[#541] Use default value if config param is unset after SIGHUP

Signed-off-by: Marina Biryukova <m.biryukova@yadro.com>

cmd/s3-gw/app.go

@@ -65,7 +65,7 @@ type (
 	App struct {
 		ctr      s3middleware.Center
 		log      *zap.Logger
-		cfg      *viper.Viper
+		cfg      *appCfg
 		pool     *pool.Pool
 		treePool *treepool.Pool
 		key      *keys.PrivateKey
@@ -161,15 +161,15 @@ func (s *loggerSettings) setMetrics(appMetrics *metrics.AppMetrics) {
 	s.appMetrics = appMetrics
 }
 
-func newApp(ctx context.Context, v *viper.Viper) *App {
+func newApp(ctx context.Context, cfg *appCfg) *App {
 	logSettings := &loggerSettings{}
-	log := pickLogger(v, logSettings)
+	log := pickLogger(cfg.config(), logSettings)
-	settings := newAppSettings(log, v)
+	settings := newAppSettings(log, cfg.config())
-	appCache := layer.NewCache(getCacheOptions(v, log.logger))
+	appCache := layer.NewCache(getCacheOptions(cfg.config(), log.logger))
 
 	app := &App{
 		log:   log.logger,
-		cfg:   v,
+		cfg:   cfg,
 		cache: appCache,
 
 		webDone: make(chan struct{}, 1),
@@ -184,6 +184,10 @@ func newApp(ctx context.Context, v *viper.Viper) *App {
 	return app
 }
 
+func (a *App) config() *viper.Viper {
+	return a.cfg.config()
+}
+
 func (a *App) init(ctx context.Context) {
 	a.initPools(ctx)
 	a.initResolver()
@@ -198,7 +202,7 @@ func (a *App) init(ctx context.Context) {
 }
 
 func (a *App) initAuthCenter(ctx context.Context) {
-	if a.cfg.IsSet(cfgContainersAccessBox) {
+	if a.config().IsSet(cfgContainersAccessBox) {
 		cnrID, err := a.resolveContainerID(ctx, cfgContainersAccessBox)
 		if err != nil {
 			a.log.Fatal(logs.CouldNotFetchAccessBoxContainerInfo, zap.Error(err))
@@ -209,11 +213,11 @@ func (a *App) initAuthCenter(ctx context.Context) {
 	cfg := tokens.Config{
 		FrostFS:                     frostfs.NewAuthmateFrostFS(frostfs.NewFrostFS(a.pool, a.key), a.log),
 		Key:                         a.key,
-		CacheConfig:                 getAccessBoxCacheConfig(a.cfg, a.log),
+		CacheConfig:                 getAccessBoxCacheConfig(a.config(), a.log),
-		RemovingCheckAfterDurations: fetchRemovingCheckInterval(a.cfg, a.log),
+		RemovingCheckAfterDurations: fetchRemovingCheckInterval(a.config(), a.log),
 	}
 
-	a.ctr = auth.New(tokens.New(cfg), a.cfg.GetStringSlice(cfgAllowedAccessKeyIDPrefixes), a.settings)
+	a.ctr = auth.New(tokens.New(cfg), a.config().GetStringSlice(cfgAllowedAccessKeyIDPrefixes), a.settings)
 }
 
 func (a *App) initLayer(ctx context.Context) {
@@ -227,7 +231,7 @@ func (a *App) initLayer(ctx context.Context) {
 	user.IDFromKey(&gateOwner, a.key.PrivateKey.PublicKey)
 
 	var corsCnrInfo *data.BucketInfo
-	if a.cfg.IsSet(cfgContainersCORS) {
+	if a.config().IsSet(cfgContainersCORS) {
 		corsCnrInfo, err = a.fetchContainerInfo(ctx, cfgContainersCORS)
 		if err != nil {
 			a.log.Fatal(logs.CouldNotFetchCORSContainerInfo, zap.Error(err))
@@ -235,7 +239,7 @@ func (a *App) initLayer(ctx context.Context) {
 	}
 
