Polly VS FluentValidation

Polly

This is probably one of the most useful "cloud" patterns out there and it is fairly easy to implement. There are great articles and implementations, like Polly, already on the internet about this pattern so why another one?

Polly Documentation: Polly Official Site Circuit Breaker Design Pattern: Microsoft Learn Microservices Best Practices: Microservices on .NET

Custom HTTP handlers are well known as a mechanism to manage cross-cutting concerns around HTTP requests. The calling application has control over the HTTP handler pipeline, so it can be reconfigured, reordered, or even rebuilt from scratch. Decorating a client with a Token Management Handler or a custom Polly policy is easy... assuming the client accepts an HttpClient parameter in its constructor, and you haven't messed with the natural order of things by obstructing the client customization in some way (I really don't want to show how).

In our applications, we should wrap all requests to remote services in code that implements a retry policy that follows one of the strategies I listed earlier. If you are a .NET developer like myself, you may be familiar with the Polly library. Golang has a library called Retry, and there are numerous third-party libraries for Python and Java.

Another question that rises is, would it be better to use some HttpClient package to handle the requests, like Refit in combination with Polly. But then again, it seems Refit also uses the HttpClient factory, which was a bad thing according to the previous?

D'Oh! Sorry, not PolySharp. I meant Polly. Too many similarly-named libraries!

Everywhere I've worked with AGs, we've worked with the application team to add retry logic to help make things a bit more seamless to end users. There are libraries out there that can make this pretty easy - Polly is one that I've used a few times, but there are others.

Fallacy 1: The network is reliable. If system 2 works perfectly well, but is not accessible for service 1 due to network issues, service 2 is still unavailable. This is why timeouts, service breakers and retry policies exist. A great tool for .NET to handle common network issues is Polly, but even when using a tool like this, the network is still not completely reliable.

I see. Then I don't have any better idea right now, but I do want to suggest that if your script is mostly API calls and you want to be able to deal with failures then take a look at the polly library: https://github.com/App-vNext/Polly

IValidator is registered as service for the following validator.

This template was built using a variety of powerful frameworks and tools, including: .NET, Ngrok, JWT (JSON Web Tokens), Entity Framework, AutoMapper, FluentValidation, Flurl, Humanizer, libphonenumber-csharp, MailKit, OAuth, Serilog, Twilio, Swagger, React.js, React Native, React Navigation, Axios, Expo Dev, Lodash, NativeWind, React Hook Form, Zustand, Visual Studio Code, Visual Studio, Android Studio, Git, GitHub Copilot, Node.js, React Native Paper, NextUI

FluentValidation is undoubtedly the most popular third-party validation library on .NET. It is a robust choice if you need clean POCOs or multiple validation maps per type. However, its performance may surprise you.

Note There is no formal documentation for inline validation. See source code.

18. FluentValidation.AspNetCore

Here is an example of Command handler with built-in Fluent Validation and fire and forget style:

There is an RFC called Problem Details (RFC7807) that standardizes how an error in an API should be responded to for the client. If you use Fluent validation, you may have noticed that the response is within this pattern.

here we're defining the input validation requirements using fluent validation rules. let's see what happens when the user input doesn't meet the above criteria. execute the same request in swagger with the following incorrect json content: