[otelcol] Allow passing confmap.Providers to otelcol.Collector (#9228)

**Description:**

One way to work toward
#4759.
This implements the second approach that I've outlined here:
#4759 (comment).

I think the main advantage of this approach is that it cleans up the API
for the package. `otelcol.ConfigProvider` is a fairly thin wrapper
around `confmap.Resolver`, so I think we could ultimately remove the
interface, and any custom functionality for config merging or
unmarshaling could be exposed to users through settings rather through a
custom implementation.

**Link to tracking Issue:**

Works toward
#4759

**Testing:**

Unit tests

**Documentation:**

Added Godoc comments.

Author: evan-bradley

.chloggen/pass-confmap-providers.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: 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 `ConfigProviderSettings` to `CollectorSettings`
+
+# One or more tracking issues or pull requests related to the change
+issues: [4759]
+
+# (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 passing a custom list of `confmap.Provider`s to `otelcol.NewCommand`.
+
+# 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: []

otelcol/collector.go

@@ -7,7 +7,6 @@ package otelcol // import "go.opentelemetry.io/collector/otelcol"
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"os"
 	"os/signal"
@@ -66,10 +65,16 @@ type CollectorSettings struct {
 	// and manually handle the signals to shutdown the collector.
 	DisableGracefulShutdown bool
 
+	// Deprecated: [v0.95.0] Use ConfigProviderSettings instead.
 	// ConfigProvider provides the service configuration.
 	// If the provider watches for configuration change, collector may reload the new configuration upon changes.
 	ConfigProvider ConfigProvider
 
+	// ConfigProviderSettings allows configuring the way the Collector retrieves its configuration
+	// The Collector will reload based on configuration changes from the ConfigProvider if any
+	// confmap.Providers watch for configuration changes.
+	ConfigProviderSettings ConfigProviderSettings
+
 	// LoggingOptions provides a way to change behavior of zap logging.
 	LoggingOptions []zap.Option
 
@@ -92,6 +97,8 @@ type CollectorSettings struct {
 type Collector struct {
 	set CollectorSettings
 
+	configProvider ConfigProvider
+
 	service *service.Service
 	state   *atomic.Int32
 
@@ -105,8 +112,14 @@ type Collector struct {
 
 // NewCollector creates and returns a new instance of Collector.
 func NewCollector(set CollectorSettings) (*Collector, error) {
-	if set.ConfigProvider == nil {
-		return nil, errors.New("invalid nil config provider")
+	var err error
+	configProvider := set.ConfigProvider
+
+	if configProvider == nil {
+		configProvider, err = NewConfigProvider(set.ConfigProviderSettings)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	state := &atomic.Int32{}
@@ -119,6 +132,7 @@ func NewCollector(set CollectorSettings) (*Collector, error) {
 		// the number of signals getting notified on is recommended.
 		signalsChannel:    make(chan os.Signal, 3),
 		asyncErrorChannel: make(chan error),
+		configProvider:    configProvider,
 	}, nil
 }
 
@@ -146,7 +160,7 @@ func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 
 	var conf *confmap.Conf
 
-	if cp, ok := col.set.ConfigProvider.(ConfmapProvider); ok {
+	if cp, ok := col.configProvider.(ConfmapProvider); ok {
 		var err error
 		conf, err = cp.GetConfmap(ctx)
 