 	var lifecycleCnrInfo *data.BucketInfo
-	if a.cfg.IsSet(cfgContainersLifecycle) {
+	if a.config().IsSet(cfgContainersLifecycle) {
 		lifecycleCnrInfo, err = a.fetchContainerInfo(ctx, cfgContainersLifecycle)
 		if err != nil {
 			a.log.Fatal(logs.CouldNotFetchLifecycleContainerInfo, zap.Error(err))
@@ -599,7 +603,7 @@ func (a *App) initMetrics() {
 		Logger:         a.log,
 		PoolStatistics: frostfs.NewPoolStatistic(a.pool),
 		TreeStatistic:  a.treePool,
-		Enabled:        a.cfg.GetBool(cfgPrometheusEnabled),
+		Enabled:        a.config().GetBool(cfgPrometheusEnabled),
 	}
 
 	a.metrics = metrics.NewAppMetrics(cfg)
@@ -609,9 +613,9 @@ func (a *App) initMetrics() {
 
 func (a *App) initFrostfsID(ctx context.Context) {
 	cli, err := ffidcontract.New(ctx, ffidcontract.Config{
-		RPCAddress:    a.cfg.GetString(cfgRPCEndpoint),
+		RPCAddress:    a.config().GetString(cfgRPCEndpoint),
-		Contract:      a.cfg.GetString(cfgFrostfsIDContract),
+		Contract:      a.config().GetString(cfgFrostfsIDContract),
-		ProxyContract: a.cfg.GetString(cfgProxyContract),
+		ProxyContract: a.config().GetString(cfgProxyContract),
 		Key:           a.key,
 		Waiter: commonclient.WaiterOptions{
 			IgnoreAlreadyExistsError: false,
@@ -623,7 +627,7 @@ func (a *App) initFrostfsID(ctx context.Context) {
 	}
 
 	a.frostfsid, err = frostfsid.NewFrostFSID(frostfsid.Config{
-		Cache:     cache.NewFrostfsIDCache(getFrostfsIDCacheConfig(a.cfg, a.log)),
+		Cache:     cache.NewFrostfsIDCache(getFrostfsIDCacheConfig(a.config(), a.log)),
 		FrostFSID: cli,
 		Logger:    a.log,
 	})
@@ -634,9 +638,9 @@ func (a *App) initFrostfsID(ctx context.Context) {
 
 func (a *App) initPolicyStorage(ctx context.Context) {
 	policyContract, err := contract.New(ctx, contract.Config{
-		RPCAddress:    a.cfg.GetString(cfgRPCEndpoint),
+		RPCAddress:    a.config().GetString(cfgRPCEndpoint),
-		Contract:      a.cfg.GetString(cfgPolicyContract),
+		Contract:      a.config().GetString(cfgPolicyContract),
-		ProxyContract: a.cfg.GetString(cfgProxyContract),
+		ProxyContract: a.config().GetString(cfgProxyContract),
 		Key:           a.key,
 		Waiter: commonclient.WaiterOptions{
 			IgnoreAlreadyExistsError: false,
@@ -649,7 +653,7 @@ func (a *App) initPolicyStorage(ctx context.Context) {
 
 	a.policyStorage = policy.NewStorage(policy.StorageConfig{
 		Contract: policyContract,
-		Cache:    cache.NewMorphPolicyCache(getMorphPolicyCacheConfig(a.cfg, a.log)),
+		Cache:    cache.NewMorphPolicyCache(getMorphPolicyCacheConfig(a.config(), a.log)),
 		Log:      a.log,
 	})
 }
@@ -665,13 +669,13 @@ func (a *App) initResolver() {
 func (a *App) getResolverConfig() *resolver.Config {
 	return &resolver.Config{
 		FrostFS:    frostfs.NewResolverFrostFS(a.pool),
-		RPCAddress: a.cfg.GetString(cfgRPCEndpoint),
+		RPCAddress: a.config().GetString(cfgRPCEndpoint),
 	}
 }
 
