Allow UTF-8 characters in metric and label names as opt-in feature (#15258)

* Allow UTF-8 characters in metric and label names as opt-in feature

---------

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

config/config.go

@@ -106,6 +106,18 @@ func Load(s string, logger *slog.Logger) (*Config, error) {
 	if !b.Labels().IsEmpty() {
 		cfg.GlobalConfig.ExternalLabels = b.Labels()
 	}
+
+	switch cfg.OTLPConfig.TranslationStrategy {
+	case UnderscoreEscapingWithSuffixes:
+	case "":
+	case NoUTF8EscapingWithSuffixes:
+		if cfg.GlobalConfig.MetricNameValidationScheme == LegacyValidationConfig {
+			return nil, errors.New("OTLP translation strategy NoUTF8EscapingWithSuffixes is not allowed when UTF8 is disabled")
+		}
+	default:
+		return nil, fmt.Errorf("unsupported OTLP translation strategy %q", cfg.OTLPConfig.TranslationStrategy)
+	}
+
 	return cfg, nil
 }
 
@@ -239,7 +251,9 @@ var (
 	}
 
 	// DefaultOTLPConfig is the default OTLP configuration.
-	DefaultOTLPConfig = OTLPConfig{}
+	DefaultOTLPConfig = OTLPConfig{
+		TranslationStrategy: UnderscoreEscapingWithSuffixes,
+	}
 )
 
 // Config is the top-level configuration for Prometheus's config files.
@@ -1402,9 +1416,20 @@ func getGoGCEnv() int {
 	return DefaultRuntimeConfig.GoGC
 }
 
+type translationStrategyOption string
+
+var (
+	// NoUTF8EscapingWithSuffixes will keep UTF-8 characters as they are, units and type suffixes will still be added.
+	NoUTF8EscapingWithSuffixes translationStrategyOption = "NoUTF8EscapingWithSuffixes"
+	// UnderscoreEscapingWithSuffixes is the default option for translating OTLP to Prometheus.
+	// This option will translate all UTF-8 characters to underscores, while adding units and type suffixes.
+	UnderscoreEscapingWithSuffixes translationStrategyOption = "UnderscoreEscapingWithSuffixes"
+)
+
 // OTLPConfig is the configuration for writing to the OTLP endpoint.
 type OTLPConfig struct {
-	PromoteResourceAttributes []string `yaml:"promote_resource_attributes,omitempty"`
+	PromoteResourceAttributes []string                  `yaml:"promote_resource_attributes,omitempty"`
+	TranslationStrategy       translationStrategyOption `yaml:"translation_strategy,omitempty"`
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.

config/config_test.go

@@ -168,6 +168,7 @@ var expectedConf = &Config{
 		PromoteResourceAttributes: []string{
 			"k8s.cluster.name", "k8s.job.name", "k8s.namespace.name",
 		},
+		TranslationStrategy: UnderscoreEscapingWithSuffixes,
 	},
 
 	RemoteReadConfigs: []*RemoteReadConfig{
@@ -1553,6 +1554,67 @@ func TestOTLPSanitizeResourceAttributes(t *testing.T) {
 	})
 }
 
+func TestOTLPAllowUTF8(t *testing.T) {
+	t.Run("good config", func(t *testing.T) {
+		fpath := filepath.Join("testdata", "otlp_allow_utf8.good.yml")
+		verify := func(t *testing.T, conf *Config, err error) {
+			t.Helper()
+			require.NoError(t, err)
+			require.Equal(t, NoUTF8EscapingWithSuffixes, conf.OTLPConfig.TranslationStrategy)
+		}
+
+		t.Run("LoadFile", func(t *testing.T) {
+			conf, err := LoadFile(fpath, false, promslog.NewNopLogger())
+			verify(t, conf, err)
+		})
+		t.Run("Load", func(t *testing.T) {
+			content, err := os.ReadFile(fpath)
+			require.NoError(t, err)
+			conf, err := Load(string(content), promslog.NewNopLogger())
+			verify(t, conf, err)
+		})
+	})
+
+	t.Run("incompatible config", func(t *testing.T) {
+		fpath := filepath.Join("testdata", "otlp_allow_utf8.incompatible.yml")
+		verify := func(t *testing.T, err error) {
+			t.Helper()
+			require.ErrorContains(t, err, `OTLP translation strategy NoUTF8EscapingWithSuffixes is not allowed when UTF8 is disabled`)
+		}
+
+		t.Run("LoadFile", func(t *testing.T) {
+			_, err := LoadFile(fpath, false, promslog.NewNopLogger())
+			verify(t, err)
+		})
+		t.Run("Load", func(t *testing.T) {
+			content, err := os.ReadFile(fpath)
+			require.NoError(t, err)
+			_, err = Load(string(content), promslog.NewNopLogger())
+			t.Log("err", err)
+			verify(t, err)
+		})
+	})
+
+	t.Run("bad config", func(t *testing.T) {
+		fpath := filepath.Join("testdata", "otlp_allow_utf8.bad.yml")
+		verify := func(t *testing.T, err error) {
+			t.Helper()
+			require.ErrorContains(t, err, `unsupported OTLP translation strategy "Invalid"`)
+		}
+
+		t.Run("LoadFile", func(t *testing.T) {
+			_, err := LoadFile(fpath, false, promslog.NewNopLogger())
+			verify(t, err)
+		})
+		t.Run("Load", func(t *testing.T) {
+			content, err := os.ReadFile(fpath)
+			require.NoError(t, err)
+			_, err = Load(string(content), promslog.NewNopLogger())
+			verify(t, err)
+		})
+	})
+}
+
 func TestLoadConfig(t *testing.T) {
 	// Parse a valid file that sets a global scrape timeout. This tests whether parsing
 	// an overwritten default field in the global config permanently changes the default.

