Ignore boring filesystems from disk plugin

Modern Linux has a lots of boring filesystem (tmpfs on /dev, devpts on
/dev/pts, lots of cgroup on /sys/fs/cgroup/*, ...).

* Ignore filesystem with 0 bytes (this cover cgroup, devpts and other).
* Add IgnoreFS to ignore additional FS by their type. Add tmpfs and
  devtmpfs as default ignored type.

etc/telegraf.conf

@@ -97,6 +97,10 @@
   # Setting mountpoints will restrict the stats to the specified mountpoints.
   # mount_points=["/"]
 
+  # Ignore some mountpoints by filesystem type. For example (dev)tmpfs (usually
+  # present on /run, /var/run, /dev/shm or /dev).
+  ignore_fs = ["tmpfs", "devtmpfs"]
+
 # Read metrics about disk IO by device
 [[inputs.diskio]]
   # By default, telegraf will gather stats for all devices including

plugins/inputs/system/disk.go

@@ -14,6 +14,7 @@ type DiskStats struct {
 	Mountpoints []string
 
 	MountPoints []string
+	IgnoreFS    []string `toml:"ignore_fs"`
 }
 
 func (_ *DiskStats) Description() string {
@@ -24,6 +25,10 @@ var diskSampleConfig = `
   ## By default, telegraf gather stats for all mountpoints.
   ## Setting mountpoints will restrict the stats to the specified mountpoints.
   # mount_points = ["/"]
+
+  # Ignore some mountpoints by filesystem type. For example (dev)tmpfs (usually
+  # present on /run, /var/run, /dev/shm or /dev).
+  ignore_fs = ["tmpfs", "devtmpfs"]
 `
 
 func (_ *DiskStats) SampleConfig() string {
@@ -36,12 +41,16 @@ func (s *DiskStats) Gather(acc telegraf.Accumulator) error {
 		s.MountPoints = s.Mountpoints
 	}
 
-	disks, err := s.ps.DiskUsage(s.MountPoints)
+	disks, err := s.ps.DiskUsage(s.MountPoints, s.IgnoreFS)
 	if err != nil {
 		return fmt.Errorf("error getting disk usage info: %s", err)
 	}
 
 	for _, du := range disks {
+		if du.Total == 0 {
+			// Skip dummy filesystem (procfs, cgroupfs, ...)
+			continue
+		}
 		tags := map[string]string{
 			"path":   du.Path,
 			"fstype": du.Fstype,

plugins/inputs/system/disk_test.go

@@ -50,9 +50,9 @@ func TestDiskStats(t *testing.T) {
 		},
 	}
 
-	mps.On("DiskUsage", []string(nil)).Return(duAll, nil)
-	mps.On("DiskUsage", []string{"/", "/dev"}).Return(duFiltered, nil)
-	mps.On("DiskUsage", []string{"/", "/home"}).Return(duAll, nil)
+	mps.On("DiskUsage", []string(nil), []string(nil)).Return(duAll, nil)
+	mps.On("DiskUsage", []string{"/", "/dev"}, []string(nil)).Return(duFiltered, nil)
+	mps.On("DiskUsage", []string{"/", "/home"}, []string(nil)).Return(duAll, nil)
 
 	err = (&DiskStats{ps: &mps}).Gather(&acc)
 	require.NoError(t, err)

plugins/inputs/system/mock_PS.go

@@ -33,8 +33,8 @@ func (m *MockPS) CPUTimes(perCPU, totalCPU bool) ([]cpu.CPUTimesStat, error) {
 	return r0, r1
 }
 
-func (m *MockPS) DiskUsage(mountPointFilter []string) ([]*disk.DiskUsageStat, error) {
-	ret := m.Called(mountPointFilter)
+func (m *MockPS) DiskUsage(mountPointFilter []string, fstypeExclude []string) ([]*disk.DiskUsageStat, error) {
+	ret := m.Called(mountPointFilter, fstypeExclude)
 
 	r0 := ret.Get(0).([]*disk.DiskUsageStat)
 	r1 := ret.Error(1)

plugins/inputs/system/ps.go

@@ -14,7 +14,7 @@ import (
 
 type PS interface {
 	CPUTimes(perCPU, totalCPU bool) ([]cpu.CPUTimesStat, error)
-	DiskUsage(mountPointFilter []string) ([]*disk.DiskUsageStat, error)
+	DiskUsage(mountPointFilter []string, fstypeExclude []string) ([]*disk.DiskUsageStat, error)
 	NetIO() ([]net.NetIOCountersStat, error)
 	NetProto() ([]net.NetProtoCountersStat, error)
 	DiskIO() (map[string]disk.DiskIOCountersStat, error)
@@ -53,6 +53,7 @@ func (s *systemPS) CPUTimes(perCPU, totalCPU bool) ([]cpu.CPUTimesStat, error) {
 
 func (s *systemPS) DiskUsage(
 	mountPointFilter []string,
+	fstypeExclude []string,
 ) ([]*disk.DiskUsageStat, error) {
 	parts, err := disk.DiskPartitions(true)
 	if err != nil {
@@ -60,9 +61,13 @@ func (s *systemPS) DiskUsage(
 	}
 
 	// Make a "set" out of the filter slice
-	filterSet := make(map[string]bool)
+	mountPointFilterSet := make(map[string]bool)
 	for _, filter := range mountPointFilter {
-		filterSet[filter] = true
+		mountPointFilterSet[filter] = true
+	}
+	fstypeExcludeSet := make(map[string]bool)
+	for _, filter := range fstypeExclude {
+		fstypeExcludeSet[filter] = true
 	}
 
 	var usage []*disk.DiskUsageStat
@@ -71,7 +76,7 @@ func (s *systemPS) DiskUsage(
 		if len(mountPointFilter) > 0 {
 			// If the mount point is not a member of the filter set,
 			// don't gather info on it.
-			_, ok := filterSet[p.Mountpoint]
+			_, ok := mountPointFilterSet[p.Mountpoint]
 			if !ok {
 				continue
 			}
@@ -81,6 +86,12 @@ func (s *systemPS) DiskUsage(
 			if err != nil {
 				return nil, err
 			}
+			// If the mount point is a member of the exclude set,
+			// don't gather info on it.
+			_, ok := fstypeExcludeSet[p.Fstype]
+			if ok {
+				continue
+			}
 			du.Fstype = p.Fstype
 			usage = append(usage, du)
 		}