The library helps you to store logs in JSON format. Why is it important? Well, it facilitates integration with Logstash.
Usage example:
import logging import json_log_formatter formatter = json_log_formatter.JSONFormatter() json_handler = logging.FileHandler(filename='/var/log/my-log.json') json_handler.setFormatter(formatter) logger = logging.getLogger('my_json') logger.addHandler(json_handler) logger.setLevel(logging.INFO) logger.info('Sign up', extra={'referral_code': '52d6ce'}) try: raise ValueError('something wrong') except ValueError: logger.error('Request failed', exc_info=True)
The log file will contain the following log record (inline).
{
"message": "Sign up",
"time": "2015年09月01日T06:06:26.524448",
"referral_code": "52d6ce"
}
{
"message": "Request failed",
"time": "2015年09月01日T06:06:26.524449",
"exc_info": "Traceback (most recent call last): ..."
}If you use a log collection and analysis system,
you might need to include the built-in
log record attributes
with VerboseJSONFormatter.
json_handler.setFormatter(json_log_formatter.VerboseJSONFormatter()) logger.error('An error has occured')
{
"filename": "tests.py",
"funcName": "test_file_name_is_testspy",
"levelname": "ERROR",
"lineno": 276,
"module": "tests",
"name": "my_json",
"pathname": "/Users/bob/json-log-formatter/tests.py",
"process": 3081,
"processName": "MainProcess",
"stack_info": null,
"thread": 4664270272,
"threadName": "MainThread",
"message": "An error has occured",
"time": "2021年07月04日T21:05:42.767726"
}If you need to flatten complex objects as strings, use FlatJSONFormatter.
json_handler.setFormatter(json_log_formatter.FlatJSONFormatter()) logger.error('An error has occured') logger.info('Sign up', extra={'request': WSGIRequest({ 'PATH_INFO': 'bogus', 'REQUEST_METHOD': 'bogus', 'CONTENT_TYPE': 'text/html; charset=utf8', 'wsgi.input': BytesIO(b''), })})
{
"message": "Sign up",
"time": "2024年10月01日T00:59:29.332888+00:00",
"request": "<WSGIRequest: BOGUS '/bogus'>"
}You can use ujson or simplejson instead of built-in json library.
import json_log_formatter import ujson formatter = json_log_formatter.JSONFormatter() formatter.json_lib = ujson
Note, ujson doesn't support dumps(default=f) argument:
if it can't serialize an attribute, it might fail with TypeError or skip an attribute.
Here is an example of how the JSON formatter can be used with Django.
LOGGING['formatters']['json'] = { '()': 'json_log_formatter.JSONFormatter', } LOGGING['handlers']['json_file'] = { 'level': 'INFO', 'class': 'logging.FileHandler', 'filename': '/var/log/my-log.json', 'formatter': 'json', } LOGGING['loggers']['my_json'] = { 'handlers': ['json_file'], 'level': 'INFO', }
Let's try to log something.
import logging logger = logging.getLogger('my_json') logger.info('Sign up', extra={'referral_code': '52d6ce'})
You will likely need a custom log formatter. For instance, you want to log
a user ID, an IP address and time as django.utils.timezone.now().
To do so you should override JSONFormatter.json_record().
class CustomisedJSONFormatter(json_log_formatter.JSONFormatter): def json_record(self, message: str, extra: dict, record: logging.LogRecord) -> dict: extra['message'] = message extra['user_id'] = current_user_id() extra['ip'] = current_ip() # Include builtins extra['level'] = record.levelname extra['name'] = record.name if 'time' not in extra: extra['time'] = django.utils.timezone.now() if record.exc_info: extra['exc_info'] = self.formatException(record.exc_info) return extra
Let's say you want datetime to be serialized as timestamp.
You can use ujson (which does it by default) and disable
ISO8601 date mutation.
class CustomisedJSONFormatter(json_log_formatter.JSONFormatter): json_lib = ujson def mutate_json_record(self, json_record): return json_record
$ pip install -r requirements.txt $ tox