Initialize hosting trace with OTEL tags for sampling

src/Hosting/Hosting/src/Internal/HostingApplication.cs

@@ -17,6 +17,13 @@ internal sealed class HostingApplication : IHttpApplication<HostingApplication.C
     private readonly DefaultHttpContextFactory? _defaultHttpContextFactory;
     private readonly HostingApplicationDiagnostics _diagnostics;
 
+    // Internal for testing purposes only
+    internal bool SuppressActivityOpenTelemetryData
+    {
+        get => _diagnostics.SuppressActivityOpenTelemetryData;
+        set => _diagnostics.SuppressActivityOpenTelemetryData = value;
+    }
+
     public HostingApplication(
         RequestDelegate application,
         ILogger logger,

src/Hosting/Hosting/src/Internal/HostingApplicationDiagnostics.cs

@@ -34,6 +34,9 @@ internal sealed class HostingApplicationDiagnostics
     private readonly HostingMetrics _metrics;
     private readonly ILogger _logger;
 
+    // Internal for testing purposes only
+    internal bool SuppressActivityOpenTelemetryData { get; set; }
+
     public HostingApplicationDiagnostics(
         ILogger logger,
         DiagnosticListener diagnosticListener,
@@ -48,6 +51,19 @@ public HostingApplicationDiagnostics(
         _propagator = propagator;
         _eventSource = eventSource;
         _metrics = metrics;
+
+        SuppressActivityOpenTelemetryData = GetSuppressActivityOpenTelemetryData();
+    }
+
+    private static bool GetSuppressActivityOpenTelemetryData()
+    {
+        // Default to true if the switch isn't set.
+        if (!AppContext.TryGetSwitch("Microsoft.AspNetCore.Hosting.SuppressActivityOpenTelemetryData", out var enabled))
+        {
+            return true;
+        }
+
+        return enabled;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -88,9 +104,9 @@ public void BeginRequest(HttpContext httpContext, HostingApplication.Context con
         var diagnosticListenerActivityCreationEnabled = (diagnosticListenerEnabled && _diagnosticListener.IsEnabled(ActivityName, httpContext));
         var loggingEnabled = _logger.IsEnabled(LogLevel.Critical);
 
-        if (loggingEnabled || diagnosticListenerActivityCreationEnabled || _activitySource.HasListeners())
+        if (ActivityCreator.IsActivityCreated(_activitySource, loggingEnabled || diagnosticListenerActivityCreationEnabled))
         {
-            context.Activity = StartActivity(httpContext, loggingEnabled, diagnosticListenerActivityCreationEnabled, out var hasDiagnosticListener);
+            context.Activity = StartActivity(httpContext, loggingEnabled || diagnosticListenerActivityCreationEnabled, out var hasDiagnosticListener);
             context.HasDiagnosticListener = hasDiagnosticListener;
 
             if (context.Activity != null)
@@ -385,10 +401,18 @@ private void RecordRequestStartMetrics(HttpContext httpContext)
     }
 
     [MethodImpl(MethodImplOptions.NoInlining)]
-    private Activity? StartActivity(HttpContext httpContext, bool loggingEnabled, bool diagnosticListenerActivityCreationEnabled, out bool hasDiagnosticListener)
+    private Activity? StartActivity(HttpContext httpContext, bool diagnosticsOrLoggingEnabled, out bool hasDiagnosticListener)
     {
+        // StartActivity is only called if an Activity is already verified to be created.
+        Debug.Assert(ActivityCreator.IsActivityCreated(_activitySource, diagnosticsOrLoggingEnabled),
+            "Activity should only be created if diagnostics or logging is enabled.");
+
         hasDiagnosticListener = false;
 
+        var initializeTags = !SuppressActivityOpenTelemetryData
+            ? CreateInitializeActivityTags(httpContext)
+            : (TagList?)null;
+
         var headers = httpContext.Request.Headers;
         var activity = ActivityCreator.CreateFromRemote(
             _activitySource,
@@ -402,9 +426,9 @@ private void RecordRequestStartMetrics(HttpContext httpContext)
             },
             ActivityName,
             ActivityKind.Server,
-            tags: null,
+            tags: initializeTags,
             links: null,
-            loggingEnabled || diagnosticListenerActivityCreationEnabled);
+            diagnosticsOrLoggingEnabled);
         if (activity is null)
         {
             return null;
@@ -425,6 +449,47 @@ private void RecordRequestStartMetrics(HttpContext httpContext)
         return activity;
     }
 
