如何仅为设置的特定StatusCode设置Polly Retry

Question

关于类似的关注，我有几个问题：我正在打电话给EmailServer，并使用Polly Policy进行WaitAndRetry。但是我希望重试仅针对特定的超时发生：5xx和429（并忽略其余的4xx）。

如何使其更优雅，同时涵盖所有5xx的可能性（因为下面的HttpStatusCode不能涵盖所有5xx的内容，也不能涵盖429）？

目前，我的代码如下（2个部分/选项）：

private readonly HttpStatusCode[] _retryHttpStatusCodesList =
    new[]
    {
        HttpStatusCode.InternalServerError,
        HttpStatusCode.NotImplemented,            
        HttpStatusCode.BadGateway,
        HttpStatusCode.ServiceUnavailable,
        HttpStatusCode.GatewayTimeout,
        HttpStatusCode.HttpVersionNotSupported,
        HttpStatusCode.RequestTimeout,
        HttpStatusCode.Unauthorized,
        HttpStatusCode.RequestEntityTooLarge
    };

选项1：

   var waitAndRetryPolicy = Policy.Handle<Exception>()
                .OrResult<HttpResponseMessage>(r =>  _retryHttpStatusCodesList.Contains(r.StatusCode))
                .RetryAsync(2, (ex, retryCount) => { Console.WriteLine($"Retry count {retryCount}"); });

选项2（我无法弄清楚如何对StatusCode进行检查）：

var waitAndRetryPolicy = Policy.Handle<Exception>()
            .WaitAndRetryAsync(_maxRetries, retryAttempt => TimeSpan.FromMinutes(Math.Pow(_waitMinutes, retryAttempt)), 
            (ex, timeSpan) => 
            { 
                Console.WriteLine($"Log Error {ex}"); 
            });

   SendGridClient client = new SendGridClient ();
   var response = await policy.ExecuteAsync (() => 
               client.SendEmailAsync(new SendGridMessage));

Answer 1

代替字典，您可以直接检查响应代码：

var retryPolicy = Policy
    .Handle<Exception>()
    .OrResult<HttpResponseMessage>(r =>
    {
        var statusCode = (int)r.StatusCode;
        return (statusCode >= 500 && statusCode <= 599) || statusCode == 429;
    })
    .RetryAsync(2, (ex, retryCount) => { Console.WriteLine($"Retry count {retryCount}"); });

为回答您的评论，您只需将对RetryAsync(...)的调用替换为WaitAndRetryAsync(...)的代码：

var waitAndRetryPolicy = Policy
    .Handle<Exception>()
    .OrResult<HttpResponseMessage>(r =>
    {
        var statusCode = (int)r.StatusCode;
        return (statusCode >= 500 && statusCode <= 599) || statusCode == 429;
    })
    .WaitAndRetryAsync(_maxRetries, retryAttempt => TimeSpan.FromMinutes(Math.Pow(_waitMinutes, retryAttempt)),
        (ex, timeSpan) =>
        {
            Console.WriteLine($"Log Error {ex}");
        });

[请记住，Polly是流利的政策制定者。这意味着您正在调用的PolicyBuilder<T>实例上的方法（例如.Handle<Exception>()和.OrResult<HttpResponseMessage>()）正在配置该构建器，以便使用诸如Policy<T>或.WaitAndRetryAsync()之类的调用来创建RetryAsync()。配置方法不在乎要创建哪种策略，因此可以将它们用于any策略类型。