如何在C#代码中获取App Insights请求ID及增强日志？

一、App Insights自动请求日志的生成逻辑 #

当你的Web API集成Microsoft.ApplicationInsights.AspNetCore SDK后，SDK会注入请求遥测中间件，自动拦截所有入站HTTP请求，生成RequestTelemetry类型的遥测数据并上报到App Insights。这些默认日志包含请求URL、响应状态码、处理时长、客户端IP等基础信息，属于SDK内置的自动采集能力。

二、给自动生成的请求日志添加自定义值 #

完全可以实现，以下是两种常用方案：

方式1：自定义遥测处理器 #

创建继承ITelemetryProcessor的处理器类，在遥测数据上报前修改RequestTelemetry，添加自定义属性：

public class CustomRequestTelemetryProcessor : ITelemetryProcessor
{
    private readonly ITelemetryProcessor _next;

    public CustomRequestTelemetryProcessor(ITelemetryProcessor next)
    {
        _next = next;
    }

    public void Process(ITelemetry item)
    {
        if (item is RequestTelemetry requestTelemetry)
        {
            // 添加自定义业务属性，示例从请求头获取业务ID
            requestTelemetry.Properties["BusinessId"] = HttpContextAccessor.HttpContext.Request.Headers["X-Business-Id"].FirstOrDefault();
            requestTelemetry.Properties["DeploymentEnv"] = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
        }

        _next.Process(item);
    }
}

在Program.cs中注册处理器：

builder.Services.AddApplicationInsightsTelemetry();
builder.Services.AddSingleton<ITelemetryProcessor, CustomRequestTelemetryProcessor>();

方式2：请求管道中直接修改 #

通过HTTP上下文获取当前RequestTelemetry，直接添加自定义字段：

app.Use(async (context, next) =>
{
    var requestTelemetry = context.Features.Get<RequestTelemetry>();
    if (requestTelemetry != null)
    {
        // 示例添加自定义关联ID
        requestTelemetry.Properties["CustomCorrelationId"] = context.Request.Headers["X-Correlation-Id"].FirstOrDefault();
    }
    await next();
});

三、获取App Insights请求ID并关联后续处理日志 #

可以通过多种方式获取App Insights生成的请求ID，实现全链路日志关联：

方式1：从HTTP上下文的RequestTelemetry获取 #

public class PostRequestProcessor
{
    private readonly IHttpContextAccessor _httpContextAccessor;
    private readonly ILogger<PostRequestProcessor> _logger;

    public PostRequestProcessor(IHttpContextAccessor httpContextAccessor, ILogger<PostRequestProcessor> logger)
    {
        _httpContextAccessor = httpContextAccessor;
        _logger = logger;
    }

    public async Task Execute()
    {
        var requestTelemetry = _httpContextAccessor.HttpContext.Features.Get<RequestTelemetry>();
        if (requestTelemetry != null)
        {
            string aiRequestId = requestTelemetry.Id;
            // 将此ID作为关联ID记录后续日志
            _logger.LogInformation("后续处理启动，关联App Insights请求ID：{AiRequestId}", aiRequestId);
            // 执行业务逻辑
        }
    }
}

注意：需先注册IHttpContextAccessor：

builder.Services.AddHttpContextAccessor();

方式2：从.NET Activity中获取 #

App Insights基于.NET Activity实现链路追踪，请求ID同步到Activity.Current.Id：

public void ProcessBusinessLogic()
{
    string requestId = Activity.Current?.Id;
    if (!string.IsNullOrEmpty(requestId))
    {
        _logger.LogInformation("业务处理中，关联请求ID：{RequestId}", requestId);
    }
}

方式3：通过TelemetryClient获取当前上下文 #

public class BusinessService
{
    private readonly TelemetryClient _telemetryClient;
    private readonly ILogger<BusinessService> _logger;

    public BusinessService(TelemetryClient telemetryClient, ILogger<BusinessService> logger)
    {
        _telemetryClient = telemetryClient;
        _logger = logger;
    }

    public void HandleTask()
    {
        string requestId = _telemetryClient.Context.Operation.Id;
        _logger.LogInformation("任务处理，App Insights请求ID：{RequestId}", requestId);
    }
}

内容的提问来源于stack exchange，提问作者Pranoy Tez