[Question]: How to prevent Exception bubbling up to the main app about polly

[martincostello]

Looking at your code, my guess is that the operation fails 6 times in a row, so you see the exception bubbling up from the sixth attempt because you're configured to allow for 5.

If you never want to see an exception thrown, you would also need to include a fallback policy to provide a value to use instead. Though for your use case of getting an access token, I assume there's nothing you can really provide as a fallback in that case.

[HossZamani]

Thanks for the pointer. That WAS the issue. I updated my code like below and it made it work.

private static AuthenticationResult GetNewToken(string token, string refreshToken, out API_AuthenticationResult API_result)
{
    var fallBackOption = new FallbackStrategyOptions<API_Response<API_AuthenticationResult>>
    {
        ShouldHandle = new PredicateBuilder<API_Response<API_AuthenticationResult>>()
            .Handle<Exception>(),
        FallbackAction =  args => 
            {
                return Outcome.FromResultAsValueTask(new API_Response<API_AuthenticationResult>()
                {
                    Code = ResponseCode.UserNotExist405,
                    Message = "Please login again."
                });
            },
        OnFallback = args =>
            {
                return default;
            }
            
    };

    var retryOptions = new RetryStrategyOptions<API_Response<API_AuthenticationResult>>
    {
        Delay = TimeSpan.FromSeconds(1),
        MaxRetryAttempts = 5,
        ShouldHandle = new PredicateBuilder<API_Response<API_AuthenticationResult>>()
            .Handle<Exception>()
    };
    var pipelineBuilder = new ResiliencePipelineBuilder<API_Response<API_AuthenticationResult>>();
    pipelineBuilder.AddFallback<API_Response<API_AuthenticationResult>>(fallBackOption);
    pipelineBuilder.AddRetry<API_Response<API_AuthenticationResult>>(retryOptions);

    var pipeline = pipelineBuilder.Build();

    var result = pipeline.Execute(() =>
    {
        var body = new
        {
            Token = token,
            RefreshToken = refreshToken
        };
        var res = DataAccess.RestAPI_GetData<API_AuthenticationResult>(CreateRibbon.Application.AppSettings.ApiBaseAddress,
                  API_Endpoints.RefreshToken,
                  null,
                  body: body);

        if (res == null)
        {
            throw new Exception("API response is null");
        }
        if (res != null && res.Code != ResponseCode.Success201)
        {
            throw new Exception(res.Message);
        }
        return res;
    });


    return ProcessAuthentication(result, out API_result);
}```