Microsoft.Extensions.Http.Polly 10.0.0

About

Microsoft.Extensions.Http.Polly integrates IHttpClientFactory with the Polly library to provide comprehensive resilience and transient fault-handling. It allows developers to express policies such as Retry, Circuit Breaker, Timeout, Bulkhead Isolation, and Fallback in a fluent and thread-safe manner.

How to Use

To use Microsoft.Extensions.Http.Polly, follow these steps:

Installation

dotnet add package Microsoft.Extensions.Http.Polly

Usage

Handle transient faults

AddTransientHttpErrorPolicy can be used define a policy that handles transient errors:

builder.Services.AddHttpClient("PollyWaitAndRetry")
    .AddTransientHttpErrorPolicy(policyBuilder =>
        policyBuilder.WaitAndRetryAsync(
            retryCount: 3,
            retryNumber => TimeSpan.FromMilliseconds(600)));

In the preceding example, failed requests are retried up to three times with a delay of 600 ms between attempts.

Dynamically select policies

To dynamically inspect a request and decide which policy apply, use the AddPolicyHandler extension method:

var timeoutPolicy = Policy.TimeoutAsync<HttpResponseMessage>(
    TimeSpan.FromSeconds(10));
var longTimeoutPolicy = Policy.TimeoutAsync<HttpResponseMessage>(
    TimeSpan.FromSeconds(30));

builder.Services.AddHttpClient("PollyDynamic")
    .AddPolicyHandler(httpRequestMessage =>
        httpRequestMessage.Method == HttpMethod.Get
            ? timeoutPolicy
            : longTimeoutPolicy);

In this example, if the outgoing request is an HTTP GET, a 10-second timeout is applied. For any other HTTP method, a 30-second timeout is used.

Main Types

The main types provided by this package are:

• PollyHttpClientBuilderExtensions: Provides extension methods for configuring PolicyHttpMessageHandler message handlers as part of an HttpClient message handler pipeline
• PolicyHttpMessageHandler: A DelegatingHandler implementation that executes request processing surrounded by a Polly.Policy
• PollyServiceCollectionExtensions: Provides convenience extension methods to register Polly.Registry.IPolicyRegistry<string> and Polly.Registry.IReadOnlyPolicyRegistry<string> in a service collection
• HttpRequestMessageExtensions: Provides extension methods for HttpRequestMessage Polly integration

Additional Documentation

For additional documentation and examples, refer to the official documentation on using Polly-based handlers in ASP.NET Core.

Feedback & Contributing

Microsoft.Extensions.Http.Polly is released as open-source under the MIT license. Bug reports and contributions are welcome at the GitHub repository.