config/testdata/otlp_allow_utf8.bad.yml

@@ -0,0 +1,4 @@
+global:
+  metric_name_validation_scheme: legacy
+otlp:
+  translation_strategy: Invalid

config/testdata/otlp_allow_utf8.good.yml

@@ -0,0 +1,2 @@
+otlp:
+  translation_strategy: NoUTF8EscapingWithSuffixes

config/testdata/otlp_allow_utf8.incompatible.yml

@@ -0,0 +1,4 @@
+global:
+  metric_name_validation_scheme: legacy
+otlp:
+  translation_strategy: NoUTF8EscapingWithSuffixes

documentation/examples/prometheus-otlp.yml

@@ -0,0 +1,31 @@
+# my global config
+global:
+  evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute.
+
+otlp:
+  # Recommended attributes to be promoted to labels.
+  promote_resource_attributes:
+    - service.instance.id
+    - service.name
+    - service.namespace
+    - cloud.availability_zone
+    - cloud.region
+    - container.name
+    - deployment.environment.name
+    - k8s.cluster.name
+    - k8s.container.name
+    - k8s.cronjob.name
+    - k8s.daemonset.name
+    - k8s.deployment.name
+    - k8s.job.name
+    - k8s.namespace.name
+    - k8s.pod.name
+    - k8s.replicaset.name
+    - k8s.statefulset.name
+  # Ingest OTLP data keeping UTF-8 characters in metric/label names.
+  translation_strategy: NoUTF8EscapingWithSuffixes
+
+storage:
+  # OTLP is a push-based protocol, Out of order samples is a common scenario.
+  tsdb:
+    out_of_order_time_window: 30m

storage/remote/otlptranslator/prometheus/helpers_from_stdlib.go

@@ -0,0 +1,106 @@
+// Copyright 2024 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// Provenance-includes-location: https://github.com/golang/go/blob/f2d118fd5f7e872804a5825ce29797f81a28b0fa/src/strings/strings.go
+// Provenance-includes-license: BSD-3-Clause
+// Provenance-includes-copyright: Copyright The Go Authors.
+
+package prometheus
+
+import "strings"
+
+// fieldsFunc is a copy of strings.FieldsFunc from the Go standard library,
+// but it also returns the separators as part of the result.
+func fieldsFunc(s string, f func(rune) bool) ([]string, []string) {
+	// A span is used to record a slice of s of the form s[start:end].
+	// The start index is inclusive and the end index is exclusive.
+	type span struct {
+		start int
+		end   int
+	}
+	spans := make([]span, 0, 32)
+	separators := make([]string, 0, 32)
+
+	// Find the field start and end indices.
+	// Doing this in a separate pass (rather than slicing the string s
+	// and collecting the result substrings right away) is significantly
+	// more efficient, possibly due to cache effects.
+	start := -1 // valid span start if >= 0
+	for end, rune := range s {
+		if f(rune) {
+			if start >= 0 {
+				spans = append(spans, span{start, end})
+				// Set start to a negative value.
+				// Note: using -1 here consistently and reproducibly
+				// slows down this code by a several percent on amd64.
+				start = ^start
+				separators = append(separators, string(s[end]))
+			}
+		} else {
+			if start < 0 {
+				start = end
+			}
+		}
+	}
+
+	// Last field might end at EOF.
+	if start >= 0 {
+		spans = append(spans, span{start, len(s)})
+	}
+
+	// Create strings from recorded field indices.
+	a := make([]string, len(spans))
+	for i, span := range spans {
+		a[i] = s[span.start:span.end]
+	}
+
+	return a, separators
+}
+
+// join is a copy of strings.Join from the Go standard library,
+// but it also accepts a slice of separators to join the elements with.
+// If the slice of separators is shorter than the slice of elements, use a default value.
+// We also don't check for integer overflow.
+func join(elems []string, separators []string, def string) string {
+	switch len(elems) {
+	case 0:
+		return ""
+	case 1:
+		return elems[0]
+	}
+
+	var n int
+	var sep string
+	sepLen := len(separators)
+	for i, elem := range elems {
+		if i >= sepLen {
+			sep = def
+		} else {
+			sep = separators[i]
+		}
+		n += len(sep) + len(elem)
+	}
+
+	var b strings.Builder
+	b.Grow(n)
+	b.WriteString(elems[0])
+	for i, s := range elems[1:] {
+		if i >= sepLen {
+			sep = def
+		} else {
+			sep = separators[i]
+		}
+		b.WriteString(sep)
+		b.WriteString(s)
+	}
+	return b.String()
+}

storage/remote/otlptranslator/prometheus/normalize_label.go

@@ -29,9 +29,9 @@ import (
 //
 // Labels that start with non-letter rune will be prefixed with "key_".
 // An exception is made for double-underscores which are allowed.
-func NormalizeLabel(label string) string {
+func NormalizeLabel(label string, allowUTF8 bool) string {
 	// Trivial case
-	if len(label) == 0 {
+	if len(label) == 0 || allowUTF8 {
 		return label
 	}
 

storage/remote/otlptranslator/prometheus/normalize_label_test.go

@@ -22,24 +22,27 @@ import (
 
 func TestNormalizeLabel(t *testing.T) {
 	tests := []struct {
-		label    string
-		expected string
+		label        string
+		expected     string
+		expectedUTF8 string
 	}{
-		{"", ""},
-		{"label:with:colons", "label_with_colons"}, // Without UTF-8 support, colons are only allowed in metric names
-		{"LabelWithCapitalLetters", "LabelWithCapitalLetters"},
-		{"label!with&special$chars)", "label_with_special_chars_"},
-		{"label_with_foreign_characters_字符", "label_with_foreign_characters___"},
-		{"label.with.dots", "label_with_dots"},
-		{"123label", "key_123label"},
-		{"_label_starting_with_underscore", "key_label_starting_with_underscore"},
-		{"__label_starting_with_2underscores", "__label_starting_with_2underscores"},
+		{"", "", ""},
+		{"label:with:colons", "label_with_colons", "label:with:colons"}, // Without UTF-8 support, colons are only allowed in metric names
+		{"LabelWithCapitalLetters", "LabelWithCapitalLetters", "LabelWithCapitalLetters"},
+		{"label!with&special$chars)", "label_with_special_chars_", "label!with&special$chars)"},
+		{"label_with_foreign_characters_字符", "label_with_foreign_characters___", "label_with_foreign_characters_字符"},
+		{"label.with.dots", "label_with_dots", "label.with.dots"},
+		{"123label", "key_123label", "123label"},
+		{"_label_starting_with_underscore", "key_label_starting_with_underscore", "_label_starting_with_underscore"},
+		{"__label_starting_with_2underscores", "__label_starting_with_2underscores", "__label_starting_with_2underscores"},
 	}
 
