Skip to main content

An Overview On Implementing Health Checks In .Net5 Application

In this article, we will discuss Healths Checks implementation in .Net5 application.

Health Checks:

To verify the state of an application .net provides health checks as a middleware configuration. Health check reports of an application can be accessed via an endpoint. Health check monitoring scenarios of an application like:
  • Health check helps to verify the status of app dependencies like Database, External Service calls, to confirm they work normally.
  • Memory and Disk Usage Monitoring.
  • Advanced scenarios like monitoring application load balancers

Create A Sample Web API App:

Let's create a sample .Net5 Web API application and do some sample examples to understand the Health Checks. For development, an IDE can be chosen on our personal preference, but the most recommended are Visual Studio 2019(Version 16.8.* supports .Net5) or Visual Studio Code.

Initial Health Check Configurations:

Initially, we need to register the 'AddHealthChecks' service and endpoint to view health reports.
Startup.cs:(ConfigureServices Method)
services.AddHealthChecks();
  • The 'AddHealthChecks' service returns an instance of 'IHeathChecksBuilder' from which health checks can be registered(in upcoming steps). This service loads from 'Microsoft.Extensions.Diagnostics.HealthChecks.HealthCheckService'.
Startup.cs:(Configure Method) 
app.UseEndpoints(endpoints =>
{
	endpoints.MapHealthChecks("/health");
	endpoints.MapControllers();
});
  • Configure the '/health' endpoint that returns a report of our app health status.
Till now we haven't registered any specific Health Checks but if we try to access the endpoint it returns 'healthy' status by default.

Types Of Health Check Results:

The 'Microsoft.Extensions.Diagnostics.HealthChecks.HealthCheckReult' returns 3 types of results like
  • Healthy(App is in good state)
  • Degraded(Not too dangerous but there are issues that need to be fixed)
  • UnHealthy(High priority issues to be fixed)
An application health check report generated based on the health check result mentioned above. For suppose if all health checks return 'Healthy' status then our overall report is 'Healthy' and if at least one health check is 'Degraded' then all our final report will be degraded and if at least one health check is 'UnHealthy' then our final report will be 'UnHealthy'. The order of preference will be like 'UnHealthy', 'Degraded', 'Healthy'. We should always try to get a 'Healthy' status for our application.

Basic Overview On AddCheck Method:

Based on the application we can implement multiple health checks. Each health check needs to be registered using the overloaded 'AddCheck' method.

Let's register a fake health check that returns the status of 'Healthy'.
Startup.cs:(ConfigureServices Method)
using Microsoft.Extensions.Diagnostics.HealthChecks;

services.AddHealthChecks()
.AddCheck("My Healthy Check", () => {
	return HealthCheckResult.Healthy("My Application Fully Helthy");
})
  • In the 'AddCheck' method, the first parameter specifies the name of our health check and the second parameter needs to be 'Microsoft.Extension.Diagnostics.HealthChecks.HealthCheckResult'. So in the second parameter here we just have written our fake logic to return 'Healthy' status.
Let's register a fake health check that returns the status of 'Degraded'
Startup.cs:(ConfigureServices Method)
services.AddHealthChecks()
.AddCheck("My Healthy Check", () => {
  return HealthCheckResult.Healthy("My Application Fully Helthy");
})
.AddCheck("My Degraded Check", () => {
  return HealthCheckResult.Degraded("My Application in Degraded state");
});
  • In our application, if anyone health check that returns 'Degraded' then the overall report will give status as 'Degraded'
Let's register a fake health check that returns the status of 'UnHealthy'
Startup.cs:(ConfigureServices Method)
services.AddHealthChecks()
.AddCheck("My Healthy Check", () => {
  return HealthCheckResult.Healthy("My Application Fully Helthy");
})
.AddCheck("My Degraded Check", () => {
  return HealthCheckResult.Degraded("My Application in Degraded state");
})
.AddCheck("My UnHealthy Check", () => {
  return HealthCheckResult.Unhealthy("My Application is in Un Healthy State");
});
  • In our application, if anyone health check that returns 'UnHealthy' then the overall report will give status as 'UnHealthy'.

Health Check Using IHealthCheck Interface:

Using the IHealthCheck interface we can create a separate file for the health check.

