Transfer large messages in WCF - Part 1

Pre Requisites

                Readers must have knowledge in creating basic WCF service and must know how to host and consume a service.

Default max received message size in WCF is 65kb, so when we try to send messages more than 65kb, WCF will give errors. Let us create a basic service which will pass a message more than 65 k and see what happens and figure out what are different ways to handle large messages in WCF.

1. Create a service contract that takes byte[] as input as shown below:

[ServiceContract] public interface IService1 {    [OperationContract]    void UploadFile(byte[] data); }

    
2.  Implement Iservice1 which will write byte[] into file on a server

public class Service1 : IService1 {   public void UploadFile(byte[] data)   {     Random x = new Random();     string fileName = string.Format(@"Test{0}.mp3", x.Next().ToString());             File.WriteAllBytes(fileName,data);   } }

3.  The app.config file for the hosting environment is given below:

<system.serviceModel>     <services>       <service name="FileUpload.Service1">         <host>           <baseAddresses>             <add baseAddress = "http://vital-pc:7998/FileUpload/Service1/" />           </baseAddresses>         </host>         <endpoint address ="" binding="basicHttpBinding" contract="FileUpload.IService1">         </endpoint>         <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>       </service>     </services>     <behaviors>       <serviceBehaviors>         <behavior>           <serviceMetadata httpGetEnabled="True"/>           <serviceDebug includeExceptionDetailInFaults="False" />         </behavior>       </serviceBehaviors>     </behaviors>   </system.serviceModel>

4.  Now consume this service in a client. Here we will convert a mp3 file into byte[] which is more than 65 kb and send it to service

FileStream fs = new FileStream(@"Test.mp3", FileMode.Open, FileAccess.Read); byte[] data = new byte[fs.Length];   fs.Read(data,0,System.Convert.ToInt32(fs.Length));   ServiceReference1.Service1Client proxy = new ServiceReference1.Service1Client(); proxy.UploadFile(data);

5.  Make sure you enable the trace at service so that we can see the detailed error messages

6.  Make sure service is running and execute the client .

7.  As expected we got an error (look into trace at service) which says “The maximum message size quota for incoming messages (65536) has been exceeded. To increase the quota, use the MaxReceivedMessageSize property on the appropriate binding element.”. So we have to increase MaxReceivedMessageSize as below

<bindings>  <basicHttpBinding>   <binding name="largeObjects" maxReceivedMessageSize="6500000" ></binding>  </basicHttpBinding> </bindings>

    
a.  You can set maxReceivedMessageSize upto 2GB (2147483647, i.e. Int32.MaxValue)

b.  Interesting point over here is when we get above error do we need to increase maxReceivedMessageSize at service or client?

                 i. If we change maxReceivedMessageSize value at a service, it refers to the maximum message size that the service can receive. We need to change this value when we get large data from client

                 ii. If we change maxReceivedMessageSize value at client, it refers to the maximum message size that the client can receive. We need to change this value when we get large data from service

Since the data we are sending from the client exceeds the maximum permissible limit on the service, it is clear that for our problem we need to increase the maximum message size at service

             c.  maxReceivedMessageSize is a local behavior setting  i.e if you do some changes to maxReceivedMessageSize value at service and try to refresh service reference at client this value will not be updated, it will be always default value(65536) at client. This make sense with explanation in point b that explains different meanings for this property at client and service .

We have seen how we can transfer large data in WCF. But when we are working with large data, the first things that come into our mind  are memory and processing overhead. These things can be addressed using

Message Transmission Optimization Mechanism (MTOM)

Streaming

Let us go into details of each one with examples in Part 2 and Part 3.

Hope this helps
Vital

Implement Publisher Subscriber model in WCF

Download Source Code here

Pre Requisites

                Readers must be having knowledge in creating basic WCF service and must know how to consume it.

Here I tried to illustrate how we can achieve publisher subscriber model in WCF

To explain this Let me take one common real world scenario Stock Exchange, Where investors register to Service and service will notify to all investors when stock got changed

My intention here is to make you understand how we can achieve publisher subscriber model in WCF not to solve above mentioned problem.

Duplex Operations

To achieve this we will use duplex operations.

Duplex operations allows client to send a request to service which contains information about endpoint at client which will be used to get communication from service

Service must be hosted with a binding that supports duplex communication. Following are the bindings that support duplex communication

·         Wsdualhttpbinding

·         Tcpbinding

·         Namedpipes

Let us start implementing duplex operations so that you will get more clarity on what I’m saying

To achieve our stock exchange scenario we need Service, Investor and Stock Exchange

Service

RegisterInvestorService: This service allows investors to register or de register to get updated when the stock price got changed

StockExchangeService: This service will be used by stock exchange to update price. When price got updated it will inform all the investors registered to the service

Investor

This consumes RegisterInvestorService and Registeritself to service and will get notifications from  RegisterInvestorService

Stock Exchange

                This consumes StockExchangeService and updates the price.

