workload: fix quantile values in openmetrics exporter

`hdrHistogram` library has quantiles in percentages rather than absolute
values. Openmetrics standard forces the quantiles values in `summary`
metric to be absolute values b/w 0 and 1 inclusive.
https://github.com/prometheus/OpenMetrics/blob/296468bc2359ebac83f24301b54a0871f2268016/specification/OpenMetrics.md?plain=1#L294

Earlier the exporter would export the percentage value, this change
intends to make it absolute to adhere to openmetrics standard

Epic: none

Release note: None

pkg/workload/histogram/exporter/exporter_test.go

@@ -209,7 +209,7 @@ func TestOpenMetricsFileWithJson(t *testing.T) {
 							return errors.Errorf("invalid summary count: %f", countValue)
 						}
 					}
-
+					quantile *= 100
 					if int64(countValue) != hist.ValueAtQuantile(quantile) {
 						return errors.Errorf("invalid summary quantile: %f", quantile)
 					}

pkg/workload/histogram/exporter/testdata/kv

@@ -2,10 +2,10 @@ echo
 {"Name":"write","Hist":{"LowestTrackableValue":100000,"HighestTrackableValue":100000000000,"SignificantFigures":1,"Counts":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,5,9,20,41,42,54,83,92,103,141,400,586,828,913,982,1127,1223,1236,1123,1009,976,850,713,706,590,483,793,438,277,154,84,52,52,29,19,22,14,9,5,3,1,5,4,4,10,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,48,16,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]},"Elapsed":5031363856,"Now":"2024-06-24T13:38:53.446733522Z"}
 ----
 # TYPE write summary
-write{quantile="50.0"} 3.276799e+06 1.719236333446e+09
-write{quantile="95.0"} 4.718591e+06 1.719236333446e+09
-write{quantile="99.0"} 6.291455e+06 1.719236333446e+09
-write{quantile="100.0"} 4.294967295e+09 1.719236333446e+09
+write{quantile="0.5"} 3.276799e+06 1.719236333446e+09
+write{quantile="0.95"} 4.718591e+06 1.719236333446e+09
+write{quantile="0.99"} 6.291455e+06 1.719236333446e+09
+write{quantile="1.0"} 4.294967295e+09 1.719236333446e+09
 write_sum 0.0 1.719236333446e+09
 write_count 16379 1.719236333446e+09
 # TYPE write_elapsed gauge

pkg/workload/histogram/exporter/testdata/tpcc_delivery

@@ -3,10 +3,10 @@ echo
 {"Name":"delivery","Hist":{"LowestTrackableValue":100000,"HighestTrackableValue":100000000000,"SignificantFigures":1,"Counts":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,2,0,0,1,2,4,2,4,5,2,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]},"Elapsed":992259494,"Now":"2024-06-24T15:47:43.790887915Z"}
 ----
 # TYPE delivery summary
-delivery{quantile="50.0"} 3.7748735e+07 1.71924406379e+09
-delivery{quantile="95.0"} 4.4040191e+07 1.71924406379e+09
-delivery{quantile="99.0"} 4.6137343e+07 1.71924406379e+09
-delivery{quantile="100.0"} 4.6137343e+07 1.71924406379e+09
+delivery{quantile="0.5"} 3.7748735e+07 1.71924406379e+09
+delivery{quantile="0.95"} 4.4040191e+07 1.71924406379e+09
+delivery{quantile="0.99"} 4.6137343e+07 1.71924406379e+09
+delivery{quantile="1.0"} 4.6137343e+07 1.71924406379e+09
 delivery_sum 0.0 1.71924406379e+09
 delivery_count 24 1.71924406379e+09
 # TYPE delivery_elapsed gauge

pkg/workload/histogram/exporter/testdata/ycsb

@@ -3,10 +3,10 @@ echo
 
 ----
 # TYPE read summary
-read{quantile="50.0"} 1.048575e+06 1.719230907083e+09
-read{quantile="95.0"} 1.835007e+06 1.719230907083e+09
-read{quantile="99.0"} 3.276799e+06 1.719230907083e+09
-read{quantile="100.0"} 1.3631487e+07 1.719230907083e+09
+read{quantile="0.5"} 1.048575e+06 1.719230907083e+09
+read{quantile="0.95"} 1.835007e+06 1.719230907083e+09
+read{quantile="0.99"} 3.276799e+06 1.719230907083e+09
+read{quantile="1.0"} 1.3631487e+07 1.719230907083e+09
 read_sum 0.0 1.719230907083e+09
 read_count 34540 1.719230907083e+09
 # TYPE read_elapsed gauge

pkg/workload/histogram/exporter/util.go

@@ -34,8 +34,13 @@ func ConvertHdrHistogramToPrometheusMetricFamily(
 		if value == 0 {
 			continue
 		}
+
+		// Openmetrics standard mandates that quantile should be b/w 0 to 1.
+		// https://github.com/prometheus/OpenMetrics/blob/296468bc2359ebac83f24301b54a0871f2268016/specification/OpenMetrics.md?plain=1#L294
+		// Since hdrHistogram has quantiles in percentage, we need to convert it
+		openMetricsQuantile := quantile / 100
 		valueQuantile := prom.Quantile{
-			Quantile: &quantile,
+			Quantile: &openMetricsQuantile,
 			Value:    &value,
 		}