How can I add a Polly retry policy to AspNetCore.HealthChecks.Uris

Question

How can I add a Polly retry policy to the AspNetCore.HealthChecks.Uris health check?

This health check is part of this repo: https://github.com/Xabaril/AspNetCore.Diagnostics.HealthChecks

I see that I can use the configureClient and configurePrimaryHttpMessageHandler call backs when using healthCheckBuilder.AddUrlGroup.

However all the examples I see for using Polly require using IClientBuilder.AddPolicyHandler(...), but I can't figure out how to access IHttpClientBuilder when using healthCheckBuilder.AddUrlGroup.

Answer 1

The configurePrimaryHttpMessageHandler as its name suggests anticipates an HttpMessageHandler as a return value. This abstract class serves as a base class for many derived classes like DelegatingHandler or HttpClientHandler. Gladly Polly's HttpClient integrations are built upon DelegatingHandlers.

Polly V7

The AddPolicyHandler registers a PolicyHttpMessageHandler which is a DelegatingHandler. So, you can configure this class inside the configurePrimaryHttpMessageHandler callback.

.ConfigurePrimaryHttpMessageHandler(() =>
{
  return new PolicyHttpMessageHandler(policy)
  {
    InnerHandler = new HttpClientHandler()
  };
});

Polly V8

Similarly, the AddResilienceHandler registers a ResilienceHandler which is a DelegatingHandler.

.ConfigurePrimaryHttpMessageHandler(() =>
{
  return new ResilienceHandler(pipeline)
  {
    InnerHandler = new HttpClientHandler()
  };
});