Python Error Logging to Amazon Web Services’ Simple Notification Service (SNS)

As part of the standard library, Python provides a very flexible logging module that includes the ability to define custom handlers. Commonly this is used to log errors to Syslog, SMTP, a database, etc. However, we can also easily adapt it to log to a Amazon Web Services Simple Notification Service (SNS) topic. Subscribers (either people or other applications) then receive these notifications via email, HTTP POST, SMS text messages, or any combination.

SNS is a great way to consolidate notifications because it eliminates the need embed email addresses in the application’s code or config files. Instead, a SNS topic URN is specified and then multiple subscribers’ email addresses or mobile phone numbers can easily be added/removed via the AWS Management Console, or programmatically via the AWS API.

Here’s the code (you’ll first need Boto, the Python library for AWS):

import logging
from boto.utils import get_instance_metadata
from boto.sns import SNSConnection

class SNSLogHandler(logging.Handler):
    def __init__(self, topic, subject, instance_id=None):
        logging.Handler.__init__(self)
        self.sns_conn = SNSConnection()
        self.topic = topic
        self.subject = subject
        self.instance_id = instance_id

    def emit(self, record):
        if self.instance_id is None:
            msg = record.message
        else:
            msg = "[from: %s] %s" % (self.instance_id, record.message)
        self.sns_conn.publish(self.topic, msg,
            subject=self.subject)

And then as part of the constructor for your object, the logging is initialized like so:

class MyClass(object):
    def __init__(self):
        # Set up the logging early here to better catch all errors.
        # Obtain the SNS URN by first creating a new topic in the AWS
        # Management Console: https://console.aws.amazon.com
        self.sns_topic = "arn:aws:sns:us-east-1:118529612345:MyTopic"
        self.sns_subject = "This is my SNS subject."
        self._init_logging()
        """
        Do more initialization stuff 
        """
        self.log.critical("Oh noes!! Something really bad happened!")

    def _init_logging(self):
        self.log = logging.getLogger('my_logger')

        # Should set the level on the logger itself to DEBUG
        # and let the handlers below do the filtering 
        self.log.setLevel(logging.DEBUG)

        # Setting console output to DEBUG for easier debugging
        ch = logging.StreamHandler()
        ch.setLevel(logging.DEBUG)
        formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
        ch.setFormatter(formatter)
        self.log.addHandler(ch)

        """
        Assuming that this script is running on an EC2 instance
        we grab the instance ID so it can be included in the SNS
        message for reference.  If you're not running this on EC2,
        remove this rather than trap the exception because the timeout
        is several seconds long.
        """
        instance_id = get_instance_metadata()['instance_id']
        sns = SNSLogHandler(self.sns_topic, self.sns_subject, instance_id)

        # We only want critical messages bothering us via AWS SNS
        sns.setLevel(logging.CRITICAL)
        sns.setFormatter(formatter)
        self.log.addHandler(sns)
Share

One thought on “Python Error Logging to Amazon Web Services’ Simple Notification Service (SNS)

  1. I think the pattern of setting up logging in the object construction is a little weird. Most of the time you would want to be alerted to all errors, not just the ones for a particular object. In Django (my framework of choice) I would try configuring the LOGGING setting so I would be notified of all errors.

    However, I do love the idea of logging errors to SNS – I’m definitely going to set this up. Thanks!

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong> <pre class="">