Add logrus Hook to write logs to stderr and stdout based on log level (…

…distribworks#1312)

cmd/dkron.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"github.com/distribworks/dkron/v3/dkron"
+	"github.com/distribworks/dkron/v3/logging"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -58,6 +59,9 @@ func initConfig() {
 	viper.SetEnvKeyReplacer(replacer)
 	viper.AutomaticEnv() // read in environment variables that match
 
+	// Add hook to set error logs to stderr and regular logs to stdout
+	logrus.AddHook(&logging.LogSplitter{})
+
 	err := viper.ReadInConfig() // Find and read the config file
 	if err != nil {             // Handle errors reading the config file
 		logrus.WithError(err).Info("No valid config found: Applying default values.")

logging/logging.go

@@ -0,0 +1,32 @@
+package logging
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+type LogSplitter struct{}
+
+// Levels returns levels that are supported by the hook
+func (l *LogSplitter) Levels() []logrus.Level {
+	return []logrus.Level{logrus.PanicLevel, logrus.FatalLevel, logrus.ErrorLevel, logrus.WarnLevel, logrus.InfoLevel, logrus.DebugLevel, logrus.TraceLevel}
+}
+
+// Fire handles logging events based on log levels.
+func (l *LogSplitter) Fire(entry *logrus.Entry) error {
+	if entry == nil {
+		return fmt.Errorf("logrus entry is nil")
+	}
+
+	switch entry.Level {
+	case logrus.WarnLevel, logrus.DebugLevel, logrus.InfoLevel, logrus.TraceLevel:
+		entry.Logger.Out = os.Stdout
+	case logrus.ErrorLevel, logrus.PanicLevel, logrus.FatalLevel:
+		entry.Logger.Out = os.Stderr
+	default:
+		entry.Logger.Out = os.Stdout
+	}
+	return nil
+}