stop propagating x-datadog-tags header (#2506)

* stop propagating `x-datadog-tags`

* restore some of the validation to ensure we _don't_ set the header

* remove code instead of commenting, we can revert this later

* restore vertical propagation of trace-level tags

tracer/src/Datadog.Trace/SpanContext.cs

@@ -21,7 +21,6 @@ public class SpanContext : ISpanContext, IReadOnlyDictionary<string, string>
             HttpHeaderNames.ParentId,
             HttpHeaderNames.SamplingPriority,
             HttpHeaderNames.Origin,
-            HttpHeaderNames.DatadogTags,
         };
 
         /// <summary>
@@ -134,16 +133,6 @@ private SpanContext(ulong? traceId, string serviceName)
         /// </summary>
         internal string Origin { get; set; }
 
-        /// <summary>
-        /// Gets or sets a collection of propagated internal Datadog tags,
-        /// formatted as "key1=value1,key2=value2".
-        /// </summary>
-        /// <remarks>
-        /// We're keeping this as the string representation to avoid having to parse.
-        /// For now, it's relatively easy to append new values when needed.
-        /// </remarks>
-        internal string DatadogTags { get; set; }
-
         /// <summary>
         /// Gets the trace context.
         /// Returns null for contexts created from incoming propagated context.
@@ -241,10 +230,6 @@ bool IReadOnlyDictionary<string, string>.TryGetValue(string key, out string valu
                     value = Origin;
                     return true;
 
-                case HttpHeaderNames.DatadogTags:
-                    value = DatadogTags;
-                    return true;
-
                 default:
                     value = null;
                     return false;

tracer/src/Datadog.Trace/SpanContextPropagator.cs

@@ -77,13 +77,6 @@ public void Inject<TCarrier>(SpanContext context, TCarrier carrier, Action<TCarr
             {
                 setter(carrier, HttpHeaderNames.SamplingPriority, samplingPriority.Value.ToString(_invariantCulture));
             }
-
-            var datadogTags = context.TraceContext?.Tags?.ToPropagationHeader() ?? context.DatadogTags;
-
-            if (datadogTags != null)
-            {
-                setter(carrier, HttpHeaderNames.DatadogTags, datadogTags);
-            }
         }
 
         /// <summary>
@@ -121,12 +114,8 @@ public void Inject<TCarrier>(SpanContext context, TCarrier carrier, Action<TCarr
             var parentId = ParseUInt64(carrier, getter, HttpHeaderNames.ParentId) ?? 0;
             var samplingPriority = ParseInt32(carrier, getter, HttpHeaderNames.SamplingPriority);
             var origin = ParseString(carrier, getter, HttpHeaderNames.Origin);
-            var datadogTags = ParseString(carrier, getter, HttpHeaderNames.DatadogTags);
 
-            return new SpanContext(traceId, parentId, samplingPriority, serviceName: null, origin)
-            {
-                DatadogTags = datadogTags
-            };
+            return new SpanContext(traceId, parentId, samplingPriority, serviceName: null, origin);
         }
 
         public IEnumerable<KeyValuePair<string, string?>> ExtractHeaderTags<T>(T headers, IEnumerable<KeyValuePair<string, string?>> headerToTagMap, string defaultTagPrefix)

tracer/src/Datadog.Trace/Tracer.cs

@@ -348,14 +348,13 @@ internal SpanContext CreateSpanContext(ISpanContext parent = null, string servic
                 traceContext = parentSpanContext.TraceContext;
                 if (traceContext == null)
                 {
-                    var traceTags = TraceTagCollection.ParseFromPropagationHeader(parentSpanContext.DatadogTags);
-                    traceContext = new TraceContext(this, traceTags);
+                    traceContext = new TraceContext(this);
                     traceContext.SetSamplingPriority(parentSpanContext.SamplingPriority ?? DistributedTracer.Instance.GetSamplingPriority());
                 }
             }
             else
             {
-                traceContext = new TraceContext(this, tags: null);
+                traceContext = new TraceContext(this);
                 traceContext.SetSamplingPriority(DistributedTracer.Instance.GetSamplingPriority());
             }
 

tracer/test/Datadog.Trace.Tests/SpanContextPropagatorTests.cs

@@ -19,7 +19,6 @@ public class SpanContextPropagatorTests
         private const ulong SpanId = 2;
         private const int SamplingPriority = SamplingPriorityValues.UserReject;
         private const string Origin = "origin";
-        private const string DatadogTags = "key1=value1;key2=value2";
 
         private static readonly CultureInfo InvariantCulture = CultureInfo.InvariantCulture;
 
