Add traceId and spanId properties in LogstashJsonFormatter output

Serilog.Sinks.Network.Test/JsonFormatter.cs

@@ -1,8 +1,12 @@
 using System;
+using System.Diagnostics;
 using System.Net;
 using System.Net.Sockets;
 using System.Threading.Tasks;
 using FluentAssertions;
+using Serilog.Core;
+using Serilog.Core.Enrichers;
+using Serilog.Events;
 using Serilog.Formatting;
 using Serilog.Sinks.Network.Formatters;
 using Xunit;
@@ -11,15 +15,22 @@
 {
     public class JsonFormatter
     {
-        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter? formatter = null)
+        private static LoggerAndSocket ConfigureTestLogger(
+            ITextFormatter? formatter = null,
+            ILogEventEnricher[] enrichers = null
+        )
         {
             var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
             socket.Bind(new IPEndPoint(IPAddress.Loopback, 0));
             socket.Listen();
 
-            var logger = new LoggerConfiguration()
-                .WriteTo.TCPSink(IPAddress.Loopback, ((IPEndPoint)socket.LocalEndPoint!).Port, null, null, formatter)
-                .CreateLogger();
+            var loggerConfiguration = new LoggerConfiguration()
+                .WriteTo.TCPSink(IPAddress.Loopback, ((IPEndPoint)socket.LocalEndPoint!).Port, null, null, formatter);
+            if (enrichers != null)
+            {
+                loggerConfiguration.Enrich.With(enrichers);
+            }
+            var logger = loggerConfiguration.CreateLogger();
 
             return new LoggerAndSocket { Logger = logger, Socket = socket };
         }
@@ -51,5 +62,81 @@
 
             receivedData.Should().Contain("\"exception\":\"System.Exception: exploding\"}");
         }
+
+        [Fact]
+        public async Task IncludesCurrentActivityTraceAndSpanIds()
+        {
+            // Create an ActivitySource, add a listener, and start an activity.
+            // StartActivity() would return null if there were no listeners.
+            using var activitySource = new ActivitySource("TestSource");
+            using var activityListener = CreateAndAddActivityListener(activitySource.Name);
+            using var activity = activitySource.StartActivity();
+            Assert.NotNull(activity);
+
+            using var fixture = ConfigureTestLogger(new LogstashJsonFormatter());
+
+            fixture.Logger.Information("arbitraryMessage");
+
+            var receivedData = await ServerPoller.PollForReceivedData(fixture.Socket);
+
+            receivedData.Should().Contain($"\"traceId\":\"{activity.TraceId}\"");
+            receivedData.Should().Contain($"\"spanId\":\"{activity.SpanId}\"");
+        }
+
+        [Fact]
+        public async Task OmitsTraceAndSpanIdsWhenThereIsNoActivity()
+        {
+            using var fixture = ConfigureTestLogger(new LogstashJsonFormatter());
+
+            fixture.Logger.Information("arbitraryMessage");
+
+            var receivedData = await ServerPoller.PollForReceivedData(fixture.Socket);
+
+            receivedData.Should().NotContain("\"traceId\"");
+            receivedData.Should().NotContain("\"spanId\"");
+        }
+
+        // The following test documents and validates the current behavior, but this could change
+        // depending on how https://github.com/serilog-contrib/Serilog.Sinks.Network/issues/39 is
+        // resolved.
+        [Fact]
+        public async Task WritesTraceAndSpanIdsBeforeDuplicatePropertiesFromEnrichers()
+        {
+            using var activitySource = new ActivitySource("TestSource");
+            using var activityListener = CreateAndAddActivityListener(activitySource.Name);
+            using var activity = activitySource.StartActivity();
+            Assert.NotNull(activity);
+
+            using var fixture = ConfigureTestLogger(
+                new LogstashJsonFormatter(), 
+                [
+                    new PropertyEnricher("traceId", "traceId-from-enricher"),
+                    new PropertyEnricher("spanId", "spanId-from-enricher")
+                ]
+            );
+
+            fixture.Logger.Information("arbitraryMessage");
+
+            var receivedData = await ServerPoller.PollForReceivedData(fixture.Socket);
+
+            var indexOfTraceId = receivedData.IndexOf($"\"traceId\":\"{activity.TraceId}\"");
+            var indexOfTraceIdFromEnricher = receivedData.IndexOf("\"traceId\":\"traceId-from-enricher\"");
+            indexOfTraceId.Should().BePositive().And.BeLessThan(indexOfTraceIdFromEnricher);
+
+            var indexOfSpanId = receivedData.IndexOf($"\"spanId\":\"{activity.SpanId}\"");
+            var indexOfSpanIdFromEnricher = receivedData.IndexOf("\"spanId\":\"spanId-from-enricher\"");
+            indexOfSpanId.Should().BePositive().And.BeLessThan(indexOfSpanIdFromEnricher);
+        }
+
+        private static ActivityListener CreateAndAddActivityListener(string sourceName)
+        {
+            var activityListener = new ActivityListener
+            {
+                ShouldListenTo = source => source.Name == sourceName,
+                Sample = (ref ActivityCreationOptions<ActivityContext> _) => ActivitySamplingResult.AllData,
+            };
+            ActivitySource.AddActivityListener(activityListener);
+            return activityListener;
+        }
     }
 }

Serilog.Sinks.Network/Formatters/LogstashJsonFormatter.cs

@@ -47,6 +47,18 @@ private static void FormatContent(LogEvent logEvent, TextWriter output)
 
       WritePropertyAndValue(output, "message", logEvent.MessageTemplate.Render(logEvent.Properties));
 
+      if (logEvent.TraceId != null)
+      {
+        output.Write(",");
+        WritePropertyAndValue(output, "traceId", logEvent.TraceId.Value.ToString());
+      }
+
+      if (logEvent.SpanId != null)
+      {
+        output.Write(",");
+        WritePropertyAndValue(output, "spanId", logEvent.SpanId.Value.ToString());
+      }
+
       if (logEvent.Exception != null)
       {
         output.Write(",");