Let's create an IHealthCheck service to add a fake health check.
HealthChecks/TestHealthCheck.cs:
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Diagnostics.HealthChecks;

namespace API.HealthChecks.HealthChecks
{
  public class TestHealthChecks : IHealthCheck
  {
   public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, 
   CancellationToken cancellationToken = default)
   {
    await Task.FromResult(0);
    return HealthCheckResult.Healthy("Im healthy");
   }
  }
}
  • Inherits 'IHealthCheck' interface then implement the 'CheckHealthAsync' method where the status of our health return
Now register our 'TestHealthChecks' in the Startup file.
Startup.cs:
services.AddHealthChecks()
.AddCheck<TestHealthChecks>("My Test Health Check");
We can pass an argument to 'TestHealtChecks' from the service register.
Startup.cs:
services.AddHealthChecks()
.AddTypeActivatedCheck<TestHealthChecks>("My Test Health Check", 
args: new object[]{"Hello"});
  • To pass an arguments to our 'TestHealthChecks' service we need to register using 'AddTypeActivatedCheck<T>' method. The 'args' parameter to pass parameters.
Now our 'TestHealthChecks' service receives parameters from the constructor.
HealthChecks/TestHealthCheck.cs:
public class TestHealthChecks : IHealthCheck
{
  public TestHealthChecks(string message)
  {
  }
  // code hidden for display purpose
}

Customized JSON String Response:

Till now our health check report delivering us a simple string as a response of status. It is also delivering the overall status output there is no extra information about each individual health checks status. So to get full health checks to report with detailed information on each health check we need to customize our health check endpoint response.
Package Manager:
Install-Package Newtonsoft.Json
.Net CLI
dotnet add package Newtonsoft.Json
Now let's add our logic to customize the health check response as below.
Startup.cs: 
private static async Task WriteResponse(HttpContext context, HealthReport report)
{
  context.Response.ContentType = "application/json";

  var json = new JObject(
	new JProperty("Status", report.Status.ToString()),
	new JProperty("Results",
	new JObject(report.Entries.Select(pair =>
	  new JProperty(pair.Key, new JObject(
	   new JProperty("Status", pair.Value.Status.ToString()),
	   new JProperty("Description", pair.Value.Description),
	   new JProperty("Data", new JObject(
		  pair.Value.Data.Select(p => new JProperty(p.Key, p.Value))
	   ))
	  ))
	  ))
	)
  );
  await context.Response.WriteAsJsonAsync(json.ToString(Formatting.Indented));
}
  • This method returns our full detailed health report as a JSON string. This method takes input parameters like 'HttpContext' and 'HealthReport'.
  • (Line: 6) Creating a top-level property 'Status' whose value is the overall status of our application.
  • (Line: 7) Creating a top-level property 'Result' whose value is the object that contains each health check name as its property.
  • (Line: 8) The 'report.Entries.Select' fetches each health check and signs its names as property to 'Results' property.
  • (Line: 10) Fetches status of each individual health check status.
  • (Line: 11) Fetches description give along with the health check status.
  • (Line: 12) Fetches any other extra information we want to return.
Let's update the health check endpoints to use our custom response
Startup.cs:
app.UseEndpoints(endpoints =>
{
  endpoints.MapHealthChecks("/health", new HealthCheckOptions(){
   ResponseWriter = WriteResponse
  });
  endpoints.MapControllers();
});

Entity Framework To Test Database Health Check:

Now it is very easy to add health checks for our database connection using entity framework core.
Package Manager:
Install-Package Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore
.Net CLI:
dotnet add package Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore
Now register entity framework core health check as below.
Startup.cs:
services.AddHealthChecks()
.AddDbContextCheck<MyWorldDbContext>("My World Db Health Check");
  • Here 'MyWorldDbContext' is my application DbContext for this context we registered health checks using the 'AddDbContextCheck' method.
Now let's test our context health checks if everything is good and health reports for context that results as below.
Now for the testing purpose just give a wrong connection string for our context and test the health report.

External API Health Checks:

Let's implement logic to monitoring health checks of external API calls by considering the time it takes to complete the request.

Here I'm not showing a detailed implementation of HttpClient, click here for the Typed HttpClient Approach.

Let's create a new health checks service for external API monitoring.
HealthChecks/ApiHealthCheck:
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using API.HealthChecks.Clients;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Diagnostics.HealthChecks;

namespace API.HealthChecks.HealthChecks
{
  public class ApiHealthCheck : IHealthCheck
  {
   private readonly JsonPlaceHolderClient _jsonPlace;
   public ApiHealthCheck(JsonPlaceHolderClient jsonPlace)
   {
	_jsonPlace = jsonPlace;
   }
   public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
   {
	Stopwatch stopWatch = new Stopwatch();
	stopWatch.Start();
	 await _jsonPlace.GetTodos();
	stopWatch.Stop();
	var time = stopWatch.Elapsed.Milliseconds;
	if (time < 350)
	{
	 return HealthCheckResult.Healthy($"Im Healthy {time} ");
	}
	return HealthCheckResult.Unhealthy($"Im Un Healthy {time}");
   }
  }
}
  • In this health check service, we are monitoring API time taken to complete the request base on time(example milliseconds) status will either 'Healthy' or 'UnHealthy'. The 'JsonPlaceHolderClient' contains my HttpClient logic.
Now register our health service in the Startup file.
Startup.cs:
services.AddHealthChecks()
.AddCheck<ApiHealthCheck>("My api health check");

services.AddScoped<ApiHealthCheck>();
  • Since we are injecting 'JsonPlaceHolderClient' into the 'ApiHealthCheck' service we need to register it with 'AddScoped'.
Similarly, we can monitor database queries if we want.