@@ -159,7 +173,7 @@ func (col *Collector) setupConfigurationComponents(ctx context.Context) error {
 	if err != nil {
 		return fmt.Errorf("failed to initialize factories: %w", err)
 	}
-	cfg, err := col.set.ConfigProvider.Get(ctx, factories)
+	cfg, err := col.configProvider.Get(ctx, factories)
 	if err != nil {
 		return fmt.Errorf("failed to get config: %w", err)
 	}
@@ -215,7 +229,7 @@ func (col *Collector) DryRun(ctx context.Context) error {
 	if err != nil {
 		return fmt.Errorf("failed to initialize factories: %w", err)
 	}
-	cfg, err := col.set.ConfigProvider.Get(ctx, factories)
+	cfg, err := col.configProvider.Get(ctx, factories)
 	if err != nil {
 		return fmt.Errorf("failed to get config: %w", err)
 	}
@@ -243,7 +257,7 @@ func (col *Collector) Run(ctx context.Context) error {
 LOOP:
 	for {
 		select {
-		case err := <-col.set.ConfigProvider.Watch():
+		case err := <-col.configProvider.Watch():
 			if err != nil {
 				col.service.Logger().Error("Config watch failed", zap.Error(err))
 				break LOOP
@@ -280,7 +294,7 @@ func (col *Collector) shutdown(ctx context.Context) error {
 	// Accumulate errors and proceed with shutting down remaining components.
 	var errs error
 
-	if err := col.set.ConfigProvider.Shutdown(ctx); err != nil {
+	if err := col.configProvider.Shutdown(ctx); err != nil {
 		errs = multierr.Append(errs, fmt.Errorf("failed to shutdown config provider: %w", err))
 	}
 

otelcol/collector_test.go

@@ -18,7 +18,6 @@ import (
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/confmap"
-	"go.opentelemetry.io/collector/confmap/converter/expandconverter"
 	"go.opentelemetry.io/collector/extension/extensiontest"
 	"go.opentelemetry.io/collector/processor/processortest"
 )
@@ -32,13 +31,10 @@ func TestStateString(t *testing.T) {
 }
 
 func TestCollectorStartAsGoRoutine(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}))
-	require.NoError(t, err)
-
 	set := CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}),
 	}
 	col, err := NewCollector(set)
 	require.NoError(t, err)
@@ -56,13 +52,10 @@ func TestCollectorStartAsGoRoutine(t *testing.T) {
 }
 
 func TestCollectorCancelContext(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}))
-	require.NoError(t, err)
-
 	set := CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}),
 	}
 	col, err := NewCollector(set)
 	require.NoError(t, err)
@@ -119,13 +112,10 @@ func TestCollectorStateAfterConfigChange(t *testing.T) {
 }
 
 func TestCollectorReportError(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}))
-	require.NoError(t, err)
-
 	col, err := NewCollector(CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}),
 	})
 	require.NoError(t, err)
 
@@ -235,13 +225,10 @@ func TestComponentStatusWatcher(t *testing.T) {
 }
 
 func TestCollectorSendSignal(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}))
-	require.NoError(t, err)
-
 	col, err := NewCollector(CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}),
 	})
 	require.NoError(t, err)
 
@@ -266,13 +253,10 @@ func TestCollectorSendSignal(t *testing.T) {
 func TestCollectorFailedShutdown(t *testing.T) {
 	t.Skip("This test was using telemetry shutdown failure, switch to use a component that errors on shutdown.")
 
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}))
-	require.NoError(t, err)
-
 	col, err := NewCollector(CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}),
 	})
 	require.NoError(t, err)
 
@@ -294,16 +278,49 @@ func TestCollectorFailedShutdown(t *testing.T) {
 }
 
 func TestCollectorStartInvalidConfig(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}))
+	col, err := NewCollector(CollectorSettings{
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}),
+	})
 	require.NoError(t, err)
+	assert.Error(t, col.Run(context.Background()))
+}
+
+func TestNewCollectorInvalidConfigProviderSettings(t *testing.T) {
+	_, err := NewCollector(CollectorSettings{
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: ConfigProviderSettings{},
+	})
+	require.Error(t, err)
+}
+
+func TestNewCollectorUseConfig(t *testing.T) {
+	set := newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")})
 
 	col, err := NewCollector(CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: set,
 	})
 	require.NoError(t, err)
-	assert.Error(t, col.Run(context.Background()))
+	require.NotNil(t, col.configProvider)
+}
+
+func TestNewCollectorValidatesResolverSettings(t *testing.T) {
+	set := ConfigProviderSettings{
+		ResolverSettings: confmap.ResolverSettings{
+			URIs: []string{filepath.Join("testdata", "otelcol-nop.yaml")},
+		},
+	}
+
+	_, err := NewCollector(CollectorSettings{
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: set,
+	})
+	require.Error(t, err)
 }
 
