Package: ratelimitingfilter
TheRateLimitingFilteris a filter for the Python logging system
that allows you to restrict the rate at which messages can pass through
your logging handlers.The filter can be useful if you’re using a handler such as Python’slogging.handlers.SMTPHandlerto send error notification emails.
Error notification emails provide a useful means of keeping an eye on
the health of a running system, but these emails have the potential to
overload a mailbox if they start arriving in quick succession due to
some kind of critical failure.TheRateLimitingFiltercan help prevent mailbox overload by
throttling messages based on a configurable rate, whilst allowing for
periodic bursts of messages which can be a useful indicator that
something somewhere has broken.CompatibilityPython 2.7, 3.4+Installing$ pip install ratelimitingfilteror$ git clone https://github.com/wkeeling/ratelimitingfilter.git
$ cd ratelimitingfilter
$ python setup.py installUsageYou can rate-limit a logging handler simply by creating a new instance of theRateLimitingFilterand adding it to the handler:fromratelimitingfilterimportRateLimitingFilter...ratelimit=RateLimitingFilter()handler.addFilter(ratelimit)Creating an instance of theRateLimitingFilterwithout any arguments
like in the example above will restrict the flow of messages to 1 every
30 seconds.You can customize the flow rate by supplying your own values for therate,perandburstattributes. For example, to allow a rate
of 1 message every 2 minutes with a periodic burst of up to 5 messages:ratelimit=RateLimitingFilter(rate=1,per=120,burst=5)handler.addFilter(ratelimit)SMTPHandler ExampleA typical use case may be to throttle error notification emails sent by
thelogging.handlers.SMTPHandler.Here’s an example of how you might set that up:importlogging.handlersimporttimefromratelimitingfilterimportRateLimitingFilterlogger=logging.getLogger('throttled_smtp_example')# Create an SMTPHandlersmtp=logging.handlers.SMTPHandler(mailhost='smtp.example.com',fromaddr='from@example.com',toaddrs='to@example.com',subject='An error has occurred')smtp.setLevel(logging.ERROR)# Create a formatter and set it on the handlerformatter=logging.Formatter('%(asctime)s-%(name)s-%(levelname)s-%(message)s')smtp.setFormatter(formatter)# Create an instance of the RateLimitingFilter, and add it to the handlerratelimit=RateLimitingFilter()smtp.addFilter(ratelimit)# Add the handler to the loggerlogger.addHandler(smtp)# Logged errors will now be restricted to 1 every 30 secondswhileTrue:logger.error('An error message')time.sleep(2)Advanced UsageIt is possible to pass some additional configuration options to theRateLimitingFilterinitializer for further control over message
throttling.Perhaps you want to selectively throttle particular error messages
whilst allowing other messages to pass through freely. This might be the
case if there is part of the application which you know can generate
large volumes of errors, whilst the rest of the application is unlikely
to.One way to achieve this might be to use separate loggers, one configured
with rate limiting, one without, for the different parts of the
application. Alternatively, you can use a single logger and configure
theRateLimitingFilterto match only those messages that you want to
throttle.Applying selective rate limiting allows for constant visbility of lower
volume errors whilst keeping the higher volume errors in check.TheRateLimitingFiltersupports two ways to selectively throttle
messages:Substring based message throttlingYou can pass a list of substrings to theRateLimitingFilterwhich it
will use to match messages to apply to.config={'match':['some error','a different error']}ratelimit=RateLimitingFilter(rate=1,per=60,burst=1,**config)smtp.addFilter(ratelimit)# Can be rate limitedlogger.error('some error occurred')# Can be rate limitedlogger.error('a different error occurred')# Will not be rate limitedlogger.error('something completely different happened')Automatic message throttlingThis is an experimental feature.You can let theRateLimitingFilterautomatically throttle messages
by setting thematchoption toauto.config={'match':'auto'}ratelimit=RateLimitingFilter(rate=1,per=60,burst=1,**config)The filter will then attempt to identify messages based on their content
in order to figure out whether to throttle them or not. It will tolerate
slight differences in content when identifying messages. So for example,
if error messages are being rapidly logged that are the same apart from
a timestamp, or perhaps an incrementing id, then these messages will be
treated as the same as far as rate limiting is concerned.LicenseMITContributingFeedback and improvements are more than welcome. Please submit a pull
request!https://github.com/wkeeling/ratelimitingfilter