Remember to download the samples from the GitHub repository.

Running

When using Visual Studio 2017 the NuGet packages should be restored automatically. If you find that they do not or if you are using an older version of Visual Studio please execute the following in a Visual Studio command prompt:

cd {extraction-folder}\Shuttle.Esb.Samples\Shuttle.PublishSubscribe
nuget restore

Once you have opened the Shuttle.PublishSubscribe.sln solution in Visual Studio set the following projects as startup projects:

  • Shuttle.PublishSubscribe.Client
  • Shuttle.PublishSubscribe.Server
  • Shuttle.PublishSubscribe.Subscriber

You will also need to create and configure a Sql Server database for this sample and remember to update the App.config connectionString settings to point to your database. Please reference the Database section below.

Implementation

Events are interesting things that happen in our system that other systems may be interested in. There may be 0..N number of subscribers for an event. Typically there should be at least one subscriber for an event else it isn’t really carrying its own weight.

In this guide we’ll create the following projects:

  • a Console Application called Shuttle.PublishSubscribe.Client
  • a Console Application called Shuttle.PublishSubscribe.Server
  • a Console Application called Shuttle.PublishSubscribe.Subscriber that will represent a subscriber of our event message
  • a Class Library called Shuttle.PublishSubscribe.Messages that will contain all our message classes

Messages

Create a new class library called Shuttle.PublishSubscribe.Messages with a solution called Shuttle.PublishSubscribe

Note: remember to change the Solution name.

RegisterMemberCommand

Rename the Class1 default file to RegisterMemberCommand and add a UserName property.

namespace Shuttle.PublishSubscribe.Messages
{
    public class RegisterMemberCommand
    {
        public string UserName { get; set; }
    }
}

MemberRegisteredEvent

Add a new class called MemberRegisteredEvent also with a UserName property.

namespace Shuttle.PublishSubscribe.Messages
{
    public class MemberRegisteredEvent
    {
        public string UserName { get; set; }
    }
}

Client

Add a new Console Application to the solution called Shuttle.PublishSubscribe.Client.

Install the Shuttle.Esb.Msmq nuget package.

This will provide access to the Msmq IQueue implementation and also include the required dependencies.

Install the Shuttle.Core.StructureMap nuget package.

This will provide access to the StructureMap dependency injection container.

Add a reference to the Shuttle.PublishSubscribe.Messages project.

Program

Implement the main client code as follows:

using System;
using Shuttle.Core.StructureMap;
using Shuttle.Esb;
using Shuttle.PublishSubscribe.Messages;
using StructureMap;

namespace Shuttle.PublishSubscribe.Client
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var smRegistry = new Registry();
            var registry = new StructureMapComponentRegistry(smRegistry);

            ServiceBus.Register(registry);

            using (var bus = ServiceBus.Create(new StructureMapComponentResolver(new Container(smRegistry))).Start())
            {
                string userName;

                while (!string.IsNullOrEmpty(userName = Console.ReadLine()))
                {
                    bus.Send(new RegisterMemberCommand
                    {
                        UserName = userName
                    });
                }
            }
        }
    }
}

App.config

Create the shuttle configuration as follows:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name='serviceBus' type="Shuttle.Esb.ServiceBusSection, Shuttle.Esb"/>
    </configSections>

    <serviceBus>
        <messageRoutes>
            <messageRoute uri="msmq://./shuttle-server-work">
                <add specification="StartsWith" value="Shuttle.PublishSubscribe.Messages" />
            </messageRoute>
        </messageRoutes>        
    </serviceBus>
</configuration>

This tells Shuttle that all messages that are sent and have a type name starting with Shuttle.PublishSubscribe.Messages should be sent to endpoint msmq://./shuttle-server-work.

Server

Add a new Console Application to the solution called Shuttle.PublishSubscribe.Server.

Install the Shuttle.Esb.Msmq nuget package.

This will provide access to the Msmq IQueue implementation and also include the required dependencies.

Install the Shuttle.Core.StructureMap nuget package.

This will provide access to the StructureMap dependency injection container.