 func (a *App) getResolverOrder() []string {
-	order := a.cfg.GetStringSlice(cfgResolveOrder)
+	order := a.config().GetStringSlice(cfgResolveOrder)
-	if a.cfg.GetString(cfgRPCEndpoint) == "" {
+	if a.config().GetString(cfgRPCEndpoint) == "" {
 		order = remove(order, resolver.NNSResolver)
 		a.log.Warn(logs.ResolverNNSWontBeUsedSinceRPCEndpointIsntProvided)
 	}
@@ -689,15 +693,15 @@ func (a *App) initTracing(ctx context.Context) {
 		instanceID = a.servers[0].Address()
 	}
 	cfg := tracing.Config{
-		Enabled:    a.cfg.GetBool(cfgTracingEnabled),
+		Enabled:    a.config().GetBool(cfgTracingEnabled),
-		Exporter:   tracing.Exporter(a.cfg.GetString(cfgTracingExporter)),
+		Exporter:   tracing.Exporter(a.config().GetString(cfgTracingExporter)),
-		Endpoint:   a.cfg.GetString(cfgTracingEndpoint),
+		Endpoint:   a.config().GetString(cfgTracingEndpoint),
 		Service:    "frostfs-s3-gw",
 		InstanceID: instanceID,
 		Version:    version.Version,
 	}
 
-	if trustedCa := a.cfg.GetString(cfgTracingTrustedCa); trustedCa != "" {
+	if trustedCa := a.config().GetString(cfgTracingTrustedCa); trustedCa != "" {
 		caBytes, err := os.ReadFile(trustedCa)
 		if err != nil {
 			a.log.Warn(logs.FailedToInitializeTracing, zap.Error(err))
@@ -712,7 +716,7 @@ func (a *App) initTracing(ctx context.Context) {
 		cfg.ServerCaCertPool = certPool
 	}
 
-	attributes, err := fetchTracingAttributes(a.cfg)
+	attributes, err := fetchTracingAttributes(a.config())
 	if err != nil {
 		a.log.Warn(logs.FailedToInitializeTracing, zap.Error(err))
 		return
@@ -760,8 +764,8 @@ func (a *App) initPools(ctx context.Context) {
 	var prm pool.InitParameters
 	var prmTree treepool.InitParameters
 
-	password := wallet.GetPassword(a.cfg, cfgWalletPassphrase)
+	password := wallet.GetPassword(a.config(), cfgWalletPassphrase)
-	key, err := wallet.GetKeyFromPath(a.cfg.GetString(cfgWalletPath), a.cfg.GetString(cfgWalletAddress), password)
+	key, err := wallet.GetKeyFromPath(a.config().GetString(cfgWalletPath), a.config().GetString(cfgWalletAddress), password)
 	if err != nil {
 		a.log.Fatal(logs.CouldNotLoadFrostFSPrivateKey, zap.Error(err))
 	}
@@ -770,36 +774,36 @@ func (a *App) initPools(ctx context.Context) {
 	prmTree.SetKey(key)
 	a.log.Info(logs.UsingCredentials, zap.String("FrostFS", hex.EncodeToString(key.PublicKey().Bytes())))
 
-	for _, peer := range fetchPeers(a.log, a.cfg) {
+	for _, peer := range fetchPeers(a.log, a.config()) {
 		prm.AddNode(peer)
 		prmTree.AddNode(peer)
 	}
 
-	connTimeout := fetchConnectTimeout(a.cfg)
+	connTimeout := fetchConnectTimeout(a.config())
 	prm.SetNodeDialTimeout(connTimeout)
 	prmTree.SetNodeDialTimeout(connTimeout)
 
-	streamTimeout := fetchStreamTimeout(a.cfg)
+	streamTimeout := fetchStreamTimeout(a.config())
 	prm.SetNodeStreamTimeout(streamTimeout)
 	prmTree.SetNodeStreamTimeout(streamTimeout)
 
-	healthCheckTimeout := fetchHealthCheckTimeout(a.cfg)
+	healthCheckTimeout := fetchHealthCheckTimeout(a.config())
 	prm.SetHealthcheckTimeout(healthCheckTimeout)
 	prmTree.SetHealthcheckTimeout(healthCheckTimeout)
 
-	rebalanceInterval := fetchRebalanceInterval(a.cfg)
+	rebalanceInterval := fetchRebalanceInterval(a.config())
 	prm.SetClientRebalanceInterval(rebalanceInterval)
 	prmTree.SetClientRebalanceInterval(rebalanceInterval)
 
-	errorThreshold := fetchErrorThreshold(a.cfg)
+	errorThreshold := fetchErrorThreshold(a.config())
 	prm.SetErrorThreshold(errorThreshold)
 
