Notify extensions of the Collector's effective configuration (#6833)

**Description:**

This adds an optional `ConfigWatcher` interface that extensions can
implement if they want to be notified of the effective configuration
that is used by the Collector.

I don't feel very strongly about any of the decisions I made in this PR,
so I am open to input if we would like to take a different approach
anywhere. I will leave some comments to explain the decisions I made.

**Link to tracking Issue:**
Closes
#6596

**Testing:**

I've made minimal unit test changes, but I expect to write more tests
once there is consensus on the direction for implementing this
functionality. I have done some manual testing to show that an extension
can get a YAML representation of the effective config using two YAML
input files.

---------

Co-authored-by: Evan Bradley <evan-bradley@users.noreply.github.com>

.chloggen/configwatcher-interface.yaml

@@ -0,0 +1,16 @@
+# 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. otlpreceiver)
+component: extension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add optional `ConfigWatcher` interface
+
+# One or more tracking issues or pull requests related to the change
+issues: [6596]
+
+# (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: Extensions implementing this interface will be notified of the Collector's effective config.

.chloggen/extension-effective-config.yaml

@@ -0,0 +1,18 @@
+# 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. otlpreceiver)
+component: otelcol
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add optional `ConfmapProvider` interface for Config Providers
+
+# One or more tracking issues or pull requests related to the change
+issues: [6596]
+
+# (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 allows providing the Collector's configuration as a marshaled confmap.Conf object
+  from a ConfigProvider

.chloggen/servicesettings-confmap.yaml

@@ -0,0 +1,17 @@
+# 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. otlpreceiver)
+component: service
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add `CollectorConf` field to `service.Settings`
+
+# One or more tracking issues or pull requests related to the change
+issues: [6596]
+
+# (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 field is intended to be used by the Collector to pass its effective configuration to the service.

extension/extension.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/confmap"
 )
 
 // Extension is the interface for objects hosted by the OpenTelemetry Collector that
@@ -32,6 +33,13 @@ type PipelineWatcher interface {
 	NotReady() error
 }
 
+// ConfigWatcher is an interface that should be implemented by an extension that
+// wishes to be notified of the Collector's effective configuration.
+type ConfigWatcher interface {
+	// NotifyConfig notifies the extension of the Collector's current effective configuration.
+	NotifyConfig(ctx context.Context, conf *confmap.Conf) error
+}
+
 // CreateSettings is passed to Factory.Create(...) function.
 type CreateSettings struct {
 	// ID returns the ID of the component that will be created.

otelcol/collector.go

@@ -18,6 +18,7 @@ import (
 	"go.uber.org/zap"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/confmap"
 	"go.opentelemetry.io/collector/connector"
 	"go.opentelemetry.io/collector/exporter"
 	"go.opentelemetry.io/collector/extension"
@@ -143,6 +144,17 @@ func (col *Collector) Shutdown() {
 func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 	col.setCollectorState(StateStarting)
 
+	var conf *confmap.Conf
+
+	if cp, ok := col.set.ConfigProvider.(ConfmapProvider); ok {
+		var err error
+		conf, err = cp.GetConfmap(ctx)
+
+		if err != nil {
+			return fmt.Errorf("failed to resolve config: %w", err)
+		}
+	}
+
 	cfg, err := col.set.ConfigProvider.Get(ctx, col.set.Factories)
 	if err != nil {
 		return fmt.Errorf("failed to get config: %w", err)
@@ -154,6 +166,7 @@ func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 
 	col.service, err = service.New(ctx, service.Settings{
 		BuildInfo:         col.set.BuildInfo,
+		CollectorConf:     conf,
 		Receivers:         receiver.NewBuilder(cfg.Receivers, col.set.Factories.Receivers),
 		Processors:        processor.NewBuilder(cfg.Processors, col.set.Factories.Processors),
 		Exporters:         exporter.NewBuilder(cfg.Exporters, col.set.Factories.Exporters),
@@ -174,6 +187,7 @@ func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 		return multierr.Combine(err, col.service.Shutdown(ctx))
 	}
 	col.setCollectorState(StateRunning)
+
 	return nil
 }
 

otelcol/collector_test.go

@@ -17,6 +17,8 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/confmap"
+	"go.opentelemetry.io/collector/confmap/converter/expandconverter"
 )
 
 func TestStateString(t *testing.T) {
@@ -369,6 +371,31 @@ func TestCollectorDryRun(t *testing.T) {
 	require.Error(t, col.DryRun(context.Background()))
 }
 
