tools/python/google/logging_utils.py

   1 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 ''' Utility functions and objects for logging.
   6 '''
   7
   8 import logging
   9 import sys
  10
  11 class StdoutStderrHandler(logging.Handler):
  12   ''' Subclass of logging.Handler which outputs to either stdout or stderr
  13   based on a threshold level.
  14   '''
  15
  16   def __init__(self, threshold=logging.WARNING, err=sys.stderr, out=sys.stdout):
  17     ''' Args:
  18           threshold: below this logging level messages are sent to stdout,
  19             otherwise they are sent to stderr
  20           err: a stream object that error messages are sent to, defaults to
  21             sys.stderr
  22           out: a stream object that non-error messages are sent to, defaults to
  23             sys.stdout
  24     '''
  25     logging.Handler.__init__(self)
  26     self._err = logging.StreamHandler(err)
  27     self._out = logging.StreamHandler(out)
  28     self._threshold = threshold
  29     self._last_was_err = False
  30
  31   def setLevel(self, lvl):
  32     logging.Handler.setLevel(self, lvl)
  33     self._err.setLevel(lvl)
  34     self._out.setLevel(lvl)
  35
  36   def setFormatter(self, formatter):
  37     logging.Handler.setFormatter(self, formatter)
  38     self._err.setFormatter(formatter)
  39     self._out.setFormatter(formatter)
  40
  41   def emit(self, record):
  42     if record.levelno < self._threshold:
  43       self._out.emit(record)
  44       self._last_was_err = False
  45     else:
  46       self._err.emit(record)
  47       self._last_was_err = False
  48
  49   def flush(self):
  50     # preserve order on the flushing, the stalest stream gets flushed first
  51     if self._last_was_err:
  52       self._out.flush()
  53       self._err.flush()
  54     else:
  55       self._err.flush()
  56       self._out.flush()
  57
  58
  59 FORMAT = "%(asctime)s %(filename)s [%(levelname)s] %(message)s"
  60 DATEFMT = "%H:%M:%S"
  61
  62 def config_root(level=logging.INFO, threshold=logging.WARNING, format=FORMAT,
  63          datefmt=DATEFMT):
  64   ''' Configure the root logger to use a StdoutStderrHandler and some default
  65   formatting.
  66     Args:
  67       level: messages below this level are ignored
  68       threshold: below this logging level messages are sent to stdout,
  69         otherwise they are sent to stderr
  70       format: format for log messages, see logger.Format
  71       datefmt: format for date in log messages
  72
  73   '''
  74   # to set the handler of the root logging object, we need to do setup
  75   # manually rather than using basicConfig
  76   root = logging.getLogger()
  77   root.setLevel(level)
  78   formatter = logging.Formatter(format, datefmt)
  79   handler = StdoutStderrHandler(threshold=threshold)
  80   handler.setLevel(level)
  81   handler.setFormatter(formatter)
  82   root.addHandler(handler)