Add 'features' command to print available feature gates (jaegertracin…

…g#6542)

## Which problem is this PR solving?
- Resolves jaegertracing#6442 

## Description of the changes
- 

## How was this change tested?
- make features

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [x] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `npm run lint` and `npm run test`

---------

Signed-off-by: cs-308-2023 <[email protected]>

cmd/jaeger/internal/features/display.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2025 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package features
+
+import (
+	"bytes"
+	"fmt"
+
+	"go.opentelemetry.io/collector/featuregate"
+)
+
+func DisplayFeatures() string {
+	f := featuregate.GlobalRegistry()
+	var buffer bytes.Buffer
+
+	f.VisitAll(func(g *featuregate.Gate) {
+		fmt.Fprintf(&buffer, "Feature:\t%s\n", g.ID())
+		if g.IsEnabled() {
+			fmt.Fprintf(&buffer, "Default state:\t%s\n", "On")
+		} else {
+			fmt.Fprintf(&buffer, "Default state:\t%s\n", "Off")
+		}
+		fmt.Fprintf(&buffer, "Description:\t%s\n", g.Description())
+		if ref := g.ReferenceURL(); ref != "" {
+			fmt.Fprintf(&buffer, "ReferenceURL:\t%s\n", ref)
+		}
+		fmt.Fprintln(&buffer)
+	})
+
+	return buffer.String()
+}

cmd/jaeger/internal/features/display_test.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2025 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package features
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/featuregate"
+
+	"github.com/jaegertracing/jaeger/pkg/testutils"
+)
+
+func TestMain(m *testing.M) {
+	testutils.VerifyGoLeaks(m)
+}
+
+func TestDisplayStageAlpha(t *testing.T) {
+	featuregate.GlobalRegistry().MustRegister(
+		"jaeger.featuresdisplay.testgate1",
+		featuregate.StageAlpha,
+		featuregate.WithRegisterDescription("testdescription"),
+		featuregate.WithRegisterReferenceURL("https://testurl.com"),
+	)
+	out := DisplayFeatures()
+	require.Contains(t, out, "jaeger.featuresdisplay.testgate")
+	require.Contains(t, out, "Off")
+}
+
+func TestDisplayStageBeta(t *testing.T) {
+	featuregate.GlobalRegistry().MustRegister(
+		"jaeger.featuresdisplay.testgate2",
+		featuregate.StageBeta,
+		featuregate.WithRegisterDescription("testdescription"),
+		featuregate.WithRegisterReferenceURL("https://testurl.com"),
+	)
+	out := DisplayFeatures()
+	require.Contains(t, out, "jaeger.featuresdisplay.testgate")
+	require.Contains(t, out, "On")
+}

cmd/jaeger/main.go

@@ -4,12 +4,15 @@
 package main
 
 import (
+	"fmt"
 	"log"
 
+	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 
 	"github.com/jaegertracing/jaeger/cmd/internal/docs"
 	"github.com/jaegertracing/jaeger/cmd/jaeger/internal"
+	"github.com/jaegertracing/jaeger/cmd/jaeger/internal/features"
 	"github.com/jaegertracing/jaeger/internal/storage/elasticsearch/mapping"
 	"github.com/jaegertracing/jaeger/pkg/config"
 	"github.com/jaegertracing/jaeger/pkg/version"
@@ -20,6 +23,7 @@ func main() {
 	command := internal.Command()
 	command.AddCommand(version.Command())
 	command.AddCommand(docs.Command(v))
+	command.AddCommand(featuresCommand())
 	command.AddCommand(mapping.Command())
 	config.AddFlags(
 		v,
@@ -30,3 +34,14 @@ func main() {
 		log.Fatal(err)
 	}
 }
+
+func featuresCommand() *cobra.Command {
+	return &cobra.Command{
+		Use:   "features",
+		Short: "Displays the list of supported features",
+		Long:  "The 'features' command shows all supported features in the current build of Jaeger.",
+		Run: func(_ *cobra.Command, _ []string) {
+			fmt.Print(features.DisplayFeatures())
+		},
+	}
+}