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Add internal localhostgate package #30774

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Jan 29, 2024
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29 changes: 29 additions & 0 deletions .chloggen/mx-psi_internal-localhostgate.yaml
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
# Use this changelog template to create an entry for release notes.

# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
change_type: enhancement

# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
component: all

# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
note: "Add `component.UseLocalHostAsDefaultHost` feature gate that changes default endpoints from 0.0.0.0 to localhost"

# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
issues: [30702]

# (Optional) One or more lines of additional information to render under the primary note.
# These lines will be padded with 2 spaces and then inserted directly into the document.
# Use pipe (|) for multiline entries.
subtext: |
This change affects the following components:
- TBF

# If your change doesn't affect end users or the exported elements of any package,
# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
# Optional: The change log or logs in which this entry should be included.
# e.g. '[user]' or '[user, api]'
# Include 'user' if the change is relevant to end users.
# Include 'api' if there is a change to a library API.
# Default: '[user]'
change_logs: []
69 changes: 69 additions & 0 deletions internal/common/localhostgate/featuregate.go
Original file line number Diff line number Diff line change
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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.uber.org/zap"

"go.opentelemetry.io/collector/featuregate"
)

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),
)
}
}
57 changes: 57 additions & 0 deletions internal/common/localhostgate/featuregate_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,57 @@
// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package localhostgate

import (
"testing"

"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"

"go.opentelemetry.io/collector/featuregate"
)

func setFeatureGateForTest(t testing.TB, gate *featuregate.Gate, enabled bool) func() {
originalValue := gate.IsEnabled()
require.NoError(t, featuregate.GlobalRegistry().Set(gate.ID(), enabled))
return func() {
require.NoError(t, featuregate.GlobalRegistry().Set(gate.ID(), originalValue))
}
}

func TestEndpointForPort(t *testing.T) {
tests := []struct {
port int
enabled bool
endpoint string
}{
{
port: 4317,
enabled: false,
endpoint: "0.0.0.0:4317",
},
{
port: 4317,
enabled: true,
endpoint: "localhost:4317",
},
{
port: 0,
enabled: false,
endpoint: "0.0.0.0:0",
},
{
port: 0,
enabled: true,
endpoint: "localhost:0",
},
}

for _, tt := range tests {
t.Run(tt.endpoint, func(t *testing.T) {
defer setFeatureGateForTest(t, useLocalHostAsDefaultHostfeatureGate, tt.enabled)()
assert.Equal(t, EndpointForPort(tt.port), tt.endpoint)
})
}
}
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