[otelcol] Obtain the Collector's effective configuration from `otelco…

…l.Config` (#10139)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

The `otelcol.ConfmapProvider` interface accurately reports the config
provided to the Collector by the user, but fails to effectively report
the Collector's effective configuration. In particular, it misses:
* Default values for fields in Config structs.
* Transformations done to Config structs by their `Unmarshal` or
`Validate` methods.
* Custom marshaling of types after we know the type of the config. This
is most obvious with `configopaque.String`, where we want these values
to always be redacted when sent out of the Collector.

I think we should attempt to get the Collector's effective configuration
from `otelcol.Config` instead of using the map compiled by the
confmap.Resolver. This also allows us to get rid of
`otelcol.ConfmapProvider`.

I have manually tested this using an OpAMP Supervisor setup, but wasn't
able to add unit tests due to the way `otelcol.Collector` is written.

---------

Co-authored-by: Pablo Baeyens <pablo.baeyens@datadoghq.com>

.chloggen/better-effective-config.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# 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: Obtain the Collector's effective config from otelcol.Config 
+
+# One or more tracking issues or pull requests related to the change
+issues: [10139]
+
+# (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: "`otelcol.Collector` will now marshal `confmap.Conf` objects from `otelcol.Config` itself."
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

.chloggen/deprecate-confmapprovider.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: deprecation
+
+# 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: Deprecate `otelcol.ConfmapProvider`
+
+# One or more tracking issues or pull requests related to the change
+issues: [10139]
+
+# (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: "`otelcol.Collector` will now marshal `confmap.Conf` objects from `otelcol.Config` itself."
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

.chloggen/deprecate-getconfmap.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: deprecation
+
+# 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: Deprecate `(*otelcol.ConfigProvider).GetConfmap`
+
+# One or more tracking issues or pull requests related to the change
+issues: [10139]
+
+# (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: Call `(*confmap.Conf).Marshal(*otelcol.Config)` to get the Collector's configuration.
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

otelcol/collector.go

@@ -163,17 +163,6 @@ func (col *Collector) Shutdown() {
 func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 	col.setCollectorState(StateStarting)
 
-	var conf *confmap.Conf
-
-	if cp, ok := col.configProvider.(ConfmapProvider); ok {
-		var err error
-		conf, err = cp.GetConfmap(ctx)
-
-		if err != nil {
-			return fmt.Errorf("failed to resolve config: %w", err)
-		}
-	}
-
 	factories, err := col.set.Factories()
 	if err != nil {
 		return fmt.Errorf("failed to initialize factories: %w", err)
@@ -189,6 +178,12 @@ func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 
 	col.serviceConfig = &cfg.Service
 
+	conf := confmap.New()
+
+	if err = conf.Marshal(cfg); err != nil {
+		return fmt.Errorf("could not marshal configuration: %w", err)
+	}
+
 	col.service, err = service.New(ctx, service.Settings{
 		BuildInfo:         col.set.BuildInfo,
 		CollectorConf:     conf,

otelcol/collector_test.go

@@ -450,24 +450,6 @@ func TestCollectorDryRun(t *testing.T) {
 	}
 }
 
-func TestPassConfmapToServiceFailure(t *testing.T) {
-	set := CollectorSettings{
-		BuildInfo: component.NewDefaultBuildInfo(),
-		Factories: nopFactories,
-		ConfigProviderSettings: ConfigProviderSettings{
-			ResolverSettings: confmap.ResolverSettings{
-				URIs:              []string{filepath.Join("testdata", "otelcol-invalid.yaml")},
-				ProviderFactories: []confmap.ProviderFactory{confmap.NewProviderFactory(newFailureProvider)},
-			},
-		},
-	}
-	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)

otelcol/configprovider.go

@@ -58,6 +58,9 @@ type ConfigProvider interface {
 //
 // The purpose of this interface is that otelcol.ConfigProvider structs do not
 // necessarily need to use confmap.Conf as their underlying config structure.
+//
+// Deprecated: [v0.105.0] This interface is deprecated. otelcol.Collector will now obtain
+// a confmap.Conf object from the unmarshaled config itself.
 type ConfmapProvider interface {
 	// GetConfmap resolves the Collector's configuration and provides it as a confmap.Conf object.
 	//
@@ -70,7 +73,6 @@ type configProvider struct {
 }
 
 var _ ConfigProvider = (*configProvider)(nil)
-var _ ConfmapProvider = (*configProvider)(nil)
 
 // ConfigProviderSettings are the settings to configure the behavior of the ConfigProvider.
 type ConfigProviderSettings struct {
@@ -143,8 +145,11 @@ func (cm *configProvider) Shutdown(ctx context.Context) error {
 	return cm.mapResolver.Shutdown(ctx)
 }
 
+// Deprecated: [v0.105.0] Call `(*confmap.Conf).Marshal(*otelcol.Config)` to get
+// the Collector's configuration instead.
 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)
 	}