Polly与HttpClient集成出现请求无限重试挂起问题求助

从你的代码和日志来看，请求挂起以及日志顺序异常主要由几个关键问题导致，下面逐一分析并给出修复方法：

1. 同步阻塞引发的死锁（最可能的挂起原因） #

在处理响应内容时，你使用了同步阻塞的.Result：

string responseContent = response.Content.ReadAsStringAsync().Result;

在异步方法中调用.Result或.Wait()会直接阻塞当前线程，尤其是在存在同步上下文（比如ASP.NET、WinForms/WPF）的环境下，极易触发死锁——异步操作完成后需要回到原上下文，但原线程正被阻塞等待结果，最终导致整个请求卡住无法继续。

修复方法：替换为异步等待await，并配合ConfigureAwait(false)规避上下文切换风险：

string responseContent = await response.Content.ReadAsStringAsync().ConfigureAwait(false);

2. 频繁创建HttpClient导致套接字耗尽 #

你在每次调用callAsync时都新建HttpClient实例：

httpcli = new HttpClient();

HttpClient的设计定位是长生命周期复用对象，频繁创建会导致系统中积累大量处于TIME_WAIT状态的套接字，最终耗尽可用端口，新请求无法发起，表现为请求挂起。

修复方法：将HttpClient设置为静态成员全局复用，初始化逻辑放在静态构造函数中：

// 静态实例，全局复用
private static readonly HttpClient _httpClient = new HttpClient();
private static readonly int _maxRetryAttempts = 3;
private static readonly TimeSpan _pauseBetweenFailures = TimeSpan.FromSeconds(10);

static YourClassName()
{
    // 初始化安全协议
    ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
    // 预设授权头
    _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", ConfigurationManager.AppSettings["XXXAuth"].ToString());
    // 移除ConnectionClose配置，让HttpClient自动管理连接池
    // _httpClient.DefaultRequestHeaders.ConnectionClose = true;
}

3. 重试日志顺序异常的原因 #

你的日志显示重试次数是3 → 2 → 1，这是因为Polly的WaitAndRetryAsync回调中，retryCount代表即将执行的重试次数，而非已完成的次数。比如设置maxRetryAttempts = 3时：

• 第一次失败后，准备执行第1次重试，retryCount=1
• 第二次失败后，准备执行第2次重试，retryCount=2
• 第三次失败后，准备执行第3次重试，retryCount=3

日志顺序错乱大概率是异步日志写入的时序问题，若要明确重试进度，可以调整日志描述：

.WaitAndRetryAsync(_maxRetryAttempts, j => _pauseBetweenFailures, (result, timeSpan, retryCount, context) => {
    Logger.WriteInfo($"Request failed with {result.Result?.StatusCode ?? HttpStatusCode.InternalServerError}. About to retry {retryCount}/{_maxRetryAttempts}. Waiting {timeSpan}...");
});

4. 不必要的ConnectionClose设置 #

你设置了httpcli.DefaultRequestHeaders.ConnectionClose = true;，这会强制每次请求后关闭TCP连接，破坏HttpClient的连接池机制，增加TCP握手开销，同时可能加剧套接字耗尽问题，建议直接移除该配置。

修复后的完整代码示例 #

// 静态HttpClient实例，全局复用
private static readonly HttpClient _httpClient = new HttpClient();
private static readonly int _maxRetryAttempts = 3;
private static readonly TimeSpan _pauseBetweenFailures = TimeSpan.FromSeconds(10);

static YourClassName()
{
    // 初始化安全协议
    ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
    // 设置默认Authorization头
    _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", ConfigurationManager.AppSettings["XXXAuth"].ToString());
}

public static async Task<ResponseWs> callAsync(int IdHeader) {
    ResponseWs w = new ResponseWs();
    w.retCode = 1;
    w.Message = "Errore Generico";
    
    getInbound(IdHeader, out int i, out string jsonObject, out string orderNum);
    string url = String.Format("{0}charge?orderNum={1}", ConfigurationManager.AppSettings["XXXUrl"], orderNum);
    Logger.WriteInfo(url);
    Logger.WriteInfo(jsonObject);

    var retryPolicy = Policy
        .Handle<HttpRequestException>()
        .OrResult<HttpResponseMessage>(r => r.StatusCode != HttpStatusCode.OK)
        .WaitAndRetryAsync(_maxRetryAttempts, j => _pauseBetweenFailures, (result, timeSpan, retryCount, context) => {
            Logger.WriteInfo($"Request failed with {result.Result?.StatusCode ?? HttpStatusCode.InternalServerError}. About to retry {retryCount}/{_maxRetryAttempts}. Waiting {timeSpan}...");
        });

    try {
        var response = await retryPolicy.ExecuteAsync(async () => {
            var cont = new StringContent(jsonObject, Encoding.UTF8, "application/json");
            // 使用构建好的目标URL，替换硬编码的测试地址
            var post = await _httpClient.PostAsync(url, cont).ConfigureAwait(false);
            return post;
        });

        if (response.IsSuccessStatusCode) {
            string responseContent = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
            XXXError sperr = JsonConvert.DeserializeObject<XXXError>(responseContent);
            if (sperr.status.Equals("OK", StringComparison.OrdinalIgnoreCase)) {
                Logger.WriteInfo("OK");
                w.retCode = 0;
                w.Message = "OK";
                return w;
            } else {
                Logger.WriteError(responseContent);
                Logger.WriteError(sperr.message);
                w.retCode = 2;
                w.Message = sperr.message;
                return w;
            }
        } else {
            Logger.WriteError($"Errore: {response.StatusCode}");
            string errorContent = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
            Logger.WriteError(errorContent);
            w.retCode = 1;
            w.Message = "Errore Chiamata MW";
            return w;
        }
    } catch (HttpRequestException e) {
        Logger.WriteError(e.Message);
        if (e.InnerException != null)
            Logger.WriteError(e.InnerException.Message);
        w.retCode = 1;
        w.Message = "Errore Chiamata MW";
        return w;
    } catch (Exception ex) {
        Logger.WriteError(ex.Message);
        if (ex.InnerException != null)
            Logger.WriteError(ex.InnerException.Message);
        w.retCode = 1;
        w.Message = "Errore Chiamata MW";
        return w;
    }
}

额外注意事项 #

• 确保maxRetryAttempts和pauseBetweenFailures的值合理，避免过度重试给目标服务造成压力；
• 即使是非成功状态码，也建议用await读取响应内容，避免同步阻塞；
• 移除了AggregateException的捕获，因为Polly在重试失败后，若为结果失败（如返回400）会直接返回失败响应，若为异常失败则抛出最后一次的异常，无需单独捕获AggregateException。

内容的提问来源于stack exchange，提问作者DottorCry DottorCry