Add Inner Ring code

pkg/util/logger/logger.go

@@ -0,0 +1,102 @@
+package logger
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/spf13/viper"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+// Logger represents the component
+// for writing messages to log.
+//
+// It is a type alias of
+// 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")
+
+// 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.EncoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
+
+	l, err := c.Build(
+		// enable trace only for current log-level
+		zap.AddStacktrace(traceLvl))
+	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")
+
+	return l.With(
+		zap.String("app_name", name),
+		zap.String("app_version", version)), nil
+}
+
+func safeLevel(lvl string) zap.AtomicLevel {
+	switch strings.ToLower(lvl) {
+	case "debug":
+		return zap.NewAtomicLevelAt(zap.DebugLevel)
+	case "warn":
+		return zap.NewAtomicLevelAt(zap.WarnLevel)
+	case "error":
+		return zap.NewAtomicLevelAt(zap.ErrorLevel)
+	case "fatal":
+		return zap.NewAtomicLevelAt(zap.FatalLevel)
+	case "panic":
+		return zap.NewAtomicLevelAt(zap.PanicLevel)
+	default:
+		return zap.NewAtomicLevelAt(zap.InfoLevel)
+	}
+}