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Structured JSON logging

Project Description


  • Tag log statements with arbitrary values for easier grouping and analysis
  • Add keyword arguments that are converted to JSON values
  • Variable substitution
  • Specifies where log calls are made from
  • Meant to be used with core Python logging (formatters, handlers, etc)
  • TRACE log level built-in


A simple log message'Hello')

{"msg": "Hello", "time": "12-12-14 10:12:01 EST", "level": "INFO", "loc": "test:log_test:20"}

Logging with tags

log.debug('Creating new user', 'MONGO', 'STORAGE')

{"msg": "Creating new user", "time": "12-12-14 10:12:09 EST", "tags": ["MONGO", "STORAGE"], "level": "DEBUG", "loc": "test:log_test:20"}

Adding JSON keys

log.debug('Some key', is_admin=True, username='papito')

{"msg": "Some key", "is_admin": true, "username": "papito", "time": "12-12-14 10:12:04 EST", "level": "DEBUG", "loc": "test:log_test:20"}

String substitution

log.debug('User "$username" admin? $is_admin', is_admin=False, username='fez')

{"msg": "User \"fez\" admin? False",  "username": "fez", "is_admin": false, "time": "12-12-14 10:12:18 EST", "level": "DEBUG", "loc": "test:log_test:20"}


Logging to console

import sys
import logging
from siftlog import SiftLog

logger = logging.getLogger()
handler = logging.StreamHandler(sys.stdout)

log = SiftLog(logger)

In this fashion, you can direct the JSON logs to any logging handler

Constants (re-occuring values)

You can define constants that will appear in every single log message. This is useful, for example, if you’d like to log process PID and hostname with every log message (recommended). This is done upon log adapter initialization:

import os
from siftlog import SyftLog
log = SiftLog(logger, pid=os.getpid(), env='INTEGRATION')

{"msg": "And here I am", "time": "12-12-14 11:12:24 EST", "pid": 37463, "env": "INTEGRATION", "level": "INFO"}

Custom time format

Define SiftLog.TIME_FORMAT, accepted by time.strftime()

Custom core key names

Core keys, such as msg and level can be overridden, if they clash with common keys you might be using.

The following can be redefined:

  • SiftLog.MESSAGE (default msg)
  • SiftLog.LEVEL (default level)
  • SiftLog.LOCATION (default loc)
  • SiftLog.TAGS (default tags)
  • SiftLog.TIME (default time)

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Source Dec 16, 2014

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