fix(hostmetricsreceiver): do not duplicate mountpoint metrics

Mountpoints can be reported multiple times for each mount into a
namespace. This causes duplicate metrics which causes issues with
some exporters. Each instance of the mountpoint will have identical
metrics, so it is safe to ignore repeated mountpoints.

Closes open-telemetry#34512

Author: tcolgate

receiver/hostmetricsreceiver/internal/scraper/filesystemscraper/filesystem_scraper.go

@@ -90,7 +90,23 @@ func (s *scraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 	}
 
 	usages := make([]*deviceUsage, 0, len(partitions))
+
+	type mountKey struct {
+		mountpoint string
+		device     string
+	}
+	seen := map[mountKey]struct{}{}
+
 	for _, partition := range partitions {
+		key := mountKey{
+			mountpoint: partition.Mountpoint,
+			device:     partition.Device,
+		}
+		if _, ok := seen[key]; partition.Mountpoint != "" && ok {
+			continue
+		}
+		seen[key] = struct{}{}
+
 		if !s.fsFilter.includePartition(partition) {
 			continue
 		}

receiver/hostmetricsreceiver/internal/scraper/filesystemscraper/filesystem_scraper_test.go

@@ -309,6 +309,41 @@ func TestScrape(t *testing.T) {
 			usageFunc:   func(context.Context, string) (*disk.UsageStat, error) { return nil, errors.New("err2") },
 			expectedErr: "err2",
 		},
+		{
+			name: "Do not report duplicate mount points",
+			config: Config{
+				MetricsBuilderConfig: metadata.DefaultMetricsBuilderConfig(),
+			},
+			usageFunc: func(context.Context, string) (*disk.UsageStat, error) {
+				return &disk.UsageStat{
+					Fstype: "fs_type_a",
+				}, nil
+			},
+			partitionsFunc: func(context.Context, bool) ([]disk.PartitionStat, error) {
+				return []disk.PartitionStat{
+					{
+						Device:     "device_a",
+						Mountpoint: "mount_point_a",
+						Fstype:     "fs_type_a",
+					},
+					{
+						Device:     "device_a",
+						Mountpoint: "mount_point_a",
+						Fstype:     "fs_type_a",
+					},
+				}, nil
+			},
+			expectMetrics:            true,
+			expectedDeviceDataPoints: 1,
+			expectedDeviceAttributes: []map[string]pcommon.Value{
+				{
+					"device":     pcommon.NewValueStr("device_a"),
+					"mountpoint": pcommon.NewValueStr("mount_point_a"),
+					"type":       pcommon.NewValueStr("fs_type_a"),
+					"mode":       pcommon.NewValueStr("unknown"),
+				},
+			},
+		},
 	}
 
 	for _, test := range testCases {