Service Implementation

Create Service Contracts as mentioned below

[ServiceContract(CallbackContract = typeof(IRegisterInvestorServiceCallback))]     public interface IRegisterInvestorService     {         [OperationContract(IsOneWay = true)]         void RegisterInvestor(Guid investorid);         [OperationContract(IsOneWay = true)]         void DeRegisterInvestor(Guid investorid);     }     public interface IRegisterInvestorServiceCallback     {         [OperationContract(IsOneWay = true)]         void StockUpdated(double price);     }     [ServiceContract()]     public interface IStockExcahangeService     {         [OperationContract(IsOneWay = true)]         void UpdateStock(double price);     }

Let me Explain Purpose of each interface

IRegisterInvestorService: This will be useful for the investors who want to register or de register to get updated when the stock price got changed

INotifyInvestors: This will be the contract which will used to notify the clients when stock got updated. Client will implement this and take action when stock price got changed

IStockExcahangeService: This will be useful for stock exchange to inform service when price got changed. Then this service will notify all its clients

When you observe above code you will find 2 peculiar things

1.       CallbackContract:  says who is the callback contract for this service contract. So that this service contract will notify all clients who registered with service using this call back contract

2.       interface INotifyInvestors contains some Operation Contract but not having ServiceContract: This is called callback contract which will be implemented by the client (investors) and called by the service

Create below class in Service where it will store registered Investors information. This contains information about how we register and de register a investor and update all client who registerd with it when price got updated

public static class MicrosoftStock     {         private static Dictionary<Guid, INotifyInvestors> registeredInvestors =         new Dictionary<Guid, INotifyInvestors>();         public static void UpdateStock(double price)         {             foreach (KeyValuePair<Guid, INotifyInvestors> obj in registeredInvestors)             {                 obj.Value.StockUpdated(price);             }         }         public static void RegisterInvestor(Guid investorid,         INotifyInvestors notifyInvestor)         {             registeredInvestors.Add(investorid, notifyInvestor);         }         public static void DegisterInvestor(Guid investorid)         {             registeredInvestors.Remove(investorid);         }     }

In above code you might have observed one thing that i kept MicrosoftStock as static so that all investors can share the information.

Implement IRegisterInvestorService

public class RegisterInvestorService : IRegisterInvestorService     {         public void RegisterInvestor(Guid investorid)         {             INotifyInvestors callback =    OperationContext.Current.GetCallbackChannel<INotifyInvestors>();             MicrosoftStock.RegisterInvestor(investorid, callback);         }         public void DeRegisterInvestor(Guid id)         {             MicrosoftStock.DegisterInvestor(id);         }     }

Implement IStockExcahangeService

public class StockExchangeService : IStockExcahangeService     {         public void UpdateStock(double price)         {             MicrosoftStock.UpdateStock(price);         }     }

Below is the config for the service which is common for any other WCF service except we are using wsdualHttpBinding which supports duplex communication as I mentioned earlier.

<system.serviceModel>     <services>       <service behaviorConfiguration="serviceBehavior" name="Stock.RegisterInvestorService">         <endpoint address="wsDual" binding="wsDualHttpBinding" contract="Stock.IRegisterInvestorService" />       </service>       <service behaviorConfiguration="serviceBehavior" name="Stock.StockExchangeService">         <endpoint address="basicHTTP" binding="basicHttpBinding" contract="Stock.IStockExcahangeService" />       </service>     </services>     <behaviors>       <serviceBehaviors>         <behavior name="serviceBehavior">           <serviceMetadata httpGetEnabled="true" />           <serviceDebug includeExceptionDetailInFaults="false" />         </behavior>         <behavior name="">           <serviceMetadata httpGetEnabled="true" />           <serviceDebug includeExceptionDetailInFaults="false" />         </behavior>       </serviceBehaviors>     </behaviors>     <serviceHostingEnvironment multipleSiteBindingsEnabled="true" />   </system.serviceModel>

Now the service is ready.. I leave it to you how you host the service

Investor Implementation

This is simple console application which consumes RegisterInvestorService(hope you are aware of how to consume WCF service)

First Step in Investor is implementing  IRegisterInvestorServiceCallback, where we will get notifications. In implementation investor can take some action when price got changed

[CallbackBehavior(UseSynchronizationContext = false)] class StockExcahageUpdates : IRegisterInvestorServiceCallback {     public void StockUpdated(double price)     {       Console.WriteLine("Stock Updted: " + price.ToString());     } }

Second step is register investor to the service and wait for notifications.

In this step you will observe one thing ServiceClient is accepting InstanceContext as parameter which is not required in traditional Request/Reply Service.

Using Instance context we will let service know to whom it needs to be notified when price got changed or we can say it as client’s end point to which service needs to be communicated

[CallbackBehavior(UseSynchronizationContext = false)] class Program {     static void Main(string[] args)     {       InstanceContext callbackInstance = new InstanceContext(new StockExcahageUpdates());       InvestorService.RegisterInvestorServiceClient proxy = new InvestorService.RegisterInvestorServiceClient(callbackInstance);       proxy.RegisterInvestor(Guid.NewGuid());       Console.WriteLine("Observing the Stock...");       Console.ReadKey();     } }

Stock Exchange Implementation

This is simple Console Application which consumes StockExchangeService and update price to the service.

static void Main(string[] args)         {             StockExchangeService.StockExcahangeServiceClient proxy = new StockExchangeService.StockExcahangeServiceClient();             proxy.UpdateStock(1000);                   }

Testing

1.       Service must be in running state

2.       Create couple investors by executing Invetors.exe couple of time. Then both investors will be registered to service and waiting for price change notification from service

3.       Run Stock exchange which will update the price in service, then you can observe  above 2 investors will get notified with updated price

Hope this helps

Vital.