Fix bug where struct slice elements were not being reported

Fix a bug where the iterator did not iterate correctly over slice
elements of type struct. Add tests that assert corresponding metrics are
reported with expected attributes.

Additionally, assert that collected values do not contain duplicates.

metrics.go

@@ -152,20 +152,18 @@ func populateObservables(ctx context.Context, tctx traversalContext, observables
 				return
 			}
 		}
-		elems, ok := tctx.field.Interface().([]any)
-		if ok {
-			for _, elem := range elems {
-				select {
-				case <-ctx.Done():
-					return
-				default:
-					populateObservables(ctx, traversalContext{
-						field:      reflect.ValueOf(elem),
-						metricName: tctx.metricName,
-						attrs:      tctx.attrs,
-						tag:        tctx.tag,
-					}, observables, commonAttrs)
-				}
+		elems := reflect.ValueOf(tctx.field.Interface())
+		for i := 0; i < elems.Len(); i++ {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				populateObservables(ctx, traversalContext{
+					field:      elems.Index(i),
+					metricName: tctx.metricName,
+					attrs:      tctx.attrs,
+					tag:        tctx.tag,
+				}, observables, commonAttrs)
 			}
 		}
 	case reflect.Map:

metrics_test.go

@@ -3,6 +3,7 @@ package fdbmeter
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"os"
 	"reflect"
 	"testing"
@@ -24,6 +25,24 @@ func TestMetricsPopulatesValues(t *testing.T) {
 						attrs:      attribute.NewSet(),
 					},
 				},
+				"cluster_processes_roles_bytes_queried_counter": {
+					{
+						int64Value: 75292021001,
+						attrs: attribute.NewSet(
+							attribute.String("active_primary_dc", "abc"),
+							attribute.String("address", "20.10.7.15:4509"),
+							attribute.String("class_source", "command_line"),
+							attribute.String("class_type", "storage"),
+							attribute.String("fault_domain", "ip-1-2-7-106"),
+							attribute.String("id", "1d43ff854cd58260"),
+							attribute.String("machine_id", "ip-1-2-7-106"),
+							attribute.String("process_id", "1e5c1cb8cafedd3b4aa335c91c008e5d"),
+							attribute.String("protocol_version", "fdb00b071010000"),
+							attribute.String("role", "storage"),
+							attribute.String("version", "7.1.33"),
+						),
+					},
+				},
 				"cluster_data_state_healthy": {
 					{int64Value: 0, attrs: attribute.NewSet(
 						attribute.String("active_primary_dc", "abc"),
@@ -63,6 +82,18 @@ func TestMetricsPopulatesValues(t *testing.T) {
 						),
 					},
 				},
+				"cluster_machines_memory_free_bytes": {
+					{
+						int64Value: 63909851136,
+						attrs: attribute.NewSet(
+							attribute.String("active_primary_dc", ""),
+							attribute.String("address", "20.10.5.192"),
+							attribute.String("machine_id", "ip-1-2-5-156"),
+							attribute.String("name", "ip-1-2-5-156"),
+							attribute.String("protocol_version", "fdb00b071010000"),
+						),
+					},
+				},
 			},
 		},
 	}
@@ -88,19 +119,38 @@ func TestMetricsPopulatesValues(t *testing.T) {
 			}
 			subject.notifyStatus(context.Background(), status)
 
+			// Assert that there are no duplicate attributes for the same metric name.
+			for metric, observables := range subject.observables {
+				seen := make(map[string]struct{})
+				for _, o := range observables {
+					key := fmt.Sprintf("%v", o)
+					if _, exists := seen[key]; exists {
+						t.Fatal("duplicate observable for metric ", metric)
+					} else {
+						seen[key] = struct{}{}
+					}
+				}
+			}
+
+		WantLoop:
 			for k, want := range test.want {
 
 				got := subject.observables[k]
-				if len(got) != len(want) {
-					t.Fatal()
-				}
-
-				for i, target := range got {
-					if !reflect.DeepEqual(want[i], target) {
-						t.Fatal(want[i], " got ", target)
+				switch len(want) {
+				case 0:
+					if len(got) != 0 {
+						t.Fatal("expected no observables")
 					}
+				default:
+					for _, target := range got {
+						for _, wantObservable := range want {
+							if reflect.DeepEqual(wantObservable, target) {
+								continue WantLoop
+							}
+						}
+					}
+					t.Fatal("did not find expected observable for ", k)
 				}
-
 			}
 		})
 	}