Whilst the previous post showed how we use Steeltoe in an ASP.NET application, sometimes we might not want to (or be able) to use all the nice methods for automatic service discovery etc.

In this post we’re going to create a simple .NET core console application and interact with the discovery service at a slightly lower level.

So…

• Create yourself a .NET core console application
• Add the NuGet package Steeltoe.Discovery.Eureka

We need to configure the discovery client. You can use your own configuration method but for this example we’ll hard code parameters into a EurekaClientConfig object.

var config = new EurekaClientConfig
{
   EurekaServerServiceUrls = "http://localhost:8761/eureka/",
   ShouldFetchRegistry = true,
   ShouldRegisterWithEureka = false
};

We’re just writing a client, hence we don’t want to register the application with Eureka, but we do want to fetch registry data.

Next we will create the discovery client, access the applications and get our weatherapi application…

var discoveryClient = new DiscoveryClient(config);
var applications = discoveryClient.Applications;
var service = applications?.GetRegisteredApplication("weatherapi");

Finally we want to find instances of the services associated with the application which are UP and get the URL associated with one of the instances.

var instance = service?.Instances.FirstOrDefault(info => info.Status == InstanceStatus.UP);
if(instance != null)                    
{
   var client = new HttpClient
   {
      BaseAddress = new Uri(instance.HomePageUrl)
   };
   var response = await client.GetAsync("weatherforecast");
   Console.WriteLine(await response.Content.ReadAsStringAsync());
}

If an instance is found we just simply use HttpClient to invoke a GET method on the service and output the response to the console, just to prove everything worked.

This code doesn’t use any load balancing strategies, I’ll leave that to the reader to look into as in a real world scenario we wouldn’t want all clients to use the first instance only.