From a0729bd779306a143a8381ba27cb4fae8f4a8334 Mon Sep 17 00:00:00 2001
From: Greg Kalapos <gergo@kalapos.net>
Date: Fri, 28 Feb 2025 18:41:57 +0100
Subject: [PATCH] Add rpc.service for the destination.service.resource
 calculation

---
 enrichments/trace/internal/elastic/span.go    |  3 +++
 .../trace/internal/elastic/span_test.go       | 27 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/enrichments/trace/internal/elastic/span.go b/enrichments/trace/internal/elastic/span.go
index 4ac174d..f352adf 100644
--- a/enrichments/trace/internal/elastic/span.go
+++ b/enrichments/trace/internal/elastic/span.go
@@ -463,6 +463,9 @@ func (s *spanEnrichmentContext) setDestinationService(span ptrace.Span) {
 				s.serverAddress, s.serverPort, // fallback
 			); res != "" {
 				destnResource = res
+			} else {
+				// fallback to RPC service
+				destnResource = s.rpcService
 			}
 		}
 	}
diff --git a/enrichments/trace/internal/elastic/span_test.go b/enrichments/trace/internal/elastic/span_test.go
index c818db0..591c1a0 100644
--- a/enrichments/trace/internal/elastic/span_test.go
+++ b/enrichments/trace/internal/elastic/span_test.go
@@ -938,6 +938,33 @@ func TestElasticSpanEnrich(t *testing.T) {
 				elasticattr.SuccessCount:            int64(1),
 			},
 		},
+		{
+			name: "rpc_span_with_only_rpc_sevice_attr",
+			input: func() ptrace.Span {
+				span := getElasticSpan()
+				span.SetName("testspan")
+				// rpc.service should be used as destination.service.resource
+				// if no other attributes are present.
+				span.Attributes().PutStr(semconv25.AttributeRPCService, "myService")
+				span.Attributes().PutStr(semconv25.AttributeRPCSystem, "grpc")
+				return span
+			}(),
+			config: config.Enabled().Span,
+			enrichedAttrs: map[string]any{
+				elasticattr.TimestampUs:                    startTs.AsTime().UnixMicro(),
+				elasticattr.SpanName:                       "testspan",
+				elasticattr.ProcessorEvent:                 "span",
+				elasticattr.SpanRepresentativeCount:        float64(1),
+				elasticattr.SpanType:                       "external",
+				elasticattr.SpanSubtype:                    "grpc",
+				elasticattr.SpanDurationUs:                 expectedDuration.Microseconds(),
+				elasticattr.EventOutcome:                   "success",
+				elasticattr.SuccessCount:                   int64(1),
+				elasticattr.ServiceTargetType:              "grpc",
+				elasticattr.ServiceTargetName:              "myService",
+				elasticattr.SpanDestinationServiceResource: "myService",
+			},
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			expectedSpan := ptrace.NewSpan()