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:

Comments

Popular posts from this blog

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

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

.Net5 Web API Managing Files Using Azure Blob Storage

In this article, we are going to understand the different file operations like uploading, reading, downloading, and deleting in .Net5 Web API application using Azure Blob Storage. Azure Blob Storage: Azure blob storage is Microsoft cloud storage. Blob storage can store a massive amount of file data as unstructured data. The unstructured data means not belong to any specific type, which means text or binary data. So something like images or pdf or videos to store in the cloud, then the most recommended is to use the blob store. The key component to creating azure blob storage resource: Storage Account:- A Storage account gives a unique namespace in Azure for all the data we will save. Every object that we store in Azure Storage has an address. The address is nothing but the unique name of our Storage Account name. The combination of the account name and the Azure Storage blob endpoint forms the base address for each object in our Storage account. For example, if our Storage Account is n

.Net5 Web API Redis Cache Using StackExchange.Redis.Extensions.AspNetCore Library

In this article, we are going to explore the integration of Redis cache in .Net5 Web API application using the 'StackExchange.Redis.Exntensions' library. Note:- Microsoft has introduced an 'IDistributedCache' interface in dotnet core which supports different cache stores like In-Memory, Redis, NCache, etc. It is simple and easy to work with  'IDistributedCache', for the Redis store with limited features but if we want more features of the Redis store we can choose to use 'StackExchange.Redis.Extensions'.  Click here for Redis Cache Integration Using IDistributedCache Interface . Overview On StackExchange.Redis.Extnesions Library: The 'StackExchange.Redis.Extension' library extended from the main library 'StackExchange.Redis'. Some of the key features of this library like: Default serialization and deserialization. Easy to save and fetch complex objects. Search key. Multiple Database Access Setup Redis Docker Instance: For this sampl

Endpoint Routing In Asp.Net Core

How Routing Works In  Core 2.1 And Below Versions?: In Asp.Net Core routing is configured using app.UseRouter() or app.UseMvc() middleware. app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); Here in Dotnet Core version 2.1 or below versions on the execution of route middleware request will be navigated appropriate controller matched to the route. An operation or functionality which is dependent on route URL or route values and that need to be implemented before the execution of route middleware can be done by accessing the route path from the current request context as below app.Use(async (context, next) => { if(context.Request.Path.Value.IndexOf("oldvehicle") != -1) { context.Response.Redirect("vehicle"); } else { await next(); } }); app.UseMvc(routes => { routes.MapRoute( name: "vehicleRoute", template: "vehicle", defaul

Asp.Net Core MVC Form Validation Techniques

Introduction: Form validations in any applications are like assures that a valid data is storing on servers. All programing frameworks have their own individual implementations for form validations. In Dotnet Core MVC application server-side validations carried on by the models with the help of Data Annotations and the client-side validations carried by the plugin jQuery Unobtrusive Validation. jQuery Unobtrusive Validation is a custom library developed by Microsoft based on the popular library  jQuery Validate . In this article, we are going to learn how the model validation and client-side validation works in Asp.Net Core MVC Application with sample examples. Getting Started: Let's create an Asp.Net Core MVC application project using preferred editors like Microsoft Visual Studio or Microsoft Visual Studio Code. Here I'm using Visual Studio. Let's create an MVC controller and name it as 'PersonController.cs' and add an action method as bel

NestJS File Upload

In this article, we are going to understand the steps to create a file uploading endpoint in the NestJS application. Key Features In NestJS File Upload: Let us know some key features of NestJS file upload before implementing a sample application. FileInterceptor: The 'FileInterceptor' will be decorated on top of the file upload endpoint. This interceptor will read single file data from the form posted to the endpoint. export declare function FilesInterceptor(fieldName: string, localOptions?: MulterOptions): Type<NestInterceptor>; Here we can observe the 'fieldName' first input parameter this value should be a match with our 'name' attribute value on the form file input field. So our interceptor read our files that are attached to the file input field. Another input parameter of 'MulterOptions' that provides configuration like file destination path, customizing file name, etc. FilesInterceptor: The 'FilesInterceptor' will be decorated on t

.NET Core MVC Application File Upload To Physical Location With Buffered Technique

Buffering Technique In File Upload: The server will use its Memory(RAM) or Disk Storage to save the files on receiving a file upload request from the client.  Usage of Memory(RAM) or Disk depends on the number of file requests and the size of the file.  Any single buffered file exceeding 64KB is moved from Memory to a temp file on disk.  If an application receives heavy traffic of uploading files there might be a chance of out of Disk or RAM memory which leads to crash application. So this Buffer technique used for small files uploading. In the following article, we create a sample for the file uploading using .NET Core MVC application. Create The .NET Core MVC Project: Let's create a .NET Core MVC project, here for this sample I'm using Visual Studio Code as below.   Check the link to use the Visual Studio Code for .NET Core Application . IFormFile: Microsoft.AspNetCore.Http.IFormFile used for file upload with buffered technique. On uploading files f

Ionic Picker Sample Code In Angular

Introduction: Ionic Picker(ion-picker) is a popup slides up from the bottom of the device screen, which contains rows with selectable column separated items. The main building block of ion-picker as follows: PickerController PickerOptions PickerController: PickerController object helps in creating an ion-picker overlay. create(opts?: Opts): Promise<Overlay> PickerController create method helps in create the picker overlay with the picker options PickerOptions: PickerOptions is a configuration object used by PickerController to display ion-picker. Single Column Ionic Picker: single.item.picker.ts: import { Component } from "@angular/core"; import { PickerController } from "@ionic/angular"; import { PickerOptions } from "@ionic/core"; @Component({ selector: "single-column-picker", templateUrl:"single.item.picker.html" }) export class SingleItemPicker { animals: string[] = ["Tiger&quo

.Net Core HttpClient JSON Extension Methods Using System.Net.Http.Json Package

.Net Core 3.0 onwards Microsoft brought up a new package called System.Net.Http.Json. This new package provides JSON extension methods for HttpClient. These JSON extension methods will have a prebuild mechanism for serializing or deserializing response data or payload of HttpClient call. System.Net.Http.Json extension methods that are provided to HttpClient, few of them are mentioned below. GetFromJsonAsync PostAsJsonAsync PutAsJsonAsync ReadFromJsonAsync In this article, we understand System.Net.Http.Json package by implementing the HttpClient samples by with and without JSON extension methods and compare them. Create A .Net Core Web API Sample Application: Let's create a .Net Core sample Web API application, from this application we will consume another Web API by implementing HttpClient calls. We can create a Web API sample application using IDE like Visual Studio 2019(Supports .Net Core 3.0 plus) or  Visual Studio Code . Create A Typed Client: In .Net Core using the Http