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"""Logging utilities for Certbot.
The best way to use this module is through `pre_arg_parse_setup` and
`post_arg_parse_setup`. `pre_arg_parse_setup` configures a minimal
terminal logger and ensures a detailed log is written to a secure
temporary file if Certbot exits before `post_arg_parse_setup` is called.
`post_arg_parse_setup` relies on the parsed command line arguments and
does the full logging setup with terminal and rotating file handling as
configured by the user. Any logged messages before
`post_arg_parse_setup` is called are sent to the rotating file handler.
Special care is taken by both methods to ensure all errors are logged
and properly flushed before program exit.
from __future__ import print_function
import functools
import logging
import logging.handlers
import os
import sys
import tempfile
import time
import traceback
from acme import messages
from certbot import constants
from certbot import errors
from certbot import util
# Logging format
CLI_FMT = "%(message)s"
FILE_FMT = "%(asctime)s:%(levelname)s:%(name)s:%(message)s"
logger = logging.getLogger(__name__)
def pre_arg_parse_setup():
"""Setup logging before command line arguments are parsed.
Terminal logging is setup using
`certbot.constants.QUIET_LOGGING_LEVEL` so Certbot is as quiet as
possible. File logging is setup so that logging messages are
buffered in memory. If Certbot exits before `post_arg_parse_setup`
is called, these buffered messages are written to a temporary file.
If Certbot doesn't exit, `post_arg_parse_setup` writes the messages
to the normal log files.
This function also sets `logging.shutdown` to be called on program
exit which automatically flushes logging handlers and
`sys.excepthook` to properly log/display fatal exceptions.
temp_handler = TempHandler()
memory_handler = MemoryHandler(temp_handler)
stream_handler = ColoredStreamHandler()
root_logger = logging.getLogger()
root_logger.setLevel(logging.DEBUG) # send all records to handlers
# logging.shutdown will flush the memory handler because flush() and
# close() are explicitly called
sys.excepthook = functools.partial(
pre_arg_parse_except_hook, memory_handler,
debug='--debug' in sys.argv, log_path=temp_handler.path)
def post_arg_parse_setup(config):
"""Setup logging after command line arguments are parsed.
This function assumes `pre_arg_parse_setup` was called earlier and
the root logging configuration has not been modified. A rotating
file logging handler is created and the buffered log messages are
sent to that handler. Terminal logging output is set to the level
requested by the user.
:param certbot.interface.IConfig config: Configuration object
file_handler, file_path = setup_log_file_handler(
config, 'letsencrypt.log', FILE_FMT)
logs_dir = os.path.dirname(file_path)
root_logger = logging.getLogger()
memory_handler = stderr_handler = None
for handler in root_logger.handlers:
if isinstance(handler, ColoredStreamHandler):
stderr_handler = handler
elif isinstance(handler, MemoryHandler):
memory_handler = handler
msg = 'Previously configured logging handlers have been removed!'
assert memory_handler is not None and stderr_handler is not None, msg
temp_handler =
if config.quiet:
level = constants.QUIET_LOGGING_LEVEL
level = -config.verbose_count * 10
logger.debug('Root logging level set at %d', level)'Saving debug log to %s', file_path)
sys.excepthook = functools.partial(
post_arg_parse_except_hook, debug=config.debug, log_path=logs_dir)
def setup_log_file_handler(config, logfile, fmt):
"""Setup file debug logging.
:param certbot.interface.IConfig config: Configuration object
:param str logfile: basename for the log file
:param str fmt: logging format string
:returns: file handler and absolute path to the log file
:rtype: tuple
# TODO: logs might contain sensitive data such as contents of the
# private key! #525
config.logs_dir, 0o700, os.geteuid(), config.strict_permissions)
log_file_path = os.path.join(config.logs_dir, logfile)
handler = logging.handlers.RotatingFileHandler(
log_file_path, maxBytes=2 ** 20,
except IOError as error:
raise errors.Error(util.PERM_ERR_FMT.format(error))
# rotate on each invocation, rollover only possible when maxBytes
# is nonzero and backupCount is nonzero, so we set maxBytes as big
# as possible not to overrun in single CLI invocation (1MB).
handler.doRollover() # TODO: creates empty letsencrypt.log.1 file
handler_formatter = logging.Formatter(fmt=fmt)
handler_formatter.converter = time.gmtime # don't use localtime
return handler, log_file_path
class ColoredStreamHandler(logging.StreamHandler):
"""Sends colored logging output to a stream.
If the specified stream is not a tty, the class works like the
standard `logging.StreamHandler`. Default red_level is
:ivar bool colored: True if output should be colored
:ivar bool red_level: The level at which to output
def __init__(self, stream=None):
# logging handlers use old style classes in Python 2.6 so
# super() cannot be used
if sys.version_info < (2, 7): # pragma: no cover
logging.StreamHandler.__init__(self, stream)
super(ColoredStreamHandler, self).__init__(stream)
self.colored = (sys.stderr.isatty() if stream is None else
self.red_level = logging.WARNING
def format(self, record):
"""Formats the string representation of record.
