Set smarter default service name

Author: bmermet

src/Datadog.Tracer.IntegrationTests/SendTracesToAgent.cs

@@ -59,7 +59,7 @@ public async void MinimalSpan()
             AssertSpanEqual(span, trace.Single());
 
             var serviceInfo = _httpRecorder.Services.Single().ServiceInfos().Single();
-            Assert.Equal(Constants.UnkownService, serviceInfo.ServiceName);
+            Assert.Equal("Datadog.Tracer", serviceInfo.ServiceName);
             Assert.Equal(Constants.UnkownApp, serviceInfo.App);
             Assert.Equal(Constants.WebAppType, serviceInfo.AppType);
         }

src/Datadog.Tracer.Tests/TracerTests.cs

@@ -15,7 +15,7 @@ public class TracerTests
         public void Ctor_DefaultValues_ShouldSendDefaultServiceInfo()
         {
             var tracer = new Tracer(_agentWriter.Object);
-            _agentWriter.Verify(x => x.WriteServiceInfo(It.Is<ServiceInfo>(y => y.ServiceName == Constants.UnkownService && y.AppType == Constants.WebAppType && y.App == Constants.UnkownApp)), Times.Once);
+            _agentWriter.Verify(x => x.WriteServiceInfo(It.Is<ServiceInfo>(y => y.ServiceName == "Datadog.Tracer" && y.AppType == Constants.WebAppType && y.App == Constants.UnkownApp)), Times.Once);
         }
 
         [Fact]
@@ -26,7 +26,7 @@ public void BuildSpan_NoParameter_DefaultParameters()
             var builder = tracer.BuildSpan("Op1");
             var span = (Span)builder.Start();
 
-            Assert.Equal(Constants.UnkownService, span.ServiceName);
+            Assert.Equal("Datadog.Tracer", span.ServiceName);
             Assert.Equal("Op1", span.OperationName);
         }
 

src/Datadog.Tracer/Tracer.cs

@@ -2,6 +2,7 @@
 using OpenTracing.Propagation;
 using System;
 using System.Collections.Generic;
+using System.Reflection;
 using System.Threading;
 
 namespace Datadog.Tracer
@@ -18,13 +19,13 @@ internal class Tracer : ITracer, IDatadogTracer
         public Tracer(IAgentWriter agentWriter, List<ServiceInfo> serviceInfo = null, string defaultServiceName = null)
         {
             _agentWriter = agentWriter;
-            // TODO:bertrand be smarter about the service name
-            _defaultServiceName = defaultServiceName ?? Constants.UnkownService;
-            if (_defaultServiceName == Constants.UnkownService)
+            _defaultServiceName = defaultServiceName;
+            if (_defaultServiceName == null)
             {
-                _services[Constants.UnkownService] = new ServiceInfo
+                _defaultServiceName = GetExecutingAssemblyName() ?? Constants.UnkownService;
+                _services[_defaultServiceName] = new ServiceInfo
                 {
-                    ServiceName = Constants.UnkownService,
+                    ServiceName = _defaultServiceName,
                     App = Constants.UnkownApp,
                     AppType = Constants.WebAppType,
                 };
@@ -42,6 +43,19 @@ public Tracer(IAgentWriter agentWriter, List<ServiceInfo> serviceInfo = null, st
             }
         }
 
+        private string GetExecutingAssemblyName()
+        {
+            try
+            {
+                var name = Assembly.GetExecutingAssembly().GetName();
+                return name.Name;
+            }
+            catch
+            {
+                return null;
+            }
+        }
+
         public ISpanBuilder BuildSpan(string operationName)
         {
             return new SpanBuilder(this, operationName);