Add support for titlecase transformation to strings processor (influx…

…data#6982)

plugins/processors/strings/README.md

@@ -5,6 +5,7 @@ The `strings` plugin maps certain go string functions onto measurement, tag, and
 Implemented functions are:
 - lowercase
 - uppercase
+- titlecase
 - trim
 - trim_left
 - trim_right
@@ -35,6 +36,10 @@ If you'd like to apply multiple processings to the same `tag_key` or `field_key`
   # [[processors.strings.uppercase]]
   #   tag = "method"
 
+  ## Convert a field value to titlecase
+  # [[processors.strings.titlecase]]
+  #   field = "status"
+
   ## Trim leading and trailing whitespace using the default cutset
   # [[processors.strings.trim]]
   #   field = "message"

plugins/processors/strings/strings.go

@@ -13,6 +13,7 @@ import (
 type Strings struct {
 	Lowercase    []converter `toml:"lowercase"`
 	Uppercase    []converter `toml:"uppercase"`
+	Titlecase    []converter `toml:"titlecase"`
 	Trim         []converter `toml:"trim"`
 	TrimLeft     []converter `toml:"trim_left"`
 	TrimRight    []converter `toml:"trim_right"`
@@ -55,6 +56,10 @@ const sampleConfig = `
   #   field = "uri_stem"
   #   dest = "uri_stem_normalised"
 
+  ## Convert a field value to titlecase
+  # [[processors.strings.titlecase]]
+  #   field = "status"
+
   ## Trim leading and trailing whitespace using the default cutset
   # [[processors.strings.trim]]
   #   field = "message"
@@ -235,6 +240,10 @@ func (s *Strings) initOnce() {
 		c.fn = strings.ToUpper
 		s.converters = append(s.converters, c)
 	}
+	for _, c := range s.Titlecase {
+		c.fn = strings.Title
+		s.converters = append(s.converters, c)
+	}
 	for _, c := range s.Trim {
 		c := c
 		if c.Cutset != "" {

plugins/processors/strings/strings_test.go

@@ -78,6 +78,21 @@ func TestFieldConversions(t *testing.T) {
 				require.Equal(t, "/MIXED/CASE/PATH/?FROM=-1D&TO=NOW", fv)
 			},
 		},
+		{
+			name: "Should change existing field to titlecase",
+			plugin: &Strings{
+				Titlecase: []converter{
+					{
+						Field: "request",
+					},
+				},
+			},
+			check: func(t *testing.T, actual telegraf.Metric) {
+				fv, ok := actual.GetField("request")
+				require.True(t, ok)
+				require.Equal(t, "/Mixed/CASE/PaTH/?From=-1D&To=Now", fv)
+			},
+		},
 		{
 			name: "Should add new lowercase field",
 			plugin: &Strings{
@@ -331,6 +346,7 @@ func TestFieldKeyConversions(t *testing.T) {
 				// Tag/field key multiple executions occur in the following order: (initOnce)
 				//   Lowercase
 				//   Uppercase
+				//   Titlecase
 				//   Trim
 				//   TrimLeft
 				//   TrimRight
@@ -595,6 +611,30 @@ func TestTagConversions(t *testing.T) {
 				require.Equal(t, "MIXEDCASE_HOSTNAME", tv)
 			},
 		},
+		{
+			name: "Should add new titlecase tag",
+			plugin: &Strings{
+				Titlecase: []converter{
+					{
+						Tag:  "s-computername",
+						Dest: "s-computername_titlecase",
+					},
+				},
+			},
+			check: func(t *testing.T, actual telegraf.Metric) {
+				tv, ok := actual.GetTag("verb")
+				require.True(t, ok)
+				require.Equal(t, "GET", tv)
+
+				tv, ok = actual.GetTag("s-computername")
+				require.True(t, ok)
+				require.Equal(t, "MIXEDCASE_hostname", tv)
+
+				tv, ok = actual.GetTag("s-computername_titlecase")
+				require.True(t, ok)
+				require.Equal(t, "MIXEDCASE_hostname", tv)
+			},
+		},
 	}
 
 	for _, tt := range tests {
@@ -736,6 +776,11 @@ func TestMultipleConversions(t *testing.T) {
 				Tag: "verb",
 			},
 		},
+		Titlecase: []converter{
+			{
+				Field: "status",
+			},
+		},
 		Replace: []converter{
 			{
 				Tag: "foo",
@@ -763,6 +808,7 @@ func TestMultipleConversions(t *testing.T) {
 			"cs-host":       "AAAbbb",
 			"ignore_number": int64(200),
 			"ignore_bool":   true,
+			"status":        "green",
 		},
 		time.Now(),
 	)
@@ -775,6 +821,7 @@ func TestMultipleConversions(t *testing.T) {
 		"ignore_bool":       true,
 		"cs-host":           "AAAbbb",
 		"cs-host_lowercase": "aaabbb",
+		"status":            "Green",
 	}
 	expectedTags := map[string]string{
 		"verb":           "GET",