config: Add UnderscoreEscapingWithoutSuffixes translation strategy (#16849)

The last permutation of the translation options does underscore translation but does not add suffixes.
This translation option already exists in Mimir as otel_metric_suffixes_enabled, indicating external demand for this strategy.
There is an accompanying update to prometheus-docs to explain the use of this mode: https://github.com/prometheus/docs/pull/2688

Signed-off-by: Owen Williams <owen.williams@grafana.com>

config/config.go

@@ -104,7 +104,7 @@ func Load(s string, logger *slog.Logger) (*Config, error) {
 	}
 
 	switch cfg.OTLPConfig.TranslationStrategy {
-	case UnderscoreEscapingWithSuffixes:
+	case UnderscoreEscapingWithSuffixes, UnderscoreEscapingWithoutSuffixes:
 	case "":
 	case NoTranslation, NoUTF8EscapingWithSuffixes:
 		if cfg.GlobalConfig.MetricNameValidationScheme == model.LegacyValidation {
@@ -1534,31 +1534,68 @@ func getGoGC() int {
 type translationStrategyOption string
 
 var (
-	// NoUTF8EscapingWithSuffixes will accept metric/label names as they are.
-	// Unit and type suffixes may be added to metric names, according to certain rules.
+	// NoUTF8EscapingWithSuffixes will accept metric/label names as they are. Unit
+	// and type suffixes may be added to metric names, according to certain rules.
 	NoUTF8EscapingWithSuffixes translationStrategyOption = "NoUTF8EscapingWithSuffixes"
-	// UnderscoreEscapingWithSuffixes is the default option for translating OTLP to Prometheus.
-	// This option will translate metric name characters that are not alphanumerics/underscores/colons to underscores,
-	// and label name characters that are not alphanumerics/underscores to underscores.
-	// Unit and type suffixes may be appended to metric names, according to certain rules.
+	// UnderscoreEscapingWithSuffixes is the default option for translating OTLP
+	// to Prometheus. This option will translate metric name characters that are
+	// not alphanumerics/underscores/colons to underscores, and label name
+	// characters that are not alphanumerics/underscores to underscores. Unit and
+	// type suffixes may be appended to metric names, according to certain rules.
 	UnderscoreEscapingWithSuffixes translationStrategyOption = "UnderscoreEscapingWithSuffixes"
+	// UnderscoreEscapingWithoutSuffixes translates metric name characters that
+	// are not alphanumerics/underscores/colons to underscores, and label name
+	// characters that are not alphanumerics/underscores to underscores, but
+	// unlike UnderscoreEscapingWithSuffixes it does not append any suffixes to
+	// the names.
+	UnderscoreEscapingWithoutSuffixes translationStrategyOption = "UnderscoreEscapingWithoutSuffixes"
 	// NoTranslation (EXPERIMENTAL): disables all translation of incoming metric
-	// and label names. This offers a way for the OTLP users to use native metric names, reducing confusion.
+	// and label names. This offers a way for the OTLP users to use native metric
+	// names, reducing confusion.
 	//
 	// WARNING: This setting has significant known risks and limitations (see
-	// https://prometheus.io/docs/practices/naming/  for details):
-	// * Impaired UX when using PromQL in plain YAML (e.g. alerts, rules, dashboard, autoscaling configuration).
-	// * Series collisions which in the best case may result in OOO errors, in the worst case a silently malformed
-	// time series. For instance, you may end up in situation of ingesting `foo.bar` series with unit
-	// `seconds` and a separate series `foo.bar` with unit `milliseconds`.
+	// https://prometheus.io/docs/practices/naming/  for details): * Impaired UX
+	// when using PromQL in plain YAML (e.g. alerts, rules, dashboard, autoscaling
+	// configuration). * Series collisions which in the best case may result in
+	// OOO errors, in the worst case a silently malformed time series. For
+	// instance, you may end up in situation of ingesting `foo.bar` series with
+	// unit `seconds` and a separate series `foo.bar` with unit `milliseconds`.
 	//
-	// As a result, this setting is experimental and currently, should not be used in
-	// production systems.
+	// As a result, this setting is experimental and currently, should not be used
+	// in production systems.
 	//
-	// TODO(ArthurSens): Mention `type-and-unit-labels` feature (https://github.com/prometheus/proposals/pull/39) once released, as potential mitigation of the above risks.
+	// TODO(ArthurSens): Mention `type-and-unit-labels` feature
+	// (https://github.com/prometheus/proposals/pull/39) once released, as
+	// potential mitigation of the above risks.
 	NoTranslation translationStrategyOption = "NoTranslation"
 )
 
