Adding a feature to get the traceidentifier for a request

Addresses : https://github.com/aspnet/HttpAbstractions/issues/117

Related changes in Helios & weblistener in separate PRs.

src/Microsoft.AspNet.Http.Interfaces/IRequestIdentifierFeature.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNet.Http.Interfaces
+{
+    /// <summary>
+    /// Feature to identify a request.
+    /// </summary>
+    public interface IRequestIdentifierFeature
+    {
+        /// <summary>
+        /// Identifier to trace a request.
+        /// </summary>
+        Guid TraceIdentifier { get; }
+    }
+}

src/Microsoft.AspNet.Owin/OwinConstants.cs

@@ -20,6 +20,14 @@ namespace Microsoft.AspNet.Owin
 
         #endregion
 
+        #region OWIN v1.1.0 - 3.2.1 Request Data
+
+        // OWIN 1.1.0 http://owin.org/html/owin.html
+
+        public const string RequestId = "owin.RequestId";
+
+        #endregion
+
         #region OWIN v1.0.0 - 3.2.2. Response Data
 
         // http://owin.org/spec/owin-1.0.0.html

src/Microsoft.AspNet.Owin/OwinEnvironment.cs

@@ -80,7 +80,7 @@ namespace Microsoft.AspNet.Owin
                 { OwinConstants.Security.User, new FeatureMap<IHttpAuthenticationFeature>(feature => feature.User,
                     ()=> null, (feature, value) => feature.User = Utilities.MakeClaimsPrincipal((IPrincipal)value),
                     () => new HttpAuthenticationFeature())
-                },
+                }
             };
 
             // owin.CallCancelled is required but the feature may not be present.
@@ -113,6 +113,9 @@ namespace Microsoft.AspNet.Owin
             }
 
             _context.Items[typeof(HttpContext).FullName] = _context; // Store for lookup when we transition back out of OWIN
+
+            // The request identifier is a string per the spec.
+            _entries[OwinConstants.RequestId] = new FeatureMap<IRequestIdentifierFeature>(feature => feature.TraceIdentifier.ToString());
         }
 
         // Public in case there's a new/custom feature interface that needs to be added.
@@ -369,7 +372,7 @@ namespace Microsoft.AspNet.Owin
             }
 
             public FeatureMap(Func<TFeature, object> getter, Func<object> defaultFactory, Action<TFeature, object> setter)
-                : base(typeof(TFeature), feature => getter((TFeature)feature), defaultFactory,(feature, value) => setter((TFeature)feature, value))
+                : base(typeof(TFeature), feature => getter((TFeature)feature), defaultFactory, (feature, value) => setter((TFeature)feature, value))
             {
             }
 

src/Microsoft.AspNet.Owin/OwinFeatureCollection.cs

@@ -32,7 +32,8 @@ namespace Microsoft.AspNet.Owin
         IHttpRequestLifetimeFeature,
         IHttpAuthenticationFeature,
         IHttpWebSocketFeature,
-        IOwinEnvironmentFeature
+        IOwinEnvironmentFeature,
+        IRequestIdentifierFeature
     {
         public IDictionary<string, object> Environment { get; set; }
         private bool _headersSent;
@@ -427,6 +428,22 @@ namespace Microsoft.AspNet.Owin
             get { return true; }
         }
 
+        Guid IRequestIdentifierFeature.TraceIdentifier
+        {
+            get
+            {
+                var requestId = Prop<string>(OwinConstants.RequestId);
+                Guid requestIdentifier;
+
+                if (requestId != null && Guid.TryParse(requestId, out requestIdentifier))
+                {
+                    return requestIdentifier;
+                }
+
+                return Guid.Empty;
+            }
+        }
+
         public bool Remove(KeyValuePair<Type, object> item)
         {
             throw new NotSupportedException();