forked from toolshed/abra
66 lines
2.1 KiB
Go
66 lines
2.1 KiB
Go
// Copyright The OpenTelemetry Authors
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// SPDX-License-Identifier: Apache-2.0
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// Package x contains support for OTel metric SDK experimental features.
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//
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// This package should only be used for features defined in the specification.
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// It should not be used for experiments or new project ideas.
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package x // import "go.opentelemetry.io/otel/sdk/metric/internal/x"
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import (
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"context"
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"os"
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)
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// Feature is an experimental feature control flag. It provides a uniform way
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// to interact with these feature flags and parse their values.
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type Feature[T any] struct {
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key string
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parse func(v string) (T, bool)
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}
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//nolint:unused
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func newFeature[T any](suffix string, parse func(string) (T, bool)) Feature[T] {
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const envKeyRoot = "OTEL_GO_X_"
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return Feature[T]{
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key: envKeyRoot + suffix,
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parse: parse,
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}
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}
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// Key returns the environment variable key that needs to be set to enable the
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// feature.
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func (f Feature[T]) Key() string { return f.key }
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// Lookup returns the user configured value for the feature and true if the
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// user has enabled the feature. Otherwise, if the feature is not enabled, a
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// zero-value and false are returned.
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func (f Feature[T]) Lookup() (v T, ok bool) {
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// https://github.com/open-telemetry/opentelemetry-specification/blob/62effed618589a0bec416a87e559c0a9d96289bb/specification/configuration/sdk-environment-variables.md#parsing-empty-value
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//
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// > The SDK MUST interpret an empty value of an environment variable the
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// > same way as when the variable is unset.
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vRaw := os.Getenv(f.key)
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if vRaw == "" {
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return v, ok
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}
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return f.parse(vRaw)
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}
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// Enabled reports whether the feature is enabled.
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func (f Feature[T]) Enabled() bool {
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_, ok := f.Lookup()
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return ok
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}
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// EnabledInstrument informs whether the instrument is enabled.
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//
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// EnabledInstrument interface is implemented by synchronous instruments.
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type EnabledInstrument interface {
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// Enabled reports whether the instrument will process measurements for the given context.
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//
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// This function can be used in places where measuring an instrument
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// would result in computationally expensive operations.
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Enabled(context.Context) bool
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}
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