How to implement structured logging through indentation?

I’d like to implement a context manager that will add some indentation to the log messages sent from within its scope.

Something like this:

from loguru import logger

# ... configure the logger in any way

logger.info('this is the "root" level')
logger.info('and so is this')

with indent_logs(logger, indent_size=4):
    logger.info("I'm at the first level")

    with indent_logs(logger, indent_size=2):
        logger.info("I'm on the second level")

    logger.info('back on level 1')

logger.info('back at root')

Which would output:

2021-04-09 14:04:14.335 | INFO     | __main__:<module>:29 - this is the "root" level
2021-04-09 14:04:14.335 | INFO     | __main__:<module>:30 - and so is this
2021-04-09 14:04:14.336 | INFO     | __main__:<module>:33 -     I'm at the first level
2021-04-09 14:04:14.336 | INFO     | __main__:<module>:36 -       I'm on the second level
2021-04-09 14:04:14.336 | INFO     | __main__:<module>:38 -     back on level 1
2021-04-09 14:04:14.336 | INFO     | __main__:<module>:40 - back at root

But I’m unsure of what is the safest way to modify the logger so that all handlers and configurations are affected properly.

Any advice?

[Delgan]

Hi @edagnin. 😃

Have you thought about using a dynamic formatter with Loguru?

By doing a quick test, I get the following result:

import sys

from loguru import logger


def formatter(record):
    base_format = "{time} {level} {name} {message} " + " " * 10
    base = base_format.format_map(record)
    lines = str(record["extra"].get("data", "")).splitlines()
    indent = "\n" + " " * len(base)
    reformatted = base + indent.join(lines)
    record["extra"]["reformatted"] = reformatted
    return "{extra[reformatted]}\n{exception}"


logger.remove()
logger.add(sys.stderr, format=formatter)


data = """---------------- Request ----------------
Headers       :   {"Accept": "*/*",
                   "Accept-Encoding": "gzip, deflate",
                   "Connection": "keep-alive",
                   "Content-Length": "20",
                   "User-Agent": "python-requests/2.27.1",
                   "cookie": "foo=bar; bar=baz",
                   "x-pretty-print": "2"}
URL           :   http://mockbin.com/request/test/1/mock?foo=bar&foo=baz
Method        :   POST
Body          :   {"foo": "bar"}"""

logger.info("Default message")
logger.bind(data=data).info("Message with data")

2022-03-15T21:48:51.694763+0100 INFO __main__ Default message           
2022-03-15T21:48:51.695066+0100 INFO __main__ Message with data           ---------------- Request ----------------
                                                                          Headers       :   {"Accept": "*/*",
                                                                                             "Accept-Encoding": "gzip, deflate",
                                                                                             "Connection": "keep-alive",
                                                                                             "Content-Length": "20",
                                                                                             "User-Agent": "python-requests/2.27.1",
                                                                                             "cookie": "foo=bar; bar=baz",
                                                                                             "x-pretty-print": "2"}
                                                                          URL           :   http://mockbin.com/request/test/1/mock?foo=bar&foo=baz
                                                                          Method        :   POST
                                                                          Body          :   {"foo": "bar"}

[edagnin]

@Delgan Thank you for your help!

I have done a bit of a cleanup and everything is working as expected.

I didn’t end using your last suggestions, since after I did the cleanup it was working AND I am not using the PropagateHandler since it’s working without that too.

So, with that said! Thank you for your help, genuinely appreciated! I hope this issue with all of its replies helps the next person too! 😃