Scott Hanselman

I'm sitting on a plane on the way back from a lovely time in Europe. I attended and spoke at some great conferences and met some cool people - some of which you'll hear on the podcast soon. Anyway, one of the things that I heard mentioned by attendees more than once was the issue of (micro) service discovery for RESTful APIs. Now if you lived through the WS*.* years you'll perhaps feel a lot of this is familiar or repeated territory, but the new stuff definitely fits together more effortlessly than in the past.

Consul is a system that does service discovery, configuration management, and health checking for your services. You can write Web APIs in lots of things, Rails, Python, and ASP.NET with WebAPI or NancyFX.

Microphone is a library by Roger Johansson that plugs into both WebAPI and Nancy and very simply and easily registers your services with Consul. It's recently been expanded to support CoreOs-ETCD as well, so it's really a general purpose framework.

I made a little .NET 4.6 console app that self hosts a WebAPI like this.

namespace ConsulSelfHostedWebAPIService
{
    class Program
    {
        static void Main(string[] args)
        {
            Cluster.Bootstrap(new WebApiProvider(), new ConsulProvider(), "HanselWebApiService", "v1");
            Console.ReadLine();
        }
    }

    public class DefaultController : ApiController
    {
        public string Get()
        {
            return "Hey it's my personal WebApi Service";
        }
    }
}

Now my Web API is registered with Consul, and now Consul itself is a RESTful Web API where I can hit http://localhost:8500/v1/agent/services and get a list of registered services. It's the Discovery Service.

Then later in a client or perhaps another Web API, I can ask for it by name and I'll get back the address and port that it's on, then call it.

var instance = await Cluster.FindServiceInstanceAsync("Heycool");

return String.Format("Look there's a service at {0}:{1}", instance.Address, instance.Port);

Here's an active debug session showing the address and port in the instance:

It will be interesting to see what will happen with Consul and systems like it if the Azure Service Fabric gains traction. Service Fabric offers a lot more, but I wonder if there is a use case for both, with Service Fabric managing lifecycles and Consul doing discovery.

This is all early days, but it's interesting. What do you think about these new discovery services for Web APIs?

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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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