c# - 尝试包装 2 个 Polly 策略时出现转换错误

Question

我试图包装两个 Polly 策略并希望返回 IAsyncPolicy，但它给出错误，

convert from Polly.Retry.RetryPolicy < System.Net.Http.HttpResponseMessage> to Polly.IAsyncPolicy

public static IAsyncPolicy CreateDefaultRetryPolicy()
    {
        var timeoutPolicy = Policy.TimeoutAsync(TimeSpan.FromSeconds(180));

        var waitAndRetryPolicy = Polly.Policy
                .Handle<HttpRequestException>()
                .OrResult<HttpResponseMessage>(r => r.StatusCode == HttpStatusCode.InternalServerError)
                .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(3, retryAttempt)),
                (result, timeSpan, context) =>
                {
                });

        return Policy.WrapAsync(timeoutPolicy, waitAndRetryPolicy);
    }

如何包装并返回？

Answer 1

按如下方式调整您的代码:

public static IAsyncPolicy<HttpResponseMessage> CreateDefaultRetryPolicy()
{
    var timeoutPolicy = Policy.TimeoutAsync(TimeSpan.FromSeconds(180));

    var waitAndRetryPolicy = Polly.Policy
            .Handle<HttpRequestException>()
            .OrResult<HttpResponseMessage>(r => r.StatusCode == HttpStatusCode.InternalServerError)
            .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(3, retryAttempt)),
            (result, timeSpan, context) =>
            {
            });

    return timeoutPolicy.WrapAsync(waitAndRetryPolicy);
}

说明

• 超时策略是非通用的，IAsyncPolicy 。
• 等待并重试策略是通用的，IAsyncPolicy<HttpResponseMessage> ，因为它处理 HttpResponseMessage结果。

要将这些组合到 PolicyWrap 中，请使用 .Wrap(...)实例方法语法:

return timeoutPolicy.WrapAsync(waitAndRetryPolicy);

作为结果的PolicyWrap处理HttpResponseMessage ，它的类型也是 IAsyncPolicy<HttpResponseMessage> ，因此方法返回类型更改为该值。

Polly 文档涵盖了 wiki 中非通用和通用策略之间的差异。 .