Include Native Log Record Attributes

[jteppinette]

We should be able to configure the logger to always include some default keys. For example, a user may want to always include a time or logger key.

This functionality is seen in the python-json-logger.

[jteppinette]

This functionality has been added by the latest 0.0.5 release.

---

Default Keys

You can request that the formatter always include certain attributes on the
log record by using the keys parameter. If the key you want to include in
your output is represented by a different attribute on the log record, then
you can use the mapping parameter to provide that key/attribute mapping.

Notice, the keys parameter defaults to ["at"] and will be overridden
by any provided keys.

import logging
from logfmter import Logfmter

formatter = Logfmter(keys=["at", "processName"])

handler = logging.StreamHandler()
handler.setFormatter(formatter)

logging.basicConfig(handlers=[handler])

logging.error("hello") # at=ERROR processName=MainProceess msg=hello

Utilizing a mapping to convert the processName attribute to process.

Notice, the mapping parameter defaults to {"at": "levelname"} and will be overridden
by any provided mapping.

import logging
from logfmter import Logfmter

formatter = Logfmter(
    keys=["at", "process"],
    mapping={"at": "levelname", "process": "processName"}
)

handler = logging.StreamHandler()
handler.setFormatter(formatter)

logging.basicConfig(handlers=[handler])

logging.error("hello") # at=ERROR process=MainProceess msg=hello

Date Formatting

If you request the asctime attribute (directly or through a mapping), then the date format
can be overridden through the datefmt parameter.

import logging
from logfmter import Logfmter

formatter = Logfmter(
    keys=["at", "when"],
    mapping={"at": "levelname", "when": "asctime"},
    datefmt="%Y-%m-%d"
)

handler = logging.StreamHandler()
handler.setFormatter(formatter)

logging.basicConfig(handlers=[handler])

logging.error("hello") # at=ERROR when=2022-04-20 msg=hello