Skip to main content

.Net5 HttpClient Retry Policy And Circuit Breaker Policy

In this article, we are going to learn about HttpClient policies like retry policy, circuit breaker policy.

Retry Policy:

By using HttpClientFactory it is very easy to configure the retry calls. We can configure the retry count. So if an HTTP call fails and if we configured our retry policy then the framework will automatically attempt to retry HTTP call up to the specified retry count number.

Circuit Breaker Policy:

The circuit breaker policy prevents our application to perform the operation that is likely to fail. An application can use both Retry Policy and Circuit Breaker Policy. 

Let's understand the circuit breaker policy flow:
  • Assume like in our application configured retry policy. Retry policy should have like count for retires and timespan between each retry.
  • Next circuit breaker policy configured with 2 parameters like count and timespan. If the number of consecutive HTTP failed calls count matches with the circuit breaker policy count then the circuit will open means subsequent requests or retry won't invoke Http Call they simply return the error message to the user directly. If we want we can write middleware to format the error response from the circuit breaker. The timespan parameter in the circuit breaker defines the period of the circuit opened.
  • After circuit timespan parameter time completed, then the circuit will be closed and flow will repeat.

Create .Net5 Web APIs:

For our demo purpose let's create 2 .Net5 Web API projects. Name them like 'MasterAPI' and 'ClienAPI'. By default, the Web API project template contains whether forecast endpoint. So our goal is to consume the 'MaserAPI' endpoint by our 'ClientAPI'. Since dotnet application locally by default run under ports like '5001' and '5000', so for 'MasterAPI' change them to '6001' and '6000'.

Typed Client:

Either using  Typed Client or Named Client techniques of HttpClient only can be configured with Retry or Circuit Breaker policies. So here I'm going to create a Typed Client in the 'ClientAPI' project to consume the endpoint from 'MaserAPI'.



Now create a Typed Client class and name it as 'TestClient.cs' and here implement our logic to fetch the data from the 'MasterAPI' endpoint.
ClientAPI/TestClient.cs:
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Json;
using System.Threading.Tasks;

namespace ClientAPI
{
    public class TestClient
    {
        private readonly HttpClient _httpClient;
        public TestClient(HttpClient httpClient)
        {
            _httpClient = httpClient;
        }

        public async Task<List<WeatherForecast>> GetWeather()
        {
            return await _httpClient.GetFromJsonAsync<List<WeatherForecast>>("WeatherForecast");
        }
    }
}
Now register our Typed Client in 'Startup.cs'
Startup.cs:
services.AddHttpClient<TestClient>(client => {
  client.BaseAddress = new Uri("https://localhost:6001");
})
.SetHandlerLifetime(TimeSpan.FromMinutes(5));
  • Registered base domain for our Typed Client.
  • Lifetime for HttpClient instance set to 5 minutes.
Now let's create a new controller like 'TestController.cs'.
Controllers/TestController.cs:
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

namespace ClientAPI.Controllers
{
    [ApiController]
    [Route("[controller]")]

    public class TestController : ControllerBase
    {
        private readonly TestClient _testClient;
        public TestController(TestClient testClient)
        {
            _testClient = testClient;
        }

        [HttpGet]
        [Route("weather")]
        public async Task<IActionResult> GetWeatherAsync()
        {
            return Ok(await _testClient.GetWeather());
        }
    }
}
Now run both 'MasterAPI' and 'ClientAPI' projects. The result of 'ClientAPI' looks as below.

Install Polly Library:

To register policies we have to install a Microsoft extension library. We have to install this library in our 'ClientAPI' project
Package Manager:
Install-Package Microsoft.Extensions.Http.Polly -Version 5.0.1
.Net CLI
dotnet add package Microsoft.Extensions.Http.Polly --version 5.0.1

Configure Retry Policy:

Now in the 'ClientAPI' project, we are going to register Retry Policy to our Typed Client(TestClient.cs).

Let's create a static method of our retry policy in 'Startup.cs'
Startup.cs:
private static IAsyncPolicy<HttpResponseMessage> GetRetryPolicy()
{
	return HttpPolicyExtensions
	.HandleTransientHttpError()
	.WaitAndRetryAsync(5, retryAttempt => TimeSpan.FromSeconds(10));
}
  • Here our policy is like on HTTP call error, the application has to retry the HTTP calls for '5' times of an interval of 10 seconds on each failure.
Let's register this policy method.
Startup.cs:
services.AddHttpClient<TestClient>(client =>
{
	client.BaseAddress = new Uri("https://localhost:6001");
})
.SetHandlerLifetime(TimeSpan.FromMinutes(5))
.AddPolicyHandler(GetRetryPolicy());
Now to test this Http calls retry, stop running the 'MasterAPI' and then run the 'ClientAPI'.
Here we can observe the HTTP calls retry. Once the retry count registered in policy exceeded then the application returns the error message to users.

Configure Circuit Breaker Policy:

Now in our 'ClientAPI' project, we will register one more policy called Circuit Breaker Policy. Circuit Breaker Policy breaks or opens the flow which means the subsequent request will receive an error message from the circuit breaker as a response without invoking the HTTP call. This will very helpful in some cases like our third-party API if they down instead of invoking them every time circuit breaker will give the error response without invoking the HTTP call for a specified amount of time, this approach will help to boost our application.

Now let's create a static method in 'Startup.cs' that implements Circuit Breaker Policy.
Startup.cs:
private static IAsyncPolicy<HttpResponseMessage> GetCircuitBreakerPolicy()
{
	return HttpPolicyExtensions
	.HandleTransientHttpError()
	.CircuitBreakerAsync(3, TimeSpan.FromMinutes(1));
}
  • Here Circuit Breaker will opens or breaks after 3 consecutive errors, so the next subsequent request will receive an error response directly from Circuit Breaker without invoking HTTP call, this will continue till the time specified, here in our sample we specified 1 minute. 
  • So for this 1-minute Circuit Breaker in opening or breaking state, once this time is finished then Circuit Breaker will close and the immediate next request will invoke the HTTP calls.
Now register Circuit Breaker to Typed Client as policy.
Startup.cs:
services.AddHttpClient<TestClient>(client =>
{
	client.BaseAddress = new Uri("https://localhost:6001");
})
.SetHandlerLifetime(TimeSpan.FromMinutes(5))
.AddPolicyHandler(GetRetryPolicy())
.AddPolicyHandler(GetCircuitBreakerPolicy());
Now to test the circuit breaker, let's stop running 'MasterAPI', then run our 'ClientAPI'.
Now request 'ClientAPI', since we have registered retry policy, our request will be automatically retiring the HTTP call on every failure.
Now on completion of 3 failure HTTP calls continually, the Circuit Breaker will open or breaks the follow and returns the error response to the client. This opening or breaking state will remains for 1-minute as we specified.
Now in another browser tab request API again, then you can observe you will receive an error immediately from the circuit breaker without invoking HTTP call.
So that all about the register Retry and Circuit breaker policies for HttpClient.

Video Session:

Support Me!
Buy Me A Coffee PayPal Me

Wrapping Up:

Hopefully, I think this article delivered some useful information on HttpClient Policies like Retry and Circuit Breaker. I love to have your feedback, suggestions, and better techniques in the comment section below.

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