Install the Shuttle.Esb.Sql.Subscription nuget package.

This will provide access to the Sql-based ISubscriptionManager implementation.

Install the Shuttle.Core.ServiceHost nuget package.

The default mechanism used to host an endpoint is by using a Windows service. However, by using the Shuttle.Core.ServiceHost assembly we are able to run the endpoint as a console application or register it as a Windows service for deployment.

Add a reference to the Shuttle.PublishSubscribe.Messages project.

Program

Implement the Program class as follows:

using Shuttle.Core.ServiceHost;

namespace Shuttle.PublishSubscribe.Server
{
    public class Program
    {
        public static void Main()
        {
            ServiceHost.Run<Host>();
        }
    }
}

This will simply run the Host implementation.

Host

Add a Host class and implement the IServiceHost interface as follows:

using Shuttle.Core.ServiceHost;
using Shuttle.Core.StructureMap;
using Shuttle.Esb;
using StructureMap;

namespace Shuttle.PublishSubscribe.Server
{
    public class Host : IServiceHost
    {
        private IServiceBus _bus;

        public void Start()
        {
            var smRegistry = new Registry();
            var registry = new StructureMapComponentRegistry(smRegistry);

            ServiceBus.Register(registry);

            _bus = ServiceBus.Create(new StructureMapComponentResolver(new Container(smRegistry))).Start();
        }

        public void Stop()
        {
            _bus.Dispose();
        }
    }
}

Database

We need a store for our subscriptions. In this example we will be using Sql Server. If you use the express version remember to change the data source value to .\sqlexpress from the standard ..

When you reference the Shuttle.Esb.Sql.Subscription package a scripts folder is included in the relevant package folder. Click on the Nuget referenced assembly in the References or Dependencies (depending on your project type) and navigate to the package folder to find the scripts folder.

The {version} bit will be in a semver format.

Create a new database called Shuttle and execute the script System.Data.SqlClient\SubscriptionManagerCreate.sql in the newly created database.

This will create the required structures that the subscription manager will use to store the subcriptions.

Whenever Publish is called the registered ISubscriptionManager instance is asked for the subscribers to the published message type. These are retrieved from the Sql Server database for the implementation we are using.

App.config

Add an Application Configuration File item to create the App.config and populate as follows:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name='serviceBus' type="Shuttle.Esb.ServiceBusSection, Shuttle.Esb"/>
    </configSections>

    <connectionStrings>
        <add name="Subscription"
             connectionString="Data Source=.;Initial Catalog=shuttle;Integrated Security=SSPI;"
             providerName="System.Data.SqlClient"/>
    </connectionStrings>

    <serviceBus>
         <inbox
            workQueueUri="msmq://./shuttle-server-work"
            errorQueueUri="msmq://./shuttle-error" />
    </serviceBus>
</configuration>

The Sql Server implementation of the ISubscriptionManager that we are using by default will try to find a connection string with a name of Subscription. However, you can override this. See the [Sql Server configuration options][sql-server] for details about how to do this.

RegisterMemberHandler

Add a new class called RegisterMemberHandler that implements the IMessageHandler<RegisterMemberCommand> interface as follows:

using System;
using Shuttle.Esb;
using Shuttle.PublishSubscribe.Messages;

namespace Shuttle.PublishSubscribe.Server
{
    public class RegisterMemberHandler : IMessageHandler<RegisterMemberCommand>
    {
        public void ProcessMessage(IHandlerContext<RegisterMemberCommand> context)
        {
            Console.WriteLine();
            Console.WriteLine("[MEMBER REGISTERED] : user name = '{0}'", context.Message.UserName);
            Console.WriteLine();

            context.Publish(new MemberRegisteredEvent
            {
                UserName = context.Message.UserName
            });
        }
    }
}

This will write out some information to the console window and publish the MemberRegisteredEvent message.

Subscriber

Add a new Console Application to the solution called Shuttle.PublishSubscribe.Subscriber.

Install the Shuttle.Esb.Msmq nuget package.

This will provide access to the Msmq IQueue implementation and also include the required dependencies.

