Support W3C Baggage header (dotnet#28328)

Author: jbogard

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

@@ -266,7 +266,11 @@ private Activity StartActivity(HttpContext httpContext, out bool hasDiagnosticLi
 
                 // We expect baggage to be empty by default
                 // Only very advanced users will be using it in near future, we encourage them to keep baggage small (few items)
-                string[] baggage = headers.GetCommaSeparatedValues(HeaderNames.CorrelationContext);
+                var baggage = headers.GetCommaSeparatedValues(HeaderNames.Baggage);
+                if (baggage.Length == 0)
+                {
+                    baggage = headers.GetCommaSeparatedValues(HeaderNames.CorrelationContext);
+                }
 
                 // AddBaggage adds items at the beginning  of the list, so we need to add them in reverse to keep the same order as the client
                 // An order could be important if baggage has two items with the same key (that is allowed by the contract)

src/Hosting/Hosting/test/HostingApplicationDiagnosticsTests.cs

@@ -271,7 +271,7 @@ public void ActivityIsAvailibleDuringRequest()
         }
 
         [Fact]
-        public void ActivityParentIdAndBaggeReadFromHeaders()
+        public void ActivityParentIdAndBaggageReadFromHeaders()
         {
             var diagnosticListener = new DiagnosticListener("DummySource");
             var hostingApplication = CreateApplication(out var features, diagnosticListener: diagnosticListener);
@@ -291,7 +291,7 @@ public void ActivityParentIdAndBaggeReadFromHeaders()
                 Headers = new HeaderDictionary()
                 {
                     {"Request-Id", "ParentId1"},
-                    {"Correlation-Context", "Key1=value1, Key2=value2"}
+                    {"baggage", "Key1=value1, Key2=value2"}
                 }
             });
             hostingApplication.CreateContext(features);
@@ -301,6 +301,67 @@ public void ActivityParentIdAndBaggeReadFromHeaders()
             Assert.Contains(Activity.Current.Baggage, pair => pair.Key == "Key2" && pair.Value == "value2");
         }
 
+        [Fact]
+        public void ActivityBaggageReadFromLegacyHeaders()
+        {
+            var diagnosticListener = new DiagnosticListener("DummySource");
+            var hostingApplication = CreateApplication(out var features, diagnosticListener: diagnosticListener);
+
+            diagnosticListener.Subscribe(new CallbackDiagnosticListener(pair => { }),
+                s =>
+                {
+                    if (s.StartsWith("Microsoft.AspNetCore.Hosting.HttpRequestIn", StringComparison.Ordinal))
+                    {
+                        return true;
+                    }
+                    return false;
+                });
+
+            features.Set<IHttpRequestFeature>(new HttpRequestFeature()
+            {
+                Headers = new HeaderDictionary()
+                {
+                    {"Request-Id", "ParentId1"},
+                    {"Correlation-Context", "Key1=value1, Key2=value2"}
+                }
+            });
+            hostingApplication.CreateContext(features);
+            Assert.Equal("Microsoft.AspNetCore.Hosting.HttpRequestIn", Activity.Current.OperationName);
+            Assert.Contains(Activity.Current.Baggage, pair => pair.Key == "Key1" && pair.Value == "value1");
+            Assert.Contains(Activity.Current.Baggage, pair => pair.Key == "Key2" && pair.Value == "value2");
+        }
+
+        [Fact]
+        public void ActivityBaggagePrefersW3CBaggageHeaderName()
+        {
+            var diagnosticListener = new DiagnosticListener("DummySource");
+            var hostingApplication = CreateApplication(out var features, diagnosticListener: diagnosticListener);
+
+            diagnosticListener.Subscribe(new CallbackDiagnosticListener(pair => { }),
+                s =>
+                {
+                    if (s.StartsWith("Microsoft.AspNetCore.Hosting.HttpRequestIn", StringComparison.Ordinal))
+                    {
+                        return true;
+                    }
+                    return false;
+                });
+
+            features.Set<IHttpRequestFeature>(new HttpRequestFeature()
+            {
+                Headers = new HeaderDictionary()
+                {
+                    {"Request-Id", "ParentId1"},
+                    {"Correlation-Context", "Key1=value1, Key2=value2"},
+                    {"baggage", "Key1=value3, Key2=value4"}
+                }
+            });
+            hostingApplication.CreateContext(features);
+            Assert.Equal("Microsoft.AspNetCore.Hosting.HttpRequestIn", Activity.Current.OperationName);
+            Assert.Contains(Activity.Current.Baggage, pair => pair.Key == "Key1" && pair.Value == "value3");
+            Assert.Contains(Activity.Current.Baggage, pair => pair.Key == "Key2" && pair.Value == "value4");
+        }
+
         [Fact]
         public void ActivityBaggagePreservesItemsOrder()
         {
@@ -322,7 +383,7 @@ public void ActivityBaggagePreservesItemsOrder()
                 Headers = new HeaderDictionary()
                 {
                     {"Request-Id", "ParentId1"},
-                    {"Correlation-Context", "Key1=value1, Key2=value2, Key1=value3"} // duplicated keys allowed by the contract
+                    {"baggage", "Key1=value1, Key2=value2, Key1=value3"} // duplicated keys allowed by the contract
                 }
             });
             hostingApplication.CreateContext(features);
@@ -359,7 +420,7 @@ public void ActivityBaggageValuesAreUrlDecodedFromHeaders()
                 Headers = new HeaderDictionary()
                 {
                     {"Request-Id", "ParentId1"},
-                    {"Correlation-Context", "Key1=value1%2F1"}
+                    {"baggage", "Key1=value1%2F1"}
                 }
             });
             hostingApplication.CreateContext(features);
@@ -389,7 +450,7 @@ public void ActivityTraceParentAndTraceStateFromHeaders()
                 {
                     {"traceparent", "00-0123456789abcdef0123456789abcdef-0123456789abcdef-01"},
                     {"tracestate", "TraceState1"},
-                    {"Correlation-Context", "Key1=value1, Key2=value2"}
+                    {"baggage", "Key1=value1, Key2=value2"}
                 }
             });
             hostingApplication.CreateContext(features);

src/Http/Headers/src/HeaderNames.cs

@@ -64,6 +64,9 @@ public static class HeaderNames
         /// <summary>Gets the <c>Authorization</c> HTTP header name.</summary>
         public static readonly string Authorization = "Authorization";
 
+        /// <summary>Gets the <c>baggage</c> HTTP header name.</summary>
+        public static readonly string Baggage = "baggage";
+
         /// <summary>Gets the <c>Cache-Control</c> HTTP header name.</summary>
         public static readonly string CacheControl = "Cache-Control";
 

src/Http/Headers/src/PublicAPI.Unshipped.txt

@@ -1,4 +1,5 @@
 #nullable enable
 Microsoft.Net.Http.Headers.MediaTypeHeaderValue.MatchesMediaType(Microsoft.Extensions.Primitives.StringSegment otherMediaType) -> bool
 Microsoft.Net.Http.Headers.RangeConditionHeaderValue.RangeConditionHeaderValue(Microsoft.Net.Http.Headers.EntityTagHeaderValue! entityTag) -> void
+static readonly Microsoft.Net.Http.Headers.HeaderNames.Baggage -> string!
 static readonly Microsoft.Net.Http.Headers.HeaderNames.ProxyConnection -> string!