objectif

Produire des logs JSON parsables pour ingestion centralisée.

code minimal

import json, logging, io

class JsonFormatter(logging.Formatter):
    def format(self, record: logging.LogRecord) -> str:
        payload = {
            "level": record.levelname,
            "name": record.name,
            "message": record.getMessage(),
        }
        return json.dumps(payload, ensure_ascii=False)

stream = io.StringIO()
handler = logging.StreamHandler(stream)
handler.setFormatter(JsonFormatter())
log = logging.getLogger("svc")
log.setLevel(logging.INFO)
log.handlers = [handler]
log.info("hello")
line = stream.getvalue().strip()
print(json.loads(line)["message"])  # attendu: hello

utilisation

import json
s = '{"level":"INFO","name":"svc","message":"ok"}'
print(json.loads(s)["level"] == "INFO")

variante(s) utile(s)

import json, logging, io
class JsonFormatter(logging.Formatter):
    def format(self, record):
        return json.dumps({"ts": record.created, "msg": record.getMessage()}, ensure_ascii=False)
buf = io.StringIO()
h = logging.StreamHandler(buf); h.setFormatter(JsonFormatter())
lg = logging.getLogger("x"); lg.setLevel(logging.INFO); lg.handlers=[h]
lg.info("x")
print("ts" in buf.getvalue())

notes

• Ajoutez timestamp, thread, correlation-id selon vos besoins.
• Évitez print() pour du logging en production.