-	prm.SetGracefulCloseOnSwitchTimeout(fetchSetGracefulCloseOnSwitchTimeout(a.cfg))
+	prm.SetGracefulCloseOnSwitchTimeout(fetchSetGracefulCloseOnSwitchTimeout(a.config()))
 
 	prm.SetLogger(a.log)
 	prmTree.SetLogger(a.log)
 
-	prmTree.SetMaxRequestAttempts(a.cfg.GetInt(cfgTreePoolMaxAttempts))
+	prmTree.SetMaxRequestAttempts(a.config().GetInt(cfgTreePoolMaxAttempts))
 
 	interceptors := []grpc.DialOption{
 		grpc.WithUnaryInterceptor(grpctracing.NewUnaryClientInteceptor()),
@@ -818,7 +822,7 @@ func (a *App) initPools(ctx context.Context) {
 		a.log.Fatal(logs.FailedToDialConnectionPool, zap.Error(err))
 	}
 
-	if a.cfg.GetBool(cfgTreePoolNetmapSupport) {
+	if a.config().GetBool(cfgTreePoolNetmapSupport) {
 		prmTree.SetNetMapInfoSource(frostfs.NewSource(frostfs.NewFrostFS(p, key), a.cache))
 	}
 
@@ -895,10 +899,10 @@ func (a *App) Serve(ctx context.Context) {
 	srv := new(http.Server)
 	srv.Handler = chiRouter
 	srv.ErrorLog = zap.NewStdLog(a.log)
-	srv.ReadTimeout = a.cfg.GetDuration(cfgWebReadTimeout)
+	srv.ReadTimeout = a.config().GetDuration(cfgWebReadTimeout)
-	srv.ReadHeaderTimeout = a.cfg.GetDuration(cfgWebReadHeaderTimeout)
+	srv.ReadHeaderTimeout = a.config().GetDuration(cfgWebReadHeaderTimeout)
-	srv.WriteTimeout = a.cfg.GetDuration(cfgWebWriteTimeout)
+	srv.WriteTimeout = a.config().GetDuration(cfgWebWriteTimeout)
-	srv.IdleTimeout = a.cfg.GetDuration(cfgWebIdleTimeout)
+	srv.IdleTimeout = a.config().GetDuration(cfgWebIdleTimeout)
 
 	a.startServices()
 
@@ -951,11 +955,11 @@ func shutdownContext() (context.Context, context.CancelFunc) {
 func (a *App) configReload(ctx context.Context) {
 	a.log.Info(logs.SIGHUPConfigReloadStarted)
 
-	if !a.cfg.IsSet(cmdConfig) && !a.cfg.IsSet(cmdConfigDir) {
+	if !a.config().IsSet(cmdConfig) && !a.config().IsSet(cmdConfigDir) {
 		a.log.Warn(logs.FailedToReloadConfigBecauseItsMissed)
 		return
 	}
-	if err := readInConfig(a.cfg); err != nil {
+	if err := a.cfg.reload(); err != nil {
 		a.log.Warn(logs.FailedToReloadConfig, zap.Error(err))
 		return
 	}
@@ -975,7 +979,7 @@ func (a *App) configReload(ctx context.Context) {
 
 	a.updateSettings()
 
-	a.metrics.SetEnabled(a.cfg.GetBool(cfgPrometheusEnabled))
+	a.metrics.SetEnabled(a.config().GetBool(cfgPrometheusEnabled))
 	a.initTracing(ctx)
 	a.setHealthStatus()
 
@@ -983,33 +987,33 @@ func (a *App) configReload(ctx context.Context) {
 }
 
 func (a *App) updateSettings() {
-	if lvl, err := getLogLevel(a.cfg); err != nil {
+	if lvl, err := getLogLevel(a.config()); err != nil {
 		a.log.Warn(logs.LogLevelWontBeUpdated, zap.Error(err))
 	} else {
 		a.settings.logLevel.SetLevel(lvl)
 	}
 
-	if err := a.settings.dialerSource.Update(fetchMultinetConfig(a.cfg, a.log)); err != nil {
+	if err := a.settings.dialerSource.Update(fetchMultinetConfig(a.config(), a.log)); err != nil {
 		a.log.Warn(logs.MultinetConfigWontBeUpdated, zap.Error(err))
 	}
 
-	a.settings.update(a.cfg, a.log)
+	a.settings.update(a.config(), a.log)
 }
 
 func (a *App) startServices() {
 	a.services = a.services[:0]
 
