Add configuration parameters

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

config/config.go

@@ -258,7 +258,9 @@ var (
 
 	// DefaultOTLPConfig is the default OTLP configuration.
 	DefaultOTLPConfig = OTLPConfig{
-		TranslationStrategy: otlptranslator.UnderscoreEscapingWithSuffixes,
+		TranslationStrategy:                  otlptranslator.UnderscoreEscapingWithSuffixes,
+		LabelNameUnderscoreSanitization:      true,
+		LabelNamePreserveMultipleUnderscores: true,
 	}
 )
 
@@ -1609,6 +1611,14 @@ type OTLPConfig struct {
 	// PromoteScopeMetadata controls whether to promote OTel scope metadata (i.e. name, version, schema URL, and attributes) to metric labels.
 	// As per OTel spec, the aforementioned scope metadata should be identifying, i.e. made into metric labels.
 	PromoteScopeMetadata bool `yaml:"promote_scope_metadata,omitempty"`
+	// LabelNameUnderscoreSanitization controls whether to enable prepending of 'key_' to labels
+	// starting with '_'. Reserved labels starting with `__` are not modified.
+	// This is only relevant when AllowUTF8 is false (i.e., when using underscore escaping).
+	LabelNameUnderscoreSanitization bool `yaml:"label_name_underscore_sanitization,omitempty"`
+	// LabelNamePreserveMultipleUnderscores enables preserving of multiple consecutive underscores
+	// in label names when AllowUTF8 is false. When false, multiple consecutive underscores are
+	// collapsed to a single underscore during label name sanitization.
+	LabelNamePreserveMultipleUnderscores bool `yaml:"label_name_preserve_multiple_underscores,omitempty"`
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.

config/config_test.go

@@ -175,7 +175,9 @@ var expectedConf = &Config{
 		PromoteResourceAttributes: []string{
 			"k8s.cluster.name", "k8s.job.name", "k8s.namespace.name",
 		},
-		TranslationStrategy: otlptranslator.UnderscoreEscapingWithSuffixes,
+		TranslationStrategy:                  otlptranslator.UnderscoreEscapingWithSuffixes,
+		LabelNameUnderscoreSanitization:      true,
+		LabelNamePreserveMultipleUnderscores: true,
 	},
 
 	RemoteReadConfigs: []*RemoteReadConfig{
@@ -1842,6 +1844,48 @@ func TestOTLPPromoteScopeMetadata(t *testing.T) {
 	})
 }
 
+func TestOTLPLabelUnderscoreSanitization(t *testing.T) {
+	t.Run("defaults to true", func(t *testing.T) {
+		conf, err := LoadFile(filepath.Join("testdata", "otlp_label_underscore_sanitization_defaults.good.yml"), false, promslog.NewNopLogger())
+		require.NoError(t, err)
+
+		// Test that default values are true
+		require.True(t, conf.OTLPConfig.LabelNameUnderscoreSanitization)
+		require.True(t, conf.OTLPConfig.LabelNamePreserveMultipleUnderscores)
+	})
+
+	t.Run("explicit enabled", func(t *testing.T) {
+		conf, err := LoadFile(filepath.Join("testdata", "otlp_label_underscore_sanitization_enabled.good.yml"), false, promslog.NewNopLogger())
+		require.NoError(t, err)
+
+		out, err := yaml.Marshal(conf)
+		require.NoError(t, err)
+		var got Config
+		require.NoError(t, yaml.UnmarshalStrict(out, &got))
+
+		require.True(t, got.OTLPConfig.LabelNameUnderscoreSanitization)
+		require.True(t, got.OTLPConfig.LabelNamePreserveMultipleUnderscores)
+	})
+
+	t.Run("explicit disabled", func(t *testing.T) {
+		conf, err := LoadFile(filepath.Join("testdata", "otlp_label_underscore_sanitization_disabled.good.yml"), false, promslog.NewNopLogger())
+		require.NoError(t, err)
+
+		// When explicitly set to false, they should be false
+		require.False(t, conf.OTLPConfig.LabelNameUnderscoreSanitization)
+		require.False(t, conf.OTLPConfig.LabelNamePreserveMultipleUnderscores)
+	})
+
+	t.Run("empty config uses defaults", func(t *testing.T) {
+		conf, err := LoadFile(filepath.Join("testdata", "otlp_empty.yml"), false, promslog.NewNopLogger())
+		require.NoError(t, err)
+
+		// Empty config should use default values (true)
+		require.True(t, conf.OTLPConfig.LabelNameUnderscoreSanitization)
+		require.True(t, conf.OTLPConfig.LabelNamePreserveMultipleUnderscores)
+	})
+}
+
 func TestOTLPAllowUTF8(t *testing.T) {
 	t.Run("good config - NoUTF8EscapingWithSuffixes", func(t *testing.T) {
 		fpath := filepath.Join("testdata", "otlp_allow_utf8.good.yml")

