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.

I want the health check to try the URL more than once before reporting a failure. — handles
– handles, Commented Jan 25 at 17:09
As far as I know, the health checks endpoints are called periodically. Because of this, the main aim here is to quickly determine whether the given resource is available or not. After N consecutive failures you can declare temporal unavailability of the resource. So, according to my understanding, adding retry to health checks does not give you extra safety. — Peter Csala
– Peter Csala, Commented Jan 25 at 18:40
Thanks, health checks can be polled periodically by using the publish functionality. Other than that, I don't think that they are. I could be wrong though. — handles
– handles, Commented Jan 25 at 22:12

Peter Csala · Accepted Answer · 2025-01-26 21:53:06Z

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()
  };
});

edited Jan 26 at 21:53

answered Jan 25 at 23:15

Peter Csala

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1 Comment

handles Jan 26 at 21:10

This is a fantastic response. Thanks for taking the time to answer. :)

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