Logging FAQ

Level

• level - importance - severity

mean	level	syslog	console	go/slog	OpenTelemetry	slf4j
Emergency	emerg	0,panic
Alert	alert	1
Critical	crit	2
Fatal	fatal				FATAL, 21-24
Error	error	3,err,error	✅	8	ERROR, 17-20
Warning	warn	4,warning,warn	✅	4	WARN, 13-16
Notice	notice	5
Information	info	6	✅	0	INFO, 9-12
Debug	debug	7	✅	-4	DEBUG, 5-8
Trace	trace		✅		TRACE, 1-4

• https://opentelemetry.io/docs/specs/otel/logs/
  • SeverityText
  • SeverityNumber

/*
Bunyan
 const levels = {
    FATAL: 60,
    ERROR: 50,
    WARN: 40,
    INFO: 30,
    DEBUG: 20,
    TRACE: 10
  }

  Pino
  const levels = {
    fatal: 60,
    error: 50,
    warn: 40,
    info: 30,
    debug: 20,
    trace: 10
  }
Winston
  const levels = {
    error: 0,
    warn: 1,
    info: 2,
    debug: 3
  }
Syslog RFC 3164
0 = Emergency
1 = Alert
2 = Critical
3 = Error
4 = Warning
5 = Notice
6 = Informational
7 = Debug
 */