config/testdata/otlp_label_underscore_sanitization_defaults.good.yml

@@ -0,0 +1,2 @@
+otlp:
+  promote_resource_attributes: ["service.name"]

config/testdata/otlp_label_underscore_sanitization_disabled.good.yml

@@ -0,0 +1,3 @@
+otlp:
+  label_name_underscore_sanitization: false
+  label_name_preserve_multiple_underscores: false

config/testdata/otlp_label_underscore_sanitization_enabled.good.yml

@@ -0,0 +1,3 @@
+otlp:
+  label_name_underscore_sanitization: true
+  label_name_preserve_multiple_underscores: true

docs/configuration/configuration.md

@@ -222,6 +222,15 @@ otlp:
   # Enables promotion of OTel scope metadata (i.e. name, version, schema URL, and attributes) to metric labels.
   # This is disabled by default for backwards compatibility, but according to OTel spec, scope metadata _should_ be identifying, i.e. translated to metric labels.
   [ promote_scope_metadata: <boolean> | default = false ]
+  # Controls whether to enable prepending of 'key_' to labels starting with '_'.
+  # Reserved labels starting with '__' are not modified.
+  # This is only relevant when translation_strategy uses underscore escaping
+  # (e.g., "UnderscoreEscapingWithSuffixes" or "UnderscoreEscapingWithoutSuffixes").
+  [ label_name_underscore_sanitization: <boolean> | default = true ]
+  # Enables preserving of multiple consecutive underscores in label names when
+  # translation_strategy uses underscore escaping. When true (default), multiple
+  # consecutive underscores are preserved during label name sanitization.
+  [ label_name_preserve_multiple_underscores: <boolean> | default = true ]
 
 # Settings related to the remote read feature.
 remote_read:

storage/remote/otlptranslator/prometheusremotewrite/helper.go

@@ -90,7 +90,7 @@ func (c *PrometheusConverter) createAttributes(resource pcommon.Resource, attrib
 
 	labelNamer := otlptranslator.LabelNamer{
 		UTF8Allowed:                 settings.AllowUTF8,
-		UnderscoreLabelSanitization: settings.LabelNameUnderscoreLabelSanitization,
+		UnderscoreLabelSanitization: settings.LabelNameUnderscoreSanitization,
 		PreserveMultipleUnderscores: settings.LabelNamePreserveMultipleUnderscores,
 	}
 
@@ -122,7 +122,7 @@ func (c *PrometheusConverter) createAttributes(resource pcommon.Resource, attrib
 		}
 	}
 
-	err := settings.PromoteResourceAttributes.addPromotedAttributes(c.builder, resourceAttrs, settings.AllowUTF8)
+	err := settings.PromoteResourceAttributes.addPromotedAttributes(c.builder, resourceAttrs, settings.AllowUTF8, settings.LabelNameUnderscoreSanitization, settings.LabelNamePreserveMultipleUnderscores)
 	if err != nil {
 		return labels.EmptyLabels(), err
 	}

storage/remote/otlptranslator/prometheusremotewrite/helper_test.go

@@ -67,15 +67,35 @@ func TestCreateAttributes(t *testing.T) {
 	attrs.PutStr("metric-attr", "metric value")
 	attrs.PutStr("metric-attr-other", "metric value other")
 