@@ -29,7 +28,6 @@ public class SpanContextPropagatorTests
             new(HttpHeaderNames.ParentId, SpanId.ToString(InvariantCulture)),
             new(HttpHeaderNames.SamplingPriority, SamplingPriority.ToString(InvariantCulture)),
             new(HttpHeaderNames.Origin, Origin),
-            new(HttpHeaderNames.DatadogTags, DatadogTags),
         };
 
         public static TheoryData<string> GetInvalidIds() => new()
@@ -44,7 +42,7 @@ public class SpanContextPropagatorTests
         [Fact]
         public void Inject_IHeadersCollection()
         {
-            var context = new SpanContext(TraceId, SpanId, SamplingPriority, serviceName: null, Origin) { DatadogTags = DatadogTags };
+            var context = new SpanContext(TraceId, SpanId, SamplingPriority, serviceName: null, Origin);
             var headers = new Mock<IHeadersCollection>();
 
             SpanContextPropagator.Instance.Inject(context, headers.Object);
@@ -55,7 +53,7 @@ public void Inject_IHeadersCollection()
         [Fact]
         public void Inject_CarrierAndDelegate()
         {
-            var context = new SpanContext(TraceId, SpanId, SamplingPriority, serviceName: null, Origin) { DatadogTags = DatadogTags };
+            var context = new SpanContext(TraceId, SpanId, SamplingPriority, serviceName: null, Origin);
 
             // using IHeadersCollection for convenience, but carrier could be any type
             var headers = new Mock<IHeadersCollection>();
@@ -68,7 +66,7 @@ public void Inject_CarrierAndDelegate()
         [Fact]
         public void Inject_TraceIdSpanIdOnly()
         {
-            var context = new SpanContext(TraceId, SpanId, samplingPriority: null, serviceName: null, origin: null) { DatadogTags = null };
+            var context = new SpanContext(TraceId, SpanId, samplingPriority: null, serviceName: null, origin: null);
             var headers = new Mock<IHeadersCollection>();
 
             SpanContextPropagator.Instance.Inject(context, headers.Object);
@@ -95,7 +93,6 @@ public void Extract_IHeadersCollection()
                            SpanId = SpanId,
                            Origin = Origin,
                            SamplingPriority = SamplingPriority,
-                           DatadogTags = DatadogTags,
                        });
         }
 
@@ -116,7 +113,6 @@ public void Extract_CarrierAndDelegate()
                            SpanId = SpanId,
                            Origin = Origin,
                            SamplingPriority = SamplingPriority,
-                           DatadogTags = DatadogTags,
                        });
         }
 
@@ -136,7 +132,6 @@ public void Extract_ReadOnlyDictionary()
                            SpanId = SpanId,
                            Origin = Origin,
                            SamplingPriority = SamplingPriority,
-                           DatadogTags = DatadogTags,
                        });
         }
 
@@ -218,7 +213,6 @@ public void Extract_InvalidSpanId(string spanId)
                            TraceId = TraceId,
                            Origin = Origin,
                            SamplingPriority = SamplingPriority,
-                           DatadogTags = DatadogTags,
                        });
         }
 
@@ -249,7 +243,6 @@ public void Extract_InvalidSamplingPriority(string samplingPriority, int? expect
                            SpanId = SpanId,
                            Origin = Origin,
                            SamplingPriority = expectedSamplingPriority,
-                           DatadogTags = DatadogTags,
                        });
         }
 
@@ -328,8 +321,6 @@ internal class SpanContextMock
 
         public int? SamplingPriority { get; set; }
 
-        public string DatadogTags { get; set; }
-
         public ISpanContext Parent { get; set; }
 
         public ulong? ParentId { get; set; }