+// ShouldEscape returns true if the translation strategy requires that metric
+// names be escaped.
+func (o translationStrategyOption) ShouldEscape() bool {
+	switch o {
+	case UnderscoreEscapingWithSuffixes, UnderscoreEscapingWithoutSuffixes:
+		return true
+	case NoTranslation, NoUTF8EscapingWithSuffixes:
+		return false
+	default:
+		return false
+	}
+}
+
+// ShouldAddSuffixes returns a bool deciding whether the given translation
+// strategy should have suffixes added.
+func (o translationStrategyOption) ShouldAddSuffixes() bool {
+	switch o {
+	case UnderscoreEscapingWithSuffixes, NoUTF8EscapingWithSuffixes:
+		return true
+	case UnderscoreEscapingWithoutSuffixes, NoTranslation:
+		return false
+	default:
+		return false
+	}
+}
+
 // OTLPConfig is the configuration for writing to the OTLP endpoint.
 type OTLPConfig struct {
 	PromoteAllResourceAttributes      bool                      `yaml:"promote_all_resource_attributes,omitempty"`

docs/configuration/configuration.md

@@ -197,6 +197,11 @@ otlp:
   # - "NoUTF8EscapingWithSuffixes" is a mode that relies on UTF-8 support in Prometheus.
   #   It preserves all special characters like dots, but still adds required metric name suffixes
   #   for units and _total, as UnderscoreEscapingWithSuffixes does.
+  # - "UnderscoreEscapingWithoutSuffixes" translates metric name characters that
+  #   are not alphanumerics/underscores/colons to underscores, and label name
+  #   characters that are not alphanumerics/underscores to underscores, but
+  #   unlike UnderscoreEscapingWithSuffixes it does not append any suffixes to
+  #   the names.
   # - (EXPERIMENTAL) "NoTranslation" is a mode that relies on UTF-8 support in Prometheus.
   #   It preserves all special character like dots and won't append special suffixes for metric
   #   unit and type.
@@ -2286,7 +2291,7 @@ The following meta labels are available on targets during [relabeling](#relabel_
 See below for the configuration options for STACKIT discovery:
 
 ```yaml
-# The STACKIT project 
+# The STACKIT project
 project: <string>
 
 # STACKIT region to use. No automatic discovery of the region is done.

storage/remote/write_handler.go

@@ -594,9 +594,10 @@ func (rw *rwExporter) ConsumeMetrics(ctx context.Context, md pmetric.Metrics) er
 	otlpCfg := rw.config().OTLPConfig
 
 	converter := otlptranslator.NewPrometheusConverter()
+
 	annots, err := converter.FromMetrics(ctx, md, otlptranslator.Settings{
-		AddMetricSuffixes:                 otlpCfg.TranslationStrategy != config.NoTranslation,
-		AllowUTF8:                         otlpCfg.TranslationStrategy != config.UnderscoreEscapingWithSuffixes,
+		AddMetricSuffixes:                 otlpCfg.TranslationStrategy.ShouldAddSuffixes(),
+		AllowUTF8:                         !otlpCfg.TranslationStrategy.ShouldEscape(),
 		PromoteResourceAttributes:         otlptranslator.NewPromoteResourceAttributes(otlpCfg),
 		KeepIdentifyingResourceAttributes: otlpCfg.KeepIdentifyingResourceAttributes,
 		ConvertHistogramsToNHCB:           otlpCfg.ConvertHistogramsToNHCB,

storage/remote/write_test.go

@@ -440,7 +440,32 @@ func TestOTLPWriteHandler(t *testing.T) {
 				},
 			},
 		},
-
+		{
+			name: "UnderscoreEscapingWithoutSuffixes",
+			otlpCfg: config.OTLPConfig{
+				TranslationStrategy: config.UnderscoreEscapingWithoutSuffixes,
+			},
+			expectedSamples: []mockSample{
+				{
+					l: labels.New(labels.Label{Name: "__name__", Value: "test_counter"},
+						labels.Label{Name: "foo_bar", Value: "baz"},
+						labels.Label{Name: "instance", Value: "test-instance"},
+						labels.Label{Name: "job", Value: "test-service"}),
+					t: timestamp.UnixMilli(),
+					v: 10.0,
+				},
+				{
+					l: labels.New(
+						labels.Label{Name: "__name__", Value: "target_info"},
+						labels.Label{Name: "host_name", Value: "test-host"},
+						labels.Label{Name: "instance", Value: "test-instance"},
+						labels.Label{Name: "job", Value: "test-service"},
+					),
+					t: timestamp.UnixMilli(),
+					v: 1,
+				},
+			},
+		},
 		{
 			name: "NoUTF8EscapingWithSuffixes",
 			otlpCfg: config.OTLPConfig{