[#736] logger: Add journald support

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/util/logger/logger.go

@@ -1,6 +1,10 @@
 package logger
 
 import (
+	"fmt"
+
+	"git.frostfs.info/TrueCloudLab/zapjournald"
+	"github.com/ssgreg/journald"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 )
@@ -35,8 +39,15 @@ type Prm struct {
 	SamplingHook func(e zapcore.Entry, sd zapcore.SamplingDecision)
 
 	// do not support runtime rereading
+	dest string
 }
 
+const (
+	DestinationUndefined = ""
+	DestinationStdout    = "stdout"
+	DestinationJournald  = "journald"
+)
+
 // SetLevelString sets the minimum logging level. Default is
 // "info".
 //
@@ -48,6 +59,16 @@ func (p *Prm) SetLevelString(s string) error {
 	return p.level.UnmarshalText([]byte(s))
 }
 
+func (p *Prm) SetDestination(d string) error {
+	if d != DestinationStdout && d != DestinationJournald {
+		return fmt.Errorf("invalid logger destination %s", d)
+	}
+	if p != nil {
+		p.dest = d
+	}
+	return nil
+}
+
 // Reload reloads configuration of a connected instance of the Logger.
 // Returns ErrLoggerNotConnected if no connection has been performed.
 // Returns any reconfiguration error from the Logger directly.
@@ -79,7 +100,17 @@ func NewLogger(prm *Prm) (*Logger, error) {
 	if prm == nil {
 		prm = defaultPrm()
 	}
+	switch prm.dest {
+	case DestinationUndefined, DestinationStdout:
+		return newConsoleLogger(prm)
+	case DestinationJournald:
+		return newJournaldLogger(prm)
+	default:
+		return nil, fmt.Errorf("unknown destination %s", prm.dest)
+	}
+}
 
+func newConsoleLogger(prm *Prm) (*Logger, error) {
 	lvl := zap.NewAtomicLevelAt(prm.level)
 
 	c := zap.NewProductionConfig()
@@ -103,6 +134,34 @@ func NewLogger(prm *Prm) (*Logger, error) {
 	return l, nil
 }
 
+func newJournaldLogger(prm *Prm) (*Logger, error) {
+	lvl := zap.NewAtomicLevelAt(prm.level)
+
+	c := zap.NewProductionConfig()
+	c.Level = lvl
+	c.Encoding = "console"
+	c.EncoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
+	if prm.SamplingHook != nil {
+		c.Sampling.Hook = prm.SamplingHook
+	}
+
+	encoder := zapjournald.NewPartialEncoder(zapcore.NewConsoleEncoder(c.EncoderConfig), zapjournald.SyslogFields)
+
+	core := zapjournald.NewCore(zap.NewAtomicLevelAt(prm.level), encoder, &journald.Journal{}, zapjournald.SyslogFields)
+	coreWithContext := core.With([]zapcore.Field{
+		zapjournald.SyslogFacility(zapjournald.LogDaemon),
+		zapjournald.SyslogIdentifier(),
+		zapjournald.SyslogPid(),
+	})
+
+	lZap := zap.New(coreWithContext, zap.AddStacktrace(zap.NewAtomicLevelAt(zap.FatalLevel)))
+
+	l := &Logger{Logger: lZap, lvl: lvl}
+	prm._log = l
+
+	return l, nil
+}
+
 func (l *Logger) reload(prm Prm) error {
 	l.lvl.SetLevel(prm.level)
 	return nil