Implement IHttpRequestIdentifierFeature on Frame

This feature generates a unique ID per request. This unique ID can be
used in event source and logging.

Also, this change improves KestrelEventSource by moving it back into the
Kestrel.Core assembly and de-coupling from the Libuv transport. This
adds two new events, RequestStart and RequestStop, which can be used to
identify the correlation between connection ID and request trace
identifier.

.vscode/tasks.json

@@ -21,7 +21,24 @@
         "build",
         "${workspaceRoot}/KestrelHttpServer.sln"
       ],
-      "problemMatcher": "$msCompile"
+      "problemMatcher": "$msCompile",
+      // these have to defined here because of https://github.com/Microsoft/vscode/issues/20740
+      "osx": {
+        "options": {
+          "env": {
+            // The location of .NET Framework reference assembiles.
+            // These may not be installed yet if you have not run build.sh.
+            "ReferenceAssemblyRoot": "${env.HOME}/.nuget/packages/netframeworkreferenceassemblies/4.6.1/content"
+          }
+        }
+      },
+      "linux": {
+        "options": {
+          "env": {
+            "ReferenceAssemblyRoot": "${env.HOME}/.nuget/packages/netframeworkreferenceassemblies/4.6.1/content"
+          }
+        }
+      }
     },
     {
       "taskName": "Compile: CodeGenerator",

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/ConnectionHandler.cs

@@ -1,25 +1,16 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System;
 using System.IO.Pipelines;
-using System.Threading;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.Http;
+using Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure;
 using Microsoft.AspNetCore.Server.Kestrel.Transport;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Internal
 {
     public class ConnectionHandler<TContext> : IConnectionHandler
     {
-        // Base32 encoding - in ascii sort order for easy text based sorting
-        private static readonly string _encode32Chars = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
-
-        // Seed the _lastConnectionId for this application instance with
-        // the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001
-        // for a roughly increasing _requestId over restarts
-        private static long _lastConnectionId = DateTime.UtcNow.Ticks;
-
         private readonly ServiceContext _serviceContext;
         private readonly IHttpApplication<TContext> _application;
 
@@ -34,7 +25,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
             var inputPipe = connectionInfo.PipeFactory.Create(GetInputPipeOptions(connectionInfo.InputWriterScheduler));
             var outputPipe = connectionInfo.PipeFactory.Create(GetOutputPipeOptions(connectionInfo.OutputWriterScheduler));
 
-            var connectionId = GenerateConnectionId(Interlocked.Increment(ref _lastConnectionId));
+            var connectionId = CorrelationIdGenerator.GetNextId();
 
             var frameContext = new FrameContext
             {
@@ -60,6 +51,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
                 OutputProducer = outputProducer
             });
 
+            _serviceContext.Log.ConnectionStart(connectionId);
+            KestrelEventSource.Log.ConnectionStart(connection, connectionInfo);
+
             // Since data cannot be added to the inputPipe by the transport until OnConnection returns,
             // Frame.RequestProcessingAsync is guaranteed to unblock the transport thread before calling
             // application code.
@@ -97,32 +91,5 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
             // null means that we have no back pressure
             return bufferSize ?? 0;
         }
-
-        private static unsafe string GenerateConnectionId(long id)
-        {
-            // The following routine is ~310% faster than calling long.ToString() on x64
-            // and ~600% faster than calling long.ToString() on x86 in tight loops of 1 million+ iterations
-            // See: https://github.com/aspnet/Hosting/pull/385
-
-            // stackalloc to allocate array on stack rather than heap
-            char* charBuffer = stackalloc char[13];
-
-            charBuffer[0] = _encode32Chars[(int)(id >> 60) & 31];
-            charBuffer[1] = _encode32Chars[(int)(id >> 55) & 31];
-            charBuffer[2] = _encode32Chars[(int)(id >> 50) & 31];
-            charBuffer[3] = _encode32Chars[(int)(id >> 45) & 31];
-            charBuffer[4] = _encode32Chars[(int)(id >> 40) & 31];
-            charBuffer[5] = _encode32Chars[(int)(id >> 35) & 31];
-            charBuffer[6] = _encode32Chars[(int)(id >> 30) & 31];
-            charBuffer[7] = _encode32Chars[(int)(id >> 25) & 31];
-            charBuffer[8] = _encode32Chars[(int)(id >> 20) & 31];
-            charBuffer[9] = _encode32Chars[(int)(id >> 15) & 31];
-            charBuffer[10] = _encode32Chars[(int)(id >> 10) & 31];
-            charBuffer[11] = _encode32Chars[(int)(id >> 5) & 31];
-            charBuffer[12] = _encode32Chars[(int)id & 31];
-
-            // string ctor overload that takes char*
-            return new string(charBuffer, 0, 13);
-        }
     }
 }

