Propagate sample rate through tracestate

sample/ApiSamples/ApiSamples.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>netcoreapp2.1;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp2.1;netcoreapp3.0;net5.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
   <ItemGroup>

sample/ApiSamples/Program.cs

@@ -3,28 +3,28 @@
 // See the LICENSE file in the project root for more information
 
 using System;
-#if NETCOREAPP3_0
 using System.Collections.Generic;
-#endif
 using System.Diagnostics;
+using System.Reflection;
 using System.Threading;
 using Elastic.Apm;
 using Elastic.Apm.Api;
 
 namespace ApiSamples
 {
 	/// <summary>
-	/// This class exercices the Public Agent API.
+	/// This class exercises the Public Agent API.
 	/// </summary>
 	internal class Program
 	{
 		private static void Main(string[] args)
 		{
-			if (args.Length == 1) //in case it's started with an argument we try to parse the argument as a DistributedTracingData
+			if (args.Length == 1) //in case it's started with arguments, parse DistributedTracingData from them
 			{
-				WriteLineToConsole($"Callee process started - continuing trace with distributed tracing data: {args[0]}");
-				var transaction2 = Agent.Tracer.StartTransaction("Transaction2", "TestTransaction",
-					DistributedTracingData.TryDeserializeFromString(args[0]));
+				var distributedTracingData = DistributedTracingData.TryDeserializeFromString(args[0]);
+
+				WriteLineToConsole($"Callee process started - continuing trace with distributed tracing data: {distributedTracingData}");
+				var transaction2 = Agent.Tracer.StartTransaction("Transaction2", "TestTransaction", distributedTracingData);
 
 				try
 				{
@@ -35,7 +35,7 @@ private static void Main(string[] args)
 					transaction2.End();
 				}
 
-				Thread.Sleep(1000);
+				Thread.Sleep(TimeSpan.FromSeconds(11));
 				WriteLineToConsole("About to exit");
 			}
 			else
@@ -45,7 +45,7 @@ private static void Main(string[] args)
 
 				//WIP: if the process terminates the agent
 				//potentially does not have time to send the transaction to the server.
-				Thread.Sleep(1000);
+				Thread.Sleep(TimeSpan.FromSeconds(11));
 
 				WriteLineToConsole("About to exit - press any key...");
 				Console.ReadKey();
@@ -160,14 +160,22 @@ public static void PassDistributedTracingData()
 
 				//We start the sample app again with a new service name and we pass DistributedTracingData to it
 				//In the main method we check for this and continue the trace.
-				var startInfo = new ProcessStartInfo();
-				startInfo.Environment["ELASTIC_APM_SERVICE_NAME"] = "Service2";
-				var outgoingDistributedTracingData = (Agent.Tracer.CurrentSpan?.OutgoingDistributedTracingData
-					?? Agent.Tracer.CurrentTransaction?.OutgoingDistributedTracingData)?.SerializeToString();
-				startInfo.FileName = "dotnet";
-				startInfo.Arguments = $"run {outgoingDistributedTracingData}";
+
+				var distributedTracingData = Agent.Tracer.CurrentSpan?.OutgoingDistributedTracingData
+					?? Agent.Tracer.CurrentTransaction?.OutgoingDistributedTracingData;
+
+				var traceParent = distributedTracingData?.SerializeToString();
+				var assembly = Assembly.GetExecutingAssembly().Location;
+
 				WriteLineToConsole(
-					$"Spawning callee process and passing outgoing distributed tracing data: {outgoingDistributedTracingData} to it...");
+					$"Spawning callee process and passing outgoing distributed tracing data: {traceParent} to it...");
+				var startInfo = new ProcessStartInfo
+				{
+					FileName = "dotnet",
+					Arguments = $"{assembly} {traceParent}"
+				};
+
+				startInfo.Environment["ELASTIC_APM_SERVICE_NAME"] = "Service2";
 				var calleeProcess = Process.Start(startInfo);
 				WriteLineToConsole("Spawned callee process");
 

src/Elastic.Apm.AspNetCore/WebRequestTransactionCreator.cs

@@ -14,6 +14,7 @@
 using Microsoft.AspNetCore.Http.Extensions;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.Primitives;
 
 namespace Elastic.Apm.AspNetCore
 {
@@ -35,23 +36,25 @@ internal static ITransaction StartTransactionAsync(HttpContext context, IApmLogg
 				ITransaction transaction;
 				var transactionName = $"{context.Request.Method} {context.Request.Path}";
 