Filter Health Checks:

By default health check middleware runs all configure health checks. Having more and more health checks should not cause any performance issue, so to do this better way we can filter health checks and run only the required health checks based on the 'tags' argument and health check endpoint.

The 'tags' argument is a collection string to register with health checks, this collection of string can be utilized in the endpoint whether to run the health check or not. Filtering health checks we need to register multiple health check endpoints.

Now let's update our health checks with the 'tags' argument
Startup.cs:
 services.AddHealthChecks()
.AddCheck<ApiHealthCheck>("My api health check", tags: new[]{"API"})
.AddDbContextCheck<MyWorldDbContext>("My World Db Health Check", tags: new[]{"DB"})
.AddCheck("My Healthy Check", () => {
  return HealthCheckResult.Healthy("My Application Fully Helthy");
},tags: new[]{"fake"})
.AddCheck("My Degraded Check", () => {
  return HealthCheckResult.Degraded("My Application in Degraded state");
},tags: new[]{"fake"})
.AddCheck("My UnHealthy Check", () => {
  return HealthCheckResult.Unhealthy("My Application is in Un Healthy State");
},tags: new[]{"fake"});
  • Here we categorized our health checks by giving them tag names like 'API', 'DB', and 'fake'.
Now add our health check endpoint which executes by validating the tags parameter.
Startup.cs:
app.UseEndpoints(endpoints =>
{
  endpoints.MapHealthChecks("/health-fake", new HealthCheckOptions(){
   ResponseWriter = WriteResponse,
   Predicate = (check) => check.Tags.Contains("Fake")
  });
  endpoints.MapHealthChecks("/health-db", new HealthCheckOptions(){
   ResponseWriter = WriteResponse,
   Predicate = (check) => check.Tags.Contains("DB")
  });
  endpoints.MapHealthChecks("/health-api", new HealthCheckOptions(){
   ResponseWriter = WriteResponse,
   Predicate = (check) => check.Tags.Contains("API")
  });
  endpoints.MapControllers();
});
  • Here we defined multiple health check endpoints. These endpoints run the health checks that are matched to tags comparison defined inside of the endpoint

Support Me!
Buy Me A Coffee PayPal Me

Wrapping Up:

Hopefully, I think this article delivered some useful information on Health Checks in .Net5 Application. I love to have your feedback, suggestions, and better techniques in the comment section below.

Refer:

Follow Me:

Labels:

Comments

Post a Comment

Popular posts from this blog

.NET6 Web API CRUD Operation With Entity Framework Core

In this article, we are going to do a small demo on AspNetCore 6 Web API CRUD operations. What Is Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, desktop apps. In simple terminology API(Application Programming Interface) means an interface module that contains a programming function that can be requested via HTTP calls to save or fetch the data for their respective clients. Some of the key characteristics of API: Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Supports default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. The ideal platform to build REST full services. Create A .NET6 Web API Application: Let's create a .Net6 Web API sample application to accomplish our
6 comments
Read more

Angular 14 Reactive Forms Example

In this article, we will explore the Angular(14) reactive forms with an example. Reactive Forms: Angular reactive forms support model-driven techniques to handle the form's input values. The reactive forms state is immutable, any form filed change creates a new state for the form. Reactive forms are built around observable streams, where form inputs and values are provided as streams of input values, which can be accessed synchronously. Some key notations that involve in reactive forms are like: FormControl - each input element in the form is 'FormControl'. The 'FormControl' tracks the value and validation status of form fields. FormGroup - Track the value and validate the state of the group of 'FormControl'. FormBuilder - Angular service which can be used to create the 'FormGroup' or FormControl instance quickly. Form Array - That can hold infinite form control, this helps to create dynamic forms. Create An Angular(14) Application: Let'
3 comments
Read more

Part-1 Angular JWT Authentication Using HTTP Only Cookie[Angular V13]

In this article, we are going to implement a sample angular application authentication using HTTP only cookie that contains a JWT token. HTTP Only JWT Cookie: In a SPA(Single Page Application) Authentication JWT token either can be stored in browser 'LocalStorage' or in 'Cookie'. Storing JWT token inside of the cookie then the cookie should be HTTP Only. The HTTP-Only cookie nature is that it will be only accessible by the server application. Client apps like javascript-based apps can't access the HTTP-Only cookie. So if we use authentication with HTTP only JWT cookie then we no need to implement custom logic like adding authorization header or storing token data, etc at our client application. Because once the user authenticated cookie will be automatically sent to the server by the browser on every API call. Authentication API: To implement JWT cookie authentication we need to set up an API. For that, I had created a mock authentication API(Using the NestJS Se
Post a Comment
Read more