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/FrameConnection.cs

@@ -73,6 +73,12 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
             }
         }
 
+        public void OnConnectionClosed()
+        {
+            Log.ConnectionStop(ConnectionId);
+            KestrelEventSource.Log.ConnectionStop(this);
+        }
+
         public async Task StopAsync()
         {
             await _frameStartedTcs.Task;

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/Frame.FeatureCollection.cs

@@ -19,7 +19,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
                                  IHttpResponseFeature,
                                  IHttpUpgradeFeature,
                                  IHttpConnectionFeature,
-                                 IHttpRequestLifetimeFeature
+                                 IHttpRequestLifetimeFeature,
+                                 IHttpRequestIdentifierFeature
     {
         // NOTE: When feature interfaces are added to or removed from this Frame class implementation,
         // then the list of `implementedFeatures` in the generated code project MUST also be updated.
@@ -75,188 +76,89 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
 
         string IHttpRequestFeature.Protocol
         {
-            get
+            get => HttpVersion;
-            {
+            set => HttpVersion = value;
-                return HttpVersion;
-            }
-
-            set
-            {
-                HttpVersion = value;
-            }
         }
 
         string IHttpRequestFeature.Scheme
         {
-            get
+            get => Scheme ?? "http";
-            {
+            set => Scheme = value;
-                return Scheme ?? "http";
-            }
-
-            set
-            {
-                Scheme = value;
-            }
         }
 
         string IHttpRequestFeature.Method
         {
-            get
+            get => Method;
-            {
+            set => Method = value;
-                return Method;
-            }
-
-            set
-            {
-                Method = value;
-            }
         }
 
         string IHttpRequestFeature.PathBase
         {
-            get
+            get => PathBase ?? "";
-            {
+            set => PathBase = value;
-                return PathBase ?? "";
-            }
-
-            set
-            {
-                PathBase = value;
-            }
         }
 
         string IHttpRequestFeature.Path
         {
-            get
+            get => Path;
-            {
+            set => Path = value;
-                return Path;
-            }
-
-            set
-            {
-                Path = value;
-            }
         }
 
         string IHttpRequestFeature.QueryString
         {
-            get
+            get => QueryString;
-            {
+            set => QueryString = value;
-                return QueryString;
-            }
-
-            set
-            {
-                QueryString = value;
-            }
         }
 
         string IHttpRequestFeature.RawTarget
         {
-            get
+            get => RawTarget;
-            {
+            set => RawTarget = value;
-                return RawTarget;
-            }
-            set
-            {
-                RawTarget = value;
-            }
         }
 
         IHeaderDictionary IHttpRequestFeature.Headers
         {
-            get
+            get => RequestHeaders;
-            {
+            set => RequestHeaders = value;
-                return RequestHeaders;
-            }
-
-            set
-            {
-                RequestHeaders = value;
-            }
         }
 
         Stream IHttpRequestFeature.Body
         {
-            get
+            get => RequestBody;
-            {
+            set => RequestBody = value;
-                return RequestBody;
-            }
-
-            set
-            {
-                RequestBody = value;
-            }
         }
 
         int IHttpResponseFeature.StatusCode
         {
-            get
+            get => StatusCode;
-            {
+            set => StatusCode = value;
-                return StatusCode;
-            }
-
-            set
-            {
-                StatusCode = value;
-            }
         }
 
         string IHttpResponseFeature.ReasonPhrase
         {
-            get
+            get => ReasonPhrase;
-            {
+            set => ReasonPhrase = value;
-                return ReasonPhrase;
-            }
-
-            set
-            {
-                ReasonPhrase = value;
-            }
         }
 
