.NET Core生产环境偶发405 Method Not Allowed错误排查求助

生产环境中有10%的请求出现错误，本地环境及通过BrowserStack测试的多种浏览器、设备中均无法复现该问题。

错误信息 #

Sentry捕获的405错误 #

"errors": [
        {
          "status": "405",
          "title": "Method Not Allowed",
          "detail": "HTTP method is not allowed"
       }
]

Angular浏览器控制台捕获的错误 #

"error": "[ProgressEvent]",
"headers": "[ti]",
"message": "Http failure response for https://api.xxxxxx:5000/api/public-web/files: 0 Unknown Error",
"name": "HttpErrorResponse",
"ok": false,
"status": 0,
"statusText": "Unknown Error",
"url": "https://api.xxxxxx:5000/api/public-web/files"

注：实际请求地址为 POST https://api.jelenzatate.rs:5000/api/public-web/files/upload，日志来自Sentry。

技术栈 #

• .Net Core 6
• Angular 15 - Universal
• 服务器：Windows 2019 → IIS 10

已执行的排查操作 #

• 仅在IIS的web.config中配置了CORS自定义响应头，未在应用侧配置
• 尝试移除WEBDAV模块
• 在IIS中开启失败请求追踪和日志，但日志中未记录相关请求

相关配置 #

最初怀疑是CORS问题，因此在IIS的web.config中添加了以下响应头，完整配置如下：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <location path="." inheritInChildApplications="false">
        <system.webServer>
            <modules>
                <remove name="WebDAVModule"/>
            </modules>
            <httpProtocol>
                <customHeaders>
                    <clear/>
                    <add name="Access-Control-Allow-Origin" value="*"/>
                    <add name="Access-Control-Allow-Methods" value="GET,POST,PATCH,PUT,DELETE,OPTIONS"/>
                    <add name="Access-Control-Allow-Headers" value="*"/>
                </customHeaders>
            </httpProtocol>
            <handlers>
                <remove name="WebDAV"/>
                <add name="aspNetCore" path="*" verb="GET,POST,PATCH,PUT,DELETE" modules="AspNetCoreModuleV2" resourceType="Unspecified" requireAccess="None"/>
            </handlers>
            <aspNetCore processPath="dotnet" arguments="\.xxxx.Api.dll" stdoutLogEnabled="false" stdoutLogFile="\.\logs\stdout" hostingModel="inprocess"/>
        </system.webServer>
    </location>
    <system.webServer>
        <tracing>
            <traceFailedRequests>
                <add path="*">
                    <traceAreas>
                        <add provider="ASP" verbosity="Verbose"/>
                        <add provider="ASPNET" areas="Infrastructure,Module,Page,AppServices" verbosity="Verbose"/>
                        <add provider="ISAPI Extension" verbosity="Verbose"/>
                        <add provider="WWW Server" areas="Authentication,Security,Filter,StaticFile,CGI,Compression,Cache,RequestNotifications,Module,FastCGI,WebSocket,ANCM,Rewrite,Cors,iisnode" verbosity="Verbose"/>
                    </traceAreas>
                    <failureDefinitions statusCodes="400-999"/>
                </add>
            </traceFailedRequests>
        </tracing>
    </system.webServer>
</configuration>

.NET Core路由代码 #

[HttpPost("upload")]
[DisableRequestSizeLimit]
public async Task<IActionResult> Upload(IFormFile file, CancellationToken cancellationToken) {
    var fileDto = await _fileService.UploadApplicationDocument(file, cancellationToken);
    return ResponseObjectStatusCode(new ResponseObject<object>(fileDto));
 }

目前观察到HTTP请求似乎根本没有到达服务器，请求协助排查该问题。

内容的提问来源于stack exchange，提问作者mmiroslav13