From cc1fcb45afdec8213ef8e02004627f8f3b846cfd Mon Sep 17 00:00:00 2001
From: Pedro Tanaka <pedro.stanaka@gmail.com>
Date: Sat, 22 Feb 2025 14:05:01 +0100
Subject: [PATCH] Drop Value() method from MultiValueEvent and fixing expansion
 logic

Signed-off-by: Pedro Tanaka <pedro.stanaka@gmail.com>
---
 pkg/event/event.go      | 34 ++++++++++++++++++++++++++--------
 pkg/event/event_test.go | 32 +++++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 13 deletions(-)

diff --git a/pkg/event/event.go b/pkg/event/event.go
index 4f8a531..66fc40f 100644
--- a/pkg/event/event.go
+++ b/pkg/event/event.go
@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+
 	"github.com/prometheus/statsd_exporter/pkg/clock"
 	"github.com/prometheus/statsd_exporter/pkg/mapper"
 )
@@ -170,20 +171,21 @@ func (m *MultiObserverEvent) Values() []float64             { return m.OValues }
 // And keep the exporter code compatible with previous versions.
 func (m *MultiObserverEvent) Expand() []Event {
 	if len(m.OValues) == 1 && m.SampleRate == 0 {
-		return []Event{m}
+		return []Event{
+			&ObserverEvent{
+				OMetricName: m.OMetricName,
+				OValue:      m.OValues[0],
+				OLabels:     copyLabels(m.OLabels),
+			},
+		}
 	}
 
 	events := make([]Event, 0, len(m.OValues))
 	for _, value := range m.OValues {
-		labels := make(map[string]string, len(m.OLabels))
-		for k, v := range m.OLabels {
-			labels[k] = v
-		}
-
 		events = append(events, &ObserverEvent{
 			OMetricName: m.OMetricName,
 			OValue:      value,
-			OLabels:     labels,
+			OLabels:     copyLabels(m.OLabels),
 		})
 	}
 
@@ -191,7 +193,14 @@ func (m *MultiObserverEvent) Expand() []Event {
 		multiplier := int(1 / m.SampleRate)
 		multipliedEvents := make([]Event, 0, len(events)*multiplier)
 		for i := 0; i < multiplier; i++ {
-			multipliedEvents = append(multipliedEvents, events...)
+			for _, event := range events {
+				e := event.(*ObserverEvent)
+				multipliedEvents = append(multipliedEvents, &ObserverEvent{
+					OMetricName: e.OMetricName,
+					OValue:      e.OValue,
+					OLabels:     copyLabels(e.OLabels),
+				})
+			}
 		}
 		return multipliedEvents
 	}
@@ -199,6 +208,15 @@ func (m *MultiObserverEvent) Expand() []Event {
 	return events
 }
 
+// Helper function to copy labels map
+func copyLabels(labels map[string]string) map[string]string {
+	newLabels := make(map[string]string, len(labels))
+	for k, v := range labels {
+		newLabels[k] = v
+	}
+	return newLabels
+}
+
 var (
 	_ ExpandableEvent = &MultiObserverEvent{}
 	_ MultiValueEvent = &MultiObserverEvent{}
diff --git a/pkg/event/event_test.go b/pkg/event/event_test.go
index a4e21d5..71cc8ad 100644
--- a/pkg/event/event_test.go
+++ b/pkg/event/event_test.go
@@ -14,11 +14,13 @@
 package event
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+
 	"github.com/prometheus/statsd_exporter/pkg/clock"
 	"github.com/prometheus/statsd_exporter/pkg/mapper"
 )
@@ -180,6 +182,7 @@ func TestMultiValueEvent(t *testing.T) {
 }
 
 func TestMultiObserverEvent_Expand(t *testing.T) {
+	t.Parallel()
 	tests := []struct {
 		name       string
 		event      *MultiObserverEvent
@@ -194,11 +197,10 @@ func TestMultiObserverEvent_Expand(t *testing.T) {
 				SampleRate:  0,
 			},
 			wantEvents: []Event{
-				&MultiObserverEvent{
+				&ObserverEvent{
 					OMetricName: "test_metric",
-					OValues:     []float64{1.0},
+					OValue:      1.0,
 					OLabels:     map[string]string{"label": "value"},
-					SampleRate:  0,
 				},
 			},
 		},
@@ -263,9 +265,29 @@ func TestMultiObserverEvent_Expand(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			got := tt.event.Expand()
-			if !reflect.DeepEqual(got, tt.wantEvents) {
-				t.Errorf("MultiObserverEvent.Expand() = %v, want %v", got, tt.wantEvents)
+			if len(tt.wantEvents) != len(got) {
+				t.Fatalf("Expected %d events, but got %d", len(tt.wantEvents), len(got))
+			}
+
+			eventCount := func(events []Event) map[string]int {
+				counts := make(map[string]int)
+				for _, event := range events {
+					oe := event.(*ObserverEvent)
+					key := fmt.Sprintf("%s%f%v", oe.OMetricName, oe.OValue, oe.OLabels)
+					counts[key]++
+				}
+				return counts
+			}
+
+			wantMap := eventCount(tt.wantEvents)
+			gotMap := eventCount(got)
+
+			for key, count := range wantMap {
+				if gotMap[key] != count {
+					t.Fatalf("Event mismatch for key %v: expected %d, got %d", key, count, gotMap[key])
+				}
 			}
 		})
 	}