         IHeaderDictionary IHttpResponseFeature.Headers
         {
-            get
+            get => ResponseHeaders;
-            {
+            set => ResponseHeaders = value;
-                return ResponseHeaders;
-            }
-
-            set
-            {
-                ResponseHeaders = value;
-            }
         }
 
         Stream IHttpResponseFeature.Body
         {
-            get
+            get => ResponseBody;
-            {
+            set => ResponseBody = value;
-                return ResponseBody;
-            }
-
-            set
-            {
-                ResponseBody = value;
-            }
         }
 
         CancellationToken IHttpRequestLifetimeFeature.RequestAborted
         {
-            get
+            get => RequestAborted;
-            {
+            set => RequestAborted = value;
-                return RequestAborted;
-            }
-            set
-            {
-                RequestAborted = value;
-            }
         }
 
-        bool IHttpResponseFeature.HasStarted
+        bool IHttpResponseFeature.HasStarted => HasResponseStarted;
-        {
-            get { return HasResponseStarted; }
-        }
 
         bool IHttpUpgradeFeature.IsUpgradableRequest => _upgrade;
 
@@ -266,38 +168,44 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
 
         IPAddress IHttpConnectionFeature.RemoteIpAddress
         {
-            get { return RemoteIpAddress; }
+            get => RemoteIpAddress;
-            set { RemoteIpAddress = value; }
+            set => RemoteIpAddress = value;
         }
 
         IPAddress IHttpConnectionFeature.LocalIpAddress
         {
-            get { return LocalIpAddress; }
+            get => LocalIpAddress;
-            set { LocalIpAddress = value; }
+            set => LocalIpAddress = value;
         }
 
         int IHttpConnectionFeature.RemotePort
         {
-            get { return RemotePort; }
+            get => RemotePort;
-            set { RemotePort = value; }
+            set => RemotePort = value;
         }
 
         int IHttpConnectionFeature.LocalPort
         {
-            get { return LocalPort; }
+            get => LocalPort;
-            set { LocalPort = value; }
+            set => LocalPort = value;
         }
 
         string IHttpConnectionFeature.ConnectionId
         {
-            get { return ConnectionIdFeature; }
+            get => ConnectionIdFeature;
-            set { ConnectionIdFeature = value; }
+            set => ConnectionIdFeature = value;
+        }
+
+        string IHttpRequestIdentifierFeature.TraceIdentifier
+        {
+            get => TraceIdentifier;
+            set => TraceIdentifier = value;
         }
 
         object IFeatureCollection.this[Type key]
         {
-            get { return FastFeatureGet(key); }
+            get => FastFeatureGet(key);
-            set { FastFeatureSet(key, value); }
+            set => FastFeatureSet(key, value);
         }
 
         TFeature IFeatureCollection.Get<TFeature>()

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/Frame.Generated.cs

@@ -47,10 +47,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
             _currentIHttpRequestFeature = this;
             _currentIHttpResponseFeature = this;
             _currentIHttpUpgradeFeature = this;
+            _currentIHttpRequestIdentifierFeature = this;
             _currentIHttpRequestLifetimeFeature = this;
             _currentIHttpConnectionFeature = this;
             
-            _currentIHttpRequestIdentifierFeature = null;
             _currentIServiceProvidersFeature = null;
             _currentIHttpAuthenticationFeature = null;
             _currentIQueryFeature = null;

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/Frame.cs

@@ -69,6 +69,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
 
         protected HttpVersion _httpVersion;
 
+        private string _requestId;
         private int _remainingRequestHeadersBytesAllowed;
         private int _requestHeadersParsed;
 
@@ -112,6 +113,24 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
         protected string ConnectionId => _frameContext.ConnectionId;
 
         public string ConnectionIdFeature { get; set; }
+
+        /// <summary>
+        /// The request id. <seealso cref="HttpContext.TraceIdentifier"/>
+        /// </summary>
+        public string TraceIdentifier
+        {
+            set => _requestId = value;
+            get
+            {
+                // don't generate an ID until it is requested
+                if (_requestId == null)
+                {
+                    _requestId = CorrelationIdGenerator.GetNextId();
+                }
+                return _requestId;
+            }
+        }
+
         public IPAddress RemoteIpAddress { get; set; }
         public int RemotePort { get; set; }
         public IPAddress LocalIpAddress { get; set; }
@@ -341,6 +360,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
 