Install the Shuttle.Core.StructureMap nuget package.

This will provide access to the StructureMap dependency injection container.

Install the Shuttle.Esb.Sql.Subscription nuget package.

This will provide access to the Sql-based ISubscriptionManager implementation.

Install the Shuttle.Core.ServiceHost nuget package.

The default mechanism used to host an endpoint is by using a Windows service. However, by using the Shuttle.Core.ServiceHost assembly we are able to run the endpoint as a console application or register it as a Windows service for deployment.

Add a reference to the Shuttle.PublishSubscribe.Messages project.

Program

Implement the Program class as follows:

using Shuttle.Core.ServiceHost;

namespace Shuttle.PublishSubscribe.Server
{
    public class Program
    {
        public static void Main()
        {
            ServiceHost.Run<Host>();
        }
    }
}

This will simply run the Host implementation.

Host

Add a Host class and implement the IServiceHost interface as follows:

using Shuttle.Core.Container;
using Shuttle.Core.ServiceHost;
using Shuttle.Core.StructureMap;
using Shuttle.Esb;
using Shuttle.PublishSubscribe.Messages;
using StructureMap;

namespace Shuttle.PublishSubscribe.Subscriber
{
    public class Host : IServiceHost
    {
        private IServiceBus _bus;

        public void Start()
        {
            var structureMapRegistry = new Registry();
            var registry = new StructureMapComponentRegistry(structureMapRegistry);

            ServiceBus.Register(registry);

            var resolver = new StructureMapComponentResolver(new Container(structureMapRegistry));

            resolver.Resolve<ISubscriptionManager>().Subscribe<MemberRegisteredEvent>();

            _bus = ServiceBus.Create(resolver).Start();
        }

        public void Stop()
        {
            _bus.Dispose();
        }
    }
}

Here we register the subscription by calling the ISubscriptionManager implementation’s Subscribe<MemberRegisteredEvent>(); method. Since we are using the Sql Server implementation of the ISubscriptionManager interface an entry will be created in the SubscriberMessageType table associating the inbox work queue uri with the message type.

It is important to note that in a production environment one would not typically register subscriptions in this manner as they may be somewhat more sensitive as we do not want any arbitrary subscriber listening in on the messages being published. For this reason the connection string should be read-only and the subscription should be registered manually or via a deployment script. Should the subscription not yet exist the creation of the subscription will fail, indicating that there is work to be done.

App.config

Add an Application Configuration File item to create the App.config and populate as follows:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name='serviceBus' type="Shuttle.Esb.ServiceBusSection, Shuttle.Esb"/>
    </configSections>

    <connectionStrings>
        <add name="Subscription"
             connectionString="Data Source=.;Initial Catalog=shuttle;Integrated Security=SSPI;"
             providerName="System.Data.SqlClient"/>
    </connectionStrings>

    <serviceBus>
         <inbox
            workQueueUri="msmq://./shuttle-subscriber-work"
            errorQueueUri="msmq://./shuttle-error" />
    </serviceBus>
</configuration>

MemberRegisteredHandler

Add a new class called MemberRegisteredHandler that implements the IMessageHandler<MemberRegisteredHandler> interface as follows:

using System;
using Shuttle.Esb;
using Shuttle.PublishSubscribe.Messages;

namespace Shuttle.PublishSubscribe.Server
{
    public class MemberRegisteredHandler : IMessageHandler<MemberRegisteredEvent>
    {
        public void ProcessMessage(IHandlerContext<MemberRegisteredEvent> context)
        {
            Console.WriteLine();
            Console.WriteLine("[EVENT RECEIVED] : user name = '{0}'", context.Message.UserName);
            Console.WriteLine();
        }
    }
}

This will write out some information to the console window.

Run

Set the client, server, and subscriber projects as startup projects.

Execute

Execute the application.

The client application will wait for you to input a user name. For this example enter my user name and press enter:

You will observe that the server application has processed the message.
The subscriber application will then process the event published by the server.

You have now completed a full publish / subscribe call chain.