 	for i, test := range tests {
 		t.Run(fmt.Sprintf("test_%d", i), func(t *testing.T) {
-			result := NormalizeLabel(test.label)
+			result := NormalizeLabel(test.label, false)
 			require.Equal(t, test.expected, result)
+			uTF8result := NormalizeLabel(test.label, true)
+			require.Equal(t, test.expectedUTF8, uTF8result)
 		})
 	}
 }

storage/remote/otlptranslator/prometheus/normalize_name.go

@@ -88,27 +88,32 @@ var perUnitMap = map[string]string{
 // See rules at https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels,
 // https://prometheus.io/docs/practices/naming/#metric-and-label-naming
 // and https://github.com/open-telemetry/opentelemetry-specification/blob/v1.38.0/specification/compatibility/prometheus_and_openmetrics.md#otlp-metric-points-to-prometheus.
-func BuildCompliantName(metric pmetric.Metric, namespace string, addMetricSuffixes bool) string {
+func BuildCompliantName(metric pmetric.Metric, namespace string, addMetricSuffixes, allowUTF8 bool) string {
 	// Full normalization following standard Prometheus naming conventions
 	if addMetricSuffixes {
-		return normalizeName(metric, namespace)
+		return normalizeName(metric, namespace, allowUTF8)
 	}
 
-	// Regexp for metric name characters that should be replaced with _.
-	invalidMetricCharRE := regexp.MustCompile(`[^a-zA-Z0-9:_]`)
-
-	// Simple case (no full normalization, no units, etc.).
-	metricName := strings.Join(strings.FieldsFunc(metric.Name(), func(r rune) bool {
-		return invalidMetricCharRE.MatchString(string(r))
-	}), "_")
+	var metricName string
+	if !allowUTF8 {
+		// Regexp for metric name characters that should be replaced with _.
+		invalidMetricCharRE := regexp.MustCompile(`[^a-zA-Z0-9:_]`)
+
+		// Simple case (no full normalization, no units, etc.).
+		metricName = strings.Join(strings.FieldsFunc(metric.Name(), func(r rune) bool {
+			return invalidMetricCharRE.MatchString(string(r))
+		}), "_")
+	} else {
+		metricName = metric.Name()
+	}
 
 	// Namespace?
 	if namespace != "" {
 		return namespace + "_" + metricName
 	}
 
-	// Metric name starts with a digit? Prefix it with an underscore.
-	if metricName != "" && unicode.IsDigit(rune(metricName[0])) {
+	// Metric name starts with a digit and utf8 not allowed? Prefix it with an underscore.
+	if metricName != "" && unicode.IsDigit(rune(metricName[0])) && !allowUTF8 {
 		metricName = "_" + metricName
 	}
 
@@ -116,17 +121,18 @@ func BuildCompliantName(metric pmetric.Metric, namespace string, addMetricSuffix
 }
 
 // Build a normalized name for the specified metric.
-func normalizeName(metric pmetric.Metric, namespace string) string {
-	// Regexp for characters that can't be in a metric name token.
-	nonTokenMetricCharRE := regexp.MustCompile(`[^a-zA-Z0-9:]`)
-
+func normalizeName(metric pmetric.Metric, namespace string, allowUTF8 bool) string {
+	var translationFunc func(rune) bool
+	if !allowUTF8 {
+		nonTokenMetricCharRE := regexp.MustCompile(`[^a-zA-Z0-9:]`)
+		translationFunc = func(r rune) bool { return nonTokenMetricCharRE.MatchString(string(r)) }
+	} else {
+		translationFunc = func(r rune) bool { return !unicode.IsLetter(r) && !unicode.IsDigit(r) && r != ':' }
+	}
 	// Split metric name into "tokens" (of supported metric name runes).
 	// Note that this has the side effect of replacing multiple consecutive underscores with a single underscore.
 	// This is part of the OTel to Prometheus specification: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.38.0/specification/compatibility/prometheus_and_openmetrics.md#otlp-metric-points-to-prometheus.
-	nameTokens := strings.FieldsFunc(
-		metric.Name(),
-		func(r rune) bool { return nonTokenMetricCharRE.MatchString(string(r)) },
-	)
+	nameTokens, separators := fieldsFunc(metric.Name(), translationFunc)
 
