Config sources to support full remote config and value substitution

component/configsource.go

@@ -0,0 +1,37 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//       http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package component // import "go.opentelemetry.io/collector/component"
+
+import (
+	"context"
+
+	"go.opentelemetry.io/collector/config"
+	"go.opentelemetry.io/collector/config/configmapprovider"
+)
+
+// ConfigSource is a component that provides a configuration map or value.
+type ConfigSource interface {
+	configmapprovider.Provider
+}
+
+// ConfigSourceCreateSettings is passed to CreateConfigSource functions.
+type ConfigSourceCreateSettings struct {
+}
+
+type ConfigSourceFactory interface {
+	Factory
+	CreateDefaultConfig() config.ConfigSource
+	CreateConfigSource(ctx context.Context, set ConfigSourceCreateSettings, cfg config.ConfigSource) (configmapprovider.Provider, error)
+}

component/factories.go

@@ -34,6 +34,9 @@ type Factories struct {
 
 	// Extensions maps extension type names in the config to the respective factory.
 	Extensions map[config.Type]ExtensionFactory
+
+	// ConfigSources maps config source type names in the config to the respective factory.
+	ConfigSources map[config.Type]ConfigSourceFactory
 }
 
 // MakeReceiverFactoryMap takes a list of receiver factories and returns a map

config/configmapprovider/file.go

@@ -22,18 +22,18 @@ import (
 	"go.opentelemetry.io/collector/config"
 )
 
-type fileMapProvider struct {
+type FileMapProvider struct {
 	fileName string
 }
 
-// NewFile returns a new Provider that reads the configuration from the given file.
-func NewFile(fileName string) Provider {
-	return &fileMapProvider{
+// NewFile returns a new MapProvider that reads the configuration from the given file.
+func NewFile(fileName string) *FileMapProvider {
+	return &FileMapProvider{
 		fileName: fileName,
 	}
 }
 
-func (fmp *fileMapProvider) Retrieve(_ context.Context, _ func(*ChangeEvent)) (Retrieved, error) {
+func (fmp *FileMapProvider) Retrieve(_ context.Context, _ func(*ChangeEvent)) (RetrievedMap, error) {
 	if fmp.fileName == "" {
 		return nil, errors.New("config file not specified")
 	}
@@ -46,6 +46,21 @@ func (fmp *fileMapProvider) Retrieve(_ context.Context, _ func(*ChangeEvent)) (R
 	return &simpleRetrieved{confMap: cp}, nil
 }
 
-func (*fileMapProvider) Shutdown(context.Context) error {
+func (fmp *FileMapProvider) RetrieveValue(_ context.Context, _ func(*ChangeEvent), selector string, paramsConfigMap *config.Map) (RetrievedValue, error) {
+	if selector == "" {
+		return nil, errors.New("config file not specified")
+	}
+
+	// TODO: support multiple file paths in selector (use some sort of delimiter).
+
+	cp, err := config.NewMapFromFile(selector)
+	if err != nil {
+		return nil, fmt.Errorf("error loading config file %q: %w", fmp.fileName, err)
+	}
+
+	return &simpleRetrievedValue{value: cp}, nil
+}
+
+func (*FileMapProvider) Shutdown(context.Context) error {
 	return nil
 }

config/configmapprovider/inmemory.go

@@ -26,11 +26,11 @@ type inMemoryMapProvider struct {
 }
 
 // NewInMemory returns a new Provider that reads the configuration, from the provided buffer, as YAML.
-func NewInMemory(buf io.Reader) Provider {
+func NewInMemory(buf io.Reader) MapProvider {
 	return &inMemoryMapProvider{buf: buf}
 }
 
-func (inp *inMemoryMapProvider) Retrieve(_ context.Context, onChange func(*ChangeEvent)) (Retrieved, error) {
+func (inp *inMemoryMapProvider) Retrieve(_ context.Context, onChange func(*ChangeEvent)) (RetrievedMap, error) {
 	cfg, err := config.NewMapFromBuffer(inp.buf)
 	if err != nil {
 		return nil, err

config/configmapprovider/default.go → config/configmapprovider/local.go

@@ -14,11 +14,10 @@
 
 package configmapprovider // import "go.opentelemetry.io/collector/config/configmapprovider"
 
-// NewDefault returns the default Provider, and it creates configuration from a file
+// NewLocal returns a local MapProvider, and it creates configuration from a file
 // defined by the given configFile and overwrites fields using properties.
-func NewDefault(configFileName string, properties []string) Provider {
-	return NewExpand(
-		NewMerge(
-			NewFile(configFileName),
-			NewProperties(properties)))
+func NewLocal(configFileName string, properties []string) MapProvider {
+	return NewMerge(
+		NewFile(configFileName),
+		NewProperties(properties))
 }

config/configmapprovider/default_test.go → config/configmapprovider/local_test.go

@@ -25,8 +25,8 @@ import (
 	"go.opentelemetry.io/collector/config"
 )
 
-func TestDefaultMapProvider(t *testing.T) {
-	mp := NewDefault("testdata/default-config.yaml", nil)
+func TestLocalMapProvider(t *testing.T) {
+	mp := NewLocal("testdata/default-config.yaml", nil)
 	retr, err := mp.Retrieve(context.Background(), nil)
 	require.NoError(t, err)
 
@@ -44,8 +44,8 @@ exporters:
 	assert.NoError(t, mp.Shutdown(context.Background()))
 }
 
-func TestDefaultMapProvider_AddNewConfig(t *testing.T) {
-	mp := NewDefault("testdata/default-config.yaml", []string{"processors.batch.timeout=2s"})
+func TestLocalMapProvider_AddNewConfig(t *testing.T) {
+	mp := NewLocal("testdata/default-config.yaml", []string{"processors.batch.timeout=2s"})
 	cp, err := mp.Retrieve(context.Background(), nil)
 	require.NoError(t, err)
 
@@ -64,8 +64,8 @@ exporters:
 	assert.NoError(t, mp.Shutdown(context.Background()))
 }
 
-func TestDefaultMapProvider_OverwriteConfig(t *testing.T) {
-	mp := NewDefault(
+func TestLocalMapProvider_OverwriteConfig(t *testing.T) {
+	mp := NewLocal(
 		"testdata/default-config.yaml",
 		[]string{"processors.batch.timeout=2s", "exporters.otlp.endpoint=localhost:1234"})
 	cp, err := mp.Retrieve(context.Background(), nil)
@@ -86,17 +86,17 @@ exporters:
 	assert.NoError(t, mp.Shutdown(context.Background()))
 }
 
-func TestDefaultMapProvider_InexistentFile(t *testing.T) {
-	mp := NewDefault("testdata/otelcol-config.yaml", nil)
+func TestLocalMapProvider_InexistentFile(t *testing.T) {
+	mp := NewLocal("testdata/otelcol-config.yaml", nil)
 	require.NotNil(t, mp)
 	_, err := mp.Retrieve(context.Background(), nil)
 	require.Error(t, err)
 
 	assert.NoError(t, mp.Shutdown(context.Background()))
 }
 
-func TestDefaultMapProvider_EmptyFileName(t *testing.T) {
-	mp := NewDefault("", nil)
+func TestLocalMapProvider_EmptyFileName(t *testing.T) {
+	mp := NewLocal("", nil)
 	_, err := mp.Retrieve(context.Background(), nil)
 	require.Error(t, err)