Include DEVLINKS in available diskio udev properties

plugins/inputs/diskio/README.md

@@ -19,6 +19,9 @@ The diskio input plugin gathers metrics about disk traffic and timing.
   ## Currently only Linux is supported via udev properties. You can view
   ## available properties for a device by running:
   ## 'udevadm info -q property -n /dev/sda'
+  ## Note: Most, but not all, udev properties can be accessed this way. Properties
+  ## that are currently accessible include the "IS_*" series and the "DEVLINKS" 
+  ## property. For more info see https://github.com/influxdata/telegraf/issues/3663
   # device_tags = ["ID_FS_TYPE", "ID_FS_USAGE"]
   #
   ## Using the same metadata source as device_tags, you can also customize the

plugins/inputs/diskio/diskio_linux.go

@@ -52,9 +52,17 @@ func (s *DiskIO) diskInfo(devName string) (map[string]string, error) {
 	defer f.Close()
 
 	scnr := bufio.NewScanner(f)
+	var devlinks []string
 	for scnr.Scan() {
 		l := scnr.Text()
-		if len(l) < 4 || l[:2] != "E:" {
+		if len(l) < 4 {
+			continue
+		}
+		if l[:2] == "S:" {
+			devlinks = append(devlinks, l[2:])
+			continue
+		}
+		if l[:2] != "E:" {
 			continue
 		}
 		kv := strings.SplitN(l[2:], "=", 2)
@@ -64,5 +72,11 @@ func (s *DiskIO) diskInfo(devName string) (map[string]string, error) {
 		di[kv[0]] = kv[1]
 	}
 
+	var devlink_str string
+	if len(devlinks) > 0 {
+		devlink_str = strings.Join(devlinks, " ")
+		di["DEVLINKS"] = devlink_str
+	}
+
 	return di, nil
 }

plugins/inputs/diskio/diskio_linux_test.go

@@ -14,6 +14,7 @@ import (
 var nullDiskInfo = []byte(`
 E:MY_PARAM_1=myval1
 E:MY_PARAM_2=myval2
+S:foo/bar/devlink foo/bar/devlink1
 `)
 
 // setupNullDisk sets up fake udev info as if /dev/null were a disk.
@@ -47,6 +48,7 @@ func TestDiskInfo(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, "myval1", di["MY_PARAM_1"])
 	assert.Equal(t, "myval2", di["MY_PARAM_2"])
+	assert.Equal(t, "foo/bar/devlink foo/bar/devlink1", di["DEVLINKS"])
 
 	// test that data is cached
 	err = clean()
@@ -56,6 +58,7 @@ func TestDiskInfo(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, "myval1", di["MY_PARAM_1"])
 	assert.Equal(t, "myval2", di["MY_PARAM_2"])
+	assert.Equal(t, "foo/bar/devlink foo/bar/devlink1", di["DEVLINKS"])
 
 	// unfortunately we can't adjust mtime on /dev/null to test cache invalidation
 }