 	// Split unit at the '/' if any
 	unitTokens := strings.SplitN(metric.Unit(), "/", 2)
@@ -137,7 +143,10 @@ func normalizeName(metric pmetric.Metric, namespace string) string {
 		var mainUnitProm, perUnitProm string
 		mainUnitOTel := strings.TrimSpace(unitTokens[0])
 		if mainUnitOTel != "" && !strings.ContainsAny(mainUnitOTel, "{}") {
-			mainUnitProm = cleanUpUnit(unitMapGetOrDefault(mainUnitOTel))
+			mainUnitProm = unitMapGetOrDefault(mainUnitOTel)
+			if !allowUTF8 {
+				mainUnitProm = cleanUpUnit(mainUnitProm)
+			}
 			if slices.Contains(nameTokens, mainUnitProm) {
 				mainUnitProm = ""
 			}
@@ -148,7 +157,10 @@ func normalizeName(metric pmetric.Metric, namespace string) string {
 		if len(unitTokens) > 1 && unitTokens[1] != "" {
 			perUnitOTel := strings.TrimSpace(unitTokens[1])
 			if perUnitOTel != "" && !strings.ContainsAny(perUnitOTel, "{}") {
-				perUnitProm = cleanUpUnit(perUnitMapGetOrDefault(perUnitOTel))
+				perUnitProm = perUnitMapGetOrDefault(perUnitOTel)
+				if !allowUTF8 {
+					perUnitProm = cleanUpUnit(perUnitProm)
+				}
 			}
 			if perUnitProm != "" {
 				perUnitProm = "per_" + perUnitProm
@@ -189,8 +201,12 @@ func normalizeName(metric pmetric.Metric, namespace string) string {
 		nameTokens = append([]string{namespace}, nameTokens...)
 	}
 
-	// Build the string from the tokens, separated with underscores
-	normalizedName := strings.Join(nameTokens, "_")
+	// Build the string from the tokens + separators.
+	// If UTF-8 isn't allowed, we'll use underscores as separators.
+	if !allowUTF8 {
+		separators = []string{}
+	}
+	normalizedName := join(nameTokens, separators, "_")
 
 	// Metric name cannot start with a digit, so prefix it with "_" in this case
 	if normalizedName != "" && unicode.IsDigit(rune(normalizedName[0])) {

storage/remote/otlptranslator/prometheus/normalize_name_test.go

@@ -25,92 +25,119 @@ import (
 )
 
 func TestByte(t *testing.T) {
-	require.Equal(t, "system_filesystem_usage_bytes", normalizeName(createGauge("system.filesystem.usage", "By"), ""))
+	require.Equal(t, "system_filesystem_usage_bytes", normalizeName(createGauge("system.filesystem.usage", "By"), "", false))
 }
 
 func TestByteCounter(t *testing.T) {
-	require.Equal(t, "system_io_bytes_total", normalizeName(createCounter("system.io", "By"), ""))
-	require.Equal(t, "network_transmitted_bytes_total", normalizeName(createCounter("network_transmitted_bytes_total", "By"), ""))
+	require.Equal(t, "system_io_bytes_total", normalizeName(createCounter("system.io", "By"), "", false))
+	require.Equal(t, "network_transmitted_bytes_total", normalizeName(createCounter("network_transmitted_bytes_total", "By"), "", false))
 }
 
 func TestWhiteSpaces(t *testing.T) {
-	require.Equal(t, "system_filesystem_usage_bytes", normalizeName(createGauge("\t system.filesystem.usage       ", "  By\t"), ""))
+	require.Equal(t, "system_filesystem_usage_bytes", normalizeName(createGauge("\t system.filesystem.usage       ", "  By\t"), "", false))
 }
 
 func TestNonStandardUnit(t *testing.T) {
-	require.Equal(t, "system_network_dropped", normalizeName(createGauge("system.network.dropped", "{packets}"), ""))
+	require.Equal(t, "system_network_dropped", normalizeName(createGauge("system.network.dropped", "{packets}"), "", false))
 }
 
 func TestNonStandardUnitCounter(t *testing.T) {
-	require.Equal(t, "system_network_dropped_total", normalizeName(createCounter("system.network.dropped", "{packets}"), ""))
+	require.Equal(t, "system_network_dropped_total", normalizeName(createCounter("system.network.dropped", "{packets}"), "", false))
 }
 
 func TestBrokenUnit(t *testing.T) {
-	require.Equal(t, "system_network_dropped_packets", normalizeName(createGauge("system.network.dropped", "packets"), ""))
-	require.Equal(t, "system_network_packets_dropped", normalizeName(createGauge("system.network.packets.dropped", "packets"), ""))
-	require.Equal(t, "system_network_packets", normalizeName(createGauge("system.network.packets", "packets"), ""))
+	require.Equal(t, "system_network_dropped_packets", normalizeName(createGauge("system.network.dropped", "packets"), "", false))
+	require.Equal(t, "system_network_packets_dropped", normalizeName(createGauge("system.network.packets.dropped", "packets"), "", false))
+	require.Equal(t, "system_network_packets", normalizeName(createGauge("system.network.packets", "packets"), "", false))
 }
 
 func TestBrokenUnitCounter(t *testing.T) {
-	require.Equal(t, "system_network_dropped_packets_total", normalizeName(createCounter("system.network.dropped", "packets"), ""))
-	require.Equal(t, "system_network_packets_dropped_total", normalizeName(createCounter("system.network.packets.dropped", "packets"), ""))
-	require.Equal(t, "system_network_packets_total", normalizeName(createCounter("system.network.packets", "packets"), ""))
+	require.Equal(t, "system_network_dropped_packets_total", normalizeName(createCounter("system.network.dropped", "packets"), "", false))
+	require.Equal(t, "system_network_packets_dropped_total", normalizeName(createCounter("system.network.packets.dropped", "packets"), "", false))
+	require.Equal(t, "system_network_packets_total", normalizeName(createCounter("system.network.packets", "packets"), "", false))
 }
 
 func TestRatio(t *testing.T) {
-	require.Equal(t, "hw_gpu_memory_utilization_ratio", normalizeName(createGauge("hw.gpu.memory.utilization", "1"), ""))
-	require.Equal(t, "hw_fan_speed_ratio", normalizeName(createGauge("hw.fan.speed_ratio", "1"), ""))
-	require.Equal(t, "objects_total", normalizeName(createCounter("objects", "1"), ""))
+	require.Equal(t, "hw_gpu_memory_utilization_ratio", normalizeName(createGauge("hw.gpu.memory.utilization", "1"), "", false))
+	require.Equal(t, "hw_fan_speed_ratio", normalizeName(createGauge("hw.fan.speed_ratio", "1"), "", false))
+	require.Equal(t, "objects_total", normalizeName(createCounter("objects", "1"), "", false))
 }
 