             ResetFeatureCollection();
 
+            TraceIdentifier = null;
             Scheme = null;
             Method = null;
             PathBase = null;
@@ -417,7 +437,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
             }
             catch (Exception ex)
             {
-                Log.ApplicationError(ConnectionId, ex);
+                Log.ApplicationError(ConnectionId, TraceIdentifier, ex);
             }
         }
 
@@ -1196,7 +1216,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
                 _applicationException = new AggregateException(_applicationException, ex);
             }
 
-            Log.ApplicationError(ConnectionId, ex);
+            Log.ApplicationError(ConnectionId, TraceIdentifier, ex);
         }
 
         public void OnStartLine(HttpMethod method, HttpVersion version, Span<byte> target, Span<byte> path, Span<byte> query, Span<byte> customMethod, bool pathEncoded)

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Http/FrameOfT.cs

@@ -6,6 +6,7 @@ using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting.Server;
+using Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure;
 using Microsoft.AspNetCore.Server.Kestrel.Transport.Exceptions;
 using Microsoft.Extensions.Logging;
 
@@ -95,6 +96,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
                         {
                             try
                             {
+                                KestrelEventSource.Log.RequestStart(this);
+
                                 await _application.ProcessRequestAsync(context).ConfigureAwait(false);
 
                                 if (Volatile.Read(ref _requestAborted) == 0)
@@ -113,6 +116,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
                             }
                             finally
                             {
+                                KestrelEventSource.Log.RequestStop(this);
+
                                 // Trigger OnStarting if it hasn't been called yet and the app hasn't
                                 // already failed. If an OnStarting callback throws we can go through
                                 // our normal error handling in ProduceEnd.

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Infrastructure/CorrelationIdGenerator.cs

@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Threading;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure
+{
+    internal static class CorrelationIdGenerator
+    {
+        // Base32 encoding - in ascii sort order for easy text based sorting
+        private static readonly string _encode32Chars = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
+
+        // Seed the _lastConnectionId for this application instance with
+        // the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001
+        // for a roughly increasing _lastId over restarts
+        private static long _lastId = DateTime.UtcNow.Ticks;
+
+        public static string GetNextId() => GenerateId(Interlocked.Increment(ref _lastId));
+
+        private static unsafe string GenerateId(long id)
+        {
+            // The following routine is ~310% faster than calling long.ToString() on x64
+            // and ~600% faster than calling long.ToString() on x86 in tight loops of 1 million+ iterations
+            // See: https://github.com/aspnet/Hosting/pull/385
+
+            // stackalloc to allocate array on stack rather than heap
+            char* charBuffer = stackalloc char[13];
+
+            charBuffer[0] = _encode32Chars[(int)(id >> 60) & 31];
+            charBuffer[1] = _encode32Chars[(int)(id >> 55) & 31];
+            charBuffer[2] = _encode32Chars[(int)(id >> 50) & 31];
+            charBuffer[3] = _encode32Chars[(int)(id >> 45) & 31];
+            charBuffer[4] = _encode32Chars[(int)(id >> 40) & 31];
+            charBuffer[5] = _encode32Chars[(int)(id >> 35) & 31];
+            charBuffer[6] = _encode32Chars[(int)(id >> 30) & 31];
+            charBuffer[7] = _encode32Chars[(int)(id >> 25) & 31];
+            charBuffer[8] = _encode32Chars[(int)(id >> 20) & 31];
+            charBuffer[9] = _encode32Chars[(int)(id >> 15) & 31];
+            charBuffer[10] = _encode32Chars[(int)(id >> 10) & 31];
+            charBuffer[11] = _encode32Chars[(int)(id >> 5) & 31];
+            charBuffer[12] = _encode32Chars[(int)id & 31];
+
+            // string ctor overload that takes char*
+            return new string(charBuffer, 0, 13);
+        }
+    }
+}

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Infrastructure/IKestrelTrace.cs

@@ -45,6 +45,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure
 
         void NotAllConnectionsAborted();
 
