Implement a watchdog for your microservices using off-the-shelf ASP.Net Healthcheck UI.

What is a watchdog

A watchdog is a service that monitor other services and take actions when it detect a service is failing.

ASP.NET starting from Core 5 has a built in UI module to monitor other services, and in few line of code you can build a watchdog for your services.

How to hook it up with your services:

Your microservices should implement health check endpoints to be monitored by the orchestration service (Kubernetes, docker storm, ... etc).

I explained in previous post on how to use built-in ASP.NET health check features to achieve build these endpoints.

I recommend reading that article because there I talked about the Microsoft package AspNetCore.Diagnostics.HealthChecks. This package contains all the middleware for build-in health checks, and as well in the same repository has a UI module that with few line of code build a UI to monitor all integrated services and monitor their health check endpoints.

How to use the UI module to build the monitoring service.

1. Create a MVC application using
   

       dotnet new mvc -n watchdog
   

2. Add required packages:
   

      dotnet add package AspNetCore.HealthChecks.UI
   

3. define in appsettings.json all the services that you want to monitor. the format of the config section is as follows:
   

       // Configuration
      {
        "HealthChecksUI": {
           "HealthChecks": [
              {
                 "Name": "Ordering HTTP Check",
                 "Uri": "http://host.docker.internal:5102/hc"
              },
             {
               "Name": "Ordering HTTP Background Check",
               "Uri": "http://host.docker.internal:5111/hc"
             },
            //...
          ]}
         }
   

   In reality when we deploy the application to AKS or any service-mesh service, we need to replace the url address. But now we are just describing the idea of the UI module.

4. add HealthCheckUI service
   
   

builder.Services..AddHealthChecksUI()
            .AddInMemoryStorage();

// ....
var app = builder.Build();
// ....

// the URL /hc-ui will display the user interface
app.UseHealthChecksUI(config => config.UIPath = "/hc-ui");

When you run the application you will see the user interface that looks like

I am going to add more on monitoring services using other built-in features, so keep following me.