 func TestHertz(t *testing.T) {
-	require.Equal(t, "hw_cpu_speed_limit_hertz", normalizeName(createGauge("hw.cpu.speed_limit", "Hz"), ""))
+	require.Equal(t, "hw_cpu_speed_limit_hertz", normalizeName(createGauge("hw.cpu.speed_limit", "Hz"), "", false))
 }
 
 func TestPer(t *testing.T) {
-	require.Equal(t, "broken_metric_speed_km_per_hour", normalizeName(createGauge("broken.metric.speed", "km/h"), ""))
-	require.Equal(t, "astro_light_speed_limit_meters_per_second", normalizeName(createGauge("astro.light.speed_limit", "m/s"), ""))
+	require.Equal(t, "broken_metric_speed_km_per_hour", normalizeName(createGauge("broken.metric.speed", "km/h"), "", false))
+	require.Equal(t, "astro_light_speed_limit_meters_per_second", normalizeName(createGauge("astro.light.speed_limit", "m/s"), "", false))
 }
 
 func TestPercent(t *testing.T) {
-	require.Equal(t, "broken_metric_success_ratio_percent", normalizeName(createGauge("broken.metric.success_ratio", "%"), ""))
-	require.Equal(t, "broken_metric_success_percent", normalizeName(createGauge("broken.metric.success_percent", "%"), ""))
+	require.Equal(t, "broken_metric_success_ratio_percent", normalizeName(createGauge("broken.metric.success_ratio", "%"), "", false))
+	require.Equal(t, "broken_metric_success_percent", normalizeName(createGauge("broken.metric.success_percent", "%"), "", false))
 }
 
 func TestEmpty(t *testing.T) {
-	require.Equal(t, "test_metric_no_unit", normalizeName(createGauge("test.metric.no_unit", ""), ""))
-	require.Equal(t, "test_metric_spaces", normalizeName(createGauge("test.metric.spaces", "   \t  "), ""))
-}
-
-func TestUnsupportedRunes(t *testing.T) {
-	require.Equal(t, "unsupported_metric_temperature_F", normalizeName(createGauge("unsupported.metric.temperature", "°F"), ""))
-	require.Equal(t, "unsupported_metric_weird", normalizeName(createGauge("unsupported.metric.weird", "+=.:,!* & #"), ""))
-	require.Equal(t, "unsupported_metric_redundant_test_per_C", normalizeName(createGauge("unsupported.metric.redundant", "__test $/°C"), ""))
+	require.Equal(t, "test_metric_no_unit", normalizeName(createGauge("test.metric.no_unit", ""), "", false))
+	require.Equal(t, "test_metric_spaces", normalizeName(createGauge("test.metric.spaces", "   \t  "), "", false))
+}
+
+func TestAllowUTF8(t *testing.T) {
+	t.Run("allow UTF8", func(t *testing.T) {
+		require.Equal(t, "unsupported.metric.temperature_°F", normalizeName(createGauge("unsupported.metric.temperature", "°F"), "", true))
+		require.Equal(t, "unsupported.metric.weird_+=.:,!* & #", normalizeName(createGauge("unsupported.metric.weird", "+=.:,!* & #"), "", true))
+		require.Equal(t, "unsupported.metric.redundant___test $_per_°C", normalizeName(createGauge("unsupported.metric.redundant", "__test $/°C"), "", true))
+		require.Equal(t, "metric_with_字符_foreign_characters_ど", normalizeName(createGauge("metric_with_字符_foreign_characters", "ど"), "", true))
+	})
+	t.Run("disallow UTF8", func(t *testing.T) {
+		require.Equal(t, "unsupported_metric_temperature_F", normalizeName(createGauge("unsupported.metric.temperature", "°F"), "", false))
+		require.Equal(t, "unsupported_metric_weird", normalizeName(createGauge("unsupported.metric.weird", "+=.:,!* & #"), "", false))
+		require.Equal(t, "unsupported_metric_redundant_test_per_C", normalizeName(createGauge("unsupported.metric.redundant", "__test $/°C"), "", false))
+		require.Equal(t, "metric_with_foreign_characters", normalizeName(createGauge("metric_with_字符_foreign_characters", "ど"), "", false))
+	})
+}
+
+func TestAllowUTF8KnownBugs(t *testing.T) {
+	// Due to historical reasons, the translator code was copied from OpenTelemetry collector codebase.
+	// Over there, they tried to provide means to translate metric names following Prometheus conventions that are documented here:
+	// https://prometheus.io/docs/practices/naming/
+	//
+	// Althogh not explicitly said, it was implied that words should be separated by a single underscore and the codebase was written
+	// with that in mind.
+	//
+	// Now that we're allowing OTel users to have their original names stored in prometheus without any transformation, we're facing problems
+	// where two (or more) UTF-8 characters are being used to separate words.
+	// TODO(arthursens): Fix it!
+
+	// We're asserting on 'NotEqual', which proves the bug.
+	require.NotEqual(t, "metric....split_=+by_//utf8characters", normalizeName(createGauge("metric....split_=+by_//utf8characters", ""), "", true))
+	// Here we're asserting on 'Equal', showing the current behavior.
+	require.Equal(t, "metric.split_by_utf8characters", normalizeName(createGauge("metric....split_=+by_//utf8characters", ""), "", true))
 }
 