-	pprofService := NewPprofService(a.cfg, a.log)
+	pprofService := NewPprofService(a.config(), a.log)
 	a.services = append(a.services, pprofService)
 	go pprofService.Start()
 
-	prometheusService := NewPrometheusService(a.cfg, a.log, a.metrics.Handler())
+	prometheusService := NewPrometheusService(a.config(), a.log, a.metrics.Handler())
 	a.services = append(a.services, prometheusService)
 	go prometheusService.Start()
 }
 
 func (a *App) initServers(ctx context.Context) {
-	serversInfo := fetchServers(a.cfg, a.log)
+	serversInfo := fetchServers(a.config(), a.log)
 
 	a.servers = make([]Server, 0, len(serversInfo))
 	for _, serverInfo := range serversInfo {
@@ -1036,7 +1040,7 @@ func (a *App) initServers(ctx context.Context) {
 }
 
 func (a *App) updateServers() error {
-	serversInfo := fetchServers(a.cfg, a.log)
+	serversInfo := fetchServers(a.config(), a.log)
 
 	a.mu.Lock()
 	defer a.mu.Unlock()
@@ -1171,7 +1175,7 @@ func (a *App) setRuntimeParameters() {
 		return
 	}
 
-	softMemoryLimit := fetchSoftMemoryLimit(a.cfg)
+	softMemoryLimit := fetchSoftMemoryLimit(a.config())
 	previous := debug.SetMemoryLimit(softMemoryLimit)
 	if softMemoryLimit != previous {
 		a.log.Info(logs.RuntimeSoftMemoryLimitUpdated,
@@ -1247,7 +1251,7 @@ func (a *App) fetchContainerInfo(ctx context.Context, cfgKey string) (info *data
 }
 
 func (a *App) resolveContainerID(ctx context.Context, cfgKey string) (cid.ID, error) {
-	containerString := a.cfg.GetString(cfgKey)
+	containerString := a.config().GetString(cfgKey)
 
 	var id cid.ID
 	if err := id.DecodeString(containerString); err != nil {

cmd/s3-gw/app_settings.go

@@ -10,6 +10,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
@@ -301,6 +302,49 @@ var ignore = map[string]struct{}{
 	cmdVersion: {},
 }
 
+type appCfg struct {
+	flags *pflag.FlagSet
+
+	mu       sync.RWMutex
+	settings *viper.Viper
+}
+
+func (a *appCfg) reload() error {
+	old := a.config()
+
+	v, err := newViper(a.flags)
+	if err != nil {
+		return err
+	}
+
+	if old.IsSet(cmdConfig) {
+		v.Set(cmdConfig, old.Get(cmdConfig))
+	}
+	if old.IsSet(cmdConfigDir) {
+		v.Set(cmdConfigDir, old.Get(cmdConfigDir))
+	}
+
+	if err = readInConfig(v); err != nil {
+		return err
+	}
+
+	a.setConfig(v)
+	return nil
+}
+
+func (a *appCfg) config() *viper.Viper {
+	a.mu.RLock()
+	defer a.mu.RUnlock()
+
+	return a.settings
+}
+
+func (a *appCfg) setConfig(v *viper.Viper) {
+	a.mu.Lock()
+	a.settings = v
+	a.mu.Unlock()
+}
+
 func fetchConnectTimeout(cfg *viper.Viper) time.Duration {
 	connTimeout := cfg.GetDuration(cfgConnectTimeout)
 	if connTimeout <= 0 {
@@ -878,7 +922,7 @@ func fetchTombstoneWorkerPoolSize(v *viper.Viper) int {
 	return tombstoneWorkerPoolSize
 }
 
-func newSettings() *viper.Viper {
+func newViper(flags *pflag.FlagSet) (*viper.Viper, error) {
 	v := viper.New()
 
 	v.AutomaticEnv()
@@ -887,6 +931,16 @@ func newSettings() *viper.Viper {
 	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
 	v.AllowEmptyEnv(true)
 
