feat(backend): allow setting custom colors for labels

This allows to have a user defined color (rgb or hex) for label values configured in the config file

go.mod

@@ -25,6 +25,7 @@ require (
 	github.com/spf13/pflag v1.0.3
 	github.com/spf13/viper v1.3.1
 	github.com/terinjokes/bakelite v0.2.0 // indirect
+	gopkg.in/go-playground/colors.v1 v1.2.0
 	gopkg.in/jarcoal/httpmock.v1 v1.0.0-20181117152235-275e9df93516
 	gopkg.in/yaml.v2 v2.2.2
 )

go.sum

@@ -275,6 +275,8 @@ gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMy
 gopkg.in/gemnasium/logrus-airbrake-hook.v2 v2.1.2/go.mod h1:Xk6kEKp8OKb+X14hQBKWaSkCsqBpgog8nAV2xsGOxlo=
 gopkg.in/go-playground/assert.v1 v1.2.1 h1:xoYuJVE7KT85PYWrN730RguIQO0ePzVRfFMXadIrXTM=
 gopkg.in/go-playground/assert.v1 v1.2.1/go.mod h1:9RXL0bg/zibRAgZUYszZSwO/z8Y/a8bDuhia5mkpMnE=
+gopkg.in/go-playground/colors.v1 v1.2.0 h1:SPweMUve+ywPrfwao+UvfD5Ah78aOLUkT5RlJiZn52c=
+gopkg.in/go-playground/colors.v1 v1.2.0/go.mod h1:AvbqcMpNXVl5gBrM20jBm3VjjKBbH/kI5UnqjU7lxFI=
 gopkg.in/go-playground/validator.v8 v8.18.2 h1:lFB4DoMU6B626w8ny76MV7VX6W2VHct2GVOI3xgiMrQ=
 gopkg.in/go-playground/validator.v8 v8.18.2/go.mod h1:RX2a/7Ha8BgOhfk7j780h4/u/RRjR0eouCJSH80/M2Y=
 gopkg.in/jarcoal/httpmock.v1 v1.0.0-20181117152235-275e9df93516 h1:H6trpavCIuipdInWrab8l34Mf+GGVfphniHostMdMaQ=

internal/config/config.go

@@ -137,6 +137,7 @@ func (config *configSchema) Read() {
 	config.Custom.JS = v.GetString("custom.js")
 	config.Debug = v.GetBool("debug")
 	config.Filters.Default = v.GetStringSlice("filters.default")
+	config.Labels.Color.Custom = map[string]map[string]string{}
 	config.Labels.Color.Static = v.GetStringSlice("labels.color.static")
 	config.Labels.Color.Unique = v.GetStringSlice("labels.color.unique")
 	config.Labels.Keep = v.GetStringSlice("labels.keep")
@@ -161,6 +162,11 @@ func (config *configSchema) Read() {
 		log.Fatal(err)
 	}
 
+	err = v.UnmarshalKey("labels.color.custom", &config.Labels.Color.Custom)
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	// accept single Alertmanager server from flag/env if nothing is set yet
 	if len(config.Alertmanager.Servers) == 0 && v.GetString("alertmanager.uri") != "" {
 		log.Info("Using simple config with a single Alertmanager server")

internal/config/config_test.go

@@ -90,6 +90,7 @@ labels:
   - abc
   - def
   color:
+    custom: {}
     static:
     - a
     - bb

internal/config/models.go

@@ -47,6 +47,7 @@ type configSchema struct {
 		Keep  []string
 		Strip []string
 		Color struct {
+			Custom map[string]map[string]string
 			Static []string
 			Unique []string
 		}

internal/transform/color_test.go

@@ -9,22 +9,23 @@ import (
 )
 
 type colorTest struct {
-	config []string
-	labels map[string]string
-	colors map[string]string
+	uniqueLabels []string
+	customLabels map[string]map[string]string
+	labels       map[string]string
+	colors       map[string]string
 }
 
