how to re-try request for 401 along with TransientHttpError ( 5XX and 408)

Question

Below code re-try 2 times when we have error from HttpRequestException, 5XX and 408 and it's works fine.

Here I want to re-try for even 401 error? how we can achieve this with Polly?

 services.AddHttpClient(Options.DefaultName)
            .ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler { })
            .AddPolicyHandler(HttpPolicyExtensions.HandleTransientHttpError()
                .WaitAndRetryAsync(2, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt))));

What is your reason for `.ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler { })`? Isn't that the default already without manually specifying it? — ProgrammingLlama, Sep 01 '21 at 05:57
Why do you want retry the same request if you receive `Unauthorized`? Issuing the same request normally does not give you new credentials. Or did I miss something? — Peter Csala, Sep 01 '21 at 07:17
@user584018 Exactly, whenever you encounter a 401 then you want to perform a *specific action* rather than issuing the same request. That's why I don't get it why do you want to include 401 into your generic retry logic. — Peter Csala, Sep 02 '21 at 06:29

ProgrammingLlama · Accepted Answer · 2021-09-01T06:00:58.423

5

Add .OrResult(r => r.StatusCode == System.Net.HttpStatusCode.Unauthorized) to your code:

services.AddHttpClient(Options.DefaultName)
        .ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler { })
        .AddPolicyHandler(HttpPolicyExtensions.HandleTransientHttpError()
        .OrResult(r => r.StatusCode == System.Net.HttpStatusCode.Unauthorized)
        .WaitAndRetryAsync(2, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt))));

I would suggest rewriting your code like this to make it easier to read:

services.AddHttpClient(Options.DefaultName)
        .AddTransientHttpErrorPolicy(builder => 
            builder
                .OrResult(r => r.StatusCode == System.Net.HttpStatusCode.Unauthorized)
                .WaitAndRetryAsync(2, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt))))
        );

edited Sep 01 '21 at 06:00

answered Sep 01 '21 at 05:53

ProgrammingLlama

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will it re-try only for 401. What if 500 comes? – user584018 Sep 01 '21 at 05:55
`HandleTransientHttpError`, which you already have, handles 5xx and 408. – ProgrammingLlama Sep 01 '21 at 05:56
what if I wanto to do something, like an OAuth authentication, before retry the request? – Angelo Bernardi Dec 22 '21 at 19:47
@AngeloBernardi I would normally create a `DelegatingHandler` for that. You can then register it using `.AddHttpMessageHandler()` – ProgrammingLlama Dec 23 '21 at 00:42

how to re-try request for 401 along with TransientHttpError ( 5XX and 408)

1 Answers1