Continuing the series of articles about "pitfalls" I can not ignore System.Net.HttpClient, which is very often used in practice, but it has several serious problems that may not be immediately visible.
 
 
A fairly common problem in programming is that developers only focus on the functionality of a component, while completely ignoring a very important nonfunctional component that can affect performance, scalability, ease of recovery in case of failures, security, etc. For example, the same HttpClient is a seemingly elementary component, but there are several questions: how many it creates parallel connections to the server, how long they live, how it behaves, if the DNS name accessed previously is switched to another IP address ? Let's try to answer these questions in the article.
 
Leakage of connections
 
The limit of simultaneous connections to the server
 
Long-lived connections and caching DNS
 
 
https://docs.microsoft.com/en-us/dotnet/standard/microservices-architecture/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests . And in addition to managing the lifetime of the connections, the new component provides the ability to create typed clients, as well as some other useful things. In this article and links there are enough information and examples on using HttpClientFactory, so I will not consider the details related to it in this article.