 func TestOTelReceivers(t *testing.T) {
-	require.Equal(t, "active_directory_ds_replication_network_io_bytes_total", normalizeName(createCounter("active_directory.ds.replication.network.io", "By"), ""))
-	require.Equal(t, "active_directory_ds_replication_sync_object_pending_total", normalizeName(createCounter("active_directory.ds.replication.sync.object.pending", "{objects}"), ""))
-	require.Equal(t, "active_directory_ds_replication_object_rate_per_second", normalizeName(createGauge("active_directory.ds.replication.object.rate", "{objects}/s"), ""))
-	require.Equal(t, "active_directory_ds_name_cache_hit_rate_percent", normalizeName(createGauge("active_directory.ds.name_cache.hit_rate", "%"), ""))
-	require.Equal(t, "active_directory_ds_ldap_bind_last_successful_time_milliseconds", normalizeName(createGauge("active_directory.ds.ldap.bind.last_successful.time", "ms"), ""))
-	require.Equal(t, "apache_current_connections", normalizeName(createGauge("apache.current_connections", "connections"), ""))
-	require.Equal(t, "apache_workers_connections", normalizeName(createGauge("apache.workers", "connections"), ""))
-	require.Equal(t, "apache_requests_total", normalizeName(createCounter("apache.requests", "1"), ""))
-	require.Equal(t, "bigip_virtual_server_request_count_total", normalizeName(createCounter("bigip.virtual_server.request.count", "{requests}"), ""))
-	require.Equal(t, "system_cpu_utilization_ratio", normalizeName(createGauge("system.cpu.utilization", "1"), ""))
-	require.Equal(t, "system_disk_operation_time_seconds_total", normalizeName(createCounter("system.disk.operation_time", "s"), ""))
-	require.Equal(t, "system_cpu_load_average_15m_ratio", normalizeName(createGauge("system.cpu.load_average.15m", "1"), ""))
-	require.Equal(t, "memcached_operation_hit_ratio_percent", normalizeName(createGauge("memcached.operation_hit_ratio", "%"), ""))
-	require.Equal(t, "mongodbatlas_process_asserts_per_second", normalizeName(createGauge("mongodbatlas.process.asserts", "{assertions}/s"), ""))
-	require.Equal(t, "mongodbatlas_process_journaling_data_files_mebibytes", normalizeName(createGauge("mongodbatlas.process.journaling.data_files", "MiBy"), ""))
-	require.Equal(t, "mongodbatlas_process_network_io_bytes_per_second", normalizeName(createGauge("mongodbatlas.process.network.io", "By/s"), ""))
-	require.Equal(t, "mongodbatlas_process_oplog_rate_gibibytes_per_hour", normalizeName(createGauge("mongodbatlas.process.oplog.rate", "GiBy/h"), ""))
-	require.Equal(t, "mongodbatlas_process_db_query_targeting_scanned_per_returned", normalizeName(createGauge("mongodbatlas.process.db.query_targeting.scanned_per_returned", "{scanned}/{returned}"), ""))
-	require.Equal(t, "nginx_requests", normalizeName(createGauge("nginx.requests", "requests"), ""))
-	require.Equal(t, "nginx_connections_accepted", normalizeName(createGauge("nginx.connections_accepted", "connections"), ""))
-	require.Equal(t, "nsxt_node_memory_usage_kilobytes", normalizeName(createGauge("nsxt.node.memory.usage", "KBy"), ""))
-	require.Equal(t, "redis_latest_fork_microseconds", normalizeName(createGauge("redis.latest_fork", "us"), ""))
+	require.Equal(t, "active_directory_ds_replication_network_io_bytes_total", normalizeName(createCounter("active_directory.ds.replication.network.io", "By"), "", false))
+	require.Equal(t, "active_directory_ds_replication_sync_object_pending_total", normalizeName(createCounter("active_directory.ds.replication.sync.object.pending", "{objects}"), "", false))
+	require.Equal(t, "active_directory_ds_replication_object_rate_per_second", normalizeName(createGauge("active_directory.ds.replication.object.rate", "{objects}/s"), "", false))
+	require.Equal(t, "active_directory_ds_name_cache_hit_rate_percent", normalizeName(createGauge("active_directory.ds.name_cache.hit_rate", "%"), "", false))
+	require.Equal(t, "active_directory_ds_ldap_bind_last_successful_time_milliseconds", normalizeName(createGauge("active_directory.ds.ldap.bind.last_successful.time", "ms"), "", false))
+	require.Equal(t, "apache_current_connections", normalizeName(createGauge("apache.current_connections", "connections"), "", false))
+	require.Equal(t, "apache_workers_connections", normalizeName(createGauge("apache.workers", "connections"), "", false))
+	require.Equal(t, "apache_requests_total", normalizeName(createCounter("apache.requests", "1"), "", false))
+	require.Equal(t, "bigip_virtual_server_request_count_total", normalizeName(createCounter("bigip.virtual_server.request.count", "{requests}"), "", false))
+	require.Equal(t, "system_cpu_utilization_ratio", normalizeName(createGauge("system.cpu.utilization", "1"), "", false))
+	require.Equal(t, "system_disk_operation_time_seconds_total", normalizeName(createCounter("system.disk.operation_time", "s"), "", false))
+	require.Equal(t, "system_cpu_load_average_15m_ratio", normalizeName(createGauge("system.cpu.load_average.15m", "1"), "", false))
+	require.Equal(t, "memcached_operation_hit_ratio_percent", normalizeName(createGauge("memcached.operation_hit_ratio", "%"), "", false))
+	require.Equal(t, "mongodbatlas_process_asserts_per_second", normalizeName(createGauge("mongodbatlas.process.asserts", "{assertions}/s"), "", false))
+	require.Equal(t, "mongodbatlas_process_journaling_data_files_mebibytes", normalizeName(createGauge("mongodbatlas.process.journaling.data_files", "MiBy"), "", false))
+	require.Equal(t, "mongodbatlas_process_network_io_bytes_per_second", normalizeName(createGauge("mongodbatlas.process.network.io", "By/s"), "", false))
+	require.Equal(t, "mongodbatlas_process_oplog_rate_gibibytes_per_hour", normalizeName(createGauge("mongodbatlas.process.oplog.rate", "GiBy/h"), "", false))
+	require.Equal(t, "mongodbatlas_process_db_query_targeting_scanned_per_returned", normalizeName(createGauge("mongodbatlas.process.db.query_targeting.scanned_per_returned", "{scanned}/{returned}"), "", false))
+	require.Equal(t, "nginx_requests", normalizeName(createGauge("nginx.requests", "requests"), "", false))
+	require.Equal(t, "nginx_connections_accepted", normalizeName(createGauge("nginx.connections_accepted", "connections"), "", false))
+	require.Equal(t, "nsxt_node_memory_usage_kilobytes", normalizeName(createGauge("nsxt.node.memory.usage", "KBy"), "", false))
+	require.Equal(t, "redis_latest_fork_microseconds", normalizeName(createGauge("redis.latest_fork", "us"), "", false))
 }
 