 var colorTests = []colorTest{
-	colorTest{
+	{
 		labels: map[string]string{},
 	},
-	colorTest{
+	{
 		labels: map[string]string{
 			"node": "localhost",
 		},
 	},
-	colorTest{
-		config: []string{"node"},
+	{
+		uniqueLabels: []string{"node"},
 		labels: map[string]string{
 			"node": "localhost",
 		},
@@ -32,8 +33,8 @@ var colorTests = []colorTest{
 			"node": "localhost",
 		},
 	},
-	colorTest{
-		config: []string{"node", "instance"},
+	{
+		uniqueLabels: []string{"node", "instance"},
 		labels: map[string]string{
 			"node":     "instance",
 			"env":      "instance",
@@ -45,8 +46,8 @@ var colorTests = []colorTest{
 			"instance": "server1",
 		},
 	},
-	colorTest{
-		config: []string{"job", "node", "instance"},
+	{
+		uniqueLabels: []string{"job", "node", "instance"},
 		labels: map[string]string{
 			"job": "node_ping",
 		},
@@ -54,11 +55,32 @@ var colorTests = []colorTest{
 			"job": "node_ping",
 		},
 	},
+	{
+		customLabels: map[string]map[string]string{
+			"node": map[string]string{"localhost": "#fff"},
+		},
+		labels: map[string]string{
+			"node": "localhost",
+		},
+		colors: map[string]string{
+			"node": "localhost",
+		},
+	},
+	{
+		customLabels: map[string]map[string]string{
+			"node": map[string]string{"localhost": "not a color"},
+		},
+		labels: map[string]string{
+			"node": "localhost",
+		},
+		colors: map[string]string{},
+	},
 }
 
 func TestColorLabel(t *testing.T) {
 	for _, testCase := range colorTests {
-		config.Config.Labels.Color.Unique = testCase.config
+		config.Config.Labels.Color.Unique = testCase.uniqueLabels
+		config.Config.Labels.Color.Custom = testCase.customLabels
 		colorStore := models.LabelsColorMap{}
 		for key, value := range testCase.labels {
 			transform.ColorLabel(colorStore, key, value)

internal/transform/colors.go

@@ -10,6 +10,7 @@ import (
 	"github.com/prymitive/karma/internal/slices"
 
 	"github.com/hansrodtang/randomcolor"
+	plcolors "gopkg.in/go-playground/colors.v1"
 
 	log "github.com/sirupsen/logrus"
 )
@@ -34,10 +35,44 @@ func labelToSeed(key string, val string) int64 {
 	return seed
 }
 
+func rgbToBrightness(r, g, b uint8) int32 {
+	return ((int32(r) * 299) + (int32(g) * 587) + (int32(b) * 114)) / 1000
+}
+
 // ColorLabel update karmaColorMap object with a color object generated
 // from label key and value passed here
 // It's used to generate unique colors for configured labels
 func ColorLabel(colorStore models.LabelsColorMap, key string, val string) {
+	// first handle custom colors
+	_, ok := config.Config.Labels.Color.Custom[key]
+	if ok {
+		c, ol := config.Config.Labels.Color.Custom[key][val]
+		if ol {
+			color, err := plcolors.Parse(c)
+			if err != nil {
+				log.Warningf("Failed to parse custom color for %s=%s: %s", key, val, err)
+				return
+			}
+			rgb := color.ToRGB()
+			bc := models.Color{
+				Red:   rgb.R,
+				Green: rgb.G,
+				Blue:  rgb.B,
+				Alpha: 255,
+			}
+			brightness := rgbToBrightness(bc.Red, bc.Green, bc.Blue)
+			if _, found := colorStore[key]; !found {
+				colorStore[key] = make(map[string]models.LabelColors)
+			}
+			colorStore[key][val] = models.LabelColors{
+				Brightness: brightness,
+				Background: bc,
+			}
+		}
+		return
+	}
+
+	// if no custom color is found then generate unique colors if needed
 	if slices.StringInSlice(config.Config.Labels.Color.Unique, key) {
 		if _, found := colorStore[key]; !found {
 			colorStore[key] = make(map[string]models.LabelColors)
@@ -54,7 +89,7 @@ func ColorLabel(colorStore models.LabelsColorMap, key string, val string) {
 			}
 			// check if color is bright or dark and pick the right background
 			// uses https://www.w3.org/WAI/ER/WD-AERT/#color-contrast method
-			brightness := ((int32(bc.Red) * 299) + (int32(bc.Green) * 587) + (int32(bc.Blue) * 114)) / 1000
+			brightness := rgbToBrightness(bc.Red, bc.Green, bc.Blue)
 			colorStore[key][val] = models.LabelColors{
 				Brightness: brightness,
 				Background: bc,