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=====================
JSON log formatter 🪵
=====================
The library helps you to store logs in JSON format. Why is it important?
Well, it facilitates integration with **Logstash**.
Usage example:
.. code-block:: python
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).
.. code-block:: json
{
"message": "Sign up",
"time": "2015-09-01T06:06:26.524448",
"referral_code": "52d6ce"
}
{
"message": "Request failed",
"time": "2015-09-01T06:06:26.524449",
"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 <https://docs.python.org/3/library/logging.html#logrecord-attributes>`_
with ``VerboseJSONFormatter``.
.. code-block:: python
json_handler.setFormatter(json_log_formatter.VerboseJSONFormatter())
logger.error('An error has occured')
.. code-block:: json
{
"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": "2021-07-04T21:05:42.767726"
}
If you need to flatten complex objects as strings, use ``FlatJSONFormatter``.
.. code-block:: python
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''),
})})
.. code-block:: json
{
"message": "Sign up",
"time": "2024-10-01T00:59:29.332888+00:00",
"request": "<WSGIRequest: BOGUS '/bogus'>"
}
JSON libraries
--------------
You can use **ujson** or **simplejson** instead of built-in **json** library.
.. code-block:: python
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.
Django integration
------------------
Here is an example of how the JSON formatter can be used with Django.
.. code-block:: python
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.
.. code-block:: python
import logging
logger = logging.getLogger('my_json')
logger.info('Sign up', extra={'referral_code': '52d6ce'})
Custom formatter
----------------
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()``.
.. code-block:: python
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.
.. code-block:: python
class CustomisedJSONFormatter(json_log_formatter.JSONFormatter):
json_lib = ujson
def mutate_json_record(self, json_record):
return json_record
Tests
-----
.. code-block:: console
$ pip install -r requirements.txt
$ tox
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