From 68c95b9b133781295676937d9fd5f04b72ae36cc Mon Sep 17 00:00:00 2001
From: Shivanth <shivanth.metchem@deliveryhero.com>
Date: Wed, 4 Dec 2024 13:03:08 +0100
Subject: [PATCH] Remove random number generator from histogram generation

---
 cmd/telemetrygen/internal/metrics/worker.go   | 68 ++++++++++++++-----
 .../internal/metrics/worker_test.go           | 18 -----
 2 files changed, 50 insertions(+), 36 deletions(-)

diff --git a/cmd/telemetrygen/internal/metrics/worker.go b/cmd/telemetrygen/internal/metrics/worker.go
index e0b2b381bac8..bde5891575fa 100644
--- a/cmd/telemetrygen/internal/metrics/worker.go
+++ b/cmd/telemetrygen/internal/metrics/worker.go
@@ -5,7 +5,6 @@ package metrics
 
 import (
 	"context"
-	rand "math/rand/v2"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -31,6 +30,53 @@ type worker struct {
 	index          int                          // worker index
 }
 
+var histogramBucketSamples = []struct {
+	bucketCounts []uint64
+	sum          int64
+}{
+	{
+		[]uint64{0, 0, 0, 0, 0},
+		0,
+	},
+
+	{
+		[]uint64{0, 1, 0, 0, 0},
+		1,
+	},
+	{
+		[]uint64{0, 1, 0, 1, 0},
+		4,
+	},
+	{
+		[]uint64{1, 1, 1, 0, 0},
+		3,
+	},
+	{
+		[]uint64{0, 0, 1, 2, 1},
+		12,
+	},
+	{
+		[]uint64{0, 0, 0, 0, 0},
+		0,
+	},
+	{
+		[]uint64{0, 1, 0, 0, 0},
+		1,
+	},
+	{
+		[]uint64{0, 2, 0, 0, 0},
+		2,
+	},
+	{
+		[]uint64{1, 0, 1, 1, 0},
+		5,
+	},
+	{
+		[]uint64{2, 0, 1, 0, 1},
+		6,
+	},
+}
+
 func (w worker) simulateMetrics(res *resource.Resource, exporterFunc func() (sdkmetric.Exporter, error), signalAttrs []attribute.KeyValue) {
 	limiter := rate.NewLimiter(w.limitPerSecond, 1)
 
@@ -39,8 +85,6 @@ func (w worker) simulateMetrics(res *resource.Resource, exporterFunc func() (sdk
 		w.logger.Error("failed to create the exporter", zap.Error(err))
 		return
 	}
-	randomPCG := rand.NewPCG(0, 0)
-	randomgenerator := rand.New(randomPCG)
 
 	defer func() {
 		w.logger.Info("stopping the exporter")
@@ -86,8 +130,9 @@ func (w worker) simulateMetrics(res *resource.Resource, exporterFunc func() (sdk
 				},
 			})
 		case metricTypeHistogram:
-			iteration := uint64(i) % 5
-			sum, bucketCounts := generateHistogramBuckets[int64](iteration, randomgenerator)
+			iteration := uint64(i) % 10
+			sum := histogramBucketSamples[iteration].sum
+			bucketCounts := histogramBucketSamples[iteration].bucketCounts
 			metrics = append(metrics, metricdata.Metrics{
 				Name: w.metricName,
 				Data: metricdata.Histogram[int64]{
@@ -133,16 +178,3 @@ func (w worker) simulateMetrics(res *resource.Resource, exporterFunc func() (sdk
 	w.logger.Info("metrics generated", zap.Int64("metrics", i))
 	w.wg.Done()
 }
-
-func generateHistogramBuckets[T int64 | float64](count uint64, randomgenerator *rand.Rand) (sum T, bucketCounts []uint64) {
-	sum = 0
-	bucketCounts = make([]uint64, 5)
-	var i uint64
-	for i = 0; i < count; i++ {
-		sample := randomgenerator.IntN(5)
-		// See bounds above
-		sum += T(sample)
-		bucketCounts[sample]++
-	}
-	return
-}
diff --git a/cmd/telemetrygen/internal/metrics/worker_test.go b/cmd/telemetrygen/internal/metrics/worker_test.go
index b8e2bd7dff14..7574ac203757 100644
--- a/cmd/telemetrygen/internal/metrics/worker_test.go
+++ b/cmd/telemetrygen/internal/metrics/worker_test.go
@@ -5,7 +5,6 @@ package metrics
 
 import (
 	"context"
-	rand "math/rand/v2"
 	"testing"
 	"time"
 
@@ -391,20 +390,3 @@ func configWithMultipleAttributes(metric metricType, qty int) *Config {
 		MetricType: metric,
 	}
 }
-
-func TestGenerateHistogramBuckets(t *testing.T) {
-	randomPCG := rand.NewPCG(0, 0)
-	randomgenerator := rand.New(randomPCG)
-	for i := uint64(0); i < 5; i++ {
-		_, buckets := generateHistogramBuckets[int64](i, randomgenerator)
-		assert.Equal(t, sumofArray(buckets), i)
-	}
-}
-
-func sumofArray[T int64 | float64 | uint64](array []T) T {
-	var sum T
-	for _, num := range array {
-		sum += num
-	}
-	return sum
-}