Use current activity if there is one

src/Elastic.Apm.AspNetCore/WebRequestTransactionCreator.cs

@@ -243,13 +243,20 @@ internal static void SetOutcomeForHttpResult(ITransaction transaction, int HttpR
 		/// <returns>default if it's not a grpc call, otherwise the Grpc method name and result as a tuple </returns>
 		private static (string methodname, string result) CollectGrpcInfo()
 		{
-			var parentActivity = Activity.Current?.Parent;
+			// gRPC info is stored on the Activity with name `Microsoft.AspNetCore.Hosting.HttpRequestIn`.
+			// Therefore we follow parent activities as long as we reach this activity.
+			// Activity.Current can e.g. be the `ElasticApm.Transaction` Activity, so we need to go up the activity chain.
+			var httpRequestInActivity = Activity.Current;
+
+			while (httpRequestInActivity != null && httpRequestInActivity.OperationName != "Microsoft.AspNetCore.Hosting.HttpRequestIn")
+				httpRequestInActivity = httpRequestInActivity.Parent;
+
 			(string methodname, string result) grpcCallInfo = default;
 
-			if (parentActivity != null)
+			if (httpRequestInActivity != null)
 			{
-				var grpcMethodName = parentActivity.Tags.FirstOrDefault(n => n.Key == "grpc.method").Value;
-				var grpcStatusCode = parentActivity.Tags.FirstOrDefault(n => n.Key == "grpc.status_code").Value;
+				var grpcMethodName = httpRequestInActivity.Tags.FirstOrDefault(n => n.Key == "grpc.method").Value;
+				var grpcStatusCode = httpRequestInActivity.Tags.FirstOrDefault(n => n.Key == "grpc.status_code").Value;
 
 				if (!string.IsNullOrEmpty(grpcMethodName) && !string.IsNullOrEmpty(grpcStatusCode))
 					grpcCallInfo = (grpcMethodName, grpcStatusCode);

src/Elastic.Apm/Model/Transaction.cs

@@ -25,12 +25,14 @@ internal class Transaction : ITransaction
 		private readonly IApmServerInfo _apmServerInfo;
 		private readonly Lazy<Context> _context = new Lazy<Context>();
 		private readonly ICurrentExecutionSegmentsContainer _currentExecutionSegmentsContainer;
-
 		private readonly IApmLogger _logger;
 		private readonly IPayloadSender _sender;
-
 		private readonly string _traceState;
 
+		// Flags whether the agent created a new Activity for this transaction.
+		// If there is an existing Activity using W3C format, no Activity will be created and this remains false.
+		private bool _createdActivity;
+
 		// This constructor is meant for serialization
 		[JsonConstructor]
 		private Transaction(Context context, string name, string type, double duration, long timestamp, string id, string traceId, string parentId,
@@ -99,26 +101,44 @@ internal Transaction(
 			HasCustomName = false;
 			Type = type;
 
-			// For each transaction start, we fire an Activity
-			// If Activity.Current is null, then we create one with this and set its traceid, which will flow to all child activities and we also reuse it in Elastic APM, so it'll be the same on all Activities and in Elastic
-			// If Activity.Current is not null, we pick up its traceid and apply it in Elastic APM
+			// For each transaction start, fire an Activity if we're not ignoring them.
+			// If Activity.Current is null, then we create one with this and set its traceid, which will flow to all child activities,
+			// and we also reuse it in Elastic APM, so it'll be the same on all Activities.
+			// If Activity.Current is not null and using W3C id format, use its traceid and apply it in Elastic APM
 			if (!ignoreActivity)
-				StartActivity();
+			{
+				var currentActivity = Activity.Current;
+				if (currentActivity != null && currentActivity.IdFormat == ActivityIdFormat.W3C)
+					_activity = currentActivity;
+				else
+					_activity = StartActivity();
+			}
 
