
using Artech.ResponsiveQueuedService.Contract;
using System.ServiceModel;
using System.Net.Security;

namespace Artech.ResponsiveQueuedService.Service
{
    
public class OrderProcessorService:IOrderProcessor
    
{
        
private void ProcessOrder(Order order)
        
{

            
if (order.OrderDate < DateTime.Today)
            
{
                
throw new Exception();
            }

        }


        
IOrderProcessor Members
    }

}

在这里我们模拟了这样的场景:先通过Order Date判断Order是否过期,如果过期创建一个FaultException,否则正确处理该Order,然后通过OrderResponseContext.Current从Incoming Message Header中获取封装在OrderResponseContext对象中的Response Address,创建Binding并调用Response Service.

3. Order Processing Service Hosting: Artech.ResponsiveQueuedService.Hosting

Configuration

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  
<appSettings>
    
<add key="msmqPath" value=".\private$\orderprocessor"/>
  
</appSettings>
  
<system.serviceModel>
    
<bindings>
      
<netMsmqBinding>
        
<binding name="MsmqBinding" exactlyOnce="false" useActiveDirectory="false">
          
<security>
            
<transport msmqAuthenticationMode="None" msmqProtectionLevel="None" />
          
</security>
        
</binding>
      
</netMsmqBinding>
    
</bindings>
    
<services>
      
<service name="Artech.ResponsiveQueuedService.Service.OrderProcessorService">
        
<endpoint address="net.msmq://localhost/private/orderprocessor" binding="netMsmqBinding"
            bindingConfiguration
="MsmqBinding" contract="Artech.ResponsiveQueuedService.Contract.IOrderProcessor" />
      
</service>
    
</services>
  
</system.serviceModel>
</configuration>

Program

using System;
using System.Collections.Generic;
using System.Text;
using Artech.ResponsiveQueuedService.Service;
using System.ServiceModel;
using System.Configuration;
using System.Messaging;

namespace Artech.ResponsiveQueuedService.Hosting
{
    
class Program
    
{
        
static void Main(string[] args)
        
{
            
string path = ConfigurationManager.AppSettings["msmqPath"];
            
if (!MessageQueue.Exists(path))
            
{
                MessageQueue.Create(path);
            }


            
using (ServiceHost host = new ServiceHost(typeof(OrderProcessorService)))
            
{
                host.Opened 
+= delegate
                
{
                    Console.WriteLine(
"The Order Processor service has begun to listen");
                }
;

                host.Open();

                Console.Read();
            }

        }

    }

}

4. Response Service: Artech.ResponsiveQueuedService.LocalService.OrderRessponseService

using System;
using System.Collections.Generic;
using System.Text;
using Artech.ResponsiveQueuedService.Contract;
using System.ServiceModel;

namespace Artech.ResponsiveQueuedService.LocalService
{
    
public class OrderRessponseService : IOrderRessponse
    
{
        
IOrderRessponse Members
    }

}


5. Response Service Hosting: Artech.ResponsiveQueuedService.LocalhHosting

Configuration

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  
<appSettings>
    
<add key="msmqPath" value=".\private$\orderresponse"/>
  
</appSettings>
  
<system.serviceModel>
    
<bindings>
      
<netMsmqBinding>
        
<binding name="msmqBinding" exactlyOnce="false">
          
<security>
            
<transport msmqAuthenticationMode="None" msmqProtectionLevel="None" />
          
</security>
        
</binding>
      
</netMsmqBinding>
    
</bindings>
    
<services>
      
<service name="Artech.ResponsiveQueuedService.LocalService.OrderRessponseService">
        
<endpoint address="net.msmq://localhost/private/orderresponse" binding="netMsmqBinding"
            bindingConfiguration
="msmqBinding" contract="Artech.ResponsiveQueuedService.Contract.IOrderRessponse" />
      
</service>
    
</services>
  
</system.serviceModel>
</configuration>

Program

using System;
using System.Collections.Generic;
using System.Text;
using Artech.ResponsiveQueuedService.LocalService;
using System.Configuration;
using System.ServiceModel;
using System.Messaging;

namespace Artech.ResponsiveQueuedService.LocalhHosting
{
    
class Program
    
{
        
static void Main(string[] args)
        
{
            
string path = ConfigurationManager.AppSettings["msmqPath"];
            
if (!MessageQueue.Exists(path))
            
{
                MessageQueue.Create(path);
            }


            
using (ServiceHost host = new ServiceHost(typeof(OrderRessponseService)))
            
