wip: allow utf8

Signed-off-by: Arthur Silva Sens <[email protected]>

exporter/prometheusexporter/README.md

@@ -60,6 +60,11 @@ Given the example, metrics will be available at `https://1.2.3.4:1234/metrics`.
 
 OpenTelemetry metric names and attributes are normalized to be compliant with Prometheus naming rules. [Details on this normalization process are described in the Prometheus translator module](../../pkg/translator/prometheus/).
 
+Prometheus 2.55.0 introduced support for UTF-8 characters behind the feature-flag `utf8-names`. Prometheus 3.0.0 and later accept UTF-8 by default. This means that name and attribute normalization is not required if you're using those versions.
+To allow UTF-8 characters to be exposed without normalization, start the collector with the feature gate: `--feature-gates=exporter.prometheus.allow_utf8`.
+
+The scraper must include `scaping=allow-utf-8` in the `Accept` header for UTF-8 characters to be exposed.
+
 ## Setting resource attributes as metric labels
 
 By default, resource attributes are added to a special metric called `target_info`. To select and group by metrics by resource attributes, you [need to do join on `target_info`](https://prometheus.io/docs/prometheus/latest/querying/operators/#many-to-one-and-one-to-many-vector-matches). For example, to select metrics with `k8s_namespace_name` attribute equal to `my-namespace`:

exporter/prometheusexporter/collector.go

@@ -109,11 +109,23 @@ func (c *collector) getMetricMetadata(metric pmetric.Metric, attributes pcommon.
 	keys := make([]string, 0, attributes.Len()+2) // +2 for job and instance labels.
 	values := make([]string, 0, attributes.Len()+2)
 
-	attributes.Range(func(k string, v pcommon.Value) bool {
-		keys = append(keys, prometheustranslator.NormalizeLabel(k))
-		values = append(values, v.AsString())
-		return true
-	})
+	var metricName string
+
+	if allowUTF8FeatureGate.IsEnabled() {
+		attributes.Range(func(k string, v pcommon.Value) bool {
+			keys = append(keys, k)
+			values = append(values, v.AsString())
+			return true
+		})
+		metricName = metric.Name()
+	} else {
+		attributes.Range(func(k string, v pcommon.Value) bool {
+			keys = append(keys, prometheustranslator.NormalizeLabel(k))
+			values = append(values, v.AsString())
+			return true
+		})
+		metricName = prometheustranslator.BuildCompliantName(metric, c.namespace, c.addMetricSuffixes)
+	}
 
 	if job, ok := extractJob(resourceAttrs); ok {
 		keys = append(keys, model.JobLabel)
@@ -125,7 +137,7 @@ func (c *collector) getMetricMetadata(metric pmetric.Metric, attributes pcommon.
 	}
 
 	return prometheus.NewDesc(
-		prometheustranslator.BuildCompliantName(metric, c.namespace, c.addMetricSuffixes),
+		metricName,
 		metric.Description(),
 		keys,
 		c.constLabels,

exporter/prometheusexporter/feature_gates.go

@@ -0,0 +1,15 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package prometheusexporter // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/prometheusexporter"
+
+import "go.opentelemetry.io/collector/featuregate"
+
+const allowUTF8FeatureGateName = "exporter.prometheus.allowUTF8"
+
+var allowUTF8FeatureGate = featuregate.GlobalRegistry().MustRegister(
+	allowUTF8FeatureGateName,
+	featuregate.StageAlpha,
+	featuregate.WithRegisterDescription("When enabled, metric names and labels will not be normalized to the traditional Prometheus naming rules, fundamentally allowing UTF-8 characters."),
+	featuregate.WithRegisterFromVersion("v0.110.0"),
+)

exporter/prometheusexporter/prometheus.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/prometheus/common/model"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/exporter"
 	"go.opentelemetry.io/collector/pdata/pmetric"
@@ -38,6 +39,11 @@ func newPrometheusExporter(config *Config, set exporter.Settings) (*prometheusEx
 	collector := newCollector(config, set.Logger)
 	registry := prometheus.NewRegistry()
 	_ = registry.Register(collector)
+
+	if allowUTF8FeatureGate.IsEnabled() {
+		model.NameValidationScheme = model.UTF8Validation
+	}
+
 	return &prometheusExporter{
 		config:       *config,
 		name:         set.ID.String(),