[exporter/elasticsearch] Add downsampling for profiling events

[rockdaboot]

The stratified downsampling is essential to reduce the query latency for profiling data.

[carsonip]

it just missed the last release (my fault!), we might need a changelog for it.

[MovieStoreGuy]

Can this be moved to be own function definition to help make it easier to debug the stack output in the event of an error?

[dmathieu]

This isn't so trivial, because the pushData method is local to SerializeProfiles, and we can't pass it as an argument (to use it with no arguments in IndexDownsampledEvent.

This would work. Is that what you expect?

diff --git a/exporter/elasticsearchexporter/internal/serializer/otelserializer/profile.go b/exporter/elasticsearchexporter/internal/serializer/otelserializer/profile.go
index eb324d8f3d..0398af40e9 100644
--- a/exporter/elasticsearchexporter/internal/serializer/otelserializer/profile.go
+++ b/exporter/elasticsearchexporter/internal/serializer/otelserializer/profile.go
@@ -20,16 +20,10 @@ const (
 	ExecutablesIndex = "profiling-executables"
 )
 
-// SerializeProfile serializes a profile and calls the `pushData` callback for each generated document.
-func SerializeProfile(resource pcommon.Resource, scope pcommon.InstrumentationScope, profile pprofile.Profile, pushData func(*bytes.Buffer, string, string) error) error {
-	pushDataAsJSON := func(data any, id, index string) error {
-		c, err := toJSON(data)
-		if err != nil {
-			return err
-		}
-		return pushData(c, id, index)
-	}
+type dataPusher func(*bytes.Buffer, string, string) error
 
+// SerializeProfile serializes a profile and calls the `pushData` callback for each generated document.
+func SerializeProfile(resource pcommon.Resource, scope pcommon.InstrumentationScope, profile pprofile.Profile, pushData dataPusher) error {
 	data, err := serializeprofiles.Transform(resource, scope, profile)
 	if err != nil {
 		return err
@@ -39,28 +33,28 @@ func SerializeProfile(resource pcommon.Resource, scope pcommon.InstrumentationSc
 		event := payload.StackTraceEvent
 
 		if event.StackTraceID != "" {
-			if err = pushDataAsJSON(event, "", AllEventsIndex); err != nil {
+			if err = pushDataAsJSON(pushData)(event, "", AllEventsIndex); err != nil {
 				return err
 			}
-			if err = serializeprofiles.IndexDownsampledEvent(event, pushDataAsJSON); err != nil {
+			if err = serializeprofiles.IndexDownsampledEvent(event, pushDataAsJSON(pushData)); err != nil {
 				return err
 			}
 		}
 
 		if payload.StackTrace.DocID != "" {
-			if err = pushDataAsJSON(payload.StackTrace, payload.StackTrace.DocID, StackTraceIndex); err != nil {
+			if err = pushDataAsJSON(pushData)(payload.StackTrace, payload.StackTrace.DocID, StackTraceIndex); err != nil {
 				return err
 			}
 		}
 
 		for _, stackFrame := range payload.StackFrames {
-			if err = pushDataAsJSON(stackFrame, stackFrame.DocID, StackFrameIndex); err != nil {
+			if err = pushDataAsJSON(pushData)(stackFrame, stackFrame.DocID, StackFrameIndex); err != nil {
 				return err
 			}
 		}
 
 		for _, executable := range payload.Executables {
-			if err = pushDataAsJSON(executable, executable.DocID, ExecutablesIndex); err != nil {
+			if err = pushDataAsJSON(pushData)(executable, executable.DocID, ExecutablesIndex); err != nil {
 				return err
 			}
 		}
@@ -76,3 +70,13 @@ func toJSON(d any) (*bytes.Buffer, error) {
 
 	return bytes.NewBuffer(c), nil
 }
+
+func pushDataAsJSON(pushData dataPusher) func(any, string, string) error {
+	return func(data any, id, index string) error {
+		c, err := toJSON(data)
+		if err != nil {
+			return err
+		}
+		return pushData(c, id, index)
+	}
+}

[rockdaboot]

@MovieStoreGuy Any opinion on what @dmathieu says or different suggestions? I'd rather keep the code as is, as I can't see why developers should have an issue with stacktraces here.

[rockdaboot]

Is there anything that needs to done to get this PR merged?