[#493] logger: Abolish non-usable options

Change logger's encoding to `console`, time encoding to `ISO8601TimeEncoder`
and leave all other options as they are in `zap.NewProductionConfig`.

Remove default values of no longer existing options in node/ir config.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/util/logger/logger.go

@@ -16,14 +16,6 @@ import (
 // go.uber.org/zap.Logger.
 type Logger = zap.Logger
 
-const (
-	formatJSON    = "json"
-	formatConsole = "console"
-
-	defaultSamplingInitial    = 100
-	defaultSamplingThereafter = 100
-)
-
 // ErrNilLogger is returned by functions that
 // expect a non-nil Logger, but received nil.
 var ErrNilLogger = errors.New("logger is nil")
@@ -31,51 +23,18 @@ var ErrNilLogger = errors.New("logger is nil")
 // NewLogger is a logger's constructor.
 func NewLogger(v *viper.Viper) (*Logger, error) {
 	c := zap.NewProductionConfig()
-
-	c.OutputPaths = []string{"stdout"}
-	c.ErrorOutputPaths = []string{"stdout"}
-
-	if v.IsSet("logger.sampling") {
-		c.Sampling = &zap.SamplingConfig{
-			Initial:    defaultSamplingInitial,
-			Thereafter: defaultSamplingThereafter,
-		}
-
-		if val := v.GetInt("logger.sampling.initial"); val > 0 {
-			c.Sampling.Initial = val
-		}
-
-		if val := v.GetInt("logger.sampling.thereafter"); val > 0 {
-			c.Sampling.Thereafter = val
-		}
-	}
-
-	// logger level
 	c.Level = safeLevel(v.GetString("logger.level"))
-	traceLvl := safeLevel(v.GetString("logger.trace_level"))
-
-	// logger format
-	switch f := v.GetString("logger.format"); strings.ToLower(f) {
-	case formatConsole:
-		c.Encoding = formatConsole
-	default:
-		c.Encoding = formatJSON
-	}
-
-	// logger time
+	c.Encoding = "console"
 	c.EncoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
 
 	l, err := c.Build(
-		// enable trace only for current log-level
-		zap.AddStacktrace(traceLvl))
+		// record a stack trace for all messages at or above fatal level
+		zap.AddStacktrace(zap.NewAtomicLevelAt(zap.FatalLevel)),
+	)
 	if err != nil {
 		return nil, err
 	}
 
-	if v.GetBool("logger.no_disclaimer") {
-		return l, nil
-	}
-
 	name := v.GetString("app.name")
 	version := v.GetString("app.version")