[TrueCloudLab#12] Support multiple configs

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

README.md

@@ -182,6 +182,23 @@ $ frostfs-http-gw --config your-config.yaml
 
 See [config](./config/config.yaml) and [defaults](./docs/gate-configuration.md) for example.
 
+#### Multiple configs
+
+You can use several config files when running application. It allows you to split configuration into parts.
+For example, you can use separate yaml file for pprof and prometheus section in config (see [config examples](./config)).
+You can either provide several files with repeating `--config` flag or provide path to the dir that contains all configs using `--config-dir` flag.
+Also, you can combine these flags:
+
+```shell
+$ frostfs-http-gw --config ./config/config.yaml --config /your/partial/config.yaml --config-dir ./config/dir
+```
+
+**Note:** next file in `--config` flag overwrites values from the previous one.
+Files from `--config-dir` directory overwrite values from `--config` files.
+So the command above run `frostfs-http-gw` to listen on `0.0.0.0:8080` address (value from `./config/config.yaml`),
+applies parameters from `/your/partial/config.yaml`,
+enable pprof (value from `./config/dir/pprof.yaml`) and prometheus (value from `./config/dir/prometheus.yaml`).
+
 ## HTTP API provided
 
 This gateway intentionally provides limited feature set and doesn't try to

app.go

@@ -380,14 +380,15 @@ LOOP:
 
 func (a *app) configReload() {
 	a.log.Info("SIGHUP config reload started")
-	if !a.cfg.IsSet(cmdConfig) {
+	if !a.cfg.IsSet(cmdConfig) && !a.cfg.IsSet(cmdConfigDir) {
 		a.log.Warn("failed to reload config because it's missed")
 		return
 	}
-	if err := readConfig(a.cfg); err != nil {
+	if err := readInConfig(a.cfg); err != nil {
 		a.log.Warn("failed to reload config", zap.Error(err))
 		return
 	}
+
 	if lvl, err := getLogLevel(a.cfg); err != nil {
 		a.log.Warn("log level won't be updated", zap.Error(err))
 	} else {

config/config.yaml

@@ -4,10 +4,10 @@ wallet:
   passphrase: pwd # Passphrase to decrypt wallet. If you're using a wallet without a password, place '' here.
 
 pprof:
-  enabled: true # Enable pprof.
+  enabled: false # Enable pprof.
   address: localhost:8083
 prometheus:
-  enabled: true # Enable metrics.
+  enabled: false # Enable metrics.
   address: localhost:8084
 
 logger:

config/dir/pprof.yaml

@@ -0,0 +1,3 @@
+pprof:
+  enabled: true
+  address: localhost:8083

config/dir/prometheus.yaml

@@ -0,0 +1,3 @@
+prometheus:
+  enabled: true
+  address: localhost:8084

settings.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"path"
 	"runtime"
 	"sort"
 	"strconv"
@@ -84,6 +85,7 @@ const (
 	cmdWallet        = "wallet"
 	cmdAddress       = "address"
 	cmdConfig        = "config"
+	cmdConfigDir     = "config-dir"
 	cmdListenAddress = "listen_address"
 )
 
@@ -114,7 +116,8 @@ func settings() *viper.Viper {
 
 	flags.StringP(cmdWallet, "w", "", `path to the wallet`)
 	flags.String(cmdAddress, "", `address of wallet account`)
-	flags.String(cmdConfig, "", "config path")
+	flags.StringArray(cmdConfig, nil, "config paths")
+	flags.String(cmdConfigDir, "", "config dir path")
 	flags.Duration(cfgConTimeout, defaultConnectTimeout, "gRPC connect timeout")
 	flags.Duration(cfgStreamTimeout, defaultStreamTimeout, "gRPC individual message timeout")
 	flags.Duration(cfgReqTimeout, defaultRequestTimeout, "gRPC request timeout")
@@ -233,10 +236,8 @@ func settings() *viper.Viper {
 		os.Exit(0)
 	}
 
-	if v.IsSet(cmdConfig) {
-		if err := readConfig(v); err != nil {
-			panic(err)
-		}
+	if err := readInConfig(v); err != nil {
+		panic(err)
 	}
 
 	if peers != nil && len(*peers) > 0 {
@@ -250,17 +251,72 @@ func settings() *viper.Viper {
 	return v
 }
 
-func readConfig(v *viper.Viper) error {
-	cfgFileName := v.GetString(cmdConfig)
-	cfgFile, err := os.Open(cfgFileName)
+func readInConfig(v *viper.Viper) error {
+	if v.IsSet(cmdConfig) {
+		if err := readConfig(v); err != nil {
+			return err
+		}
+	}
+
+	if v.IsSet(cmdConfigDir) {
+		if err := readConfigDir(v); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func readConfigDir(v *viper.Viper) error {
+	cfgSubConfigDir := v.GetString(cmdConfigDir)
+	entries, err := os.ReadDir(cfgSubConfigDir)
 	if err != nil {
 		return err
 	}
-	if err = v.ReadConfig(cfgFile); err != nil {
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		ext := path.Ext(entry.Name())
+		if ext != ".yaml" && ext != ".yml" {
+			continue
+		}
+
+		if err = mergeConfig(v, path.Join(cfgSubConfigDir, entry.Name())); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func readConfig(v *viper.Viper) error {
+	for _, fileName := range v.GetStringSlice(cmdConfig) {
+		if err := mergeConfig(v, fileName); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func mergeConfig(v *viper.Viper, fileName string) error {
+	cfgFile, err := os.Open(fileName)
+	if err != nil {
 		return err
 	}
 
-	return cfgFile.Close()
+	defer func() {
+		if errClose := cfgFile.Close(); errClose != nil {
+			panic(errClose)
+		}
+	}()
+
+	if err = v.MergeConfig(cfgFile); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 // newLogger constructs a zap.Logger instance for current application.