+	// Setup resources with underscores for sanitization tests
+	resourceAttrsWithUnderscores := map[string]string{
+		"service.name":        "service name",
+		"service.instance.id": "service ID",
+		"_private":            "private value",
+		"__reserved__":        "reserved value",
+		"label___multi":       "multi value",
+	}
+	resourceWithUnderscores := pcommon.NewResource()
+	for k, v := range resourceAttrsWithUnderscores {
+		resourceWithUnderscores.Attributes().PutStr(k, v)
+	}
+	attrsWithUnderscores := pcommon.NewMap()
+	attrsWithUnderscores.PutStr("_metric_private", "private metric")
+	attrsWithUnderscores.PutStr("metric___multi", "multi metric")
+
 	testCases := []struct {
-		name                         string
-		scope                        scope
-		promoteAllResourceAttributes bool
-		promoteResourceAttributes    []string
-		promoteScope                 bool
-		ignoreResourceAttributes     []string
-		ignoreAttrs                  []string
-		expectedLabels               labels.Labels
+		name                                 string
+		resource                             pcommon.Resource
+		attrs                                pcommon.Map
+		scope                                scope
+		promoteAllResourceAttributes         bool
+		promoteResourceAttributes            []string
+		promoteScope                         bool
+		ignoreResourceAttributes             []string
+		ignoreAttrs                          []string
+		labelNameUnderscoreLabelSanitization bool
+		labelNamePreserveMultipleUnderscores bool
+		expectedLabels                       labels.Labels
 	}{
 		{
 			name:                      "Successful conversion without resource attribute promotion and without scope promotion",
@@ -251,6 +271,121 @@ func TestCreateAttributes(t *testing.T) {
 				"otel_scope_attr2", "value2",
 			),
 		},
+		// Label sanitization test cases
+		{
+			name:                                 "Underscore sanitization enabled - prepends key_ to labels starting with single _",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"_private"},
+			labelNameUnderscoreLabelSanitization: true,
+			labelNamePreserveMultipleUnderscores: true,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"key_private", "private value",
+				"key_metric_private", "private metric",
+				"metric___multi", "multi metric",
+			),
+		},
+		{
+			name:                                 "Underscore sanitization disabled - keeps labels with _ as-is",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"_private"},
+			labelNameUnderscoreLabelSanitization: false,
+			labelNamePreserveMultipleUnderscores: true,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"_private", "private value",
+				"_metric_private", "private metric",
+				"metric___multi", "multi metric",
+			),
+		},
+		{
+			name:                                 "Multiple underscores preserved - keeps consecutive underscores",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"label___multi"},
+			labelNameUnderscoreLabelSanitization: false,
+			labelNamePreserveMultipleUnderscores: true,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"label___multi", "multi value",
+				"_metric_private", "private metric",
+				"metric___multi", "multi metric",
+			),
+		},
+		{
+			name:                                 "Multiple underscores collapsed - collapses to single underscore",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"label___multi"},
+			labelNameUnderscoreLabelSanitization: false,
+			labelNamePreserveMultipleUnderscores: false,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"label_multi", "multi value",
+				"_metric_private", "private metric",
+				"metric_multi", "multi metric",
+			),
+		},
+		{
+			name:                                 "Both sanitization options enabled",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"_private", "label___multi"},
+			labelNameUnderscoreLabelSanitization: true,
+			labelNamePreserveMultipleUnderscores: true,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"key_private", "private value",
+				"label___multi", "multi value",
+				"key_metric_private", "private metric",
+				"metric___multi", "multi metric",
+			),
+		},
+		{
+			name:                                 "Both sanitization options disabled",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"_private", "label___multi"},
+			labelNameUnderscoreLabelSanitization: false,
+			labelNamePreserveMultipleUnderscores: false,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"_private", "private value",
+				"label_multi", "multi value",
+				"_metric_private", "private metric",
+				"metric_multi", "multi metric",
+			),
+		},
+		{
+			name:                                 "Reserved labels (starting with __) are never modified",
+			resource:                             resourceWithUnderscores,
+			attrs:                                attrsWithUnderscores,
+			promoteResourceAttributes:            []string{"__reserved__"},
+			labelNameUnderscoreLabelSanitization: true,
+			labelNamePreserveMultipleUnderscores: false,
+			expectedLabels: labels.FromStrings(
+				"__name__", "test_metric",
+				"instance", "service ID",
+				"job", "service name",
+				"__reserved__", "reserved value",
+				"key_metric_private", "private metric",
+				"metric_multi", "multi metric",
+			),
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -261,9 +396,24 @@ func TestCreateAttributes(t *testing.T) {
 					PromoteResourceAttributes:    tc.promoteResourceAttributes,
 					IgnoreResourceAttributes:     tc.ignoreResourceAttributes,
 				}),
-				PromoteScopeMetadata: tc.promoteScope,
+				PromoteScopeMetadata:                 tc.promoteScope,
+				LabelNameUnderscoreSanitization:      tc.labelNameUnderscoreLabelSanitization,
+				LabelNamePreserveMultipleUnderscores: tc.labelNamePreserveMultipleUnderscores,
+			}
+			// Use test case specific resource/attrs if provided, otherwise use defaults
+			// Check if tc.resource is initialized (non-zero) by trying to get its attributes
+			testResource := resource
+			testAttrs := attrs
+			// For pcommon types, we can check if they're non-zero by seeing if they have attributes
+			// Since zero-initialized Resource is not valid, we use a simple heuristic:
+			// if the struct has been explicitly set in the test case, use it
+			if tc.resource != (pcommon.Resource{}) {
+				testResource = tc.resource
+			}
+			if tc.attrs != (pcommon.Map{}) {
+				testAttrs = tc.attrs
 			}
-			lbls, err := c.createAttributes(resource, attrs, tc.scope, settings, tc.ignoreAttrs, false, Metadata{}, model.MetricNameLabel, "test_metric")
+			lbls, err := c.createAttributes(testResource, testAttrs, tc.scope, settings, tc.ignoreAttrs, false, Metadata{}, model.MetricNameLabel, "test_metric")
 			require.NoError(t, err)
 
