[otlp] Implement Span and SpanLink flags (#5563)

Co-authored-by: Mikel Blanchard <[email protected]>

Author: stevejgordon

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -7,6 +7,12 @@
   to `OTel-OTLP-Exporter-Dotnet/{NuGet Package Version}`.
   ([#5528](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5528))
 
+* Implementation of [OTLP
+  specification](https://github.com/open-telemetry/opentelemetry-proto/blob/v1.2.0/opentelemetry/proto/trace/v1/trace.proto#L112-L133)
+  for propagating `Span` and `SpanLink` flags containing W3C trace flags and
+  `parent_is_remote` information.
+  ([#5563](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5563))
+
 ## 1.8.1
 
 Released 2024-Apr-17

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ActivityExtensions.cs

@@ -174,6 +174,8 @@ internal static Span ToOtlpSpan(this Activity activity, SdkLimitOptions sdkLimit
         };
         otlpLinks.EnumerateLinks(activity, sdkLimitOptions.SpanLinkCountLimit ?? int.MaxValue);
 
+        otlpSpan.Flags = ToOtlpSpanFlags(activity.Context.TraceFlags, activity.HasRemoteParent);
+
         return otlpSpan;
     }
 
@@ -250,6 +252,8 @@ private static Span.Types.Link ToOtlpLink(in ActivityLink activityLink, SdkLimit
             }
         }
 
+        otlpLink.Flags = ToOtlpSpanFlags(activityLink.Context.TraceFlags, activityLink.Context.IsRemote);
+
         return otlpLink;
     }
 
@@ -281,6 +285,21 @@ private static Span.Types.Event ToOtlpEvent(in ActivityEvent activityEvent, SdkL
         return otlpEvent;
     }
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static uint ToOtlpSpanFlags(ActivityTraceFlags activityTraceFlags, bool isRemote)
+    {
+        SpanFlags flags = (SpanFlags)activityTraceFlags;
+
+        flags |= SpanFlags.ContextHasIsRemoteMask;
+
+        if (isRemote)
+        {
+            flags |= SpanFlags.ContextIsRemoteMask;
+        }
+
+        return (uint)flags;
+    }
+
     private struct TagEnumerationState : PeerServiceResolver.IPeerServiceState
     {
         public SdkLimitOptions SdkLimitOptions;

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs

@@ -401,6 +401,10 @@ public void ToOtlpSpanTest()
         {
             OtlpTestHelpers.AssertOtlpAttributes(childLinks[i].Tags.ToList(), otlpSpan.Links[i].Attributes);
         }
+
+        var flags = (OtlpTrace.SpanFlags)otlpSpan.Flags;
+        Assert.True(flags.HasFlag(OtlpTrace.SpanFlags.ContextHasIsRemoteMask));
+        Assert.False(flags.HasFlag(OtlpTrace.SpanFlags.ContextIsRemoteMask));
     }
 
     [Fact]
@@ -731,4 +735,99 @@ public void NamedOptionsMutateSeparateInstancesTest()
         Assert.Equal("http://localhost/traces", tracerOptions.Endpoint.OriginalString);
         Assert.Equal("http://localhost/metrics", meterOptions.Endpoint.OriginalString);
     }
+
+    [Theory]
+    [InlineData(true, true)]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    [InlineData(false, false)]
+    public void SpanFlagsTest(bool isRecorded, bool isRemote)
+    {
+        using var activitySource = new ActivitySource(nameof(this.SpanFlagsTest));
+
+        ActivityContext ctx = new ActivityContext(
+            ActivityTraceId.CreateRandom(),
+            ActivitySpanId.CreateRandom(),
+            isRecorded ? ActivityTraceFlags.Recorded : ActivityTraceFlags.None,
+            isRemote: isRemote);
+
+        using var rootActivity = activitySource.StartActivity("root", ActivityKind.Server, ctx);
+
+        var otlpSpan = rootActivity.ToOtlpSpan(DefaultSdkLimitOptions);
+
+        var flags = (OtlpTrace.SpanFlags)otlpSpan.Flags;
+
+        ActivityTraceFlags traceFlags = (ActivityTraceFlags)(flags & OtlpTrace.SpanFlags.TraceFlagsMask);
+
+        if (isRecorded)
+        {
+            Assert.True(traceFlags.HasFlag(ActivityTraceFlags.Recorded));
+        }
+        else
+        {
+            Assert.False(traceFlags.HasFlag(ActivityTraceFlags.Recorded));
+        }
+
+        Assert.True(flags.HasFlag(OtlpTrace.SpanFlags.ContextHasIsRemoteMask));
+
+        if (isRemote)
+        {
+            Assert.True(flags.HasFlag(OtlpTrace.SpanFlags.ContextIsRemoteMask));
+        }
+        else
+        {
+            Assert.False(flags.HasFlag(OtlpTrace.SpanFlags.ContextIsRemoteMask));
+        }
+    }
+
+    [Theory]
+    [InlineData(true, true)]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    [InlineData(false, false)]
+    public void SpanLinkFlagsTest(bool isRecorded, bool isRemote)
+    {
+        using var activitySource = new ActivitySource(nameof(this.SpanLinkFlagsTest));
+
+        ActivityContext ctx = new ActivityContext(
+            ActivityTraceId.CreateRandom(),
+            ActivitySpanId.CreateRandom(),
+            isRecorded ? ActivityTraceFlags.Recorded : ActivityTraceFlags.None,
+            isRemote: isRemote);
+
+        var links = new[]
+        {
+            new ActivityLink(ctx),
+        };
+
+        using var rootActivity = activitySource.StartActivity("root", ActivityKind.Server, default(ActivityContext), links: links);
+
+        var otlpSpan = rootActivity.ToOtlpSpan(DefaultSdkLimitOptions);
+
+        var spanLink = Assert.Single(otlpSpan.Links);
+
+        var flags = (OtlpTrace.SpanFlags)spanLink.Flags;
+
+        ActivityTraceFlags traceFlags = (ActivityTraceFlags)(flags & OtlpTrace.SpanFlags.TraceFlagsMask);
+
+        if (isRecorded)
+        {
+            Assert.True(traceFlags.HasFlag(ActivityTraceFlags.Recorded));
+        }
+        else
+        {
+            Assert.False(traceFlags.HasFlag(ActivityTraceFlags.Recorded));
+        }
+
+        Assert.True(flags.HasFlag(OtlpTrace.SpanFlags.ContextHasIsRemoteMask));
+
+        if (isRemote)
+        {
+            Assert.True(flags.HasFlag(OtlpTrace.SpanFlags.ContextIsRemoteMask));
+        }
+        else
+        {
+            Assert.False(flags.HasFlag(OtlpTrace.SpanFlags.ContextIsRemoteMask));
+        }
+    }
 }