feat: add tracing enrichment and prometheus exporter

src/Core/TakeoutSaaS.Shared.Web/Middleware/CorrelationIdMiddleware.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
@@ -14,23 +15,43 @@ namespace TakeoutSaaS.Shared.Web.Middleware;
 public sealed class CorrelationIdMiddleware(RequestDelegate next, ILogger<CorrelationIdMiddleware> logger, IIdGenerator idGenerator)
 {
     private const string TraceHeader = "X-Trace-Id";
+    private const string SpanHeader = "X-Span-Id";
     private const string RequestHeader = "X-Request-Id";
 
     public async Task InvokeAsync(HttpContext context)
     {
-        var traceId = ResolveTraceId(context);
+        var ownsActivity = Activity.Current is null;
+        var activity = Activity.Current ?? new Activity("TakeoutSaaS.Request");
+
+        if (activity.Id is null)
+        {
+            activity.SetIdFormat(ActivityIdFormat.W3C);
+            activity.Start();
+        }
+
+        var traceId = activity.TraceId.ToString();
+        var spanId = activity.SpanId.ToString();
+
+        if (string.IsNullOrWhiteSpace(traceId))
+        {
+            traceId = ResolveTraceId(context);
+        }
+
         context.TraceIdentifier = traceId;
         TraceContext.TraceId = traceId;
+        TraceContext.SpanId = spanId;
 
         context.Response.OnStarting(() =>
         {
             context.Response.Headers[TraceHeader] = traceId;
+            context.Response.Headers[SpanHeader] = spanId;
             return Task.CompletedTask;
         });
 
         using (logger.BeginScope(new Dictionary<string, object>
                {
-                   ["TraceId"] = traceId
+                   ["TraceId"] = traceId,
+                   ["SpanId"] = spanId
                }))
         {
             try
@@ -40,6 +61,10 @@ public sealed class CorrelationIdMiddleware(RequestDelegate next, ILogger<Correl
             finally
             {
                 TraceContext.Clear();
+                if (ownsActivity)
+                {
+                    activity.Stop();
+                }
             }
         }
     }