{
                host.Opened 
+= delegate
                
{
                    Console.WriteLine(
"The Order Response service has begun to listen");
                }
;

                host.Open();

                Console.Read();
            }

        }

    }

}

6. Client: Artech.ResponsiveQueuedService.Client

Configuration:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  
<appSettings>
    
<add key="msmqPath" value="net.msmq://localhost/private/orderresponse"/>
  
</appSettings>
  
<system.serviceModel>
    
<bindings>
      
<netMsmqBinding>
        
<binding name="MsmqBinding" exactlyOnce="false" useActiveDirectory="false">
          
<security>
            
<transport msmqAuthenticationMode="None" msmqProtectionLevel="None" />
          
</security>
        
</binding>
      
</netMsmqBinding>
    
</bindings>
    
<client>
      
<endpoint address="net.msmq://localhost/private/orderprocessor" binding="netMsmqBinding"
            bindingConfiguration
="MsmqBinding" contract="Artech.ResponsiveQueuedService.Contract.IOrderProcessor" name="defaultEndpoint" />
    
</client>
  
</system.serviceModel>
</configuration>

Program:

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.ServiceModel;
using Artech.ResponsiveQueuedService.Contract;
using System.Messaging;

namespace Artech.ResponsiveQueuedService.Clinet
{
    
class Program
    
{
        
static void Main(string[] args)
        
{
            Order order1 
= new Order(Guid.NewGuid(), DateTime.Today.AddDays(5), Guid.NewGuid(), "Supplier A");
            Order order2 
= new Order(Guid.NewGuid(), DateTime.Today.AddDays(-5), Guid.NewGuid(), "Supplier A");

            
string path = ConfigurationManager.AppSettings["msmqPath"];
            Uri address 
= new Uri(path);
            OrderResponseContext context 
= new OrderResponseContext();
            context.ResponseAddress 
= address;

            ChannelFactory
<IOrderProcessor> channelFactory = new ChannelFactory<IOrderProcessor>("defaultEndpoint");
            IOrderProcessor orderProcessor 
= channelFactory.CreateChannel();

            
using (OperationContextScope contextScope = new OperationContextScope(orderProcessor as IContextChannel))
            
{
                Console.WriteLine(
"Submit the order of order No.: {0}", order1.OrderNo);
                OrderResponseContext.Current 
= context;
                orderProcessor.Submit(order1);
            }


            
using (OperationContextScope contextScope = new OperationContextScope(orderProcessor as IContextChannel))
            
{
                Console.WriteLine(
"Submit the order of order No.: {0}", order2.OrderNo);
                OrderResponseContext.Current 
= context;
                orderProcessor.Submit(order2);
            }


            Console.Read();
        }

    }

}

我创建了两个Order对象, 其中一个已经过期。从Configuration中取出Response Address并购建一个OrderResponseContext,然后分两次将这两个Order向Order Processing Service递交。在调用Order Processing Order的Operation Context Scope中,通过OrderResponseContext.Current将OrderResponseContext对象插入Outcoming Message Header中。

我们现在运行一下整个程序,看看最终的输出结果:

Client:


Order Processing:


Order Response:


Reference:
Build a Queued WCF Response Service

WCF相关内容:
[原创]我的WCF之旅(1):创建一个简单的WCF程序
[原创]我的WCF之旅(2):Endpoint Overview
[原创]我的WCF之旅(3):在WCF中实现双向通信(Bi-directional Communication)
[原创]我的WCF之旅(4):WCF中的序列化(Serialization)- Part I
[原创]我的WCF之旅(4):WCF中的序列化(Serialization)- Part II
[原创]我的WCF之旅(5):Service Contract中的重载(Overloading)
[原创]我的WCF之旅(6):在Winform Application中调用Duplex Service出现TimeoutException的原因和解决方案
[原创]我的WCF之旅(7):面向服务架构(SOA)和面向对象编程(OOP)的结合——如何实现Service Contract的继承
[原创]我的WCF之旅(8):WCF中的Session和Instancing Management
[原创]我的WCF之旅(9):如何在WCF中使用tcpTrace来进行Soap Trace
[原创]我的WCF之旅(10): 如何在WCF进行Exception Handling
[原创]我的WCF之旅(11):再谈WCF的双向通讯-基于Http的双向通讯 V.S. 基于TCP的双向通讯

[原创]我的WCF之旅(12):使用MSMQ进行Reliable Messaging
[原创]我的WCF之旅(13):创建基于MSMQ的Responsive Service

posted @ 2007-07-01 16:06 Artech 阅读(...) 评论(...) 编辑 收藏