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Enhancing HttpClient Performance in .NET Core Applications – Codingvila


The HttpClient class within the System.Net.Http namespace serves as a pivotal tool for managing HTTP requests and responses from resources identified by URIs. By encapsulating a range of settings applied universally across its requests, each instance of HttpClient ensures the integrity and isolation of its operations through its dedicated connection pool. Starting from .NET Core 2.1 onwards, the SocketsHttpHandler class plays a fundamental role in ensuring consistent functionality across diverse platforms.

When integrating HttpClient into an application, there are two primary approaches to consider, each tailored to specific client lifetime management requirements.

For clients with prolonged lifespans, it’s advisable to instantiate a static or singleton instance utilizing the HttpClient class, alongside configuring the PooledConnectionLifetime property.

For clients with shorter lifespans, employing clients generated by the IHttpClientFactory interface is the preferred method.

In scenarios where clients persist over extended durations, it’s crucial to address DNS resolution issues. HttpClient, by default, only resolves DNS entries upon connection creation, failing to update dynamically with DNS server changes. To mitigate this, managing the connection’s lifetime becomes imperative. By setting the PooledConnectionLifetime property, one can specify a duration after which the connection is terminated, triggering a fresh DNS lookup upon replacement.

Consider the subsequent example, where HttpClient is configured to maintain connections for 5 minutes. Upon the expiration of the specified TimeSpan, denoted by PooledConnectionLifetime, the existing connection is terminated, prompting the creation of a new one:

var handler = new SocketsHttpHandler
    PooledConnectionLifetime = TimeSpan.FromMinutes(5) // Recreate after every 5 minutes
var client = new HttpClient(handler);

Connection Pooling

The HttpClient’s connection pooling mechanism is closely linked to its underlying SocketsHttpHandler. When HttpClient releases existing connections from its pool, subsequent requests to the identical server necessitate establishing fresh connections. This process incurs performance overhead due to unnecessary connection setup. Moreover, TCP ports may not be promptly released upon closure, potentially leading to port exhaustion, especially during periods of high request rates. To address port exhaustion concerns, it’s recommended to reuse HttpClient instances for multiple HTTP requests whenever possible.

Transient Client Instances

The inception of the IHttpClientFactory in .NET Core 2.1 revolutionized the process of generating HttpClient instances by offering a convenient factory abstraction. This abstraction simplifies the creation of HttpClient instances while allowing for customized configurations tailored to specific needs. It simplifies the incorporation of third-party middleware for various HTTP-based tasks within .NET applications. By leveraging the AddHttpClient extension methods, the integration of the IHttpClientFactory and its associated services seamlessly merges into the IServiceCollection.

Implementations of IHttpClientFactory

For those adhering to modern application development principles, the IHttpClientFactory provides a vital factory abstraction for creating HttpClient instances with tailored configurations. This feature, introduced in .NET Core 2.1, allows for the seamless integration of resilient and transient-fault-handling third-party middleware into common HTTP-based .NET workloads.

With the evolving landscape of modern application development, adhering to best practices becomes paramount. The IHttpClientFactory, a part of the Microsoft.Extensions.Http package, offers a factory abstraction for creating HttpClient instances with customized configurations, aligning well with these principles. Introduced in .NET Core 2.1, this feature facilitates the utilization of resilient and transient-fault-handling third-party middleware for common HTTP-based .NET workloads.

When setting up Dependency Injection in the Startup class, integrating the IHttpClientFactory is straightforward. By invoking the AddHttpClient method within the ConfigureServices method, HttpClient instances become readily available for use throughout the application.

HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);

In application code, creating an HttpClient instance is as simple as calling CreateClient on the IHttpClientFactory.

using HttpClient client = httpClientFactory.CreateClient();

Consumption of the IHttpClientFactory can manifest in various patterns within an application:

1. Basic Usage: Adding HttpClientFactory registration involves invoking AddHttpClient in the ConfigureServices method.


2. Named Clients: Named clients offer flexibility when an application requires multiple HttpClient implementations, each with distinct configurations. During registration on the IServiceCollection, these configurations can be specified for a named HttpClient.

builder.Services.AddHttpClient("ActionHttpClientName"client => {
    client.BaseAddress = new Uri("");

In the provided code snippet, a client named “ActionHttpClientName” is configured with a base address of “” and an added apiKey for authentication purposes.

Usage of a named client involves creating the client using its specified name.

using HttpClient client = _httpClientFactory.CreateClient("ActionHttpClientName");

3. HttpClient Lifetime Management: The IHttpClientFactory ensures proper management of HttpClient instances’ lifetimes. Each call to CreateClient returns a new HttpClient instance, and one HttpClientHandler instance is created per client name. The factory effectively manages the lifetimes of these HttpClientHandler instances, caching them to minimize resource consumption. Reusing HttpClientHandler instances from the cache reduces the risk of socket exhaustion and connection delays, as handlers typically manage their own underlying HTTP connection pool. Additionally, caching handlers enables them to react to DNS changes effectively, as some handlers may keep connections open indefinitely.


Guidelines for using HttpClient

HTTP support in .NET

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