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# Copyright 2016 Red Hat, Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import logging
from time import monotonic as monotonic_clock
class _LogRateLimit(logging.Filter):
def __init__(self, burst, interval, except_level=None):
logging.Filter.__init__(self)
self.burst = burst
self.interval = interval
self.except_level = except_level
self.logger = logging.getLogger()
self._reset()
def _reset(self, now=None):
if now is None:
now = monotonic_clock()
self.counter = 0
self.end_time = now + self.interval
self.emit_warn = False
def filter(self, record):
if (self.except_level is not None
and record.levelno >= self.except_level):
# don't limit levels >= except_level
return True
timestamp = monotonic_clock()
if timestamp >= self.end_time:
self._reset(timestamp)
self.counter += 1
return True
self.counter += 1
if self.counter <= self.burst:
return True
if self.emit_warn:
# Allow to log our own warning: self.logger is also filtered by
# rate limiting
return True
if self.counter == self.burst + 1:
self.emit_warn = True
self.logger.error("Logging rate limit: "
"drop after %s records/%s sec",
self.burst, self.interval)
self.emit_warn = False
# Drop the log
return False
def _iter_loggers():
"""Iterate on existing loggers."""
# Sadly, Logger.manager and Manager.loggerDict are not documented,
# but there is no logging public function to iterate on all loggers.
# The root logger is not part of loggerDict.
yield logging.getLogger()
manager = logging.Logger.manager
for logger in manager.loggerDict.values():
if isinstance(logger, logging.PlaceHolder):
continue
yield logger
_LOG_LEVELS = {
'CRITICAL': logging.CRITICAL,
'ERROR': logging.ERROR,
'INFO': logging.INFO,
'WARNING': logging.WARNING,
'DEBUG': logging.DEBUG,
}
def install_filter(burst, interval, except_level='CRITICAL'):
"""Install a rate limit filter on existing and future loggers.
Limit logs to *burst* messages every *interval* seconds, except of levels
>= *except_level*. *except_level* is a log level name like 'CRITICAL'. If
*except_level* is an empty string, all levels are filtered.
The filter uses a monotonic clock, the timestamp of log records is not
used.
Raise an exception if a rate limit filter is already installed.
"""
if install_filter.log_filter is not None:
raise RuntimeError("rate limit filter already installed")
try:
except_levelno = _LOG_LEVELS[except_level]
except KeyError:
raise ValueError("invalid log level name: %r" % except_level)
log_filter = _LogRateLimit(burst, interval, except_levelno)
install_filter.log_filter = log_filter
install_filter.logger_class = logging.getLoggerClass()
class RateLimitLogger(install_filter.logger_class):
def __init__(self, *args, **kw):
logging.Logger.__init__(self, *args, **kw)
self.addFilter(log_filter)
# Setup our own logger class to automatically add the filter
# to new loggers.
logging.setLoggerClass(RateLimitLogger)
# Add the filter to all existing loggers
for logger in _iter_loggers():
logger.addFilter(log_filter)
install_filter.log_filter = None
install_filter.logger_class = None
def uninstall_filter():
"""Uninstall the rate filter installed by install_filter().
Do nothing if the filter was already uninstalled.
"""
if install_filter.log_filter is None:
# not installed (or already uninstalled)
return
# Restore the old logger class
logging.setLoggerClass(install_filter.logger_class)
# Remove the filter from all existing loggers
for logger in _iter_loggers():
logger.removeFilter(install_filter.log_filter)
install_filter.logger_class = None
install_filter.log_filter = None
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