+func TestPassConfmapToServiceFailure(t *testing.T) {
+	factories, err := nopFactories()
+	require.NoError(t, err)
+
+	cfgProvider, err := NewConfigProvider(ConfigProviderSettings{
+		ResolverSettings: confmap.ResolverSettings{
+			URIs:       []string{filepath.Join("testdata", "otelcol-invalid.yaml")},
+			Providers:  makeMapProvidersMap(newFailureProvider()),
+			Converters: []confmap.Converter{expandconverter.New()},
+		},
+	})
+	require.NoError(t, err)
+
+	set := CollectorSettings{
+		BuildInfo:      component.NewDefaultBuildInfo(),
+		Factories:      factories,
+		ConfigProvider: cfgProvider,
+	}
+	col, err := NewCollector(set)
+	require.NoError(t, err)
+
+	err = col.Run(context.Background())
+	require.Error(t, err)
+}
+
 func startCollector(ctx context.Context, t *testing.T, col *Collector) *sync.WaitGroup {
 	wg := &sync.WaitGroup{}
 	wg.Add(1)
@@ -378,3 +405,21 @@ func startCollector(ctx context.Context, t *testing.T, col *Collector) *sync.Wai
 	}()
 	return wg
 }
+
+type failureProvider struct{}
+
+func newFailureProvider() confmap.Provider {
+	return &failureProvider{}
+}
+
+func (fmp *failureProvider) Retrieve(_ context.Context, _ string, _ confmap.WatcherFunc) (*confmap.Retrieved, error) {
+	return nil, errors.New("a failure occurred during configuration retrieval")
+}
+
+func (*failureProvider) Scheme() string {
+	return "file"
+}
+
+func (*failureProvider) Shutdown(context.Context) error {
+	return nil
+}

otelcol/configprovider.go

@@ -50,10 +50,26 @@ type ConfigProvider interface {
 	Shutdown(ctx context.Context) error
 }
 
+// ConfmapProvider is an optional interface to be implemented by ConfigProviders
+// to provide confmap.Conf objects representing a marshaled version of the
+// Collector's configuration.
+//
+// The purpose of this interface is that otelcol.ConfigProvider structs do not
+// necessarily need to use confmap.Conf as their underlying config structure.
+type ConfmapProvider interface {
+	// GetConfmap resolves the Collector's configuration and provides it as a confmap.Conf object.
+	//
+	// Should never be called concurrently with itself or any ConfigProvider method.
+	GetConfmap(ctx context.Context) (*confmap.Conf, error)
+}
+
 type configProvider struct {
 	mapResolver *confmap.Resolver
 }
 
+var _ ConfigProvider = &configProvider{}
+var _ ConfmapProvider = &configProvider{}
+
 // ConfigProviderSettings are the settings to configure the behavior of the ConfigProvider.
 type ConfigProviderSettings struct {
 	// ResolverSettings are the settings to configure the behavior of the confmap.Resolver.
@@ -106,6 +122,15 @@ func (cm *configProvider) Shutdown(ctx context.Context) error {
 	return cm.mapResolver.Shutdown(ctx)
 }
 
+func (cm *configProvider) GetConfmap(ctx context.Context) (*confmap.Conf, error) {
+	conf, err := cm.mapResolver.Resolve(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("cannot resolve the configuration: %w", err)
+	}
+
+	return conf, nil
+}
+
 func newDefaultConfigProviderSettings(uris []string) ConfigProviderSettings {
 	return ConfigProviderSettings{
 		ResolverSettings: confmap.ResolverSettings{

otelcol/configprovider_test.go

@@ -11,69 +11,36 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"go.uber.org/zap/zapcore"
+	"gopkg.in/yaml.v3"
 
-	"go.opentelemetry.io/collector/component"
-	"go.opentelemetry.io/collector/config/configtelemetry"
 	"go.opentelemetry.io/collector/confmap"
 	"go.opentelemetry.io/collector/confmap/provider/fileprovider"
 	"go.opentelemetry.io/collector/confmap/provider/yamlprovider"
-	"go.opentelemetry.io/collector/connector/connectortest"
-	"go.opentelemetry.io/collector/exporter/exportertest"
-	"go.opentelemetry.io/collector/extension/extensiontest"
-	"go.opentelemetry.io/collector/processor/processortest"
-	"go.opentelemetry.io/collector/receiver/receivertest"
-	"go.opentelemetry.io/collector/service"
-	"go.opentelemetry.io/collector/service/pipelines"
-	"go.opentelemetry.io/collector/service/telemetry"
 )
 