-        void ApplicationError(string connectionId, Exception ex);
+        void ApplicationError(string connectionId, string traceIdentifier, Exception ex);
     }
 }

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Infrastructure/KestrelEventSource.cs

@@ -4,6 +4,7 @@
 using System.Diagnostics.Tracing;
 using System.Runtime.CompilerServices;
 using Microsoft.AspNetCore.Server.Kestrel.Internal.Http;
+using Microsoft.AspNetCore.Server.Kestrel.Transport;
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure
 {
@@ -25,16 +26,16 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure
         // - Avoid renaming methods or parameters marked with EventAttribute. EventSource uses these to form the event object.
 
         [NonEvent]
-        public void ConnectionStart(Connection connection)
+        public void ConnectionStart(IConnectionContext context, IConnectionInformation information)
         {
             // avoid allocating strings unless this event source is enabled
             if (IsEnabled())
             {
                 ConnectionStart(
-                    connection.ConnectionId,
+                    context.ConnectionId,
-                    connection.ListenerContext.ListenOptions.Scheme,
+                    information.ListenOptions.Scheme,
-                    connection.LocalEndPoint.ToString(),
+                    information.LocalEndPoint.ToString(),
-                    connection.RemoteEndPoint.ToString());
+                    information.RemoteEndPoint.ToString());
             }
         }
 
@@ -55,7 +56,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure
         }
 
         [NonEvent]
-        public void ConnectionStop(Connection connection)
+        public void ConnectionStop(IConnectionContext connection)
         {
             if (IsEnabled())
             {
@@ -69,5 +70,39 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure
         {
             WriteEvent(2, connectionId);
         }
+
+        [NonEvent]
+        public void RequestStart(Frame frame)
+        {
+            // avoid allocating the trace identifier unless logging is enabled
+            if (IsEnabled())
+            {
+                RequestStart(frame.ConnectionIdFeature, frame.TraceIdentifier);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        [Event(3, Level = EventLevel.Verbose)]
+        private void RequestStart(string connectionId, string requestId)
+        {
+            WriteEvent(3, connectionId, requestId);
+        }
+
+        [NonEvent]
+        public void RequestStop(Frame frame)
+        {
+            // avoid allocating the trace identifier unless logging is enabled
+            if (IsEnabled())
+            {
+                RequestStop(frame.ConnectionIdFeature, frame.TraceIdentifier);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        [Event(4, Level = EventLevel.Verbose)]
+        private void RequestStop(string connectionId, string requestId)
+        {
+            WriteEvent(4, connectionId, requestId);
+        }
     }
 }

src/Microsoft.AspNetCore.Server.Kestrel.Core/Internal/Infrastructure/KestrelTrace.cs

@@ -45,8 +45,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
 
         // ConnectionWriteCallback: Reserved: 12
 
-        private static readonly Action<ILogger, string, Exception> _applicationError =
+        private static readonly Action<ILogger, string, string, Exception> _applicationError =
-            LoggerMessage.Define<string>(LogLevel.Error, 13, @"Connection id ""{ConnectionId}"": An unhandled exception was thrown by the application.");
+            LoggerMessage.Define<string, string>(LogLevel.Error, 13, @"Connection id ""{ConnectionId}"", Request id ""{TraceIdentifier}"": An unhandled exception was thrown by the application.");
 
         private static readonly Action<ILogger, string, Exception> _connectionError =
             LoggerMessage.Define<string>(LogLevel.Information, 14, @"Connection id ""{ConnectionId}"" communication error.");
@@ -142,9 +142,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
             // Reserved: Event ID 12
         }
 
-        public virtual void ApplicationError(string connectionId, Exception ex)
+        public virtual void ApplicationError(string connectionId, string traceIdentifier, Exception ex)
         {
-            _applicationError(_logger, connectionId, ex);
+            _applicationError(_logger, connectionId, traceIdentifier, ex);
         }
 
         public virtual void ConnectionError(string connectionId, Exception ex)

src/Microsoft.AspNetCore.Server.Kestrel.Core/Transport/IConnectionContext.cs

@@ -14,6 +14,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Transport
         IPipeReader Output { get; }
 
