[v2] Add temporary expvar extension

Signed-off-by: Yuri Shkuro <github@ysh.us>

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

@@ -1,5 +1,5 @@
 service:
-  extensions: [jaeger_storage, jaeger_query, remote_sampling, healthcheckv2]
+  extensions: [jaeger_storage, jaeger_query, remote_sampling, healthcheckv2, expvar]
   pipelines:
     traces:
       receivers: [otlp, jaeger, zipkin]
@@ -33,13 +33,16 @@ extensions:
     #   initial_sampling_probability: 0.1
     http:
     grpc:
-  
+
   healthcheckv2:
     use_v2: true
     http:
       endpoint: "0.0.0.0:13133"
     grpc:
 
+  expvar:
+    port: 27777
+
 receivers:
   otlp:
     protocols:

cmd/jaeger/internal/components.go

@@ -30,6 +30,7 @@ import (
 	"go.opentelemetry.io/collector/receiver/otlpreceiver"
 
 	"github.com/jaegertracing/jaeger/cmd/jaeger/internal/exporters/storageexporter"
+	"github.com/jaegertracing/jaeger/cmd/jaeger/internal/extension/expvar"
 	"github.com/jaegertracing/jaeger/cmd/jaeger/internal/extension/jaegerquery"
 	"github.com/jaegertracing/jaeger/cmd/jaeger/internal/extension/jaegerstorage"
 	"github.com/jaegertracing/jaeger/cmd/jaeger/internal/extension/remotesampling"
@@ -69,6 +70,7 @@ func (b builders) build() (otelcol.Factories, error) {
 		jaegerstorage.NewFactory(),
 		storagecleaner.NewFactory(),
 		remotesampling.NewFactory(),
+		expvar.NewFactory(),
 	)
 	if err != nil {
 		return otelcol.Factories{}, err

cmd/jaeger/internal/extension/expvar/README.md

@@ -0,0 +1,6 @@
+# expvar extension
+
+Adds a standard expvar HTTP handler to a port that allows introspection.
+
+This is a temporary implementaion until upstream ticket is address:
+https://github.com/open-telemetry/opentelemetry-collector/issues/11081

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

@@ -0,0 +1,17 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"github.com/asaskevich/govalidator"
+)
+
+type Config struct {
+	Port int `mapstructure:"port"`
+}
+
+func (cfg *Config) Validate() error {
+	_, err := govalidator.ValidateStruct(cfg)
+	return err
+}

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

@@ -0,0 +1,16 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestExtensionConfig(t *testing.T) {
+	config := createDefaultConfig().(*Config)
+	err := config.Validate()
+	require.NoError(t, err)
+}

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

@@ -0,0 +1,63 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"context"
+	"errors"
+	"expvar"
+	"fmt"
+	"net/http"
+	"time"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/component/componentstatus"
+	"go.opentelemetry.io/collector/extension"
+	"go.uber.org/zap"
+)
+
+var _ extension.Extension = (*expvarExtension)(nil)
+
+const (
+	Port = 27777
+)
+
+type expvarExtension struct {
+	config *Config
+	server *http.Server
+	telset component.TelemetrySettings
+}
+
+func newExtension(config *Config, telset component.TelemetrySettings) *expvarExtension {
+	return &expvarExtension{
+		config: config,
+		telset: telset,
+	}
+}
+
+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,
+	}
+	c.telset.Logger.Info("Starting expvar server", zap.String("addr", c.server.Addr))
+	go func() {
+		if err := c.server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			err = fmt.Errorf("error starting expvar server: %w", err)
+			componentstatus.ReportStatus(host, componentstatus.NewFatalErrorEvent(err))
+		}
+	}()
+
+	return nil
+}
+
+func (c *expvarExtension) Shutdown(ctx context.Context) error {
+	if c.server != nil {
+		if err := c.server.Shutdown(ctx); err != nil {
+			return fmt.Errorf("error shutting down expvar server: %w", err)
+		}
+	}
+	return nil
+}

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

@@ -0,0 +1,53 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/storage/storagetest"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestExpvarExtension(t *testing.T) {
+	tests := []struct {
+		name   string
+		status int
+	}{
+		{
+			name:   "good storage",
+			status: http.StatusOK,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			config := &Config{
+				Port: Port,
+			}
+			s := newExtension(config, component.TelemetrySettings{
+				Logger: zaptest.NewLogger(t),
+			})
+			require.NoError(t, s.Start(context.Background(), storagetest.NewStorageHost()))
+			defer s.Shutdown(context.Background())
+
+			addr := fmt.Sprintf("http://0.0.0.0:%d/", Port)
+			client := &http.Client{}
+			require.Eventually(t, func() bool {
+				r, err := http.NewRequest(http.MethodPost, addr, nil)
+				require.NoError(t, err)
+				resp, err := client.Do(r)
+				require.NoError(t, err)
+				defer resp.Body.Close()
+				return test.status == resp.StatusCode
+			}, 5*time.Second, 100*time.Millisecond)
+		})
+	}
+}

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

@@ -0,0 +1,40 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"context"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/extension"
+)
+
+// componentType is the name of this extension in configuration.
+var componentType = component.MustNewType("expvar")
+
+// ID is the identifier of this extension.
+var ID = component.NewID(componentType)
+
+func NewFactory() extension.Factory {
+	return extension.NewFactory(
+		componentType,
+		createDefaultConfig,
+		createExtension,
+		component.StabilityLevelBeta,
+	)
+}
+
+func createDefaultConfig() component.Config {
+	return &Config{
+		Port: Port,
+	}
+}
+
+func createExtension(
+	_ context.Context,
+	set extension.Settings,
+	cfg component.Config,
+) (extension.Extension, error) {
+	return newExtension(cfg.(*Config), set.TelemetrySettings), nil
+}

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

@@ -0,0 +1,28 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component/componenttest"
+	"go.opentelemetry.io/collector/extension/extensiontest"
+)
+
+func TestCreateDefaultConfig(t *testing.T) {
+	cfg := createDefaultConfig().(*Config)
+	require.NotNil(t, cfg, "failed to create default config")
+	require.NoError(t, componenttest.CheckConfigStruct(cfg))
+}
+
+func TestCreateExtension(t *testing.T) {
+	cfg := createDefaultConfig().(*Config)
+	f := NewFactory()
+	r, err := f.CreateExtension(context.Background(), extensiontest.NewNopSettings(), cfg)
+	require.NoError(t, err)
+	assert.NotNil(t, r)
+}

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

@@ -0,0 +1,14 @@
+// Copyright (c) 2024 The Jaeger Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package expvar
+
+import (
+	"testing"
+
+	"github.com/jaegertracing/jaeger/pkg/testutils"
+)
+
+func TestMain(m *testing.M) {
+	testutils.VerifyGoLeaks(m)
+}