Added parameters "Devices" and "SkipSerialNumber to DiskIO plugin.

"Devices" can be used to specify storage devices on which stats
should be reported. "SkipSerialNumber" can be used to omit
the device serial number.

Added tests to verify the new parameters.

closes #344

plugins/system/disk.go

@@ -18,8 +18,7 @@ func (_ *DiskStats) Description() string {
 
 var diskSampleConfig = `
   # By default, telegraf gather stats for all mountpoints.
-  # Setting mountpoints will restrict the stats to the specified ones.
-  # mountpoints.
+  # Setting mountpoints will restrict the stats to the specified mountpoints.
   # Mountpoints=["/"]
 `
 
@@ -64,13 +63,27 @@ func (s *DiskStats) Gather(acc plugins.Accumulator) error {
 
 type DiskIOStats struct {
 	ps PS
+
+	Devices          []string
+	SkipSerialNumber bool
 }
 
 func (_ *DiskIOStats) Description() string {
 	return "Read metrics about disk IO by device"
 }
 
-func (_ *DiskIOStats) SampleConfig() string { return "" }
+var diskIoSampleConfig = `
+  # By default, telegraf will gather stats for all devices including 
+  # disk partitions.
+  # Setting devices will restrict the stats to the specified devcies.
+  # Devices=["sda","sdb"]
+  # Uncomment the following line if you do not need disk serial numbers.
+  # SkipSerialNumber = true
+`
+
+func (_ *DiskIOStats) SampleConfig() string {
+	return diskIoSampleConfig
+}
 
 func (s *DiskIOStats) Gather(acc plugins.Accumulator) error {
 	diskio, err := s.ps.DiskIO()
@@ -78,12 +91,25 @@ func (s *DiskIOStats) Gather(acc plugins.Accumulator) error {
 		return fmt.Errorf("error getting disk io info: %s", err)
 	}
 
+	var restrictDevices bool
+	devices := make(map[string]bool)
+	if len(s.Devices) != 0 {
+		restrictDevices = true
+		for _, dev := range s.Devices {
+			devices[dev] = true
+		}
+	}
+
 	for _, io := range diskio {
+		_, member := devices[io.Name]
+		if restrictDevices && !member {
+			continue
+		}
 		tags := map[string]string{}
 		if len(io.Name) != 0 {
 			tags["name"] = io.Name
 		}
-		if len(io.SerialNumber) != 0 {
+		if len(io.SerialNumber) != 0 && !s.SkipSerialNumber {
 			tags["serial"] = io.SerialNumber
 		}
 

plugins/system/system_test.go

@@ -73,7 +73,8 @@ func TestSystemStats_GenerateStats(t *testing.T) {
 
 	mps.On("DiskUsage").Return(du, nil)
 
-	diskio := disk.DiskIOCountersStat{
+	diskio1 := disk.DiskIOCountersStat{
+
 		ReadCount:    888,
 		WriteCount:   5341,
 		ReadBytes:    100000,
@@ -84,8 +85,19 @@ func TestSystemStats_GenerateStats(t *testing.T) {
 		IoTime:       123552,
 		SerialNumber: "ab-123-ad",
 	}
+	diskio2 := disk.DiskIOCountersStat{
+		ReadCount:    444,
+		WriteCount:   2341,
+		ReadBytes:    200000,
+		WriteBytes:   400000,
+		ReadTime:     3123,
+		WriteTime:    6087,
+		Name:         "sdb1",
+		IoTime:       246552,
+		SerialNumber: "bb-123-ad",
+	}
 
-	mps.On("DiskIO").Return(map[string]disk.DiskIOCountersStat{"sda1": diskio}, nil)
+	mps.On("DiskIO").Return(map[string]disk.DiskIOCountersStat{"sda1": diskio1, "sdb1": diskio2}, nil)
 
 	netio := net.NetIOCountersStat{
 		Name:        "eth0",
@@ -262,21 +274,55 @@ func TestSystemStats_GenerateStats(t *testing.T) {
 	assert.NoError(t, acc.ValidateTaggedValue("drop_in", uint64(7), ntags))
 	assert.NoError(t, acc.ValidateTaggedValue("drop_out", uint64(1), ntags))
 
