Enterprise Service Bus libraries for .NET – Nimbus

Monday, 20 November 2017

One in a series of posts giving a quick overview of ESB libraries for .NET

Nimbus primarily supports the Azure Service Bus as a transport, so if your application is going to run in Azure, then this could be a good choice.

https://github.com/NimbusAPI/Nimbus/wiki/Publishing-an-Event-on-the-Bus

Messages

Event messages should implement IBusEvent

Publishing

Publish with an instance of IBus

_bus.Publish(new NewOrderReceived {CustomerName = "Ricky Bobby"});

Subscribing

Handle events by implementing IHandleMulticastEvent

public class ListenForNewOrders : IHandleMulticastEvent
{
 
    public async Task Handle(NewOrderReceived busEvent)
    {
        Console.WriteLine("I heard about a new order from " + busEvent.CustomerName);
 
        //Do more stuff
    }
}

Enterprise Service Bus libraries for .NET – MassTransit

Wednesday, 15 November 2017

One in a series of posts giving a quick overview of ESB libraries for .NET

MassTransit is an open-source library which apparently began as a response to some perceived deficiencies in the version of NServiceBus that was around in 2007. The project did a major rewrite in 2014, introducing async support and switching from MSMQ to RabbitMQ as the preferred transport.

Messages

Messages are POCO classes. There is no requirement to inherit from any base class or implement a specific interface.

Publishing

http://masstransit-project.com/MassTransit/usage/producing-messages.html

Messages are published using IPublishEndpoint, which is provided by ConsumeContext for consumers or by the IBus interface

public async Task NotifyOrderSubmitted(IPublishEndpoint publishEndpoint)
{
    await publishEndpoint.Publish<OrderSubmitted>(new
    {
        OrderId = "27",
        OrderDate = DateTime.UtcNow,
    });
}

Subscribing

http://masstransit-project.com/MassTransit/usage/message-consumers.html

A subscribing class (or consumer) implements the IConsumer<T> interface.
public class UpdateCustomerConsumer :
    IConsumer<UpdateCustomerAddress>
{
    public async Task Consume(ConsumeContext<UpdateCustomerAddress> context)
    {
        await Console.Out.WriteLineAsync($"Updating customer: {context.Message.CustomerId}");

        // update the customer address
    }
}

A consumer needs to be connected to an endpoint to receive messages

var busControl = Bus.Factory.CreateUsingRabbitMq(cfg =>
{
    var host = cfg.Host(new Uri("rabbitmq://localhost/"), h =>
    {
        h.Username("guest");
        h.Password("guest");
    });

    cfg.ReceiveEndpoint(host, "customer_update_queue", e =>
    {
        e.Consumer<UpdateCustomerConsumer>();
    });
});

Enterprise Service Bus libraries for .NET – NServiceBus

Tuesday, 14 November 2017

One in a series of posts giving a quick overview of ESB libraries for .NET

Originally an open-source library developed by Udi Dahan, the licensing was changed after version 2 to put it on a more commercial footing, and the software is now developed and supported by Udi’s company – Particular Software. The source code remains on Github.

NServiceBus is a tried and tested library. It has grown a lot since it's humble beginnings and now is once part of a suite of tools and libraries for building distributed applications. It's no surprise that Udi Dahan just happens to be highly regarded as an expert in distributed software architecture.

https://docs.particular.net/nservicebus/messaging/publish-subscribe/publish-handle-event

Messages

Messages need to either implement a marker interface or use defined conventions.
namespace Domain.Messages
{
  public class UserCreatedEvent : IEvent
  {
    public string Name { get; set; }
  }
}
Or
var conventions = endpointConfiguration.Conventions();

conventions.DefiningEventsAs(
 type =>

     {
       return type.Namespace == "MyNamespace.Messages.Events";
 });

Publishing

You can publish an event from within another handler or when you create an endpoint.
This example shows publishing an event from an endpoint:

var endpointInstance = await Endpoint.Start(endpointConfiguration)
    .ConfigureAwait(false);
    await endpointInstance.Publish(new MyEvent())
      .ConfigureAwait(false);

Subscribing

To handle an event, implement IHandleMessages<T>

public class UserCreatedHandler : IHandleMessages<UserCreatedEvent>
{
  public Task Handle(UserCreatedEvent message, IMessageHandlerContext context)
  { … }
}

NServiceBus will automatically locate handlers by looking for implementations of IHandleMessages<T>



Enterprise Service Bus libraries for .NET

Sunday, 5 November 2017

As a software application becomes larger, you may want to break it into separate parts, both to manage complexity but also to aid scalability. But if you break an application apart, how will the separate parts communicate? One approach is to employ messaging using a publish/subscribe (pub/sub) bus.

