NServiceBus Host

The NServiceBus Host takes a more opinionated approach to hosting. It allows the execution as both a windows service and a console application (for development).

The NServiceBus host automates some parts of the windows service deployment. See Installation.

To use the host just create a new C# class library and reference the NServiceBus.Host NuGet package. The package also creates an example endpoint configuration and sets the NServiceBus.Host.exe as the startup project for the endpoint.

Configuring your endpoint

The NServiceBus.Host.exe scans the runtime directory for assemblies containing a class that implements the IConfigureThisEndpoint interface. This class will contain the configuration for this endpoint. You can read more on how NServiceBus does assembly scanning here

If you want to avoid the scanning process you can explicitly configure the type of your endpoint configuration by adding the following to the NServiceBus.Host.exe.config file. The below example show the exact syntax:

    <add key="EndpointConfigurationType" 
         value="YourNamespace.YourTypeName, YourAssembly"/>

Application Domains

The NServiceBus.Host.exe creates a separate service Application Domain to run NServiceBus and the user code. The new domain is assigned a configuration file named after the dll that contains the class implementing IConfigureThisEndpoint. All the configuration should be done in that file (as opposed to NServiceBus.Host.exe.config). In most cases that means just adding the app.config file to the project and letting MSBuild take care of renaming it while moving to the bin folder.

When the endpoint configuration is not specified explicitly, the host scans all the assemblies to find it and it does so in the context of the host application domain, not the new service domain. Because of that, when reditecting assembly versions, the assemblyBinding element needs to be present in both NServiceBus.Host.exe.config and app.config.

Custom initialization and startup

As of NServiceBus version 5 you customize the endpoint behavior using the IConfigureThisEndpoint.Customize method on your endpoint configuration class. Just call the appropriate methods on the BusConfiguration parameter passed to the method.

class CustomizingHost : IConfigureThisEndpoint
    public void Customize(BusConfiguration busConfiguration)
        // To customize, use the configuration parameter. 
        // For example, to customize the endpoint name:

NServiceBus version 4 and version 3

To change core settings such as assembly scanning, container, and serialization format, implement IWantCustomInitialization on the endpoint configuration class (the same class that implements IConfigureThisEndpoint). You must start the configuration expression With

Do not perform any startup behaviors in the Init method.

After the custom initialization is done the regular core INeedInitalization implementations found will be called in the same way as when you're self hosting.

Defer all startup behavior until all initialization has been completed. At this point, NServiceBus invokes classes that implement the IWantToRunWhenBusStartsAndStops (IWantToRunWhenTheBusStarts in version 3.x) interface. An example of behavior suitable to implement with IWantToRunWhenBusStartsAndStops (IWantToRunWhenTheBusStarts in version 3.x) is the opening of the main form in a Windows Forms application. In the back-end Windows Services, classes implementing IWantToRunWhenBusStartsAndStops(IWantToRunWhenTheBusStarts in version 3.x) should kick off things such as web crawling, data mining, and batch processes.


As of NServiceBus version 5 logging for the host is controlled with the same API as the core. This is documented here.

You can add the logging API calls as mentioned in the above article directly in your implementation of IConfigureThisEndoint.Customize method.

NServiceBus version 4 and version 3

To change the host's logging infrastructure, implement the IWantCustomLogging interface. In the Init method, configure your custom setup. To make NServiceBus use your logger, use the NServiceBus.SetLoggingLibrary.Log4Net() API, described in the logging documentation and shown below:

class MyEndpointConfig : IConfigureThisEndpoint, IWantCustomLogging
    public void Init()
        // setup your logging infrastructure then call
        SetLoggingLibrary.Log4Net(null, new MyLogger());

You may want to specify different logging levels (DEBUG, WARN, etc.) and possibly different targets (CONSOLE, FILE, etc.). The host provides a mechanism for changing these permutations with no code or configuration changes, via profiles.

Roles - Built-in configurations

As of version 5 roles are obsoleted and should not be used. Most of the functionality of AsA_Server, and AsA_Publisher has been made defaults in the core and can be safely removed. If you still need the AsA_Client behavior please add the following to your configuration.

BusConfiguration busConfiguration = new BusConfiguration();


NServiceBus version 4 and version 3

The rest of the code specifying transport, subscription storage, and other technologies isn't here, because of the AsA_Server built-in configuration described next.

While NServiceBus allows you to pick and choose which technologies to use and how to configure each of them, the host packages these choices into three built-in options: AsA_Client, AsA_Server, and AsA_Publisher. All these options make use of XmlSerializer, MsmqTransport, and UnicastBus. The difference is in the configuration:

  • AsA_Client sets MsmqTransport as non-transactional and purges its queue of messages on startup. This means that it starts afresh every time, not remembering anything before a crash. Also, it processes messages using its own permissions, not those of the message sender.
  • AsA_Server sets MsmqTransport as transactional and does not purge messages from its queue on startup. This makes it fault-tolerant.
  • AsA_Publisher extends AsA_Server and indicates to the infrastructure to set up storage for subscription requests, described in the profiles page.


When running the endpoint within the context of Visual Studio debugger, when the endpoint starts, the needed queues are created on startup to facilitate development. However, when deploying this endpoint to a server, starting the endpoint from the command prompt will not create the needed queues if the queues aren't already present. Creation of queues is a one time cost that will happen during installation only.

To install your process as a Windows Service, you need to pass /install on the command line to the host. By default, the name of the service is the name of your endpoint and the endpoint name is the namespace of your endpoint configuration class. To enable side-by-side operations, use the /sideBySide switch to add the SemVer version to the service name. Passing /install also causes the host to invoke the installers .

To override this and specify additional details for installation:

NServiceBus.Host.exe [/install [/serviceName]
[/uninstall [/serviceName]
[/instance:Instance Name ]

You can get to this list by running the following at the command line:

NServiceBus.Host.exe /?

To set the actual name of the Windows Services in the registry, specify /serviceName:YourServiceName. This is different from what you see in the Windows Service Manager.

To set the name of the Windows Service as you see it in the Windows Service Manager, specify /displayName:YourService.

If you do not specify /displayName, but do specify /serviceName, the display name does not become what was passed in the /serviceName, but rather the default described above.

To set the description shown in the Windows Service Manager, specify /description:DescriptionOfYourService.

To install multiple instances of the same service by providing each a different instance name, use the 'instance' flag. For example: /instance:Instance5.

By default, Windows Services start automatically when the operating system starts. To change that, add /startManually to the /install command.

To specify under which account you want your service to run, pass in the username and password of that account.

Following is an example of the /install command line:

NServiceBus.Host.exe /install /serviceName:"MyPublisher" 
/displayName:"My Publisher Service"
/description:"Service for publishing event messages"
/endpointConfigurationType:"YourNameSpace.YourEndpointConfigType, YourAssembly"
/password:"p@ssw0rd!" NServiceBus.Production
When installing the Host using a custom user account, as in the above sample, the user account is added to the Performance Monitor Users and is granted run as a service privileges. If, at a later time, the user needs to be changed it is suggested to uninstall the Host and re-install it in order to guarantee that the new user is correctly setup.

To uninstall, call

NServiceBus.Host.exe /uninstall

If you specify a service name or instance name when installing your service, you need to pass them in to the uninstall command as well:

NServiceBus.Host.exe [/uninstall  [/serviceName] [/instance]]

For example:

NServiceBus.Host.exe /uninstall /serviceName:YourServiceName /instance:YourInstanceName

To invoke the infrastructure installers, run the host with the /installInfrastructure switch.


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Last modified 2015-11-25 00:19:32Z