Use confighttp in expvar extension (#6227)

## Which problem is this PR solving?
- expvar extension configuration was using non-standard config that did
not allow specifying host to listen to

## Description of the changes
- Change it to use OTEL helper

## How was this change tested?
- `go run ./cmd/jaeger`
- `curl http://localhost:27777`

---------

Signed-off-by: Yuri Shkuro <[email protected]>

cmd/jaeger/internal/all-in-one.yaml

@@ -46,7 +46,7 @@ extensions:
     grpc:
 
   expvar:
-    port: 27777
+    endpoint: "${env:JAEGER_LISTEN_HOST:-localhost}:27777"
 
 receivers:
   otlp:

cmd/jaeger/internal/extension/expvar/config.go

@@ -5,10 +5,11 @@ package expvar
 
 import (
 	"github.com/asaskevich/govalidator"
+	"go.opentelemetry.io/collector/config/confighttp"
 )
 
 type Config struct {
-	Port int `mapstructure:"port"`
+	confighttp.ServerConfig `mapstructure:",squash"`
 }
 
 func (cfg *Config) Validate() error {

cmd/jaeger/internal/extension/expvar/extension.go

@@ -8,8 +8,9 @@ import (
 	"errors"
 	"expvar"
 	"fmt"
+	"net"
 	"net/http"
-	"time"
+	"sync"
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/component/componentstatus"
@@ -27,6 +28,8 @@ type expvarExtension struct {
 	config *Config
 	server *http.Server
 	telset component.TelemetrySettings
+
+	shutdownWG sync.WaitGroup
 }
 
 func newExtension(config *Config, telset component.TelemetrySettings) *expvarExtension {
@@ -36,20 +39,26 @@ func newExtension(config *Config, telset component.TelemetrySettings) *expvarExt
 	}
 }
 
-func (c *expvarExtension) Start(_ context.Context, host component.Host) error {
-	c.server = &http.Server{
-		Addr:              fmt.Sprintf(":%d", c.config.Port),
-		Handler:           expvar.Handler(),
-		ReadHeaderTimeout: 3 * time.Second,
+func (c *expvarExtension) Start(ctx context.Context, host component.Host) error {
+	server, err := c.config.ToServer(ctx, host, c.telset, expvar.Handler())
+	if err != nil {
+		return err
+	}
+	c.server = server
+	var hln net.Listener
+	if hln, err = c.config.ToListener(ctx); err != nil {
+		return err
 	}
-	c.telset.Logger.Info("Starting expvar server", zap.String("addr", c.server.Addr))
+	c.telset.Logger.Info("Starting expvar server", zap.Stringer("addr", hln.Addr()))
+	c.shutdownWG.Add(1)
 	go func() {
-		if err := c.server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		defer c.shutdownWG.Done()
+
+		if err := c.server.Serve(hln); err != nil && !errors.Is(err, http.ErrServerClosed) {
 			err = fmt.Errorf("error starting expvar server: %w", err)
 			componentstatus.ReportStatus(host, componentstatus.NewFatalErrorEvent(err))
 		}
 	}()
-
 	return nil
 }
 
@@ -58,6 +67,7 @@ func (c *expvarExtension) Shutdown(ctx context.Context) error {
 		if err := c.server.Shutdown(ctx); err != nil {
 			return fmt.Errorf("error shutting down expvar server: %w", err)
 		}
+		c.shutdownWG.Wait()
 	}
 	return nil
 }

cmd/jaeger/internal/extension/expvar/extension_test.go

@@ -13,6 +13,8 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/storage/storagetest"
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/configauth"
+	"go.opentelemetry.io/collector/config/confighttp"
 	"go.uber.org/zap/zaptest"
 )
 
@@ -30,7 +32,9 @@ func TestExpvarExtension(t *testing.T) {
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			config := &Config{
-				Port: Port,
+				ServerConfig: confighttp.ServerConfig{
+					Endpoint: "0.0.0.0:27777",
+				},
 			}
 			s := newExtension(config, component.TelemetrySettings{
 				Logger: zaptest.NewLogger(t),
@@ -51,3 +55,21 @@ func TestExpvarExtension(t *testing.T) {
 		})
 	}
 }
+
+func TestExpvarExtension_StartError(t *testing.T) {
+	config := &Config{
+		ServerConfig: confighttp.ServerConfig{
+			Endpoint: "0.0.0.0:27777",
+			Auth: &confighttp.AuthConfig{
+				Authentication: configauth.Authentication{
+					AuthenticatorID: component.MustNewID("invalid_auth"),
+				},
+			},
+		},
+	}
+	s := newExtension(config, component.TelemetrySettings{
+		Logger: zaptest.NewLogger(t),
+	})
+	err := s.Start(context.Background(), storagetest.NewStorageHost())
+	require.ErrorContains(t, err, "invalid_auth")
+}

cmd/jaeger/internal/extension/expvar/factory.go

@@ -5,8 +5,10 @@ package expvar
 
 import (
 	"context"
+	"fmt"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/confighttp"
 	"go.opentelemetry.io/collector/extension"
 )
 
@@ -27,7 +29,9 @@ func NewFactory() extension.Factory {
 
 func createDefaultConfig() component.Config {
 	return &Config{
-		Port: Port,
+		ServerConfig: confighttp.ServerConfig{
+			Endpoint: fmt.Sprintf("0.0.0.0:%d", Port),
+		},
 	}
 }