         // TODO: Remove these (Use Pipes instead?)
+        void OnConnectionClosed();
         Task StopAsync();
         void Abort(Exception ex);
         void Timeout();

src/Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv/Internal/Http/Connection.cs

@@ -71,9 +71,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
                 _connectionContext = ConnectionHandler.OnConnection(this);
                 ConnectionId = _connectionContext.ConnectionId;
 
-                Log.ConnectionStart(ConnectionId);
-                KestrelEventSource.Log.ConnectionStart(this);
-
                 Input = _connectionContext.Input;
                 Output = new SocketOutputConsumer(_connectionContext.Output, Thread, _socket, this, ConnectionId, Log);
 
@@ -109,9 +106,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal.Http
         {
             _socket.Dispose();
 
-            Log.ConnectionStop(ConnectionId);
+            _connectionContext.OnConnectionClosed();
-
-            KestrelEventSource.Log.ConnectionStop(this);
 
             Input.Complete(new TaskCanceledException("The request was aborted"));
             _socketClosedTcs.TrySetResult(null);

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/EventSourceTests.cs

@@ -27,10 +27,12 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
         public async Task EmitsConnectionStartAndStop()
         {
             string connectionId = null;
+            string requestId = null;
             int port;
             using (var server = new TestServer(context =>
             {
                 connectionId = context.Features.Get<IHttpConnectionFeature>().ConnectionId;
+                requestId = context.TraceIdentifier;
                 return Task.CompletedTask;
             }))
             {
@@ -47,16 +49,33 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
 
             // capture list here as other tests executing in parallel may log events
             Assert.NotNull(connectionId);
+            Assert.NotNull(requestId);
+
             var events = _listener.EventData.Where(e => e != null && GetProperty(e, "connectionId") == connectionId).ToList();
 
-            var start = Assert.Single(events, e => e.EventName == "ConnectionStart");
+            {
-            Assert.All(new[] { "connectionId", "scheme", "remoteEndPoint", "localEndPoint" }, p => Assert.Contains(p, start.PayloadNames));
+                var start = Assert.Single(events, e => e.EventName == "ConnectionStart");
-            Assert.Equal("http", GetProperty(start, "scheme"));
+                Assert.All(new[] { "connectionId", "scheme", "remoteEndPoint", "localEndPoint" }, p => Assert.Contains(p, start.PayloadNames));
-            Assert.Equal($"127.0.0.1:{port}", GetProperty(start, "localEndPoint"));
+                Assert.Equal("http", GetProperty(start, "scheme"));
-
+                Assert.Equal($"127.0.0.1:{port}", GetProperty(start, "localEndPoint"));
-            var stop = Assert.Single(events, e => e.EventName == "ConnectionStop");
+            }
-            Assert.All(new[] { "connectionId" }, p => Assert.Contains(p, stop.PayloadNames));
+            {
-            Assert.Same(KestrelEventSource.Log, stop.EventSource);
+                var stop = Assert.Single(events, e => e.EventName == "ConnectionStop");
+                Assert.All(new[] { "connectionId" }, p => Assert.Contains(p, stop.PayloadNames));
+                Assert.Same(KestrelEventSource.Log, stop.EventSource);
+            }
+            {
+                var requestStart = Assert.Single(events, e => e.EventName == "RequestStart");
+                Assert.All(new[] { "connectionId", "requestId" }, p => Assert.Contains(p, requestStart.PayloadNames));
+                Assert.Equal(requestId, GetProperty(requestStart, "requestId"));
+                Assert.Same(KestrelEventSource.Log, requestStart.EventSource);
+            }
+            {
+                var requestStop = Assert.Single(events, e => e.EventName == "RequestStop");
+                Assert.All(new[] { "connectionId", "requestId" }, p => Assert.Contains(p, requestStop.PayloadNames));
+                Assert.Equal(requestId, GetProperty(requestStop, "requestId"));
+                Assert.Same(KestrelEventSource.Log, requestStop.EventSource);
+            }
         }
 
         private string GetProperty(EventWrittenEventArgs data, string propName)

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/RequestTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Concurrent;
 using System.Globalization;
 using System.IO;
 using System.Net;
@@ -566,6 +567,72 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
             }
         }
 