+	setDefaults(v, flags)
+
+	if v.IsSet(cfgServer+".0."+cfgTLSKeyFile) && v.IsSet(cfgServer+".0."+cfgTLSCertFile) {
+		v.Set(cfgServer+".0."+cfgTLSEnabled, true)
+	}
+
+	return v, bindFlags(v, flags)
+}
+
+func newSettings() *appCfg {
 	// flags setup:
 	flags := pflag.NewFlagSet("commandline", pflag.ExitOnError)
 	flags.SetOutput(os.Stdout)
@@ -914,15 +968,71 @@ func newSettings() *viper.Viper {
 	flags.String(cfgTLSCertFile, "", "TLS certificate file to use")
 	flags.String(cfgTLSKeyFile, "", "TLS key file to use")
 
-	peers := flags.StringArrayP(cfgPeers, "p", nil, "set FrostFS nodes")
+	flags.StringArrayP(cfgPeers, "p", nil, "set FrostFS nodes")
 
 	flags.StringP(cfgRPCEndpoint, "r", "", "set RPC endpoint")
-	resolveMethods := flags.StringSlice(cfgResolveOrder, []string{resolver.DNSResolver}, "set bucket name resolve order")
+	flags.StringSlice(cfgResolveOrder, []string{resolver.DNSResolver}, "set bucket name resolve order")
 
-	domains := flags.StringSliceP(cfgListenDomains, "d", nil, "set domains to be listened")
+	flags.StringSliceP(cfgListenDomains, "d", nil, "set domains to be listened")
 
-	// set defaults:
+	if err := flags.Parse(os.Args); err != nil {
+		panic(err)
+	}
 
+	v, err := newViper(flags)
+	if err != nil {
+		panic(fmt.Errorf("bind flags: %w", err))
+	}
+
+	switch {
+	case help != nil && *help:
+		fmt.Printf("FrostFS S3 gateway %s\n", version.Version)
+		flags.PrintDefaults()
+
+		fmt.Println()
+		fmt.Println("Default environments:")
+		fmt.Println()
+		keys := v.AllKeys()
+		sort.Strings(keys)
+
+		for i := range keys {
+			if _, ok := ignore[keys[i]]; ok {
+				continue
+			}
+
+			defaultValue := v.GetString(keys[i])
+			if len(defaultValue) == 0 {
+				continue
+			}
+
+			k := strings.Replace(keys[i], ".", "_", -1)
+			fmt.Printf("%s_%s = %s\n", envPrefix, strings.ToUpper(k), defaultValue)
+		}
+
+		fmt.Println()
+		fmt.Println("Peers preset:")
+		fmt.Println()
+
+		fmt.Printf("%s_%s_[N]_ADDRESS = string\n", envPrefix, strings.ToUpper(cfgPeers))
+		fmt.Printf("%s_%s_[N]_WEIGHT = 0..1 (float)\n", envPrefix, strings.ToUpper(cfgPeers))
+
+		os.Exit(0)
+	case versionFlag != nil && *versionFlag:
+		fmt.Printf("FrostFS S3 Gateway\nVersion: %s\nGoVersion: %s\n", version.Version, runtime.Version())
+		os.Exit(0)
+	}
+
+	if err = readInConfig(v); err != nil {
+		panic(err)
+	}
+
+	return &appCfg{
+		flags:    flags,
+		settings: v,
+	}
+}
+
+func setDefaults(v *viper.Viper, flags *pflag.FlagSet) {
 	v.SetDefault(cfgAccessBoxCacheRemovingCheckInterval, defaultAccessBoxCacheRemovingCheckInterval)
 
 	// logger:
@@ -986,78 +1096,21 @@ func newSettings() *viper.Viper {
 	// multinet
 	v.SetDefault(cfgMultinetFallbackDelay, defaultMultinetFallbackDelay)
 
-	// Bind flags
+	if resolveMethods, err := flags.GetStringSlice(cfgResolveOrder); err == nil {
-	if err := bindFlags(v, flags); err != nil {
+		v.SetDefault(cfgResolveOrder, resolveMethods)
-		panic(fmt.Errorf("bind flags: %w", err))
 	}
 
