Add lowercase and uppercase relabel action (prometheus#10641)

Signed-off-by: Julien Pivotto <roidelapluie@o11y.eu>

Author: Julien Pivotto

config/config_test.go

@@ -858,6 +858,17 @@ var expectedConf = &Config{
 			Scheme:           DefaultScrapeConfig.Scheme,
 			HTTPClientConfig: config.DefaultHTTPClientConfig,
 
+			RelabelConfigs: []*relabel.Config{
+				{
+					Action:       relabel.Uppercase,
+					Regex:        relabel.DefaultRelabelConfig.Regex,
+					Replacement:  relabel.DefaultRelabelConfig.Replacement,
+					Separator:    relabel.DefaultRelabelConfig.Separator,
+					SourceLabels: model.LabelNames{"instance"},
+					TargetLabel:  "instance",
+				},
+			},
+
 			ServiceDiscoveryConfigs: discovery.Configs{
 				&hetzner.SDConfig{
 					HTTPClientConfig: config.HTTPClientConfig{
@@ -1197,6 +1208,30 @@ var expectedErrors = []struct {
 		filename: "labelmap.bad.yml",
 		errMsg:   "\"l-$1\" is invalid 'replacement' for labelmap action",
 	},
+	{
+		filename: "lowercase.bad.yml",
+		errMsg:   "relabel configuration for lowercase action requires 'target_label' value",
+	},
+	{
+		filename: "lowercase2.bad.yml",
+		errMsg:   "\"42lab\" is invalid 'target_label' for lowercase action",
+	},
+	{
+		filename: "lowercase3.bad.yml",
+		errMsg:   "'replacement' can not be set for lowercase action",
+	},
+	{
+		filename: "uppercase.bad.yml",
+		errMsg:   "relabel configuration for uppercase action requires 'target_label' value",
+	},
+	{
+		filename: "uppercase2.bad.yml",
+		errMsg:   "\"42lab\" is invalid 'target_label' for uppercase action",
+	},
+	{
+		filename: "uppercase3.bad.yml",
+		errMsg:   "'replacement' can not be set for uppercase action",
+	},
 	{
 		filename: "rules.bad.yml",
 		errMsg:   "invalid rule file path",

config/testdata/conf.good.yml

@@ -328,6 +328,10 @@ scrape_configs:
           key_file: valid_key_file
 
   - job_name: hetzner
+    relabel_configs:
+      - action: uppercase
+        source_labels: [instance]
+        target_label: instance
     hetzner_sd_configs:
       - role: hcloud
         authorization:

config/testdata/lowercase.bad.yml

@@ -0,0 +1,5 @@
+scrape_configs:
+  - job_name: prometheus
+    relabel_configs:
+      - action: lowercase
+        source_labels: [__name__]

config/testdata/lowercase2.bad.yml

@@ -0,0 +1,6 @@
+scrape_configs:
+  - job_name: prometheus
+    relabel_configs:
+      - action: lowercase
+        source_labels: [__name__]
+        target_label: 42lab

config/testdata/lowercase3.bad.yml

@@ -0,0 +1,7 @@
+scrape_configs:
+  - job_name: prometheus
+    relabel_configs:
+      - action: lowercase
+        source_labels: [__name__]
+        target_label: __name__
+        replacement: bar

config/testdata/uppercase.bad.yml

@@ -0,0 +1,5 @@
+scrape_configs:
+  - job_name: prometheus
+    relabel_configs:
+      - action: uppercase
+        source_labels: [__name__]

config/testdata/uppercase2.bad.yml

@@ -0,0 +1,6 @@
+scrape_configs:
+  - job_name: prometheus
+    relabel_configs:
+      - action: uppercase
+        source_labels: [__name__]
+        target_label: 42lab

config/testdata/uppercase3.bad.yml

@@ -0,0 +1,7 @@
+scrape_configs:
+  - job_name: prometheus
+    relabel_configs:
+      - action: uppercase
+        source_labels: [__name__]
+        target_label: __name__
+        replacement: bar

docs/configuration/configuration.md

@@ -2536,6 +2536,8 @@ anchored on both ends. To un-anchor the regex, use `.*<regex>.*`.
   `target_label` to `replacement`, with match group references
   (`${1}`, `${2}`, ...) in `replacement` substituted by their value. If `regex`
   does not match, no replacement takes place.
+* `lowercase`: Maps the concatenated `source_labels` to their lower case.
+* `uppercase`: Maps the concatenated `source_labels` to their upper case.
 * `keep`: Drop targets for which `regex` does not match the concatenated `source_labels`.
 * `drop`: Drop targets for which `regex` matches the concatenated `source_labels`.
 * `hashmod`: Set `target_label` to the `modulus` of a hash of the concatenated `source_labels`.

model/relabel/relabel.go

@@ -54,6 +54,10 @@ const (
 	LabelDrop Action = "labeldrop"
 	// LabelKeep drops any label not matching the regex.
 	LabelKeep Action = "labelkeep"
+	// Lowercase maps input letters to their lower case.
+	Lowercase Action = "lowercase"
+	// Uppercase maps input letters to their upper case.
+	Uppercase Action = "uppercase"
 )
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.
@@ -63,7 +67,7 @@ func (a *Action) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		return err
 	}
 	switch act := Action(strings.ToLower(s)); act {
-	case Replace, Keep, Drop, HashMod, LabelMap, LabelDrop, LabelKeep:
+	case Replace, Keep, Drop, HashMod, LabelMap, LabelDrop, LabelKeep, Lowercase, Uppercase:
 		*a = act
 		return nil
 	}
@@ -106,12 +110,15 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	if c.Modulus == 0 && c.Action == HashMod {
 		return errors.Errorf("relabel configuration for hashmod requires non-zero modulus")
 	}
-	if (c.Action == Replace || c.Action == HashMod) && c.TargetLabel == "" {
+	if (c.Action == Replace || c.Action == HashMod || c.Action == Lowercase || c.Action == Uppercase) && c.TargetLabel == "" {
 		return errors.Errorf("relabel configuration for %s action requires 'target_label' value", c.Action)
 	}
-	if c.Action == Replace && !relabelTarget.MatchString(c.TargetLabel) {
+	if (c.Action == Replace || c.Action == Lowercase || c.Action == Uppercase) && !relabelTarget.MatchString(c.TargetLabel) {
 		return errors.Errorf("%q is invalid 'target_label' for %s action", c.TargetLabel, c.Action)
 	}
+	if (c.Action == Lowercase || c.Action == Uppercase) && c.Replacement != DefaultRelabelConfig.Replacement {
+		return errors.Errorf("'replacement' can not be set for %s action", c.Action)
+	}
 	if c.Action == LabelMap && !relabelTarget.MatchString(c.Replacement) {
 		return errors.Errorf("%q is invalid 'replacement' for %s action", c.Replacement, c.Action)
 	}
@@ -228,6 +235,10 @@ func relabel(lset labels.Labels, cfg *Config) labels.Labels {
 			break
 		}
 		lb.Set(string(target), string(res))
+	case Lowercase:
+		lb.Set(cfg.TargetLabel, strings.ToLower(val))
+	case Uppercase:
+		lb.Set(cfg.TargetLabel, strings.ToUpper(val))
 	case HashMod:
 		mod := sum64(md5.Sum([]byte(val))) % cfg.Modulus
 		lb.Set(cfg.TargetLabel, fmt.Sprintf("%d", mod))