[xpack][metricbeats][gcp] don't skip first value in histogram calculations

CHANGELOG.next.asciidoc

@@ -217,6 +217,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Fix Kubernetes metadata sometimes not being present after startup {pull}41216[41216]
 - Do not report non-existant 0 values for RSS metrics in docker/memory {pull}41449[41449]
 - Log Cisco Meraki `getDevicePerformanceScores` errors without stopping metrics collection. {pull}41622[41622]
+- Don't skip first bucket value in GCP metrics metricset for distribution type metrics {pull}41822[41822]
 
 
 *Osquerybeat*

x-pack/metricbeat/module/gcp/distribution.go

@@ -79,13 +79,13 @@ func DistributionHistogramToES(d *distribution.Distribution) mapstr.M {
 		bucket := d.BucketOptions.GetExponentialBuckets()
 
 		for i := range d.BucketCounts {
-			values = append(values, calcExponentialUpperBound(bucket, i+1))
+			values = append(values, calcExponentialUpperBound(bucket, i))
 		}
 	case d.BucketOptions.GetLinearBuckets() != nil:
 		bucket := d.BucketOptions.GetLinearBuckets()
 
 		for i := range d.BucketCounts {
-			values = append(values, calcLinearUpperBound(bucket, i+1))
+			values = append(values, calcLinearUpperBound(bucket, i))
 		}
 	}
 

x-pack/metricbeat/module/gcp/distribution_test.go

@@ -64,7 +64,7 @@ func TestDistributionHistogramToES(t *testing.T) {
 					},
 					expected: mapstr.M{
 						"counts": []uint64{0, 0, 3, 1},
-						"values": []float64{6, 12, 24, 48},
+						"values": []float64{3, 6, 12, 24},
 					},
 				},
 			},
@@ -87,7 +87,7 @@ func TestDistributionHistogramToES(t *testing.T) {
 					},
 					expected: mapstr.M{
 						"counts": []uint64{0, 1, 2, 0},
-						"values": []float64{20, 35, 50, 65},
+						"values": []float64{5, 20, 35, 50},
 					},
 				},
 			},