Unit Testing Asp.NetCore Web API Using xUnit[.NET6]

In this article, we are going to write test cases to an Asp.NetCore Web API(.NET6) application using the xUnit. xUnit For .NET: The xUnit for .Net is a free, open-source, community-focused unit testing tool for .NET applications. By default .Net also provides a xUnit project template to implement test cases. Unit test cases build upon the 'AAA' formula that means 'Arrange', 'Act' and 'Assert' Arrange - Declaring variables, objects, instantiating mocks, etc. Act - Calling or invoking the method that needs to be tested. Assert - The assert ensures that code behaves as expected means yielding expected output. Create An API And Unit Test Projects: Let's create a .Net6 Web API and xUnit sample applications to accomplish our demo. We can use either Visual Studio 2022 or Visual Studio Code(using .NET CLI commands) to create any.Net6 application. For this demo, I'm using the 'Visual Studio Code'(using the .NET CLI command) editor. Create a fo
6 comments
Read more

A Small Guide On NestJS Queues

NestJS Application Queues helps to deal with application scaling and performance challenges. When To Use Queues?: API request that mostly involves in time taking operations like CPU bound operation, doing them synchronously which will result in thread blocking. So to avoid these issues, it is an appropriate way to make the CPU-bound operation separate background job.  In nestjs one of the best solutions for these kinds of tasks is to implement the Queues. For queueing mechanism in the nestjs application most recommended library is '@nestjs/bull'(Bull is nodejs queue library). The 'Bull' depends on Redis cache for data storage like a job. So in this queueing technique, we will create services like 'Producer' and 'Consumer'. The 'Producer' is used to push our jobs into the Redis stores. The consumer will read those jobs(eg: CPU Bound Operations) and process them. So by using this queues technique user requests processed very fastly because actually
7 comments
Read more

Angular 14 State Management CRUD Example With NgRx(14)

In this article, we are going to implement the Angular(14) state management CRUD example with NgRx(14) NgRx Store For State Management: In an angular application to share consistent data between multiple components, we use NgRx state management. Using NgRx state helps to avoid unwanted API calls, easy to maintain consistent data, etc. The main building blocks for the NgRx store are: Actions - NgRx actions represents event to trigger the reducers to save the data into the stores. Reducer - Reducer's pure function, which is used to create a new state on data change. Store - The store is the model or entity that holds the data. Selector - Selector to fetch the slices of data from the store to angular components. Effects - Effects deals with external network calls like API. The effect gets executed based the action performed Ngrx State Management flow: The angular component needs data for binding.  So angular component calls an action that is responsible for invoking the API call.  Aft
7 comments
Read more

Usage Of CancellationToken In Asp.Net Core Applications

When To Use CancellationToken?: In a web application request abortion or orphan, requests are quite common. On users disconnected by network interruption or navigating between multiple pages before proper response or closing of the browser, tabs make the request aborted or orphan. An orphan request can't deliver a response to the client, but it will execute all steps(like database calls, HTTP calls, etc) at the server. Complete execution of an orphan request at the server might not be a problem generally if at all requests need to work on time taking a job at the server in those cases might be nice to terminate the execution immediately. So CancellationToken can be used to terminate a request execution at the server immediately once the request is aborted or orphan. Here we are going to see some sample code snippets about implementing a CancellationToken for Entity FrameworkCore, Dapper ORM, and HttpClient calls in Asp.NetCore MVC application. Note: The sample codes I will show in
2 comments
Read more

Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication. Main Building Blocks Of Blazor WebAssembly Authentication: The core concepts of blazor webassembly authentication are: AuthenticationStateProvider Service AuthorizeView Component Task<AuthenticationState> Cascading Property CascadingAuthenticationState Component AuthorizeRouteView Component AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider. AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider
6 comments
Read more

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr
Post a Comment
Read more

Angular 14 Crud Example

In this article, we will implement CRUD operation in the Angular 14 application. Angular: Angular is a framework that can be used to build a single-page application. Angular applications are built with components that make our code simple and clean. Angular components compose of 3 files like TypeScript File(*.ts), Html File(*.html), CSS File(*.cs) Components typescript file and HTML file support 2-way binding which means data flow is bi-directional Component typescript file listens for all HTML events from the HTML file. Create Angular(14) Application: Let's create an Angular(14) application to begin our sample. Make sure to install the Angular CLI tool into our local machine because it provides easy CLI commands to play with the angular application. Command To Install Angular CLI npm install -g @angular/cli Run the below command to create the angular application. Command To Create Angular Application ng new name_of_your_app Note: While creating the app, you will see a noti
4 comments
Read more