+    private static TagList CreateInitializeActivityTags(HttpContext httpContext)
+    {
+        // The tags here are set when the activity is created. They can be used in sampling decisions.
+        // Most values in semantic conventions that are present at creation are specified:
+        // https://github.com/open-telemetry/semantic-conventions/blob/27735ccca3746d7bb7fa061dfb73d93bcbae2b6e/docs/http/http-spans.md#L581-L592
+        // Missing values recommended by the spec are:
+        // - url.query (need configuration around redaction to do properly)
+        // - http.request.header.<key>
+
+        var request = httpContext.Request;
+        var creationTags = new TagList();
+
+        if (request.Host.HasValue)
+        {
+            creationTags.Add(HostingTelemetryHelpers.AttributeServerAddress, request.Host.Host);
+
+            if (HostingTelemetryHelpers.TryGetServerPort(request.Host, request.Scheme, out var port))
+            {
+                creationTags.Add(HostingTelemetryHelpers.AttributeServerPort, port);
+            }
+        }
+
+        HostingTelemetryHelpers.SetActivityHttpMethodTags(ref creationTags, request.Method);
+
+        if (request.Headers.TryGetValue("User-Agent", out var values))
+        {
+            var userAgent = values.Count > 0 ? values[0] : null;
+            if (!string.IsNullOrEmpty(userAgent))
+            {
+                creationTags.Add(HostingTelemetryHelpers.AttributeUserAgentOriginal, userAgent);
+            }
+        }
+
+        creationTags.Add(HostingTelemetryHelpers.AttributeUrlScheme, request.Scheme);
+
+        var path = (request.PathBase.HasValue || request.Path.HasValue) ? (request.PathBase + request.Path).ToString() : "/";
+        creationTags.Add(HostingTelemetryHelpers.AttributeUrlPath, path);
+
+        return creationTags;
+    }
+
     [MethodImpl(MethodImplOptions.NoInlining)]
     private void StopActivity(HttpContext httpContext, Activity activity, bool hasDiagnosticListener)
     {

src/Hosting/Hosting/src/Internal/HostingMetrics.cs

@@ -1,9 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Collections.Frozen;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.Diagnostics.Metrics;
 using Microsoft.AspNetCore.Http;
 
@@ -55,7 +53,7 @@ public void RequestEnd(string protocol, string scheme, string method, string? ro
 
         if (!disableHttpRequestDurationMetric && _requestDuration.Enabled)
         {
-            if (TryGetHttpVersion(protocol, out var httpVersion))
+            if (HostingTelemetryHelpers.TryGetHttpVersion(protocol, out var httpVersion))
             {
                 tags.Add("network.protocol.version", httpVersion);
             }
@@ -65,7 +63,7 @@ public void RequestEnd(string protocol, string scheme, string method, string? ro
             }
 
             // Add information gathered during request.
-            tags.Add("http.response.status_code", GetBoxedStatusCode(statusCode));
+            tags.Add("http.response.status_code", HostingTelemetryHelpers.GetBoxedStatusCode(statusCode));
             if (route != null)
             {
                 tags.Add("http.route", route);
@@ -104,73 +102,6 @@ public void Dispose()
     private static void InitializeRequestTags(ref TagList tags, string scheme, string method)
     {
         tags.Add("url.scheme", scheme);
-        tags.Add("http.request.method", ResolveHttpMethod(method));
-    }
-
-    private static readonly object[] BoxedStatusCodes = new object[512];
-
-    private static object GetBoxedStatusCode(int statusCode)
-    {
-        object[] boxes = BoxedStatusCodes;
-        return (uint)statusCode < (uint)boxes.Length
-            ? boxes[statusCode] ??= statusCode
-            : statusCode;
-    }
-
-    private static readonly FrozenDictionary<string, string> KnownMethods = FrozenDictionary.ToFrozenDictionary(new[]
-    {
-        KeyValuePair.Create(HttpMethods.Connect, HttpMethods.Connect),
-        KeyValuePair.Create(HttpMethods.Delete, HttpMethods.Delete),
-        KeyValuePair.Create(HttpMethods.Get, HttpMethods.Get),
-        KeyValuePair.Create(HttpMethods.Head, HttpMethods.Head),
-        KeyValuePair.Create(HttpMethods.Options, HttpMethods.Options),
-        KeyValuePair.Create(HttpMethods.Patch, HttpMethods.Patch),
-        KeyValuePair.Create(HttpMethods.Post, HttpMethods.Post),
-        KeyValuePair.Create(HttpMethods.Put, HttpMethods.Put),
-        KeyValuePair.Create(HttpMethods.Trace, HttpMethods.Trace)
-    }, StringComparer.OrdinalIgnoreCase);
-
-    private static string ResolveHttpMethod(string method)
-    {
-        // TODO: Support configuration for configuring known methods
-        if (KnownMethods.TryGetValue(method, out var result))
-        {
-            // KnownMethods ignores case. Use the value returned by the dictionary to have a consistent case.
-            return result;
-        }
-        return "_OTHER";
-    }
-
-    private static bool TryGetHttpVersion(string protocol, [NotNullWhen(true)] out string? version)
-    {
-        if (HttpProtocol.IsHttp11(protocol))
-        {
-            version = "1.1";
-            return true;
-        }
-        if (HttpProtocol.IsHttp2(protocol))
-        {
-            // HTTP/2 only has one version.
-            version = "2";
-            return true;
-        }
-        if (HttpProtocol.IsHttp3(protocol))
-        {
-            // HTTP/3 only has one version.
-            version = "3";
-            return true;
-        }
-        if (HttpProtocol.IsHttp10(protocol))
-        {
-            version = "1.0";
-            return true;
-        }
-        if (HttpProtocol.IsHttp09(protocol))
-        {
-            version = "0.9";
-            return true;
-        }
-        version = null;
-        return false;
+        tags.Add("http.request.method", HostingTelemetryHelpers.GetNormalizedHttpMethod(method));
     }
 }

