[#44] adm: Support multiple configs

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

cmd/frostfs-adm/internal/commonflags/flags.go

@@ -5,6 +5,9 @@ const (
 	ConfigFlagShorthand = "c"
 	ConfigFlagUsage     = "Config file"
 
+	ConfigDirFlag      = "config-dir"
+	ConfigDirFlagUsage = "Config directory"
+
 	Verbose          = "verbose"
 	VerboseShorthand = "v"
 	VerboseUsage     = "Verbose output"

cmd/frostfs-adm/internal/modules/root.go

@@ -9,6 +9,7 @@ import (
 	"github.com/TrueCloudLab/frostfs-node/cmd/frostfs-adm/internal/modules/storagecfg"
 	"github.com/TrueCloudLab/frostfs-node/misc"
 	"github.com/TrueCloudLab/frostfs-node/pkg/util/autocomplete"
+	utilConfig "github.com/TrueCloudLab/frostfs-node/pkg/util/config"
 	"github.com/TrueCloudLab/frostfs-node/pkg/util/gendoc"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -34,6 +35,7 @@ func init() {
 	rootCmd.SetOut(os.Stdout)
 
 	rootCmd.PersistentFlags().StringP(commonflags.ConfigFlag, commonflags.ConfigFlagShorthand, "", commonflags.ConfigFlagUsage)
+	rootCmd.PersistentFlags().String(commonflags.ConfigDirFlag, "", commonflags.ConfigDirFlagUsage)
 	rootCmd.PersistentFlags().BoolP(commonflags.Verbose, commonflags.VerboseShorthand, false, commonflags.VerboseUsage)
 	_ = viper.BindPFlag(commonflags.Verbose, rootCmd.PersistentFlags().Lookup(commonflags.Verbose))
 	rootCmd.Flags().Bool("version", false, "Application version")
@@ -62,11 +64,22 @@ func entryPoint(cmd *cobra.Command, args []string) error {
 
 func initConfig(cmd *cobra.Command) {
 	configFile, err := cmd.Flags().GetString(commonflags.ConfigFlag)
-	if err != nil || configFile == "" {
+	if err != nil {
 		return
 	}
 
+	if configFile != "" {
 		viper.SetConfigType("yml")
 		viper.SetConfigFile(configFile)
 		_ = viper.ReadInConfig() // if config file is set but unavailable, ignore it
 	}
+
+	configDir, err := cmd.Flags().GetString(commonflags.ConfigDirFlag)
+	if err != nil {
+		return
+	}
+
+	if configDir != "" {
+		_ = utilConfig.ReadConfigDir(viper.GetViper(), configDir) // if config files cannot be read, ignore it
+	}
+}

config/example/README.md

@@ -29,7 +29,8 @@ $ ./bin/frotsfs-node --config ./config/example/node.yaml --config-dir ./dir/with
 When the `--config-dir` flag set, the application:
 * reads all `*.y[a]ml` files from provided directory,
 * use Viper's [MergeConfig](https://pkg.go.dev/github.com/spf13/viper#MergeConfig) functionality to produce the final configuration,
-* files are being processing in alphanumerical order so that `01.yaml` may be extended with contents of `02.yaml`.
+* files are being processing in alphanumerical order so that `01.yaml` may be extended with contents of `02.yaml`, so
+if a field is specified in multiple files, the latest occurrence takes effect.
 
 So if we have the following files:
 ```yaml