Formatting message does not work

Comienza en fluent.handler.FluentRecordFormatter y reproduce la configuración de logging proporcionada, comparando el tratamiento del campo message con el de los demás campos formateados. Se considera terminado cuando el valor configurado "%(message).5s" se emite como cinco caracteres en la salida de Fluentd, con una prueba de regresión que cubra este comportamiento.

While trying to truncate the message part using formatter. fluent.handler.FluentRecordFormatter works normally with all fields except message

configuration

LOGGING = {
    'version': 1,
    'disable_existing_loggers': True,
    'formatters': {
        'verbose': {
            'format': "[%(levelname)s %(asctime)s %(module)s -> %(lineno)d] %(message)s",
            'datefmt': "%Y-%b-%d %H:%M:%S"
        },
        'console': {
            'format': '[%(levelname)s %(asctime)s] %(message)s',
            'datefmt': "%Y-%b-%d %H:%M:%S"
        },
        'fluent_fmt': {
            '()': "fluent.handler.FluentRecordFormatter",
            'format': {
                'lvl': '%(levelname)s',
                'host': '%(hostname)s',
                'mod': '%(module)s',
                'line': '%(lineno)d',
                'tms': '%(created)d',
                'trace': '%(exc_text)s',
                "proc": '%(processName)s',
                "message": "%(message).5s"
            }
        },
    },
    'handlers': {
        'console': {
            'level': 'INFO',
            'class': 'logging.StreamHandler',
            'formatter': 'verbose'
        },
        'file': {
            'level': 'INFO',
            'class': 'logging.handlers.TimedRotatingFileHandler',
            'filename': 'celery_nohup',
            'when': 'D',  # this specifies the interval
            'interval': 1,  # defaults to 1, only necessary for other values
            'formatter': 'verbose',
        },
        'fluentd': {
            'level': 'INFO',
            'class': 'fluent.handler.FluentHandler',
            'formatter': 'fluent_fmt',
            'tag': 'default.log',
            'host': 'localhost',
            'port': 24224,
            'timeout':3.0,
            'verbose': False,
            "msgpack_kwargs":{'default' : str}
        }, 

    },
    'loggers': {
        'django': {
            'handlers': ['console'],
            'level': "INFO",
            'propagate': True,
        },
        'celery': {
            'handlers': ['console', 'fluentd'],
            'level': "INFO",
            'propagate': True,
        },
        'ap_scheduler': {
            'handlers': ['console', 'fluentd'],
            'level': "INFO",
            'propagate': True,
        },
    },
}

expected output: message truncated to 5 characters
fluentd_1 | 2022-06-02 18:58:43.000000000 +0000 default.log: {"lvl":"INFO","host":"E7440","mod":"mingle","line":"40","tms":"1654196323","trace":"None","proc":"MainProcess","message":"mingl"}

obtained output
fluentd_1 | 2022-06-02 18:58:43.000000000 +0000 default.log: {"lvl":"INFO","host":"E7440","mod":"mingle","line":"40","tms":"1654196323","trace":"None","proc":"MainProcess","message":"mingle: searching for neighbors"}