-				if (context.Request.Headers.ContainsKey(TraceContext.TraceParentHeaderNamePrefixed)
-					|| context.Request.Headers.ContainsKey(TraceContext.TraceParentHeaderName))
-				{
-					var headerValue = context.Request.Headers.ContainsKey(TraceContext.TraceParentHeaderName)
-						? context.Request.Headers[TraceContext.TraceParentHeaderName].ToString()
-						: context.Request.Headers[TraceContext.TraceParentHeaderNamePrefixed].ToString();
+				var containsPrefixedTraceParentHeader =
+					context.Request.Headers.TryGetValue(TraceContext.TraceParentHeaderNamePrefixed, out var traceParentHeader);
+
+				var containsTraceParentHeader = false;
+				if (!containsPrefixedTraceParentHeader)
+					containsTraceParentHeader = context.Request.Headers.TryGetValue(TraceContext.TraceParentHeaderName, out traceParentHeader);
 
-					var tracingData = context.Request.Headers.ContainsKey(TraceContext.TraceStateHeaderName)
-						? TraceContext.TryExtractTracingData(headerValue, context.Request.Headers[TraceContext.TraceStateHeaderName].ToString())
-						: TraceContext.TryExtractTracingData(headerValue);
+				if (containsPrefixedTraceParentHeader || containsTraceParentHeader)
+				{
+					var tracingData = context.Request.Headers.TryGetValue(TraceContext.TraceStateHeaderName, out var traceStateHeader)
+						? TraceContext.TryExtractTracingData(traceParentHeader, traceStateHeader)
+						: TraceContext.TryExtractTracingData(traceParentHeader);
 
 					if (tracingData != null)
 					{
 						logger.Debug()
 							?.Log(
 								"Incoming request with {TraceParentHeaderName} header. DistributedTracingData: {DistributedTracingData}. Continuing trace.",
-								TraceContext.TraceParentHeaderNamePrefixed, tracingData);
+								containsPrefixedTraceParentHeader? TraceContext.TraceParentHeaderNamePrefixed : TraceContext.TraceParentHeaderName, tracingData);
 
 						transaction = tracer.StartTransaction(transactionName, ApiConstants.TypeRequest, tracingData);
 					}
@@ -60,7 +63,7 @@ internal static ITransaction StartTransactionAsync(HttpContext context, IApmLogg
 						logger.Debug()
 							?.Log(
 								"Incoming request with invalid {TraceParentHeaderName} header (received value: {TraceParentHeaderValue}). Starting trace with new trace id.",
-								TraceContext.TraceParentHeaderNamePrefixed, headerValue);
+								containsPrefixedTraceParentHeader? TraceContext.TraceParentHeaderNamePrefixed : TraceContext.TraceParentHeaderName, traceParentHeader);
 
 						transaction = tracer.StartTransaction(transactionName, ApiConstants.TypeRequest);
 					}

src/Elastic.Apm.AspNetFullFramework/ElasticApmModule.cs

@@ -16,6 +16,7 @@
 using Elastic.Apm.Helpers;
 using Elastic.Apm.Logging;
 using Elastic.Apm.Model;
+using TraceContext = Elastic.Apm.DistributedTracing.TraceContext;
 using Elastic.Apm.Reflection;
 
 namespace Elastic.Apm.AspNetFullFramework
@@ -138,7 +139,7 @@ private void ProcessBeginRequest(object sender)
 				_logger.Debug()
 					?.Log(
 						"Incoming request with {TraceParentHeaderName} header. DistributedTracingData: {DistributedTracingData} - continuing trace",
-						DistributedTracing.TraceContext.TraceParentHeaderNamePrefixed, distributedTracingData);
+						TraceContext.TraceParentHeaderName, distributedTracingData);
 