-var configNop = &Config{
-	Receivers:  map[component.ID]component.Config{component.NewID("nop"): receivertest.NewNopFactory().CreateDefaultConfig()},
-	Processors: map[component.ID]component.Config{component.NewID("nop"): processortest.NewNopFactory().CreateDefaultConfig()},
-	Exporters:  map[component.ID]component.Config{component.NewID("nop"): exportertest.NewNopFactory().CreateDefaultConfig()},
-	Connectors: map[component.ID]component.Config{component.NewIDWithName("nop", "con"): connectortest.NewNopFactory().CreateDefaultConfig()},
-	Extensions: map[component.ID]component.Config{component.NewID("nop"): extensiontest.NewNopFactory().CreateDefaultConfig()},
-	Service: service.Config{
-		Extensions: []component.ID{component.NewID("nop")},
-		Pipelines: pipelines.Config{
-			component.NewID("traces"): {
-				Receivers:  []component.ID{component.NewID("nop")},
-				Processors: []component.ID{component.NewID("nop")},
-				Exporters:  []component.ID{component.NewID("nop"), component.NewIDWithName("nop", "con")},
-			},
-			component.NewID("metrics"): {
-				Receivers:  []component.ID{component.NewID("nop")},
-				Processors: []component.ID{component.NewID("nop")},
-				Exporters:  []component.ID{component.NewID("nop")},
-			},
-			component.NewID("logs"): {
-				Receivers:  []component.ID{component.NewID("nop"), component.NewIDWithName("nop", "con")},
-				Processors: []component.ID{component.NewID("nop")},
-				Exporters:  []component.ID{component.NewID("nop")},
-			},
-		},
-		Telemetry: telemetry.Config{
-			Logs: telemetry.LogsConfig{
-				Level:       zapcore.InfoLevel,
-				Development: false,
-				Encoding:    "console",
-				Sampling: &telemetry.LogsSamplingConfig{
-					Initial:    100,
-					Thereafter: 100,
-				},
-				OutputPaths:       []string{"stderr"},
-				ErrorOutputPaths:  []string{"stderr"},
-				DisableCaller:     false,
-				DisableStacktrace: false,
-				InitialFields:     map[string]any(nil),
-			},
-			Metrics: telemetry.MetricsConfig{
-				Level:   configtelemetry.LevelBasic,
-				Address: "localhost:8888",
-			},
-		},
-	},
+func newConfig(yamlBytes []byte, factories Factories) (*Config, error) {
+	var stringMap = map[string]interface{}{}
+	err := yaml.Unmarshal(yamlBytes, stringMap)
+
+	if err != nil {
+		return nil, err
+	}
+
+	conf := confmap.NewFromStringMap(stringMap)
+
+	cfg, err := unmarshal(conf, factories)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Config{
+		Receivers:  cfg.Receivers.Configs(),
+		Processors: cfg.Processors.Configs(),
+		Exporters:  cfg.Exporters.Configs(),
+		Connectors: cfg.Connectors.Configs(),
+		Extensions: cfg.Extensions.Configs(),
+		Service:    cfg.Service,
+	}, nil
 }
 
 func TestConfigProviderYaml(t *testing.T) {
@@ -97,6 +64,10 @@ func TestConfigProviderYaml(t *testing.T) {
 
 	cfg, err := cp.Get(context.Background(), factories)
 	require.NoError(t, err)
+
+	configNop, err := newConfig(yamlBytes, factories)
+	require.NoError(t, err)
+
 	assert.EqualValues(t, configNop, cfg)
 }
 
@@ -118,5 +89,41 @@ func TestConfigProviderFile(t *testing.T) {
 
 	cfg, err := cp.Get(context.Background(), factories)
 	require.NoError(t, err)
+
+	yamlBytes, err := os.ReadFile(filepath.Join("testdata", "otelcol-nop.yaml"))
+	require.NoError(t, err)
+
+	configNop, err := newConfig(yamlBytes, factories)
+	require.NoError(t, err)
+
 	assert.EqualValues(t, configNop, cfg)
 }
+
+func TestGetConfmap(t *testing.T) {
+	uriLocation := "file:" + filepath.Join("testdata", "otelcol-nop.yaml")
+	provider := fileprovider.New()
+	set := ConfigProviderSettings{
+		ResolverSettings: confmap.ResolverSettings{
+			URIs:      []string{uriLocation},
+			Providers: map[string]confmap.Provider{provider.Scheme(): provider},
+		},
+	}
+
+	configBytes, err := os.ReadFile(filepath.Join("testdata", "otelcol-nop.yaml"))
+	require.NoError(t, err)
+
+	yamlMap := map[string]any{}
+	err = yaml.Unmarshal(configBytes, yamlMap)
+	require.NoError(t, err)
+
+	cp, err := NewConfigProvider(set)
+	require.NoError(t, err)
+
+	cmp, ok := cp.(ConfmapProvider)
+	require.True(t, ok)
+
+	cmap, err := cmp.GetConfmap(context.Background())
+	require.NoError(t, err)
+
+	assert.EqualValues(t, yamlMap, cmap.ToStringMap())
+}

service/extensions/extensions.go

@@ -12,6 +12,7 @@ import (
 	"go.uber.org/multierr"
 
 	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/confmap"
 	"go.opentelemetry.io/collector/extension"
 	"go.opentelemetry.io/collector/service/internal/components"
 	"go.opentelemetry.io/collector/service/internal/zpages"
@@ -72,6 +73,17 @@ func (bes *Extensions) NotifyPipelineNotReady() error {
 	return errs
 }
 
+func (bes *Extensions) NotifyConfig(ctx context.Context, conf *confmap.Conf) error {
+	var errs error
+	for _, ext := range bes.extMap {
+		if cw, ok := ext.(extension.ConfigWatcher); ok {
+			clonedConf := confmap.NewFromStringMap(conf.ToStringMap())
+			errs = multierr.Append(errs, cw.NotifyConfig(ctx, clonedConf))
+		}
+	}
+	return errs
+}
+
 func (bes *Extensions) GetExtensions() map[component.ID]component.Component {
 	result := make(map[component.ID]component.Component, len(bes.extMap))
 	for extID, v := range bes.extMap {