[chore] service/telemetry: introduce Factory interface

service/telemetry/otelconftelemetry/factory.go

@@ -4,7 +4,6 @@
 package otelconftelemetry // import "go.opentelemetry.io/collector/service/telemetry/otelconftelemetry"
 
 import (
-	"context"
 	"time"
 
 	config "go.opentelemetry.io/contrib/otelconf/v0.3.0"
@@ -23,29 +22,10 @@ var useLocalHostAsDefaultMetricsAddressFeatureGate = featuregate.GlobalRegistry(
 	featuregate.WithRegisterDescription("controls whether default Prometheus metrics server use localhost as the default host for their endpoints"),
 )
 
-// Factory is factory interface for telemetry providers.
-// This interface cannot be directly implemented. Implementations must
-// use the NewFactory to implement it.
-//
-// NOTE This API is experimental and will change soon - use at your own risk.
-// See https://github.com/open-telemetry/opentelemetry-collector/issues/4970
-type Factory interface {
-	// CreateDefaultConfig creates the default configuration for the telemetry.
-	CreateDefaultConfig() component.Config
-
-	// CreateProviders creates telemetry providers.
-	CreateProviders(context.Context, telemetry.Settings, component.Config) (telemetry.Providers, error)
-
-	// unexportedFactoryFunc is used to prevent external implementations of Factory.
-	unexportedFactoryFunc()
-}
-
-// NewFactory creates a new Factory.
-//
-// NOTE This API is experimental and will change soon - use at your own risk.
-// See https://github.com/open-telemetry/opentelemetry-collector/issues/4970
-func NewFactory() Factory {
-	return newFactory(createDefaultConfig, createProviders)
+// NewFactory creates a new telemetry.Factory that uses otelconf
+// to configure opentelemetry-go SDK telemetry providers.
+func NewFactory() telemetry.Factory {
+	return telemetry.NewFactory(createDefaultConfig, createProviders)
 }
 
 func createDefaultConfig() component.Config {

service/telemetry/telemetry.go

@@ -7,8 +7,11 @@ import (
 	"context"
 
 	"go.opentelemetry.io/otel/log"
+	nooplog "go.opentelemetry.io/otel/log/noop"
 	"go.opentelemetry.io/otel/metric"
+	noopmetric "go.opentelemetry.io/otel/metric/noop"
 	"go.opentelemetry.io/otel/trace"
+	nooptrace "go.opentelemetry.io/otel/trace/noop"
 	"go.uber.org/zap"
 
 	"go.opentelemetry.io/collector/component"
@@ -35,7 +38,7 @@ type Providers interface {
 	// Logger returns a zap.Logger that may be used by components to
 	// log their internal operations.
 	//
-	// NOTE: from the perspective of the Telemetry implementation,
+	// NOTE: from the perspective of the Providers implementation,
 	// this Logger and the LoggerProvider are independent. However,
 	// the service package will arrange for logs written to this
 	// logger to be copied to the LoggerProvider. The effective
@@ -57,7 +60,7 @@ type Providers interface {
 	TracerProvider() trace.TracerProvider
 }
 
-// Settings holds configuration for building Telemetry.
+// Settings holds configuration for building Providers.
 type Settings struct {
 	// BuildInfo contains build information about the collector.
 	BuildInfo component.BuildInfo
@@ -66,5 +69,94 @@ type Settings struct {
 	ZapOptions []zap.Option
 }
 