 				// we set ignoreActivity to true to avoid the HttpContext W3C DiagnosticSource issue (see https://github.com/elastic/apm-agent-dotnet/issues/867#issuecomment-650170150)
 				transaction = Agent.Instance.Tracer.StartTransaction(transactionName, ApiConstants.TypeRequest, distributedTracingData, true);
@@ -162,27 +163,23 @@ private void ProcessBeginRequest(object sender)
 		/// <returns>Null if traceparent is not set, otherwise the filled DistributedTracingData instance</returns>
 		private DistributedTracingData ExtractIncomingDistributedTracingData(HttpRequest request)
 		{
-			var traceParentHeaderValue = request.Unvalidated.Headers.Get(DistributedTracing.TraceContext.TraceParentHeaderName);
+			var traceParentHeaderValue = request.Unvalidated.Headers.Get(TraceContext.TraceParentHeaderName);
 			// ReSharper disable once InvertIf
 			if (traceParentHeaderValue == null)
 			{
-				traceParentHeaderValue = request.Unvalidated.Headers.Get(DistributedTracing.TraceContext.TraceParentHeaderNamePrefixed);
+				traceParentHeaderValue = request.Unvalidated.Headers.Get(TraceContext.TraceParentHeaderNamePrefixed);
 
 				if (traceParentHeaderValue == null)
 				{
 					_logger.Debug()
 						?.Log("Incoming request doesn't have {TraceParentHeaderName} header - " +
-							"it means request doesn't have incoming distributed tracing data",
-							DistributedTracing.TraceContext.TraceParentHeaderNamePrefixed);
+							"it means request doesn't have incoming distributed tracing data", TraceContext.TraceParentHeaderNamePrefixed);
 					return null;
 				}
 			}
 
-			var traceStateHeaderValue = request.Unvalidated.Headers.Get(DistributedTracing.TraceContext.TraceStateHeaderName);
-
-			return traceStateHeaderValue != null
-				? DistributedTracing.TraceContext.TryExtractTracingData(traceParentHeaderValue, traceStateHeaderValue)
-				: DistributedTracing.TraceContext.TryExtractTracingData(traceParentHeaderValue);
+			var traceStateHeaderValue = request.Unvalidated.Headers.Get(TraceContext.TraceStateHeaderName);
+			return TraceContext.TryExtractTracingData(traceParentHeaderValue, traceStateHeaderValue);
 		}
 
 		private static void FillSampledTransactionContextRequest(HttpRequest request, ITransaction transaction)

src/Elastic.Apm/Api/DistributedTracingData.cs

@@ -8,15 +8,17 @@
 namespace Elastic.Apm.Api
 {
 	/// <summary>
-	/// An object encapsulating data passed from the caller to the callee in distributed tracing in order to correlate between
-	/// them.
-	/// Its purpose is similar to that of "traceparent" header described at https://www.w3.org/TR/trace-context/
-	/// See samples/ApiSamples/Program.cs for an example on how to manually pass distributed tracing data between the caller
-	/// and the callee.
+	/// Encapsulates distributed tracing data passed from the caller to the callee in order to correlate calls between them.
+	/// Its purpose is similar to that of traceparent and tracestate headers described in the
+	/// <a href="https://www.w3.org/TR/trace-context/">Trace Context specification</a>
 	/// </summary>
+	/// <example>
+	/// See sample/ApiSamples/Program.cs for an example on how to manually pass distributed tracing data between the caller
+	/// and the callee
+	/// </example>
 	public class DistributedTracingData
 	{
-		internal DistributedTracingData(string traceId, string parentId, bool flagRecorded, string traceState = null)
+		internal DistributedTracingData(string traceId, string parentId, bool flagRecorded, TraceState traceState = null)
 		{
 			TraceId = traceId;
 			ParentId = parentId;
@@ -25,11 +27,10 @@ internal DistributedTracingData(string traceId, string parentId, bool flagRecord
 		}
 