+        [Fact]
+        public async Task AppCanSetTraceIdentifier()
+        {
+            const string knownId = "xyz123";
+            using (var server = new TestServer(async context =>
+            {
+                context.TraceIdentifier = knownId;
+                await context.Response.WriteAsync(context.TraceIdentifier);
+            }))
+            {
+                var requestId = await HttpClientSlim.GetStringAsync($"http://{server.EndPoint}")
+                    .TimeoutAfter(TimeSpan.FromSeconds(10));
+                Assert.Equal(knownId, requestId);
+            }
+        }
+
+        [Fact]
+        public async Task TraceIdentifierIsUnique()
+        {
+            const int IdentifierLength = 13;
+            const int iterations = 10;
+
+            using (var server = new TestServer(async context =>
+            {
+                Assert.Equal(IdentifierLength, Encoding.ASCII.GetByteCount(context.TraceIdentifier));
+                context.Response.ContentLength = IdentifierLength;
+                await context.Response.WriteAsync(context.TraceIdentifier);
+            }))
+            {
+                var usedIds = new ConcurrentBag<string>();
+                var uri = $"http://{server.EndPoint}";
+
+                // requests on separate connections in parallel
+                Parallel.For(0, iterations, async i =>
+                {
+                    var id = await HttpClientSlim.GetStringAsync(uri);
+                    Assert.DoesNotContain(id, usedIds.ToArray());
+                    usedIds.Add(id);
+                });
+
+                // requests on same connection
+                using (var connection = server.CreateConnection())
+                {
+                    var buffer = new char[IdentifierLength];
+                    for (var i = 0; i < iterations; i++)
+                    {
+                        await connection.Send("GET / HTTP/1.1",
+                            "",
+                            "");
+
+                        await connection.Receive($"HTTP/1.1 200 OK",
+                           $"Date: {server.Context.DateHeaderValue}",
+                           $"Content-Length: {IdentifierLength}",
+                           "",
+                           "").TimeoutAfter(TimeSpan.FromSeconds(10));
+
+                        var read = await connection.Reader.ReadAsync(buffer, 0, IdentifierLength);
+                        Assert.Equal(IdentifierLength, read);
+                        var id = new string(buffer, 0, read);
+                        Assert.DoesNotContain(id, usedIds.ToArray());
+                        usedIds.Add(id);
+                    }
+                }
+            }
+        }
+
         private async Task TestRemoteIPAddress(string registerAddress, string requestAddress, string expectAddress)
         {
             var builder = new WebHostBuilder()

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/ResponseTests.cs

@@ -635,8 +635,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
             var logTcs = new TaskCompletionSource<object>();
             var mockTrace = new Mock<IKestrelTrace>();
             mockTrace
-                .Setup(trace => trace.ApplicationError(It.IsAny<string>(), It.IsAny<InvalidOperationException>()))
+                .Setup(trace => trace.ApplicationError(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<InvalidOperationException>()))
-                .Callback<string, Exception>((connectionId, ex) =>
+                .Callback<string, string, Exception>((connectionId, requestId, ex) =>
                 {
                     logTcs.SetResult(null);
                 });
@@ -675,6 +675,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
 
             mockTrace.Verify(trace =>
                 trace.ApplicationError(
+                    It.IsAny<string>(),
                     It.IsAny<string>(),
                     It.Is<InvalidOperationException>(ex =>
                         ex.Message.Equals($"Response Content-Length mismatch: too few bytes written (12 of 13).", StringComparison.Ordinal))));
@@ -724,7 +725,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
             }
 
             // With the server disposed we know all connections were drained and all messages were logged.
-            mockTrace.Verify(trace => trace.ApplicationError(It.IsAny<string>(), It.IsAny<InvalidOperationException>()), Times.Never);
+            mockTrace.Verify(trace => trace.ApplicationError(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<InvalidOperationException>()), Times.Never);
         }
 
