Add a function for enabling sys logs (#8215)

pkg/logging/logger.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"log/syslog"
 	"os"
 	"reflect"
 	"runtime"
@@ -13,6 +14,7 @@ import (
 	"time"
 
 	"github.com/sirupsen/logrus"
+	lSyslog "github.com/sirupsen/logrus/hooks/syslog"
 	"gopkg.in/natefinch/lumberjack.v2"
 )
 
@@ -65,6 +67,7 @@ var (
 	formatterInitOnce sync.Once
 	defaultLogger     = logrus.New()
 	openLoggers       []io.Closer
+	syslogOnce        sync.Once
 )
 
 func Level() string {
@@ -394,6 +397,40 @@ func ContextUnavailable() Logger {
 	}
 }
 
+func ContextUnavailableWithSysLogs(sysLogsLevel string) Logger {
+	// wrap formatter with our own formatter that overrides caller
+	formatterInitOnce.Do(func() {
+		defaultLogger.SetReportCaller(true)
+		defaultLogger.SetNoLock()
+		defaultLogger.Formatter = logrusCallerFormatter{defaultLogger.Formatter}
+	})
+	syslogOnce.Do(func() {
+		var hook *lSyslog.SyslogHook
+		var err error
+		switch strings.ToLower(sysLogsLevel) {
+		// There's no syslog level for trace, using debug instead.
+		case "trace", "debug":
+			hook, err = lSyslog.NewSyslogHook("", "", syslog.LOG_DEBUG, "")
+		case "info":
+			hook, err = lSyslog.NewSyslogHook("", "", syslog.LOG_INFO, "")
+		case "warn", "warning":
+			hook, err = lSyslog.NewSyslogHook("", "", syslog.LOG_WARNING, "")
+		case "error":
+			hook, err = lSyslog.NewSyslogHook("", "", syslog.LOG_ERR, "")
+		case "panic", "null", "none":
+			hook, err = lSyslog.NewSyslogHook("", "", syslog.LOG_CRIT, "")
+		}
+		if err != nil {
+			defaultLogger.WithError(err).Error("failed to set syslog hook")
+		} else {
+			defaultLogger.AddHook(hook)
+		}
+	})
+	return &logrusEntryWrapper{
+		e: logrus.NewEntry(defaultLogger),
+	}
+}
+
 // GetFieldsFromContext returns the logging fields on ctx or nil.
 func GetFieldsFromContext(ctx context.Context) Fields {
 	fields := ctx.Value(LogFieldsContextKey)