Skip to main content

Why To Use HttpClientFactory In .Net Core

HttpClient instance was used to invoke or consume the external rest API by clients like console applications or web applications.

What Is Socket?:

A Socket is a system communication protocol providing a communication channel over TCP connection.

In programming, terminology socket can be defined as the combination of Url and Port Number to make communication channels.

HttpClient Working Flow:

Let's assume that we have .Net Core application, which will consume an external API using HttpClient. The steps involved in communication are as follows:
  1. The user requests our application, in which we need to call an external API to serve results to the user.
  2. On receiving user request our application creates an instance of HttpClient.
  3. Next HttpClient looks for HttpRequestHandler object in the pool of HttpRequestHandlers. Then HttpClient picks up one of the HttpRequestHandler objects and gives all input information like Url, payload, tokens, etc to make an external API call.
  4. Then HttpRequestHandler looks for Port Number on the server system. Then HttpRequestHandler grabs the Port Number and opens a Web Socket to open a communication channel.
  5. On successfully establishing the communication channel, the external API response will be delivered to the user who requested our application.

Never Destroy HttpClient Object With C# Using Statement:

One of the most common mistakes or bad way of implementing HttpClient is destroying it by using C# Using statement. The reason behind this bad practice is the HttpClient implement 'IDisposible' interface. Because of 'IDisposible' interface, every developer believed it is good to destroy the HttpClient object to free up the resource but it is an incorrect assumption. One of the main problem caused by HttpClient object destruction is orphan web sockets that leads Port Number issues.

Example of destroying HttpClient object with Using Statement:
Using(var httpClient = new HttpClient())
  // code sample

Let's understand what happens if we destroy the HttpClient object in upcoming steps. To understand let's assume we have .Net Core application hosted on a server, let's assume we have only 3 port numbers available on the hosting server to create WebSocket(note:- in real server port numbers will be in 1000's).
  1. Now in our application, let's assume we have implemented HttpClient to be destroyed once it's usage is finished.
  2. Now the first user requested our application, on receiving request application creates a new HttpClient object inside the c# Using Statement(which means HttpClient object destroyed once code executes out of Using statement)
  3. HttpClient object picks up a HttpRequestMessageHandler object from its pool.
  4. Now HttpRequestMessageHandler object picks '1' port number available in the pool of port number(we assumed total '3' port numbers in the pool).
  5. Now using port number and information in HttpRequestMessageHandler opens WebSocket to create a communication channel.
  6. WebSocket once creates will not be closed immediately once its job is done. Because sockets are costly resources so they will wait for some time to serve if any new request comes from the application. So that the existing socket will be effectively used for the subsequent requests. But domain should be the same for subsequent requests to serve by the existing socket if the domain different new Websocket will be created.
  7. Now let's think our WebSocket created communication channel, then receiving output it will return a response to the application code.
  8. Now we got our response once our code execution comes out of C# Using statement, it will call the IDisposible interface which will destroy the HttpClient object.
  9. Destroying the HttpClient object means it will also break the communication with the WebSocket and HttpRequestMessageHandler. Now Websocket lost its communication with HttpRequestMessage, but WebSocket still alive as Orphan Websocket this means port number still be used by this Orphan Websocket and this Orphan WebSocket can't be used by any application. So here we can observe Server resources like the port number in a working mode without any purpose or we can say all those resources in useless mode. This leads to resource unavailability for subsequent requests to our application.
  10. Similarly, let's assume that same time we got 2 more user requests, now the same process we discussed in the above steps will execute for these 2 requests. So now we have 3 requests from the user to our application means our application creates 3 WebSockets to build a communication channel. This means all these WebSocket will be  Orphan WebSockets. So from this, we can understand we are out resource to create new WebSocket because now we don't have another port number to create 4th WebSocket.
  11. Now let's assume we got 4th user request now our application will search for the port number to create a WebSocket, but there no port numbers available at currently for the application because all ports are in use, so application waits for some time for the port number, finally it will throw an error like 'WebSockets Exhausted'(example exception), 'time out exception' etc.
  12. This is the main reason we need to avoid the destroying of the HttpClient object.

Solution Provided By HttpClientFactory:

HttpClienFactory will create a static instance of a HttpClient per Domain of the third-party API. So HttpRequestMessageHandler object will be lives a long time by connecting with WebSocket by setting the expiration time. By default expiration, time will 2 minutes for HttpRequestMessageHandler but we can increase that value based on our application requirements. Using this approach we can avoid orphan WebSocket and consumes fewer resources on the server.

Let's understand the steps of HttpClientFactory flow as follows:
  1. Let's assume User Requested (R1) to our application.
  2. Then in HttpClientFactory create a static instance of HttpClient. The static instance is for single time creation. HttpClientFactory creates a static instance per domain of third party API. All the requests for specific third party API will be handled by that HttpClient instance.
  3. Then HttpClient instance looks for the HttpRequestMessageHandler(HRMH1) object in the HttpRequestMessageHandler pool.
  4. Now HttpRequestMessageHandler(HRMH1) object contains all information to make API calls like Url, Payload, Token, Header's, etc.
  5. HttpRequestMessageHandler(HRMH1) object looks for the port number on the server. Then creates a WebSocket(WS1) that establishes a communication channel.
  6. Now let's assume another User Requested(R2) to our application. If (R1) and (R2) aim the same external API then HttpClientFactory provides the HttpClient instance which is created in previous steps. If (R1) and (R2) are requested for different third party API then the HttpClientFactory Provides the new static HttpClient instance. 
  7. So in our case let's assume both (R1) and (R2) user requests want the same external API. Now HttpClient instance looks HttpRequestMessageHandler object. For (R1) we know the (HRMH1) object is used. So now HttpClient checks if (HRMH1) is free to serve (R2). If (HRMH1) is free and it has a connection with active WebSocket(WS1) to serve (R2). Here we can observe (WS1) serve both (R1) and (R2) instead of creating new WebSocket(WS2). So in this process, we are efficiently utilizing our server resource. Let's check another case also like (HRMH1) is busy serving (R1) request which means (R1) request still in progress, then HttpClient instance picks up another HttpRequestMessageHander(HRMH2) object. Then (HRMH2) picks up a new port number on the server and creates a new WebSocket(WS2).
  8. The similar way all the user requests will be effectively controlled by the HttpClientFactory.

Support Me!
Buy Me A Coffee PayPal Me

Wrapping Up:

Hopefully, I think this article delivered some useful information about the HttpClientFactory in .Net Core. I love to have your feedback, suggestions, and better techniques in the comment section below.

Follow Me:


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

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'

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

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

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

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

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

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

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