 func TestCollectorStartWithTraceContextPropagation(t *testing.T) {
@@ -318,13 +335,10 @@ func TestCollectorStartWithTraceContextPropagation(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.file, func(t *testing.T) {
-			cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", tt.file)}))
-			require.NoError(t, err)
-
 			set := CollectorSettings{
-				BuildInfo:      component.NewDefaultBuildInfo(),
-				Factories:      nopFactories,
-				ConfigProvider: cfgProvider,
+				BuildInfo:              component.NewDefaultBuildInfo(),
+				Factories:              nopFactories,
+				ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", tt.file)}),
 			}
 
 			col, err := NewCollector(set)
@@ -353,13 +367,10 @@ func TestCollectorRun(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.file, func(t *testing.T) {
-			cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", tt.file)}))
-			require.NoError(t, err)
-
 			set := CollectorSettings{
-				BuildInfo:      component.NewDefaultBuildInfo(),
-				Factories:      nopFactories,
-				ConfigProvider: cfgProvider,
+				BuildInfo:              component.NewDefaultBuildInfo(),
+				Factories:              nopFactories,
+				ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", tt.file)}),
 			}
 			col, err := NewCollector(set)
 			require.NoError(t, err)
@@ -374,13 +385,10 @@ func TestCollectorRun(t *testing.T) {
 }
 
 func TestCollectorShutdownBeforeRun(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}))
-	require.NoError(t, err)
-
 	set := CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-nop.yaml")}),
 	}
 	col, err := NewCollector(set)
 	require.NoError(t, err)
@@ -396,14 +404,11 @@ func TestCollectorShutdownBeforeRun(t *testing.T) {
 }
 
 func TestCollectorClosedStateOnStartUpError(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}))
-	require.NoError(t, err)
-
 	// Load a bad config causing startup to fail
 	set := CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}),
 	}
 	col, err := NewCollector(set)
 	require.NoError(t, err)
@@ -416,14 +421,11 @@ func TestCollectorClosedStateOnStartUpError(t *testing.T) {
 }
 
 func TestCollectorDryRun(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}))
-	require.NoError(t, err)
-
 	// Load a bad config causing startup to fail
 	set := CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo:              component.NewDefaultBuildInfo(),
+		Factories:              nopFactories,
+		ConfigProviderSettings: newDefaultConfigProviderSettings([]string{filepath.Join("testdata", "otelcol-invalid.yaml")}),
 	}
 	col, err := NewCollector(set)
 	require.NoError(t, err)
@@ -432,19 +434,15 @@ func TestCollectorDryRun(t *testing.T) {
 }
 
 func TestPassConfmapToServiceFailure(t *testing.T) {
-	cfgProvider, err := NewConfigProvider(ConfigProviderSettings{
-		ResolverSettings: confmap.ResolverSettings{
-			URIs:       []string{filepath.Join("testdata", "otelcol-invalid.yaml")},
-			Providers:  makeMapProvidersMap(newFailureProvider()),
-			Converters: []confmap.Converter{expandconverter.New(confmap.ConverterSettings{})},
-		},
-	})
-	require.NoError(t, err)
-
 	set := CollectorSettings{
-		BuildInfo:      component.NewDefaultBuildInfo(),
-		Factories:      nopFactories,
-		ConfigProvider: cfgProvider,
+		BuildInfo: component.NewDefaultBuildInfo(),
+		Factories: nopFactories,
+		ConfigProviderSettings: ConfigProviderSettings{
+			ResolverSettings: confmap.ResolverSettings{
+				URIs:      []string{filepath.Join("testdata", "otelcol-invalid.yaml")},
+				Providers: makeMapProvidersMap(newFailureProvider()),
+			},
+		},
 	}
 	col, err := NewCollector(set)
 	require.NoError(t, err)