How do I add a Polly policy to a Refit Client created with a factory?

Question

I have a refit client (IMyRefitClient) that returns

Task<ApiResponse<ADomainModel>>

I can't inject this refit client in Program.cs with HostBuilder.ConfigureServices because the url isn't known until runtime. Therefore, I'm using a factory class like:

return RestService.For<IMyRefitClient>(hostUrl);

I know how to add a policy in ConfigureServices. It would look like:

services.AddRefitClient<IMyRefitClient>()
        .AddPolicyHandler(PollyHelpers.GetRetryPolicy());

Is there a way that I can add this policy when using the factory class?

Answer 1

Polly has a concept of PolicyRegister, which is basically a IEnumerable<KeyValuePair<string, IsPolicy>> collection.

So, it is a container where you can register policies with arbitrary names:

var register = new PolicyRegistry()
{
    { "CB_aware_Retry", GetRetryPolicy() },
    { "500_aware_CB", GetCircuitBreakerPolicy() },
    { "Retry_CB_combined", Policy.WrapAsync(GetRetryPolicy(), GetCircuitBreakerPolicy()) }
};

On the ServiceCollection you can register a new container or an existing one:

services.AddPolicyRegistry(registry)

You can access the policies by relying on the IReadOnlyPolicyRegistry:

public class MyRefitClient 
{
    private readonly IAsyncPolicy<ApiResponse<ADomainModel>>> combined;
    public MyRefitClient(..., IReadOnlyPolicyRegistry<string> registry, ...)
    {
       ...
       combined = registry.Get<IAsyncPolicy<ApiResponse<ADomainModel>>>>("Retry_CB_combined");
    } 
}