apm: don't delete decision maker tag from span (#25485) (#25566)

(cherry picked from commit adf6116)

Co-authored-by: Andrew Glaude <[email protected]>

pkg/trace/agent/normalizer.go

@@ -197,13 +197,14 @@ func setChunkAttributes(chunk *pb.TraceChunk, root *pb.Span) {
  }
 
  if _, ok := chunk.Tags[tagDecisionMaker]; !ok {
- var set bool
  for _, span := range chunk.Spans {
- if dm, ok := span.Meta[tagDecisionMaker]; !set && ok {
+ // First span wins
+ if dm, ok := span.Meta[tagDecisionMaker]; ok {
  chunk.Tags[tagDecisionMaker] = dm
- set = true
+ break
  }
- delete(span.Meta, tagDecisionMaker)
+ // There are downstream systems that rely on this tag being on the span
+ // delete(span.Meta, tagDecisionMaker)
  }
  }
 }

pkg/trace/agent/normalizer_test.go

@@ -584,6 +584,7 @@ func TestTagDecisionMaker(t *testing.T) {
  traceutil.SetMeta(chunk.Spans[2], tagDecisionMaker, "wrong")
  setChunkAttributes(chunk, root)
  assert.Equal("right", chunk.Tags[tagDecisionMaker])
+ assert.Equal("right", chunk.Spans[1].Meta[tagDecisionMaker])
 }
 
 func BenchmarkNormalization(b *testing.B) {