NServiceBus Distributor in only 2 steps?

Question

Im having a bit of trouble figuring out how to do the following correctly with the Distributor:

Create a service (distributor) which sends commands, that are distributed among workers. If I start a Distributor with IWantToRunAtStartup implementation I can achieve this behaviour. See below.
Create a service (worker) which handles these commands. This worker I would then start X number of instances of to scale out.
This is all on the same machine so far.

The samples which are included with NSB are a bit hard to understand or maybe its just me :).

Example, I have a distributor and a worker:

Distributor:

class MessageCreator: IWantToRunAtStartup
{
    public IBus Bus { get; set; }

    public void Run()
    {
        Thread.Sleep(5000); //Allow workers to checkin
        for (int i = 0; i < 1000; i++ )
        {
            Bus.Send(new DoWorkForCustomerCommand { CustomerID = i });
        }

    }

    public void Stop() { }
}

...

public class EndpointConfig : IConfigureThisEndpoint, AsA_Server
{
    public void Init()
    {
        Configure.Instance.RunDistributor();
    }
}

app.config

<configSections>
    <section name="Logging" type="NServiceBus.Config.Logging, NServiceBus.Core" />
    <section name="UnicastBusConfig" type="NServiceBus.Config.UnicastBusConfig, NServiceBus.Core" /> 
    <section name="MessageForwardingInCaseOfFaultConfig" type="NServiceBus.Config.MessageForwardingInCaseOfFaultConfig, NServiceBus.Core" />
</configSections>

<MessageForwardingInCaseOfFaultConfig ErrorQueue="error"/>
<Logging Threshold="INFO" />
<UnicastBusConfig>
    <MessageEndpointMappings>
      <add Messages="Messages" Endpoint="Worker" />
    </MessageEndpointMappings>
 </UnicastBusConfig>

Worker:

public class MessageHandler: IHandleMessages<DoWorkForCustomerCommand >
{
    public void Handle(DoWorkForCustomerCommand message)
    {
        Console.WriteLine("Handled customer with Id: " + message.CustomerID );
    }
}

...

public class EndpointConfig : IConfigureThisEndpoint, AsA_Publisher
{
    public void Init()
    {
        Configure.Instance.EnlistWithDistributor();
        // For some reason this: Configure.Instance.RunDistributor(); achieves the same thing.
    }
}

app.config

<configSections>
    <section name="MessageForwardingInCaseOfFaultConfig" type="NServiceBus.Config.MessageForwardingInCaseOfFaultConfig, NServiceBus.Core" />
</configSections>
<MessageForwardingInCaseOfFaultConfig ErrorQueue="error" />

This works on my machine and distributes nicely to any number of workers I start, but am i not missing out on something, the ScaleOut example seems more complex?

And why can i start the worker as a distributor and then see the worker act as if it was a worker when in fact is was started as a distributor?

Will this not work across machines if I just add a queue name/endpoint in the worker app.config?

Adam Fyles Adam Fyles · Accepted Answer · 2013-03-04T14:36:24

By default if you RunDistributor(), then NSB will run a Distributor with a Worker node in the same process. This is why you see a Worker despite the RunDistributor() configuration. To disable this, use RunDistributorWithNoWorkerOnItsEndpoint() instead. All of this will work across machines by changing the config.

I might suggest using the Profiles instead as this simplifies the config a bit. You can use the NServiceBus.Distributor and NServicerBus.Worker profiles. The profiles will give you more diagnostic information if you have not configured things quite right. Hope this helps.

NServiceBus Distributor in only 2 steps?

1 Answers