Manage the lifetime of HttpMessageHandler to avoid the mentioned problems/issues that can occur when managing HttpClient lifetimes yourself.You can register HTTP clients into the factory and you can use a Polly handler to use Polly policies for Retry, CircuitBreakers, and so on. HttpClient already has the concept of delegating handlers that could be linked together for outgoing HTTP requests.Codify the concept of outgoing middleware via delegating handlers in HttpClient and implementing Polly-based middleware to take advantage of Polly's policies for resiliency.For example, you may configure a client (Service Agent) that's pre-configured to access a specific microservice. Provides a central location for naming and configuring logical HttpClient objects.The current implementation of IHttpClientFactory, that also implements IHttpMessageHandlerFactory, offers the following benefits: Polly is a transient-fault-handling library that helps developers add resiliency to their applications, by using some pre-defined policies in a fluent and thread-safe manner. It also provides extensions for Polly-based middleware to take advantage of delegating handlers in HttpClient. NET Core 2.1 introduced the IHttpClientFactory interface which can be used to configure and create HttpClient instances in an app through Dependency Injection (DI). To address the issues mentioned above and to make HttpClient instances manageable. However, the issue isn't really with HttpClient per se, but with the default constructor for HttpClient, because it creates a new concrete instance of HttpMessageHandler, which is the one that has sockets exhaustion and DNS changes issues mentioned above. In a situation where the HttpClient is instantiated as a singleton or a static object, it fails to handle the DNS changes as described in this issue of the dotnet/runtime GitHub repository. This can be a good solution for short-lived console apps or similar, that run a few times a day.Īnother issue that developers run into is when using a shared instance of HttpClient in long-running processes. Possible approaches to solve that problem are based on the creation of the HttpClient object as singleton or static, as explained in this Microsoft article on HttpClient usage. That issue will result in SocketException errors. Instantiating an HttpClient class for every request will exhaust the number of sockets available under heavy loads. Therefore, HttpClient is intended to be instantiated once and reused throughout the life of an application. For more information about this issue, see the blog post You're using HttpClient wrong and it's destabilizing your software. Though this class implements IDisposable, declaring and instantiating it within a using statement is not preferred because when the HttpClient object gets disposed of, the underlying socket is not immediately released, which can lead to a socket exhaustion problem. The original and well-known HttpClient class can be easily used, but in some cases, it isn't being properly used by many developers. Issues with the original HttpClient class available in. NET Core 2.1, for creating HttpClient instances to be used in your applications. IHttpClientFactory is a contract implemented by DefaultHttpClientFactory, an opinionated factory, available since.
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