 			var isSamplingFromDistributedTracingData = false;
 			if (distributedTracingData == null)
 			{
-				// Here we ignore Activity.Current.ActivityTraceFlags because it starts out without setting the IsSampled flag, so relying on that would mean a transaction is never sampled.
+				// Here we ignore Activity.Current.ActivityTraceFlags because it starts out without setting the IsSampled flag,
+				// so relying on that would mean a transaction is never sampled.
 				// To be sure activity creation was successful let's check on it
 				if (_activity != null)
 				{
-					// In case activity creation was successful, let's reuse the ids
-					Id = _activity.SpanId.ToHexString();
+					// If an activity was created, reuse its id, otherwise generate a new one.
+					if (_createdActivity)
+						Id = _activity.SpanId.ToHexString();
+					else
+					{
+						var idBytes = new byte[8];
+						Id = RandomGenerator.GenerateRandomBytesAsString(idBytes);
+					}
+
 					TraceId = _activity.TraceId.ToHexString();
+					_traceState = _activity.TraceStateString;
 
 					var idBytesFromActivity = new Span<byte>(new byte[16]);
 					_activity.TraceId.CopyTo(idBytesFromActivity);
-					// Read right most bits. From W3C TraceContext: "it is important for trace-id to carry "uniqueness" and "randomness" in the right part of the trace-id..."
+
+					// Read right most bits. From W3C TraceContext: "it is important for trace-id to carry "uniqueness" and "randomness"
+					// in the right part of the trace-id..."
 					idBytesFromActivity = idBytesFromActivity.Slice(8);
 					IsSampled = sampler.DecideIfToSample(idBytesFromActivity.ToArray());
 				}
@@ -133,12 +153,12 @@ internal Transaction(
 					TraceId = RandomGenerator.GenerateRandomBytesAsString(idBytes);
 				}
 
-				// PrentId could be also set here, but currently in the UI each trace must start with a transaction where the ParentId is null,
+				// ParentId could be also set here, but currently in the UI each trace must start with a transaction where the ParentId is null,
 				// so to avoid https://github.com/elastic/apm-agent-dotnet/issues/883 we don't set it yet.
 			}
 			else
 			{
-				if (_activity != null)
+				if (_activity != null && _createdActivity)
 					Id = _activity.SpanId.ToHexString();
 				else
 				{
@@ -177,13 +197,15 @@ internal Transaction(
 						" Start time: {Time} (as timestamp: {Timestamp})",
 						this, IsSampled, sampler, TimeUtils.FormatTimestampForLog(Timestamp), Timestamp);
 			}
+		}
 
-			void StartActivity()
-			{
-				_activity = new Activity(ApmTransactionActivityName);
-				_activity.SetIdFormat(ActivityIdFormat.W3C);
-				_activity.Start();
-			}
+		private Activity StartActivity()
+		{
+			var activity = new Activity(ApmTransactionActivityName);
+			activity.SetIdFormat(ActivityIdFormat.W3C);
+			activity.Start();
+			_createdActivity = true;
+			return activity;
 		}
 
 		/// <summary>
@@ -192,7 +214,7 @@ void StartActivity()
 		/// With this, in case Activity.Current is null, the agent will set it and when the next Activity gets created it'll
 		/// have this activity as its parent and the TraceId will flow to all Activity instances.
 		/// </summary>
-		private Activity _activity;
+		private readonly Activity _activity;
 
 		private bool _isEnded;
 
@@ -306,6 +328,7 @@ public Outcome Outcome
 
 		internal Service Service;
 
+
 		[JsonProperty("span_count")]
 		public SpanCount SpanCount { get; set; }
 
@@ -398,7 +421,8 @@ public void End()
 						TimeUtils.FormatTimestampForLog(endTimestamp), endTimestamp, Duration);
 			}
 
-			_activity?.Stop();
+			if (_createdActivity)
+				_activity?.Stop();
 
 			var isFirstEndCall = !_isEnded;
 			_isEnded = true;