Health Checks on your ASP.NET Core Application

Ricardo Mauro -

Health Endpoint Monitoring pattern

Health Check in .NET 5 is very simple. With just a few lines of code, you can set up everything to monitor the Health of our Application.

Implement functional checks in an application that external tools can access through exposed endpoints at regular intervals. This can help to verify that applications and services are performing correctly.

Reference to: https://docs.microsoft.com/en-us/azure/architecture/patterns/health-endpoint-monitoring

Introduction

In this series of posts, we walk through Health Checks and monitoring your web application / Web APIs.

  1. How to Add Health Checks to ASP.Net Core Application [this post]
  2. Adding UI Health Check
  3. Endpoint Monitoring with Azure Application Insights
  4. Using Azure App Services Endpoint Monitoring

In this post, we'll add an endpoint to monitor our existing ASP.NET Core Application health status.

We'll understand how it's pretty simple in .NET Core / .NET 5 Applications.
With just a few lines of code, all the infrastructure is ready to display the health status of our ASP.NET Applications.

We can monitor services such as:

  • Database services, such as SQL Server, Oracle, MySql, MongoDB, among others;
  • External API connectivity - external URLs;
  • Disk connectivity (read/write);
  • Cache services, such as Redis, Memcache, among others;
  • Custom implementations (something unique to you).

Anything you need is here. If you don't find an implementation that suits you, we can create our custom implementation.

Adding a Basic Health Check to ASP.NET Services

First, modify the ConfigureServices method as described below. It will add the HealthChecks service to our DI Container.

public void ConfigureServices(IServiceCollection services)
{
    //adding health check services to container
    services.AddHealthChecks();
}

Startup.cs

Second, add on Configure pipeline the health check endpoint.

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
        if (env.IsDevelopment())
            app.UseDeveloperExceptionPage();

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapGet("/", async context =>
            {
                await context.Response.WriteAsync("Hello World!");
            });

            endpoints.MapDefaultControllerRoute();

            endpoints.MapHealthChecks("/healthcheck");
        });
}

Startup.cs

Build, run, and access the URL http://{YOUR-URL}/healthcheck you should see something like this.

All set and done to start adding services to the monitoring list. Now let's add one service to the monitor list - Mongo Db.

Adding Mongo Db as a monitor service

Let's pick from xabaril's list. xabaril's Github repository contains a large number of AspNetCore.Diagnostics.HealthChecks packages ready for use.

  • AspNetCore.HealthChecks.System
  • AspNetCore.HealthChecks.Network
  • AspNetCore.HealthChecks.SqlServer
  • AspNetCore.HealthChecks.MongoDb
  • AspNetCore.HealthChecks.Npgsql
  • AspNetCore.HealthChecks.Elasticsearch
  • AspNetCore.HealthChecks.Redis
  • AspNetCore.HealthChecks.MySql

https://github.com/xabaril/AspNetCore.Diagnostics.HealthChecks

Add the Nuget package AspNetCore.HealthChecks.MongoDb to your project and modify the AddHealthChecks method to include the Mongo Db Health Check.

public void ConfigureServices(IServiceCollection services)
{
    //adding health check services to container
    services.AddHealthChecks()
        .AddMongoDb(mongodbConnectionString: "YOUR-CONNECTION-STRING",
        name: "mongo", 
        failureStatus: HealthStatus.Unhealthy); //adding MongoDb Health Check
}

Startup.cs

After that, we are good to start monitoring the Mongo Db connectivity. Let's run our application again and retest the health status page.

Adding a second endpoint with more details

Let's create a second endpoint with more information about the status, such as which health check is failing.

using System.Linq;
using Microsoft.Extensions.Diagnostics.HealthChecks;
using System.Text.Json;

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    /*existing code*/

    app.UseEndpoints(endpoints =>
    {
        /*existing code*/

        endpoints.MapHealthChecks("/healthcheck");

        endpoints.MapHealthChecks("/healthcheck-details",
            new HealthCheckOptions
            {
                ResponseWriter = async (context, report) =>
                {
                    var result = JsonSerializer.Serialize(
                        new
                        {
                            status = report.Status.ToString(),
                            monitors = report.Entries.Select(e => new { key = e.Key, value = Enum.GetName(typeof(HealthStatus), e.Value.Status) })
                        });
                    context.Response.ContentType = MediaTypeNames.Application.Json;
                    await context.Response.WriteAsync(result);
                }
            }
        );
    });
}

Startup.cs

Run again and access the endpoints /healthcheck-details.

Now you can customize the response of your Health Check Endpoint with anything you need.

In the next article, I'll show you how to put a good UI (user interface) to it.

Source Code

https://github.com/ricardodemauro/HerosApi-Blog