Log Levels Reference

Reference des niveaux de log standards pour differents systemes.

Comparaison des Standards

Severite	Syslog	Python	Log4j/SLF4J	JavaScript	RFC 5424
EMERGENCY	0	-	-	-	0
ALERT	1	-	-	-	1
CRITICAL	2	50	FATAL	-	2
ERROR	3	40	ERROR	error	3
WARNING	4	30	WARN	warn	4
NOTICE	5	-	-	-	5
INFO	6	20	INFO	info/log	6
DEBUG	7	10	DEBUG	debug	7
TRACE	-	-	TRACE	trace	-

Description des Niveaux

Syslog Facilities

Calculateur Priority (Syslog)

Priority = Facility × 8 + Severity

Facility 0 - kern 1 - user 2 - mail 3 - daemon 4 - auth 5 - syslog 6 - lpr 7 - news 8 - uucp 9 - cron 10 - authpriv 11 - ftp 16 - local0 17 - local1 18 - local2 19 - local3 20 - local4 21 - local5 22 - local6 23 - local7

Severity 0 - emerg 1 - alert 2 - crit 3 - err 4 - warning 5 - notice 6 - info 7 - debug

Priority: 14 <14>

Exemples par Langage

Python JavaScript Java Bash

import logging

# Configuration basique
logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)

logger = logging.getLogger(__name__)

logger.debug('Message de debug')
logger.info('Information')
logger.warning('Attention')
logger.error('Erreur')
logger.critical('Critique')

// Console native
console.debug('Debug message');
console.log('Log message');
console.info('Info message');
console.warn('Warning message');
console.error('Error message');

// Avec winston
const winston = require('winston');
const logger = winston.createLogger({
  level: 'debug',
  format: winston.format.json(),
  transports: [
    new winston.transports.Console()
  ]
});

logger.debug('Debug');
logger.info('Info');
logger.warn('Warning');
logger.error('Error');

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MyClass {
    private static final Logger logger =
        LoggerFactory.getLogger(MyClass.class);

    public void example() {
        logger.trace("Trace message");
        logger.debug("Debug message");
        logger.info("Info message");
        logger.warn("Warning message");
        logger.error("Error message");
    }
}

#!/bin/bash

# Syslog via logger
logger -p user.info "Information message"
logger -p user.warning "Warning message"
logger -p user.err "Error message"

# Avec tag
logger -t myapp -p local0.info "Application message"

# Priority numerique
logger -p 14 "Priority 14 = user.info"

# Vers fichier specifique
logger -p local0.info -f /var/log/myapp.log "Message"

Bonnes Pratiques

Niveau	Quand l'utiliser
ERROR	Erreur necessitant une intervention
WARN	Comportement inattendu mais non bloquant
INFO	Evenements normaux importants
DEBUG	Details pour le debug (dev uniquement)