src/Hosting/Hosting/src/Internal/HostingTelemetryHelpers.cs

@@ -0,0 +1,132 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Frozen;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Hosting;
+
+internal static class HostingTelemetryHelpers
+{
+    // Semantic Conventions for HTTP.
+    // Note: Not all telemetry code is using these const attribute names yet.
+    public const string AttributeHttpRequestMethod = "http.request.method";
+    public const string AttributeHttpRequestMethodOriginal = "http.request.method_original";
+    public const string AttributeUrlScheme = "url.scheme";
+    public const string AttributeUrlPath = "url.path";
+    public const string AttributeServerAddress = "server.address";
+    public const string AttributeServerPort = "server.port";
+    public const string AttributeUserAgentOriginal = "user_agent.original";
+
+    // The value "_OTHER" is used for non-standard HTTP methods.
+    // https://github.com/open-telemetry/semantic-conventions/blob/v1.23.0/docs/http/http-spans.md#common-attributes
+    private const string OtherHttpMethod = "_OTHER";
+
+    private static readonly object[] BoxedStatusCodes = new object[512];
+
+    private static readonly FrozenDictionary<string, string> KnownHttpMethods = FrozenDictionary.ToFrozenDictionary([
+        KeyValuePair.Create(HttpMethods.Connect, HttpMethods.Connect),
+        KeyValuePair.Create(HttpMethods.Delete, HttpMethods.Delete),
+        KeyValuePair.Create(HttpMethods.Get, HttpMethods.Get),
+        KeyValuePair.Create(HttpMethods.Head, HttpMethods.Head),
+        KeyValuePair.Create(HttpMethods.Options, HttpMethods.Options),
+        KeyValuePair.Create(HttpMethods.Patch, HttpMethods.Patch),
+        KeyValuePair.Create(HttpMethods.Post, HttpMethods.Post),
+        KeyValuePair.Create(HttpMethods.Put, HttpMethods.Put),
+        KeyValuePair.Create(HttpMethods.Trace, HttpMethods.Trace)
+    ], StringComparer.OrdinalIgnoreCase);
+
+    // Boxed port values for HTTP and HTTPS.
+    private static readonly object HttpPort = 80;
+    private static readonly object HttpsPort = 443;
+
+    public static bool TryGetServerPort(HostString host, string scheme, [NotNullWhen(true)] out object? port)
+    {
+        if (host.Port.HasValue)
+        {
+            port = host.Port.Value;
+            return true;
+        }
+
+        // If the port is not specified, use the default port for the scheme.
+        if (string.Equals(scheme, "http", StringComparison.OrdinalIgnoreCase))
+        {
+            port = HttpPort;
+            return true;
+        }
+        else if (string.Equals(scheme, "https", StringComparison.OrdinalIgnoreCase))
+        {
+            port = HttpsPort;
+            return true;
+        }
+
+        // Unknown scheme, no default port.
+        port = null;
+        return false;
+    }
+
+    public static object GetBoxedStatusCode(int statusCode)
+    {
+        object[] boxes = BoxedStatusCodes;
+        return (uint)statusCode < (uint)boxes.Length
+            ? boxes[statusCode] ??= statusCode
+            : statusCode;
+    }
+
+    public static string GetNormalizedHttpMethod(string method)
+    {
+        // TODO: Support configuration for configuring known methods
+        if (method != null && KnownHttpMethods.TryGetValue(method, out var result))
+        {
+            // KnownHttpMethods ignores case. Use the value returned by the dictionary to have a consistent case.
+            return result;
+        }
+        return OtherHttpMethod;
+    }
+
+    public static bool TryGetHttpVersion(string protocol, [NotNullWhen(true)] out string? version)
+    {
+        if (HttpProtocol.IsHttp11(protocol))
+        {
+            version = "1.1";
+            return true;
+        }
+        if (HttpProtocol.IsHttp2(protocol))
+        {
+            // HTTP/2 only has one version.
+            version = "2";
+            return true;
+        }
+        if (HttpProtocol.IsHttp3(protocol))
+        {
+            // HTTP/3 only has one version.
+            version = "3";
+            return true;
+        }
+        if (HttpProtocol.IsHttp10(protocol))
+        {
+            version = "1.0";
+            return true;
+        }
+        if (HttpProtocol.IsHttp09(protocol))
+        {
+            version = "0.9";
+            return true;
+        }
+        version = null;
+        return false;
+    }
+
+    public static void SetActivityHttpMethodTags(ref TagList tags, string originalHttpMethod)
+    {
+        var normalizedHttpMethod = GetNormalizedHttpMethod(originalHttpMethod);
+        tags.Add(AttributeHttpRequestMethod, normalizedHttpMethod);
+
+        if (originalHttpMethod != normalizedHttpMethod)
+        {
+            tags.Add(AttributeHttpRequestMethodOriginal, originalHttpMethod);
+        }
+    }
+}