 		internal bool FlagRecorded { get; }
-
-		internal bool HasTraceState => !string.IsNullOrEmpty(TraceState);
+		internal bool HasTraceState => TraceState != null;
 		internal string ParentId { get; }
 		internal string TraceId { get; }
-		internal string TraceState { get; }
+		internal TraceState TraceState { get; }
 
 		/// <summary>
 		/// Serializes this instance to a string.
@@ -55,7 +56,10 @@ internal DistributedTracingData(string traceId, string parentId, bool flagRecord
 
 		public override string ToString() => new ToStringBuilder(nameof(DistributedTracingData))
 		{
-			{ "TraceId", TraceId }, { "ParentId", ParentId }, { "FlagRecorded", FlagRecorded }
+			{ nameof(TraceId), TraceId },
+			{ nameof(ParentId), ParentId },
+			{ nameof(FlagRecorded), FlagRecorded },
+			{ nameof(TraceState), TraceState?.ToTextHeader() }
 		}.ToString();
 	}
 }

src/Elastic.Apm/Config/IConfigurationReader.cs

@@ -190,6 +190,11 @@ public interface IConfigurationReader
 		/// These apply for example to HTTP headers and application/x-www-form-urlencoded data.
 		/// </summary>
 		IReadOnlyList<WildcardMatcher> SanitizeFieldNames { get; }
+
+		/// <summary>
+		/// A secret token to ensure that only your agents can send data to your APM server.
+		/// Both agents and APM server have to be configured with the same secret token.
+		/// </summary>
 		string SecretToken { get; }
 
 		/// <summary>
@@ -206,7 +211,7 @@ public interface IConfigurationReader
 		IReadOnlyList<Uri> ServerUrls { get; }
 
 		/// <summary>
-		/// The URL for APM server
+		/// The URL for APM server.
 		/// </summary>
 		Uri ServerUrl { get; }
 
@@ -269,12 +274,17 @@ public interface IConfigurationReader
 		/// </summary>
 		int TransactionMaxSpans { get; }
 
+		/// <summary>
+		/// The sample rate for transactions.
+		/// By default, the agent will sample every transaction (e.g. a request to your service). To reduce overhead and storage requirements,
+		/// the sample rate can be set to a value between 0.0 and 1.0. The agent still records the overall time and result for unsampled
+		/// transactions, but no context information, labels, or spans are recorded.
+		/// </summary>
 		double TransactionSampleRate { get; }
 
 		/// <summary>
-		/// If true, for all outgoing HTTP requests the agent stores the traceparent in a header prefixed with elastic-apm
-		/// (elastic-apm-traceparent)
-		/// otherwise it'll use the official header name from w3c, which is "traceparewnt".
+		/// If <c>true</c>, for all outgoing HTTP requests the agent stores the traceparent in a "elastic-apm-traceparent" header name.
+		/// Otherwise, it'll use the official w3c "traceparent" header name.
 		/// </summary>
 		bool UseElasticTraceparentHeader { get; }
 

src/Elastic.Apm/DiagnosticListeners/HttpDiagnosticListenerCoreImpl.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using System;
+using System.Collections.Generic;
 using System.Net.Http;
 
 namespace Elastic.Apm.DiagnosticListeners
@@ -25,6 +26,15 @@ public HttpDiagnosticListenerCoreImpl(IApmAgent agent)
 		protected override bool RequestHeadersContain(HttpRequestMessage request, string headerName)
 			=> request.Headers.Contains(headerName);
 