         [Fact]

test/Microsoft.AspNetCore.Server.Kestrel.Performance/Mocks/MockTrace.cs

@@ -9,7 +9,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Performance
 {
     public class MockTrace : IKestrelTrace
     {
-        public void ApplicationError(string connectionId, Exception ex) { }
+        public void ApplicationError(string connectionId, string requestId, Exception ex) { }
         public IDisposable BeginScope<TState>(TState state) => null;
         public void ConnectionBadRequest(string connectionId, BadHttpRequestException ex) { }
         public void ConnectionDisconnect(string connectionId) { }

test/Microsoft.AspNetCore.Server.KestrelTests/FrameTests.cs

@@ -123,6 +123,33 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
             Assert.Equal("http", ((IFeatureCollection)_frame).Get<IHttpRequestFeature>().Scheme);
         }
 
+        [Fact]
+        public void ResetResetsTraceIdentifier()
+        {
+            _frame.TraceIdentifier = "xyz";
+
+            _frame.Reset();
+
+            var nextId = ((IFeatureCollection)_frame).Get<IHttpRequestIdentifierFeature>().TraceIdentifier;
+            Assert.NotEqual("xyz", nextId);
+
+            _frame.Reset();
+            var secondId = ((IFeatureCollection)_frame).Get<IHttpRequestIdentifierFeature>().TraceIdentifier;
+            Assert.NotEqual(nextId, secondId);
+        }
+
+        [Fact]
+        public void TraceIdentifierGeneratesWhenNull()
+        {
+            _frame.TraceIdentifier = null;
+            var id = _frame.TraceIdentifier;
+            Assert.NotNull(id);
+            Assert.Equal(id, _frame.TraceIdentifier);
+
+            _frame.TraceIdentifier = null;
+            Assert.NotEqual(id, _frame.TraceIdentifier);
+        }
+
         [Fact]
         public async Task ResetResetsHeaderLimits()
         {

test/Microsoft.AspNetCore.Server.KestrelTests/KestrelEventSourceTests.cs

@@ -4,7 +4,7 @@
 using System;
 using System.Diagnostics.Tracing;
 using System.Reflection;
-using Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv;
+using Microsoft.AspNetCore.Server.Kestrel;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Server.KestrelTests
@@ -14,7 +14,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         [Fact]
         public void ExistsWithCorrectId()
         {
-            var esType = typeof(LibuvTransportFactory).GetTypeInfo().Assembly.GetType(
+            var esType = typeof(KestrelServer).GetTypeInfo().Assembly.GetType(
                 "Microsoft.AspNetCore.Server.Kestrel.Internal.Infrastructure.KestrelEventSource",
                 throwOnError: true,
                 ignoreCase: false

test/Microsoft.AspNetCore.Server.KestrelTests/TestHelpers/MockConnectionHandler.cs

@@ -47,6 +47,11 @@ namespace Microsoft.AspNetCore.Server.KestrelTests.TestHelpers
             public IPipeWriter Input { get; set; }
             public IPipeReader Output { get; set; }
 
+            public void OnConnectionClosed()
+            {
+                throw new NotImplementedException();
+            }
+
             public Task StopAsync()
             {
                 throw new NotImplementedException();

test/shared/TestConnection.cs

@@ -32,6 +32,8 @@ namespace Microsoft.AspNetCore.Testing
             Create(port, addressFamily);
         }
 
+        public StreamReader Reader => _reader;
+
         public void Create(int port, AddressFamily addressFamily)
         {
             _socket = CreateConnectedLoopbackSocket(port, addressFamily);

test/shared/TestServer.cs

@@ -59,6 +59,7 @@ namespace Microsoft.AspNetCore.Testing
             }
         }
 
+        public IPEndPoint EndPoint => _listenOptions.IPEndPoint;
         public int Port => _listenOptions.IPEndPoint.Port;
         public AddressFamily AddressFamily => _listenOptions.IPEndPoint.AddressFamily;
 

tools/CodeGenerator/FrameFeatureCollection.cs

@@ -61,8 +61,9 @@ namespace CodeGenerator
                 typeof(IHttpRequestFeature),
                 typeof(IHttpResponseFeature),
                 typeof(IHttpUpgradeFeature),
+                typeof(IHttpRequestIdentifierFeature),
                 typeof(IHttpRequestLifetimeFeature),
-                typeof(IHttpConnectionFeature)
+                typeof(IHttpConnectionFeature),
             };
 
             return $@"// Copyright (c) .NET Foundation. All rights reserved.