-	if err := flags.Parse(os.Args); err != nil {
+	if peers, err := flags.GetStringArray(cfgPeers); err == nil {
-		panic(err)
+		for i := range peers {
-	}
+			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".address", peers[i])
-
-	if v.IsSet(cfgServer+".0."+cfgTLSKeyFile) && v.IsSet(cfgServer+".0."+cfgTLSCertFile) {
-		v.Set(cfgServer+".0."+cfgTLSEnabled, true)
-	}
-
-	if resolveMethods != nil {
-		v.SetDefault(cfgResolveOrder, *resolveMethods)
-	}
-
-	if peers != nil && len(*peers) > 0 {
-		for i := range *peers {
-			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".address", (*peers)[i])
 			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".weight", 1)
 			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".priority", 1)
 		}
 	}
 
-	if domains != nil && len(*domains) > 0 {
+	if domains, err := flags.GetStringSlice(cfgListenDomains); err == nil && len(domains) > 0 {
-		v.SetDefault(cfgListenDomains, *domains)
+		v.SetDefault(cfgListenDomains, domains)
 	}
-
-	switch {
-	case help != nil && *help:
-		fmt.Printf("FrostFS S3 gateway %s\n", version.Version)
-		flags.PrintDefaults()
-
-		fmt.Println()
-		fmt.Println("Default environments:")
-		fmt.Println()
-		keys := v.AllKeys()
-		sort.Strings(keys)
-
-		for i := range keys {
-			if _, ok := ignore[keys[i]]; ok {
-				continue
-			}
-
-			defaultValue := v.GetString(keys[i])
-			if len(defaultValue) == 0 {
-				continue
-			}
-
-			k := strings.Replace(keys[i], ".", "_", -1)
-			fmt.Printf("%s_%s = %s\n", envPrefix, strings.ToUpper(k), defaultValue)
-		}
-
-		fmt.Println()
-		fmt.Println("Peers preset:")
-		fmt.Println()
-
-		fmt.Printf("%s_%s_[N]_ADDRESS = string\n", envPrefix, strings.ToUpper(cfgPeers))
-		fmt.Printf("%s_%s_[N]_WEIGHT = 0..1 (float)\n", envPrefix, strings.ToUpper(cfgPeers))
-
-		os.Exit(0)
-	case versionFlag != nil && *versionFlag:
-		fmt.Printf("FrostFS S3 Gateway\nVersion: %s\nGoVersion: %s\n", version.Version, runtime.Version())
-		os.Exit(0)
-	}
-
-	if err := readInConfig(v); err != nil {
-		panic(err)
-	}
-
-	return v
 }
 
 func bindFlags(v *viper.Viper, flags *pflag.FlagSet) error {

cmd/s3-gw/app_settings_test.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/resolver"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConfigReload(t *testing.T) {
+	f, err := os.CreateTemp("", "conf")
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, os.Remove(f.Name()))
+	}()
+
+	confData := `
+pprof:
+  enabled: true
+
+frostfsid:
+  contract: name.nns
+
+resolve_order:
+  - nns
+`
+
+	_, err = f.WriteString(confData)
+	require.NoError(t, err)
+	require.NoError(t, f.Close())
+
+	cfg := newSettings()
+
+	require.NoError(t, cfg.flags.Parse([]string{"--config", f.Name(), "--max_clients_count", "10"}))
+	require.NoError(t, cfg.reload())
+
+	require.True(t, cfg.config().GetBool(cfgPProfEnabled))
+	require.Equal(t, "name.nns", cfg.config().GetString(cfgFrostfsIDContract))
+	require.Equal(t, []string{resolver.NNSResolver}, cfg.config().GetStringSlice(cfgResolveOrder))
+	require.Equal(t, 10, cfg.config().GetInt(cfgMaxClientsCount))
+
+	require.NoError(t, os.Truncate(f.Name(), 0))
+	require.NoError(t, cfg.reload())
+
+	require.False(t, cfg.config().GetBool(cfgPProfEnabled))
+	require.Equal(t, "frostfsid.frostfs", cfg.config().GetString(cfgFrostfsIDContract))
+	require.Equal(t, []string{resolver.DNSResolver}, cfg.config().GetStringSlice(cfgResolveOrder))
+	require.Equal(t, 10, cfg.config().GetInt(cfgMaxClientsCount))
+}

cmd/s3-gw/main.go

@@ -8,9 +8,9 @@ import (
 
 func main() {
 	g, _ := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
-	v := newSettings()
+	cfg := newSettings()
 
-	a := newApp(g, v)
+	a := newApp(g, cfg)
 
 	go a.Serve(g)