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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
// Package x contains support for OTel metric SDK experimental features.
//
// This package should only be used for features defined in the specification.
// It should not be used for experiments or new project ideas.
package x // import "go.opentelemetry.io/otel/sdk/metric/internal/x"
import (
"os"
"strconv"
"strings"
)
var (
// Exemplars is an experimental feature flag that defines if exemplars
// should be recorded for metric data-points.
//
// To enable this feature set the OTEL_GO_X_EXEMPLAR environment variable
// to the case-insensitive string value of "true" (i.e. "True" and "TRUE"
// will also enable this).
Exemplars = newFeature("EXEMPLAR", func(v string) (string, bool) {
if strings.ToLower(v) == "true" {
return v, true
}
return "", false
})
// CardinalityLimit is an experimental feature flag that defines if
// cardinality limits should be applied to the recorded metric data-points.
//
// To enable this feature set the OTEL_GO_X_CARDINALITY_LIMIT environment
// variable to the integer limit value you want to use.
//
// Setting OTEL_GO_X_CARDINALITY_LIMIT to a value less than or equal to 0
// will disable the cardinality limits.
CardinalityLimit = newFeature("CARDINALITY_LIMIT", func(v string) (int, bool) {
n, err := strconv.Atoi(v)
if err != nil {
return 0, false
}
return n, true
})
)
// Feature is an experimental feature control flag. It provides a uniform way
// to interact with these feature flags and parse their values.
type Feature[T any] struct {
key string
parse func(v string) (T, bool)
}
func newFeature[T any](suffix string, parse func(string) (T, bool)) Feature[T] {
const envKeyRoot = "OTEL_GO_X_"
return Feature[T]{
key: envKeyRoot + suffix,
parse: parse,
}
}
// Key returns the environment variable key that needs to be set to enable the
// feature.
func (f Feature[T]) Key() string { return f.key }
// Lookup returns the user configured value for the feature and true if the
// user has enabled the feature. Otherwise, if the feature is not enabled, a
// zero-value and false are returned.
func (f Feature[T]) Lookup() (v T, ok bool) {
// https://github.com/open-telemetry/opentelemetry-specification/blob/62effed618589a0bec416a87e559c0a9d96289bb/specification/configuration/sdk-environment-variables.md#parsing-empty-value
//
// > The SDK MUST interpret an empty value of an environment variable the
// > same way as when the variable is unset.
vRaw := os.Getenv(f.key)
if vRaw == "" {
return v, ok
}
return f.parse(vRaw)
}
// Enabled returns if the feature is enabled.
func (f Feature[T]) Enabled() bool {
_, ok := f.Lookup()
return ok
}
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