 func TestTrimPromSuffixes(t *testing.T) {
@@ -144,8 +171,8 @@ func TestTrimPromSuffixes(t *testing.T) {
 }
 
 func TestNamespace(t *testing.T) {
-	require.Equal(t, "space_test", normalizeName(createGauge("test", ""), "space"))
-	require.Equal(t, "space_test", normalizeName(createGauge("#test", ""), "space"))
+	require.Equal(t, "space_test", normalizeName(createGauge("test", ""), "space", false))
+	require.Equal(t, "space_test", normalizeName(createGauge("#test", ""), "space", false))
 }
 
 func TestCleanUpUnit(t *testing.T) {
@@ -180,28 +207,28 @@ func TestRemoveItem(t *testing.T) {
 }
 
 func TestBuildCompliantNameWithSuffixes(t *testing.T) {
-	require.Equal(t, "system_io_bytes_total", BuildCompliantName(createCounter("system.io", "By"), "", true))
-	require.Equal(t, "system_network_io_bytes_total", BuildCompliantName(createCounter("network.io", "By"), "system", true))
-	require.Equal(t, "_3_14_digits", BuildCompliantName(createGauge("3.14 digits", ""), "", true))
-	require.Equal(t, "envoy_rule_engine_zlib_buf_error", BuildCompliantName(createGauge("envoy__rule_engine_zlib_buf_error", ""), "", true))
-	require.Equal(t, ":foo::bar", BuildCompliantName(createGauge(":foo::bar", ""), "", true))
-	require.Equal(t, ":foo::bar_total", BuildCompliantName(createCounter(":foo::bar", ""), "", true))
+	require.Equal(t, "system_io_bytes_total", BuildCompliantName(createCounter("system.io", "By"), "", true, false))
+	require.Equal(t, "system_network_io_bytes_total", BuildCompliantName(createCounter("network.io", "By"), "system", true, false))
+	require.Equal(t, "_3_14_digits", BuildCompliantName(createGauge("3.14 digits", ""), "", true, false))
+	require.Equal(t, "envoy_rule_engine_zlib_buf_error", BuildCompliantName(createGauge("envoy__rule_engine_zlib_buf_error", ""), "", true, false))
+	require.Equal(t, ":foo::bar", BuildCompliantName(createGauge(":foo::bar", ""), "", true, false))
+	require.Equal(t, ":foo::bar_total", BuildCompliantName(createCounter(":foo::bar", ""), "", true, false))
 	// Gauges with unit 1 are considered ratios.
-	require.Equal(t, "foo_bar_ratio", BuildCompliantName(createGauge("foo.bar", "1"), "", true))
+	require.Equal(t, "foo_bar_ratio", BuildCompliantName(createGauge("foo.bar", "1"), "", true, false))
 	// Slashes in units are converted.
-	require.Equal(t, "system_io_foo_per_bar_total", BuildCompliantName(createCounter("system.io", "foo/bar"), "", true))
-	require.Equal(t, "metric_with_foreign_characters_total", BuildCompliantName(createCounter("metric_with_字符_foreign_characters", ""), "", true))
+	require.Equal(t, "system_io_foo_per_bar_total", BuildCompliantName(createCounter("system.io", "foo/bar"), "", true, false))
+	require.Equal(t, "metric_with_foreign_characters_total", BuildCompliantName(createCounter("metric_with_字符_foreign_characters", ""), "", true, false))
 }
 
 func TestBuildCompliantNameWithoutSuffixes(t *testing.T) {
-	require.Equal(t, "system_io", BuildCompliantName(createCounter("system.io", "By"), "", false))
-	require.Equal(t, "system_network_io", BuildCompliantName(createCounter("network.io", "By"), "system", false))
-	require.Equal(t, "system_network_I_O", BuildCompliantName(createCounter("network (I/O)", "By"), "system", false))
-	require.Equal(t, "_3_14_digits", BuildCompliantName(createGauge("3.14 digits", "By"), "", false))
-	require.Equal(t, "envoy__rule_engine_zlib_buf_error", BuildCompliantName(createGauge("envoy__rule_engine_zlib_buf_error", ""), "", false))
-	require.Equal(t, ":foo::bar", BuildCompliantName(createGauge(":foo::bar", ""), "", false))
-	require.Equal(t, ":foo::bar", BuildCompliantName(createCounter(":foo::bar", ""), "", false))
-	require.Equal(t, "foo_bar", BuildCompliantName(createGauge("foo.bar", "1"), "", false))
-	require.Equal(t, "system_io", BuildCompliantName(createCounter("system.io", "foo/bar"), "", false))
-	require.Equal(t, "metric_with___foreign_characters", BuildCompliantName(createCounter("metric_with_字符_foreign_characters", ""), "", false))
+	require.Equal(t, "system_io", BuildCompliantName(createCounter("system.io", "By"), "", false, false))
+	require.Equal(t, "system_network_io", BuildCompliantName(createCounter("network.io", "By"), "system", false, false))
+	require.Equal(t, "system_network_I_O", BuildCompliantName(createCounter("network (I/O)", "By"), "system", false, false))
+	require.Equal(t, "_3_14_digits", BuildCompliantName(createGauge("3.14 digits", "By"), "", false, false))
+	require.Equal(t, "envoy__rule_engine_zlib_buf_error", BuildCompliantName(createGauge("envoy__rule_engine_zlib_buf_error", ""), "", false, false))
+	require.Equal(t, ":foo::bar", BuildCompliantName(createGauge(":foo::bar", ""), "", false, false))
+	require.Equal(t, ":foo::bar", BuildCompliantName(createCounter(":foo::bar", ""), "", false, false))
+	require.Equal(t, "foo_bar", BuildCompliantName(createGauge("foo.bar", "1"), "", false, false))
+	require.Equal(t, "system_io", BuildCompliantName(createCounter("system.io", "foo/bar"), "", false, false))
+	require.Equal(t, "metric_with___foreign_characters", BuildCompliantName(createCounter("metric_with_字符_foreign_characters", ""), "", false, false))
 }

