ResilientHtttpClient

HttpClient.cs

using Flurl.Http;
using Polly;
using Polly.Retry;
using System;
using System.Linq;
using System.Net;
using System.Threading.Tasks;

namespace ResilientHttpClient
{
    public class HttpClient
    {
        public HttpClient()
        {

        }

        public async Task<T> GetJsonAsync<T>(string url, object headers = null)
        {
            var policy = BuildRetryPolicy();

            return await policy.ExecuteAsync(() => url
                .WithHeaders(headers)
                .GetJsonAsync<T>()
            );
        }

        private AsyncRetryPolicy BuildRetryPolicy()
        {
            var retryPolicy = Policy
               .Handle<FlurlHttpException>(IsTransientError)
               .WaitAndRetryAsync(3, retryAttempt =>
               {
                   var nextAttemptIn = TimeSpan.FromSeconds(Math.Pow(2, retryAttempt));
                   Console.WriteLine($"Retry attempt {retryAttempt} to make request. Next try on {nextAttemptIn.TotalSeconds} seconds.");
                   return nextAttemptIn;
               });

            return retryPolicy;
        }

        private bool IsTransientError(FlurlHttpException exception)
        {
            int[] httpStatusCodesWorthRetrying =
            {
                (int)HttpStatusCode.RequestTimeout, // 408
                (int)HttpStatusCode.BadGateway, // 502
                (int)HttpStatusCode.ServiceUnavailable, // 503
                (int)HttpStatusCode.GatewayTimeout // 504
            };

            return exception.StatusCode.HasValue && httpStatusCodesWorthRetrying.Contains(exception.StatusCode.Value);
        }
    }
}