Twisted Network Programming Essentials, 2nd Edition

Chapter 7. Logging

Twisted has its own logging systems that we’ve already seen used under the hood by twistd. This system plays nicely with Twisted-specific concepts like Failures but is also compatible with Python’s standard library logging facilities.

Basic In-Application Logging

The simplest way to add logging to your Twisted application is to import twisted.python.log, start logging to a file or stdout, and log events at particular log levels as you would with the Python standard logging module. For instance, Example 7-1 adds logging to a file for our echo server from Chapter 2.

Example 7-1. logging_echoserver.py

from twisted.internet import protocol, reactor
from twisted.python import log

class Echo(protocol.Protocol):
    def dataReceived(self, data):
        log.msg(data)
        self.transport.write(data)

class EchoFactory(protocol.Factory):
    def buildProtocol(self, addr):
        return Echo()

log.startLogging(open('echo.log', 'w'))
reactor.listenTCP(8000, EchoFactory())
reactor.run()

Logging starts once log.startLogging has been called. After that, information can be logged with log.msg or log.err; use log.msg to log strings and use log.err to log exceptions and failures. The default logging format produces output like this log of the echo server starting up, echoing one message, and terminating:

2012-11-15 20:26:37-0500 [-] Log opened. 2012-11-15 20:26:37-0500 [-] EchoFactory starting on 8000 2012-11-15 20:26:37-0500 [-] Starting factory <__main__.EchoFactory ... 2012-11-15 20:26:40-0500 [Echo,0,127.0.0.1] ...