use a custom logger

log/log.go

@@ -0,0 +1,107 @@
+// Provides a simple way of logging with different levels.
+// Time/Data are not logged on purpose because systemd adds
+// them for us.
+package log
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+var DebugWriter io.Writer = os.Stderr
+var InfoWriter io.Writer = os.Stderr
+var WarnWriter io.Writer = os.Stderr
+var ErrorWriter io.Writer = os.Stderr
+
+func init() {
+	if lvl, ok := os.LookupEnv("LOGLEVEL"); ok {
+		switch lvl {
+		case "err", "fatal":
+			WarnWriter = io.Discard
+			fallthrough
+		case "warn":
+			InfoWriter = io.Discard
+			fallthrough
+		case "info":
+			DebugWriter = io.Discard
+		case "debug":
+			// Nothing to do...
+		default:
+			Warnf("environment variable LOGLEVEL has invalid value %#v", lvl)
+		}
+	}
+}
+
+func Debug(v ...interface{}) {
+	if DebugWriter != io.Discard {
+		v = append([]interface{}{"[DEBUG]"}, v...)
+		fmt.Fprintln(DebugWriter, v...)
+	}
+}
+
+func Info(v ...interface{}) {
+	if InfoWriter != io.Discard {
+		v = append([]interface{}{"[INFO]"}, v...)
+		fmt.Fprintln(InfoWriter, v...)
+	}
+}
+
+func Print(v ...interface{}) {
+	Info(v...)
+}
+
+func Warn(v ...interface{}) {
+	if WarnWriter != io.Discard {
+		v = append([]interface{}{"[WARNING]"}, v...)
+		fmt.Fprintln(WarnWriter, v...)
+	}
+}
+
+func Error(v ...interface{}) {
+	if ErrorWriter != io.Discard {
+		v = append([]interface{}{"[ERROR]"}, v...)
+		fmt.Fprintln(ErrorWriter, v...)
+	}
+}
+
+func Fatal(v ...interface{}) {
+	if ErrorWriter != io.Discard {
+		v = append([]interface{}{"[FATAL]"}, v...)
+		fmt.Fprintln(ErrorWriter, v...)
+	}
+}
+
+func Debugf(format string, v ...interface{}) {
+	if DebugWriter != io.Discard {
+		fmt.Fprintf(DebugWriter, "[DEBUG] "+format+"\n", v...)
+	}
+}
+
+func Infof(format string, v ...interface{}) {
+	if InfoWriter != io.Discard {
+		fmt.Fprintf(InfoWriter, "[INFO] "+format+"\n", v...)
+	}
+}
+
+func Printf(format string, v ...interface{}) {
+	Infof(format, v...)
+}
+
+func Warnf(format string, v ...interface{}) {
+	if WarnWriter != io.Discard {
+		fmt.Fprintf(WarnWriter, "[WARNING] "+format+"\n", v...)
+	}
+}
+
+func Errorf(format string, v ...interface{}) {
+	if ErrorWriter != io.Discard {
+		fmt.Fprintf(ErrorWriter, "[ERROR] "+format+"\n", v...)
+	}
+}
+
+func Fatalf(format string, v ...interface{}) {
+	if ErrorWriter != io.Discard {
+		fmt.Fprintf(ErrorWriter, "[FATAL] "+format+"\n", v...)
+	}
+}