:param logging.LogRecord record: Record to be formatted
:returns: Formatted, string representation of record
:rtype: str
out = (logging.StreamHandler.format(self, record)
if sys.version_info < (2, 7)
else super(ColoredStreamHandler, self).format(record))
if self.colored and record.levelno >= self.red_level:
return ''.join((util.ANSI_SGR_RED, out, util.ANSI_SGR_RESET))
return out
class MemoryHandler(logging.handlers.MemoryHandler):
"""Buffers logging messages in memory until the buffer is flushed.
This differs from `logging.handlers.MemoryHandler` in that flushing
only happens when flush(force=True) is called.
def __init__(self, target=None):
# capacity doesn't matter because should_flush() is overridden
capacity = float('inf')
# logging handlers use old style classes in Python 2.6 so
# super() cannot be used
if sys.version_info < (2, 7): # pragma: no cover
self, capacity, target=target)
super(MemoryHandler, self).__init__(capacity, target=target)
def close(self):
"""Close the memory handler, but don't set the target to None."""
# This allows the logging module which may only have a weak
# reference to the target handler to properly flush and close it.
target =
if sys.version_info < (2, 7): # pragma: no cover
super(MemoryHandler, self).close() = target
def flush(self, force=False): # pylint: disable=arguments-differ
"""Flush the buffer if force=True.
If force=False, this call is a noop.
:param bool force: True if the buffer should be flushed.
# This method allows flush() calls in logging.shutdown to be a
# noop so we can control when this handler is flushed.
if force:
if sys.version_info < (2, 7): # pragma: no cover
super(MemoryHandler, self).flush()
def shouldFlush(self, record):
"""Should the buffer be automatically flushed?
:param logging.LogRecord record: log record to be considered
:returns: False because the buffer should never be auto-flushed
:rtype: bool
return False
class TempHandler(logging.StreamHandler):
"""Safely logs messages to a temporary file.
The file is created with permissions 600. If no log records are sent
to this handler, the temporary file is deleted when the handler is
:ivar str path: file system path to the temporary log file
def __init__(self):
stream = tempfile.NamedTemporaryFile('w', delete=False)
# logging handlers use old style classes in Python 2.6 so
# super() cannot be used
if sys.version_info < (2, 7): # pragma: no cover
logging.StreamHandler.__init__(self, stream)
super(TempHandler, self).__init__(stream)
self.path =
self._delete = True
def emit(self, record):
"""Log the specified logging record.
:param logging.LogRecord record: Record to be formatted
self._delete = False
# logging handlers use old style classes in Python 2.6 so
# super() cannot be used
if sys.version_info < (2, 7): # pragma: no cover
logging.StreamHandler.emit(self, record)
super(TempHandler, self).emit(record)
def close(self):
"""Close the handler and the temporary log file.
The temporary log file is deleted if it wasn't used.
# StreamHandler.close() doesn't close the stream to allow a
# stream like stderr to be used
if self._delete:
self._delete = False
if sys.version_info < (2, 7): # pragma: no cover
super(TempHandler, self).close()
def pre_arg_parse_except_hook(memory_handler, *args, **kwargs):
"""A simple wrapper around post_arg_parse_except_hook.
The additional functionality provided by this wrapper is the memory
handler will be flushed before Certbot exits. This allows us to
write logging messages to a temporary file if we crashed before
logging was fully configured.
Since sys.excepthook isn't called on SystemExit exceptions, the
memory handler will not be flushed in this case which prevents us
from creating temporary log files when argparse exits because a
command line argument was invalid or -h, --help, or --version was
provided on the command line.
:param MemoryHandler memory_handler: memory handler to flush
:param tuple args: args for post_arg_parse_except_hook
:param dict kwargs: kwargs for post_arg_parse_except_hook
post_arg_parse_except_hook(*args, **kwargs)
# flush() is called here so messages logged during
# post_arg_parse_except_hook are also flushed.
def post_arg_parse_except_hook(exc_type, exc_value, trace, debug, log_path):
"""Logs fatal exceptions and reports them to the user.
If debug is True, the full exception and traceback is shown to the
user, otherwise, it is suppressed. sys.exit is always called with a
nonzero status.
:param type exc_type: type of the raised exception
:param BaseException exc_value: raised exception
:param traceback trace: traceback of where the exception was raised
:param bool debug: True if the traceback should be shown to the user
:param str log_path: path to file or directory containing the log
exc_info = (exc_type, exc_value, trace)
# constants.QUIET_LOGGING_LEVEL or higher should be used to
# display message the user, otherwise, a lower level like
# logger.DEBUG should be used
if debug or not issubclass(exc_type, Exception):
assert constants.QUIET_LOGGING_LEVEL <= logging.ERROR
logger.error('Exiting abnormally:', exc_info=exc_info)
logger.debug('Exiting abnormally:', exc_info=exc_info)
if issubclass(exc_type, errors.Error):
print('An unexpected error occurred:', file=sys.stderr)
if messages.is_acme_error(exc_value):
# Remove the ACME error prefix from the exception
_, _, exc_str = str(exc_value).partition(':: ')
print(exc_str, file=sys.stderr)
traceback.print_exception(exc_type, exc_value, None)
def exit_with_log_path(log_path):
"""Print a message about the log location and exit.
The message is printed to stderr and the program will exit with a
nonzero status.
:param str log_path: path to file or directory containing the log
msg = 'Please see the '
if os.path.isdir(log_path):
msg += 'logfiles in {0} '.format(log_path)
msg += "logfile '{0}' ".format(log_path)
msg += 'for more details.'
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