Add support of env vars on config_sources section (#312)

Author: pjanotti

internal/configprovider/parser.go

@@ -18,9 +18,11 @@ package configprovider
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cast"
 	"go.opentelemetry.io/collector/config"
+	"go.opentelemetry.io/collector/config/experimental/configsource"
 )
 
 const (
@@ -37,16 +39,46 @@ type (
 
 // Load reads the configuration for ConfigSource objects from the given parser and returns a map
 // from the full name of config sources to the respective ConfigSettings.
-func Load(_ context.Context, v *config.Parser, factories Factories) (map[string]ConfigSettings, error) {
+func Load(ctx context.Context, v *config.Parser, factories Factories) (map[string]ConfigSettings, error) {
+	processedParser, err := processParser(ctx, v)
+	if err != nil {
+		return nil, err
+	}
 
-	cfgSrcSettings, err := loadSettings(cast.ToStringMap(v.Get(configSourcesKey)), factories)
+	cfgSrcSettings, err := loadSettings(cast.ToStringMap(processedParser.Get(configSourcesKey)), factories)
 	if err != nil {
 		return nil, err
 	}
 
 	return cfgSrcSettings, nil
 }
 
+// processParser prepares a config.Parser to be used to load config source settings.
+func processParser(ctx context.Context, v *config.Parser) (*config.Parser, error) {
+	// Use a manager to resolve environment variables with a syntax consistent with
+	// the config source usage.
+	manager := newManager(make(map[string]configsource.ConfigSource))
+	defer func() {
+		_ = manager.Close(ctx)
+	}()
+
+	processedParser := config.NewParser()
+	for _, key := range v.AllKeys() {
+		if !strings.HasPrefix(key, configSourcesKey) {
+			// In Load we only care about config sources, ignore everything else.
+			continue
+		}
+
+		value, err := manager.expandStringValues(ctx, v.Get(key))
+		if err != nil {
+			return nil, err
+		}
+		processedParser.Set(key, value)
+	}
+
+	return processedParser, nil
+}
+
 func loadSettings(css map[string]interface{}, factories Factories) (map[string]ConfigSettings, error) {
 	// Prepare resulting map.
 	cfgSrcToSettings := make(map[string]ConfigSettings)
@@ -55,8 +87,6 @@ func loadSettings(css map[string]interface{}, factories Factories) (map[string]C
 	for key, value := range css {
 		settingsParser := config.NewParserFromStringMap(cast.ToStringMap(value))
 
-		// TODO: expand env vars.
-
 		// Decode the key into type and fullName components.
 		componentID, err := config.IDFromString(key)
 		if err != nil {

internal/configprovider/parser_test.go

@@ -17,6 +17,7 @@ package configprovider
 
 import (
 	"context"
+	"os"
 	"path"
 	"testing"
 
@@ -35,6 +36,7 @@ func TestConfigSourceParser(t *testing.T) {
 	tests := []struct {
 		factories Factories
 		expected  map[string]ConfigSettings
+		envvars   map[string]string
 		wantErr   error
 		name      string
 		file      string
@@ -61,6 +63,31 @@ func TestConfigSourceParser(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:      "env_var_on_load",
+			file:      "env_var_on_load",
+			factories: testFactories,
+			envvars: map[string]string{
+				"ENV_VAR_ENDPOINT": "env_var_endpoint",
+				"ENV_VAR_TOKEN":    "env_var_token",
+			},
+			expected: map[string]ConfigSettings{
+				"tstcfgsrc": &mockCfgSrcSettings{
+					Settings: Settings{
+						TypeVal: "tstcfgsrc",
+						NameVal: "tstcfgsrc",
+					},
+					Endpoint: "https://env_var_endpoint:8200",
+					Token:    "env_var_token",
+				},
+			},
+		},
+		{
+			name:      "cfgsrc_load_cannot_use_cfgsrc",
+			file:      "cfgsrc_load_use_cfgsrc",
+			factories: testFactories,
+			wantErr:   &errUnknownConfigSource{},
+		},
 		{
 			name:      "bad_name",
 			file:      "bad_name",
@@ -94,6 +121,14 @@ func TestConfigSourceParser(t *testing.T) {
 			v, err := config.NewParserFromFile(cfgFile)
 			require.NoError(t, err)
 
+			for key, value := range tt.envvars {
+				require.NoError(t, os.Setenv(key, value))
+				keyToUnset := key
+				defer func() {
+					assert.NoError(t, os.Unsetenv(keyToUnset))
+				}()
+			}
+
 			cfgSrcSettings, err := Load(ctx, v, tt.factories)
 			require.IsType(t, tt.wantErr, err)
 			assert.Equal(t, tt.expected, cfgSrcSettings)

internal/configprovider/testdata/cfgsrc_load_use_cfgsrc.yaml

@@ -0,0 +1,5 @@
+config_sources:
+  tstcfgsrc:
+  tstcfgsrc/named:
+    # It is not valid to use a dynamic config source when defining other one.
+    endpoint: $tstcfgsrc:str_value

internal/configprovider/testdata/env_var_on_load.yaml

@@ -0,0 +1,6 @@
+config_sources:
+  tstcfgsrc:
+    endpoint: https://${ENV_VAR_ENDPOINT}:8200
+    token: $ENV_VAR_TOKEN
+ignored_by_parser:
+  some_field: $ENV_VAR_TOKEN