 			testutil.RequireEqual(t, lbls, tc.expectedLabels)

storage/remote/otlptranslator/prometheusremotewrite/metrics_to_prw.go

@@ -54,9 +54,9 @@ type Settings struct {
 	// PromoteScopeMetadata controls whether to promote OTel scope metadata to metric labels.
 	PromoteScopeMetadata    bool
 	EnableTypeAndUnitLabels bool
-	// LabelNameUnderscoreLabelSanitization controls whether to enable prepending of 'key' to labels
+	// LabelNameUnderscoreSanitization controls whether to enable prepending of 'key' to labels
 	// starting with '_'. Reserved labels starting with `__` are not modified.
-	LabelNameUnderscoreLabelSanitization bool
+	LabelNameUnderscoreSanitization bool
 	// LabelNamePreserveMultipleUnderscores enables preserving of multiple
 	// consecutive underscores in label names when AllowUTF8 is false.
 	LabelNamePreserveMultipleUnderscores bool
@@ -310,12 +310,16 @@ func NewPromoteResourceAttributes(otlpCfg config.OTLPConfig) *PromoteResourceAtt
 }
 
 // addPromotedAttributes adds labels for promoted resourceAttributes to the builder.
-func (s *PromoteResourceAttributes) addPromotedAttributes(builder *labels.Builder, resourceAttributes pcommon.Map, allowUTF8 bool) error {
+func (s *PromoteResourceAttributes) addPromotedAttributes(builder *labels.Builder, resourceAttributes pcommon.Map, allowUTF8, underscoreSanitization, preserveMultipleUnderscores bool) error {
 	if s == nil {
 		return nil
 	}
 
-	labelNamer := otlptranslator.LabelNamer{UTF8Allowed: allowUTF8}
+	labelNamer := otlptranslator.LabelNamer{
+		UTF8Allowed:                 allowUTF8,
+		UnderscoreLabelSanitization: underscoreSanitization,
+		PreserveMultipleUnderscores: preserveMultipleUnderscores,
+	}
 	if s.promoteAll {
 		var err error
 		resourceAttributes.Range(func(name string, value pcommon.Value) bool {

storage/remote/write_handler.go

@@ -649,15 +649,17 @@ func (rw *rwExporter) ConsumeMetrics(ctx context.Context, md pmetric.Metrics) er
 	combinedAppender := otlptranslator.NewCombinedAppender(app, rw.logger, rw.ingestCTZeroSample, rw.metrics)
 	converter := otlptranslator.NewPrometheusConverter(combinedAppender)
 	annots, err := converter.FromMetrics(ctx, md, otlptranslator.Settings{
-		AddMetricSuffixes:                 otlpCfg.TranslationStrategy.ShouldAddSuffixes(),
-		AllowUTF8:                         !otlpCfg.TranslationStrategy.ShouldEscape(),
-		PromoteResourceAttributes:         otlptranslator.NewPromoteResourceAttributes(otlpCfg),
-		KeepIdentifyingResourceAttributes: otlpCfg.KeepIdentifyingResourceAttributes,
-		ConvertHistogramsToNHCB:           otlpCfg.ConvertHistogramsToNHCB,
-		PromoteScopeMetadata:              otlpCfg.PromoteScopeMetadata,
-		AllowDeltaTemporality:             rw.allowDeltaTemporality,
-		LookbackDelta:                     rw.lookbackDelta,
-		EnableTypeAndUnitLabels:           rw.enableTypeAndUnitLabels,
+		AddMetricSuffixes:                    otlpCfg.TranslationStrategy.ShouldAddSuffixes(),
+		AllowUTF8:                            !otlpCfg.TranslationStrategy.ShouldEscape(),
+		PromoteResourceAttributes:            otlptranslator.NewPromoteResourceAttributes(otlpCfg),
+		KeepIdentifyingResourceAttributes:    otlpCfg.KeepIdentifyingResourceAttributes,
+		ConvertHistogramsToNHCB:              otlpCfg.ConvertHistogramsToNHCB,
+		PromoteScopeMetadata:                 otlpCfg.PromoteScopeMetadata,
+		AllowDeltaTemporality:                rw.allowDeltaTemporality,
+		LookbackDelta:                        rw.lookbackDelta,
+		EnableTypeAndUnitLabels:              rw.enableTypeAndUnitLabels,
+		LabelNameUnderscoreSanitization:      otlpCfg.LabelNameUnderscoreSanitization,
+		LabelNamePreserveMultipleUnderscores: otlpCfg.LabelNamePreserveMultipleUnderscores,
 	})
 
 	defer func() {