-	err = (&DiskIOStats{&mps}).Gather(&acc)
+	preDiskIOPoints := len(acc.Points)
+
+	err = (&DiskIOStats{ps: &mps}).Gather(&acc)
 	require.NoError(t, err)
 
-	dtags := map[string]string{
+	numDiskIOPoints := len(acc.Points) - preDiskIOPoints
+	expectedAllDiskIOPoints := 14
+	assert.Equal(t, expectedAllDiskIOPoints, numDiskIOPoints)
+
+	dtags1 := map[string]string{
 		"name":   "sda1",
 		"serial": "ab-123-ad",
 	}
+	dtags2 := map[string]string{
+		"name":   "sdb1",
+		"serial": "bb-123-ad",
+	}
 
-	assert.True(t, acc.CheckTaggedValue("reads", uint64(888), dtags))
-	assert.True(t, acc.CheckTaggedValue("writes", uint64(5341), dtags))
-	assert.True(t, acc.CheckTaggedValue("read_bytes", uint64(100000), dtags))
-	assert.True(t, acc.CheckTaggedValue("write_bytes", uint64(200000), dtags))
-	assert.True(t, acc.CheckTaggedValue("read_time", uint64(7123), dtags))
-	assert.True(t, acc.CheckTaggedValue("write_time", uint64(9087), dtags))
-	assert.True(t, acc.CheckTaggedValue("io_time", uint64(123552), dtags))
+	assert.True(t, acc.CheckTaggedValue("reads", uint64(888), dtags1))
+	assert.True(t, acc.CheckTaggedValue("writes", uint64(5341), dtags1))
+	assert.True(t, acc.CheckTaggedValue("read_bytes", uint64(100000), dtags1))
+	assert.True(t, acc.CheckTaggedValue("write_bytes", uint64(200000), dtags1))
+	assert.True(t, acc.CheckTaggedValue("read_time", uint64(7123), dtags1))
+	assert.True(t, acc.CheckTaggedValue("write_time", uint64(9087), dtags1))
+	assert.True(t, acc.CheckTaggedValue("io_time", uint64(123552), dtags1))
+	assert.True(t, acc.CheckTaggedValue("reads", uint64(444), dtags2))
+	assert.True(t, acc.CheckTaggedValue("writes", uint64(2341), dtags2))
+	assert.True(t, acc.CheckTaggedValue("read_bytes", uint64(200000), dtags2))
+	assert.True(t, acc.CheckTaggedValue("write_bytes", uint64(400000), dtags2))
+	assert.True(t, acc.CheckTaggedValue("read_time", uint64(3123), dtags2))
+	assert.True(t, acc.CheckTaggedValue("write_time", uint64(6087), dtags2))
+	assert.True(t, acc.CheckTaggedValue("io_time", uint64(246552), dtags2))
+
+	// We expect 7 more DiskIOPoints to show up with an explicit match on "sdb1"
+	// and serial should be missing from the tags with SkipSerialNumber set
+	err = (&DiskIOStats{ps: &mps, Devices: []string{"sdb1"}, SkipSerialNumber: true}).Gather(&acc)
+	assert.Equal(t, preDiskIOPoints+expectedAllDiskIOPoints+7, len(acc.Points))
+
+	dtags3 := map[string]string{
+		"name": "sdb1",
+	}
+
+	assert.True(t, acc.CheckTaggedValue("reads", uint64(444), dtags3))
+	assert.True(t, acc.CheckTaggedValue("writes", uint64(2341), dtags3))
+	assert.True(t, acc.CheckTaggedValue("read_bytes", uint64(200000), dtags3))
+	assert.True(t, acc.CheckTaggedValue("write_bytes", uint64(400000), dtags3))
+	assert.True(t, acc.CheckTaggedValue("read_time", uint64(3123), dtags3))
+	assert.True(t, acc.CheckTaggedValue("write_time", uint64(6087), dtags3))
+	assert.True(t, acc.CheckTaggedValue("io_time", uint64(246552), dtags3))
 
 	err = (&MemStats{&mps}).Gather(&acc)
 	require.NoError(t, err)