HttpClient retry policy with Polly

How to implement a retry policy with Polly in HttpClient

Required packages

To implement a retry policy with Polly in HttpClient, install the following NuGet packages:

• Microsoft.Extensions.Http.Polly — integrates Polly with IHttpClientFactory and provides HttpPolicyExtensions.
• Polly.Contrib.WaitAndRetry — provides the Backoff.DecorrelatedJitterBackoffV2 helper used below.

Retry policy

The following code snippet shows how to implement a retry policy using Polly's built-in Decorrelated Jitter Backoff V2. Unlike a fixed delay, jittered backoff randomizes each retry interval, which helps avoid many clients retrying in sync and overwhelming a downstream service that's already struggling (a "retry storm"). The method takes 2 parameters: the median first retry delay (TimeSpan.FromMilliseconds(100)) and the retry count (5).

var exponentialBackoffRetryPolicy =
    HttpPolicyExtensions.HandleTransientHttpError()
        .WaitAndRetryAsync(
            Backoff.DecorrelatedJitterBackoffV2(TimeSpan.FromMilliseconds(100), 5),
            onRetryAsync: (result, _) =>
            {
                // You can log the retry here
                return Task.CompletedTask;
            });

Applying the retry policy

The retry policy can be applied to a typed client, such as SomeApiClient, which has an HttpClient instance injected into it during registration. It will apply to all calls made through that HttpClient instance.

services.AddHttpClient<ISomeApiClient, SomeApiClient>()
    .AddPolicyHandler(exponentialBackoffRetryPolicy);