A few years ago, I worked on an application that used NServiceBus just for this purpose, but I thought it would be useful to survey the .NET landscape to find out what’s available today.

Here’s a summary of the libraries I’ll be looking at over the next few blog posts:

Name URL Transports Minimum Framework License Dependencies
NServiceBus v6 https://docs.particular.net/nservicebus Azure Service Bus, In-memory?, MSMQ, RabbitMQ, SQL Server 4.5.2 Commercial -
MassTransit http://masstransit-project.com/ Azure Service Bus, In-memory, RabbitMQ 4.5(.2?) Apache 2.0 GreenPipes (>= 1.2.0)
NewId (>= 3.0.1)
Newtonsoft.Json (>= 10.0.3)
Newtonsoft.Json.Bson (>= 1.0.1)
NimbusAPI https://github.com/NimbusAPI/Nimbus Azure Service Bus 4.5 MIT Microsoft.WindowsAzure.ConfigurationManager (= 2.0.3)
Nimbus.InfrastructureContracts (>= 2.0.0.98)
Nimbus.MessageContracts (>= 2.0.0.98)
WindowsAzure.ServiceBus (>= 2.1.3 && <= 2.1.4)
Shuttle.Esb http://shuttle.github.io/shuttle-esb/ MSMQ, RabbitMQ, SQL Server 4.0? BSD 3 Shuttle.Core.Infrastructure (>= 8.0.6)
Rebus https://github.com/rebus-org/Rebus Azure Service Bus, MSMQ, RabbitMQ 4.5 MIT Newtonsoft.Json (>= 9.0.1)

These libraries range from the relatively simple and tightly focused to the complete ‘enterprise-level’ configurable, extensible and/or fully supported.

Some of these libraries distinguish between an ‘event’ (notify subscribers that something has happened) and a ‘command’ (tell subscribers that they should perform an action). Some support long-running business processes, often known as ‘sagas’. Some support distributed transactions. Some use dependency injection and can integrate with an inversion-of-control container.

And because the feature sets vary so widely, I’ll just be highlighting how each library implements publishing an ‘event’ message, and how you subscribe to these messages.

Conditionally format rows in Excel depending on date range

Tuesday, 17 October 2017

Sometimes I get asked Excel questions. This is one of those times!

Given a spreadsheet with rows that contain a start and finish date, format the rows in the past, present and future in different colours, so that it looks like this:

Spreadsheet showing rows with different colours

I initially tried using a formula with Excel’s Conditional Formatting feature. Despite this being the recommended solution in some search results, I just found it set the one format for all the rows – not what I wanted. This post by Joseph D’Emanuele put me on the right track.

Here’s what I ended up doing:

  1. Add a new column next to your existing data
    Spreadsheet with extra Status column added
  2. In the first cell of this new column, insert the formula
    =IF(B2 < TODAY(), "Past", IF(A2 > TODAY(), "Future", "Current"))
  3. Copy this formula down to the remaining rows. eg.
    Spreadsheet with Status column populated
  4. Now select all the rows you want to format (for me that’s A2:D5)
  5. On the Home menu tab, select Conditional Formatting, then Manage Rules
  6. You will add 3 rules – one for each status.
  7. Click New Rule
  8. Select Use a formula to determine which cells to format
  9. In Format values where this formula is true, enter =INDIRECT("D" &ROW()) = "Future"
  10. Click Format and choose the desired formatting to apply for Future dates
  11. Click OK and repeat adding new rules for “Current” and “Past”
  12. You should end up with something like this:
    Excel's Conditional Formatting Rules Manager dialog box
  13. Click OK and you should have rows formatted different colours depending on whether the start/finish date is in the past, current or in the future!
  14. You can optionally choose to hide the Status row if you’d rather not see it all the time.

Note that the formula in the conditional formatting (=INDIRECT("D" &ROW()) = "Future") is hard-coded to the column – “D” in my case. If you move data around, you’ll need to update this to refer to the new column letter.