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featuregate.go
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featuregate.go
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
// package localhostgate defines a feature gate that controls whether server-like receivers and extensions use localhost as the default host for their endpoints.
// This package is duplicated across core and contrib to avoid exposing the feature gate as part of the public API.
// To do this we define a `registerOrLoad` helper and try to register the gate in both modules.
// IMPORTANT NOTE: ANY CHANGES TO THIS PACKAGE MUST BE MIRRORED IN THE CORE COUNTERPART.
// See https://github.com/open-telemetry/opentelemetry-collector/blob/main/internal/localhostgate/featuregate.go
package localhostgate // import "github.com/open-telemetry/opentelemetry-collector-contrib/internal/common/localhostgate"
import (
"errors"
"fmt"
"go.opentelemetry.io/collector/featuregate"
"go.uber.org/zap"
)
const UseLocalHostAsDefaultHostID = "component.UseLocalHostAsDefaultHost"
// useLocalHostAsDefaultHostfeatureGate is the feature gate that controls whether
// server-like receivers and extensions such as the OTLP receiver use localhost as the default host for their endpoints.
var useLocalHostAsDefaultHostfeatureGate = mustRegisterOrLoad(
featuregate.GlobalRegistry(),
UseLocalHostAsDefaultHostID,
featuregate.StageAlpha,
featuregate.WithRegisterDescription("controls whether server-like receivers and extensions such as the OTLP receiver use localhost as the default host for their endpoints"),
)
// mustRegisterOrLoad tries to register the feature gate and loads it if it already exists.
// It panics on any other error.
func mustRegisterOrLoad(reg *featuregate.Registry, id string, stage featuregate.Stage, opts ...featuregate.RegisterOption) *featuregate.Gate {
gate, err := reg.Register(id, stage, opts...)
if errors.Is(err, featuregate.ErrAlreadyRegistered) {
// Gate is already registered; find it.
// Only a handful of feature gates are registered, so it's fine to iterate over all of them.
reg.VisitAll(func(g *featuregate.Gate) {
if g.ID() == id {
gate = g
return
}
})
} else if err != nil {
panic(err)
}
return gate
}
// EndpointForPort gets the endpoint for a given port using localhost or 0.0.0.0 depending on the feature gate.
func EndpointForPort(port int) string {
host := "localhost"
if !useLocalHostAsDefaultHostfeatureGate.IsEnabled() {
host = "0.0.0.0"
}
return fmt.Sprintf("%s:%d", host, port)
}
// LogAboutUseLocalHostAsDefault logs about the upcoming change from 0.0.0.0 to localhost on server-like components.
func LogAboutUseLocalHostAsDefault(logger *zap.Logger) {
if !useLocalHostAsDefaultHostfeatureGate.IsEnabled() {
logger.Warn(
"The default endpoints for all servers in components will change to use localhost instead of 0.0.0.0 in a future version. Use the feature gate to preview the new default.",
zap.String("feature gate ID", UseLocalHostAsDefaultHostID),
)
}
}