Intercept Python Logging

Thu, 26 Jul 2018 00:00:00 +0000

The problem:

I need to ship specific log record and had formatter written in python. It is pretty complex transformation.

I thought of using Logstash but I then need to either convert this python logic or write a plugin to use already written python parser. Plus I need to install logstash… I wanted a simpler solution

How to solve it

Use custom python logging Handler and Filter!

import logging

messages = []
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)


class ListenFilter(logging.Filter):

 def filter(self, record):
 """Determine which log records to output.
 Returns 0 for no, nonzero for yes.
 """
 if record.getMessage().startswith('dont: '):
 return False
 return True


class RequestsHandler(logging.Handler):
 def emit(self, record):
 """Send the log records (created by loggers) to
 the appropriate destination.
 """
 messages.append(record.getMessage())


handler = RequestsHandler()
logger.addHandler(handler)

filter_ = ListenFilter()
logger.addFilter(filter_)

# log I want
logger.info("logme: Howdy!")


# log i want to skip
logger.info("dont: I'm doing great!")

# prints ['logme: Howdy!']
print(messages)

Cheers!

Logging on the art of simplicity

Intercept Python Logging

The problem:

How to solve it