-// TODO create abstract Factory interface that is implemented by otelconftelemetry.
+// Factory is a factory interface for internal telemetry.
+//
+// This interface cannot be directly implemented. Implementations must
+// use the NewFactory to implement it.
+//
+// NOTE This API is experimental and will change soon - use at your own risk.
 // See https://github.com/open-telemetry/opentelemetry-collector/issues/4970
+type Factory interface {
+	// CreateDefaultConfig creates the default configuration for the telemetry.
+	CreateDefaultConfig() component.Config
+
+	// CreateProviders creates the logger, meter, and tracer providers for
+	// the collector's internal telemetry.
+	CreateProviders(context.Context, Settings, component.Config) (Providers, error)
+
+	// unexportedFactoryFunc is used to prevent external implementations of Factory.
+	unexportedFactoryFunc()
+}
+
+type FactoryOption interface {
+	applyOption(*factory)
+}
+
+// factoryOptionFunc is an FactoryOption created through a function.
+type factoryOptionFunc func(*factory)
+
+func (f factoryOptionFunc) applyOption(o *factory) {
+	f(o)
+}
+
+type factory struct {
+	component.CreateDefaultConfigFunc
+	createProvidersFunc CreateProvidersFunc
+}
+
+// NewFactory returns a Factory.
+//
+// If createProviders is nil, then the returned Factory's CreateProviders
+// method will return a Providers with noop telemetry providers.
+func NewFactory(
+	createDefaultConfig component.CreateDefaultConfigFunc,
+	createProviders CreateProvidersFunc,
+	opts ...FactoryOption,
+) Factory {
+	f := &factory{
+		CreateDefaultConfigFunc: createDefaultConfig,
+		createProvidersFunc:     createProviders,
+	}
+	for _, opt := range opts {
+		opt.applyOption(f)
+	}
+	return f
+}
+
+// CreateProvidersFunc is the equivalent of Factory.CreateProviders.
+type CreateProvidersFunc func(context.Context, Settings, component.Config) (Providers, error)
+
+func (*factory) unexportedFactoryFunc() {}
+
+func (f *factory) CreateProviders(ctx context.Context, settings Settings, cfg component.Config) (Providers, error) {
+	if f.createProvidersFunc == nil {
+		return nopProviders{}, nil
+	}
+	return f.createProvidersFunc(ctx, settings, cfg)
+}
+
+type nopProviders struct{}
+
+func (nopProviders) Shutdown(context.Context) error {
+	return nil
+}
+
+func (nopProviders) Resource() pcommon.Resource {
+	return pcommon.NewResource()
+}
+
+func (nopProviders) Logger() *zap.Logger {
+	return zap.NewNop()
+}
+
+func (nopProviders) LoggerProvider() log.LoggerProvider {
+	return nooplog.NewLoggerProvider()
+}
+
+func (nopProviders) MeterProvider() metric.MeterProvider {
+	return noopmetric.NewMeterProvider()
+}
+
+func (nopProviders) TracerProvider() trace.TracerProvider {
+	return nooptrace.NewTracerProvider()
+}

service/telemetry/telemetry_test.go

@@ -0,0 +1,73 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package telemetry // import "go.opentelemetry.io/collector/service/telemetry"
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	nooplog "go.opentelemetry.io/otel/log/noop"
+	noopmetric "go.opentelemetry.io/otel/metric/noop"
+	nooptrace "go.opentelemetry.io/otel/trace/noop"
+	"go.uber.org/zap"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/pdata/pcommon"
+)
+
+func TestNewFactory(t *testing.T) {
+	type contextKey struct{}
+	var config component.Config = new(struct{})
+	settings := Settings{BuildInfo: component.NewDefaultBuildInfo()}
+	ctx := context.WithValue(context.Background(), contextKey{}, 123)
+
+	var providers struct {
+		Providers
+	}
+	createProvidersFunc := func(ctx context.Context, set Settings, cfg component.Config) (Providers, error) {
+		assert.Equal(t, 123, ctx.Value(contextKey{}))
+		assert.Equal(t, settings, set)
+		assert.Equal(t, config, cfg)
+		return &providers, errors.New("not implemented")
+	}
+	factory := NewFactory(func() component.Config { return config }, createProvidersFunc)
+	require.NotNil(t, factory)
+
+	assert.Equal(t, config, factory.CreateDefaultConfig())
+	result, err := factory.CreateProviders(ctx, settings, config)
+	assert.Equal(t, &providers, result)
+	assert.EqualError(t, err, "not implemented")
+}
+
+func TestNewFactory_Nop(t *testing.T) {
+	// If the createProvidersFunc is nil, the factory will return
+	// a Providers implementation with no-op providers.
+	factory := NewFactory(nil, nil)
+	require.NotNil(t, factory)
+
+	providers, err := factory.CreateProviders(context.Background(), Settings{}, nil)
+	require.NoError(t, err)
+	require.NotNil(t, providers)
+
+	assert.Equal(t, pcommon.NewResource(), providers.Resource())
+	assert.Equal(t, zap.NewNop(), providers.Logger())
+	assert.Equal(t, nooplog.NewLoggerProvider(), providers.LoggerProvider())
+	assert.Equal(t, noopmetric.NewMeterProvider(), providers.MeterProvider())
+	assert.Equal(t, nooptrace.NewTracerProvider(), providers.TracerProvider())
+	assert.NoError(t, providers.Shutdown(context.Background()))
+}
+
+func TestNewFactory_Options(t *testing.T) {
+	var called []string
+	factory := NewFactory(nil, nil, factoryOptionFunc(func(*factory) {
+		called = append(called, "option1")
+	}), factoryOptionFunc(func(*factory) {
+		called = append(called, "option2")
+	}))
+	require.NotNil(t, factory)
+	assert.Equal(t, []string{"option1", "option2"}, called)
+}