storage/remote/otlptranslator/prometheusremotewrite/helper.go

@@ -157,7 +157,7 @@ func createAttributes(resource pcommon.Resource, attributes pcommon.Map, setting
 	// map ensures no duplicate label names.
 	l := make(map[string]string, maxLabelCount)
 	for _, label := range labels {
-		var finalKey = prometheustranslator.NormalizeLabel(label.Name)
+		var finalKey = prometheustranslator.NormalizeLabel(label.Name, settings.AllowUTF8)
 		if existingValue, alreadyExists := l[finalKey]; alreadyExists {
 			l[finalKey] = existingValue + ";" + label.Value
 		} else {
@@ -166,7 +166,7 @@ func createAttributes(resource pcommon.Resource, attributes pcommon.Map, setting
 	}
 
 	for _, lbl := range promotedAttrs {
-		normalized := prometheustranslator.NormalizeLabel(lbl.Name)
+		normalized := prometheustranslator.NormalizeLabel(lbl.Name, settings.AllowUTF8)
 		if _, exists := l[normalized]; !exists {
 			l[normalized] = lbl.Value
 		}
@@ -205,7 +205,7 @@ func createAttributes(resource pcommon.Resource, attributes pcommon.Map, setting
 		}
 		// internal labels should be maintained
 		if !(len(name) > 4 && name[:2] == "__" && name[len(name)-2:] == "__") {
-			name = prometheustranslator.NormalizeLabel(name)
+			name = prometheustranslator.NormalizeLabel(name, settings.AllowUTF8)
 		}
 		l[name] = extras[i+1]
 	}

storage/remote/otlptranslator/prometheusremotewrite/histograms_test.go

@@ -762,7 +762,7 @@ func TestPrometheusConverter_addExponentialHistogramDataPoints(t *testing.T) {
 				Settings{
 					ExportCreatedMetric: true,
 				},
-				prometheustranslator.BuildCompliantName(metric, "", true),
+				prometheustranslator.BuildCompliantName(metric, "", true, true),
 			)
 			require.NoError(t, err)
 			require.Empty(t, annots)

storage/remote/otlptranslator/prometheusremotewrite/metrics_to_prw.go

@@ -38,6 +38,7 @@ type Settings struct {
 	ExportCreatedMetric       bool
 	AddMetricSuffixes         bool
 	SendMetadata              bool
+	AllowUTF8                 bool
 	PromoteResourceAttributes []string
 }
 
@@ -84,7 +85,7 @@ func (c *PrometheusConverter) FromMetrics(ctx context.Context, md pmetric.Metric
 					continue
 				}
 
-				promName := prometheustranslator.BuildCompliantName(metric, settings.Namespace, settings.AddMetricSuffixes)
+				promName := prometheustranslator.BuildCompliantName(metric, settings.Namespace, settings.AddMetricSuffixes, settings.AllowUTF8)
 
 				// handle individual metrics based on type
 				//exhaustive:enforce

storage/remote/otlptranslator/prometheusremotewrite/otlp_to_openmetrics_metadata.go

@@ -43,7 +43,7 @@ func otelMetricTypeToPromMetricType(otelMetric pmetric.Metric) prompb.MetricMeta
 	return prompb.MetricMetadata_UNKNOWN
 }
 
-func OtelMetricsToMetadata(md pmetric.Metrics, addMetricSuffixes bool) []*prompb.MetricMetadata {
+func OtelMetricsToMetadata(md pmetric.Metrics, addMetricSuffixes, allowUTF8 bool) []*prompb.MetricMetadata {
 	resourceMetricsSlice := md.ResourceMetrics()
 
 	metadataLength := 0
@@ -65,7 +65,7 @@ func OtelMetricsToMetadata(md pmetric.Metrics, addMetricSuffixes bool) []*prompb
 				metric := scopeMetrics.Metrics().At(k)
 				entry := prompb.MetricMetadata{
 					Type:             otelMetricTypeToPromMetricType(metric),
-					MetricFamilyName: prometheustranslator.BuildCompliantName(metric, "", addMetricSuffixes),
+					MetricFamilyName: prometheustranslator.BuildCompliantName(metric, "", addMetricSuffixes, allowUTF8),
 					Help:             metric.Description(),
 				}
 				metadata = append(metadata, &entry)

storage/remote/write_handler.go

@@ -513,6 +513,7 @@ func (h *otlpWriteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	converter := otlptranslator.NewPrometheusConverter()
 	annots, err := converter.FromMetrics(r.Context(), req.Metrics(), otlptranslator.Settings{
 		AddMetricSuffixes:         true,
+		AllowUTF8:                 otlpCfg.TranslationStrategy == config.NoUTF8EscapingWithSuffixes,
 		PromoteResourceAttributes: otlpCfg.PromoteResourceAttributes,
 	})
 	if err != nil {