+		protected override bool RequestTryGetHeader(HttpRequestMessage request, string headerName, out string value)
+		{
+			var contains = request.Headers.TryGetValues(headerName, out var values);
+			value = contains
+				? string.Join(",", values)
+				: null;
+			return contains;
+		}
+
 		protected override void RequestHeadersAdd(HttpRequestMessage request, string headerName, string headerValue)
 		{
 			if(!string.IsNullOrEmpty(headerValue))

src/Elastic.Apm/DiagnosticListeners/HttpDiagnosticListenerFullFrameworkImpl.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using System;
+using System.Collections.Generic;
 using System.Net;
 using System.Reflection;
 using Elastic.Apm.Logging;
@@ -24,11 +25,8 @@ public HttpDiagnosticListenerFullFrameworkImpl(IApmAgent agent)
 
 		protected override string RequestGetMethod(HttpWebRequest request) => request.Method;
 
-		protected override bool RequestHeadersContain(HttpWebRequest request, string headerName)
-		{
-			var values = request.Headers.GetValues(headerName);
-			return values != null && values.Length > 0;
-		}
+		protected override bool RequestHeadersContain(HttpWebRequest request, string headerName) =>
+			RequestTryGetHeader(request, headerName, out _);
 
 		protected override void RequestHeadersAdd(HttpWebRequest request, string headerName, string headerValue)
 		{
@@ -38,6 +36,12 @@ protected override void RequestHeadersAdd(HttpWebRequest request, string headerN
 
 		protected override int ResponseGetStatusCode(HttpWebResponse response) => (int)response.StatusCode;
 
+		protected override bool RequestTryGetHeader(HttpWebRequest request, string headerName, out string value)
+		{
+			value = request.Headers.Get(headerName);
+			return value != null;
+		}
+
 		/// <summary>
 		/// In Full Framework "System.Net.Http.Desktop.HttpRequestOut.Ex.Stop" does not send the exception property.
 		/// Therefore we have a specialized ProcessExceptionEvent for Full Framework.

src/Elastic.Apm/DiagnosticListeners/HttpDiagnosticListenerImplBase.cs

@@ -43,6 +43,8 @@ protected HttpDiagnosticListenerImplBase(IApmAgent agent) : base(agent) { }
 
 		protected abstract int ResponseGetStatusCode(TResponse response);
 
+		protected abstract bool RequestTryGetHeader(TRequest request, string headerName, out string value);
+
 		protected abstract string ExceptionEventKey { get; }
 
 		internal abstract string StartEventKey { get; }
@@ -153,12 +155,15 @@ private void ProcessStartEvent(TRequest request, Uri requestUrl)
 				}
 			}
 
-			if (!RequestHeadersContain(request, TraceContext.TraceStateHeaderName) && transaction.OutgoingDistributedTracingData != null
-				&& transaction.OutgoingDistributedTracingData.HasTraceState)
-			{
-				RequestHeadersAdd(request, TraceContext.TraceStateHeaderName,
-					TraceContext.BuildTraceState(transaction.OutgoingDistributedTracingData));
-			}
+			if (!RequestHeadersContain(request, TraceContext.TraceStateHeaderName) && span.OutgoingDistributedTracingData != null && span.OutgoingDistributedTracingData.HasTraceState)
+				RequestHeadersAdd(request, TraceContext.TraceStateHeaderName, span.OutgoingDistributedTracingData.TraceState.ToTextHeader());
+
+			//if (!RequestHeadersContain(request, TraceContext.TraceStateHeaderName) && transaction.OutgoingDistributedTracingData != null
+			//	&& transaction.OutgoingDistributedTracingData.HasTraceState)
+			//{
+			//	RequestHeadersAdd(request, TraceContext.TraceStateHeaderName,
+			//		TraceContext.BuildTraceState(transaction.OutgoingDistributedTracingData));
+			//}
 
 			if (span is Span spanInstance)
 			{