Docker Container Host

Docker containers provide the ability to deploy endpoints in a self-contained manner. To create and host an endpoint in a Docker container, install the Docker container template and create a new project using dotnet new nsbdockercontainer. The project that is created will have the required endpoint setup infrastructure in addition to the Dockerfile needed to create and deploy a container hosting one endpoint.

Template overview

The nsbdockercontainer template creates a project that contains all of the files necessary to build an endpoint that can be deployed to Docker.

license.xml

Each Docker container must have a license.xml file included in it. A placeholder for this file is created when the template is used to create a new endpoint. This file must be replaced with a valid license.xml file prior to building the Docker container.

An endpoint running in Docker will look for the license.xml file in the same locations as it would in any other hosting situation. By default, a project created using the nsbdockercontainer template will put the license.xml file in the correct location in a Docker image.

Dockerfile

This file contains the instructions for compiling the endpoint and creating the Docker image.

The endpoint will be hosted in a container that is based on the mcr.microsoft.com/dotnet/core/runtime:3.1 image. Once built, the container image contains the compiled artifacts of the endpoint project, and it will launch that endpoint when the container is run.

To compile the endpoint and create the Docker image, run the following command:

docker build -f Dockerfile -t MyEndpoint ./..

Building the container will compile and publish the endpoint in Release mode.

RUN dotnet publish -c Release -o /app

The compiled endpoint is added to the docker image, the endpoint is configured to start when the container is run, and the container is built.

COPY --from=build /app .
ENTRYPOINT ["dotnet", "MyEndpoint.dll"]

Program.cs

The endpoint's configuration must be added to the CreateHostBuilder method.

static IHostBuilder CreateHostBuilder(string[] args)
{
    return Host.CreateDefaultBuilder(args)
        .UseConsoleLifetime()
        .UseNServiceBus(ctx =>
        {
            // TODO: consider moving common endpoint configuration into a shared project
            // for use by all endpoints in the system

            // TODO: give the endpoint an appropriate name
            var endpointConfiguration = new EndpointConfiguration("EndpointName");

            // TODO: ensure the most appropriate serializer is chosen
            // https://docs.particular.net/nservicebus/serialization/
            endpointConfiguration.UseSerialization<NewtonsoftSerializer>();

            endpointConfiguration.DefineCriticalErrorAction(OnCriticalError);

            // TODO: remove this condition after choosing a transport, persistence and deployment method suitable for production
            if (Environment.UserInteractive && Debugger.IsAttached)
            {
                // TODO: choose a durable transport for production
                // https://docs.particular.net/transports/
                var transportExtensions = endpointConfiguration.UseTransport<LearningTransport>();

                // TODO: choose a durable persistence for production
                // https://docs.particular.net/persistence/
                endpointConfiguration.UsePersistence<LearningPersistence>();

                // TODO: create a script for deployment to production
                endpointConfiguration.EnableInstallers();
            }

            // TODO: replace the license.xml file with a valid license file

            return endpointConfiguration;
        });
}

There are also methods that handle endpoint failures and exceptions, which can be modified to fit the needs of the endpoint.

static async Task OnCriticalError(ICriticalErrorContext context)
{
    // TODO: decide if stopping the endpoint and exiting the process is the best response to a critical error
    // https://docs.particular.net/nservicebus/hosting/critical-errors
    try
    {
        await context.Stop();
    }
    finally
    {
        FailFast($"Critical error, shutting down: {context.Error}", context.Exception);
    }
}

static void FailFast(string message, Exception exception)
{
    try
    {
        log.Fatal(message, exception);

        // TODO: when using an external logging framework it is important to flush any pending entries prior to calling FailFast
        // https://docs.particular.net/nservicebus/hosting/critical-errors#when-to-override-the-default-critical-error-action
    }
    finally
    {
        Environment.FailFast(message, exception);
    }
}

Samples

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