Simon Willison’s Weblog

Optimizing for Taste. David Cramer’s detailed explanation as to why his company Sentry mostly avoids A/B testing. David wrote this as an internal blog post originally, but is now sharing it with the world. I found myself nodding along vigorously as I read this—lots of astute observations here.

I particularly appreciated his closing note: “The strength of making a decision is making it. You can always make a new one later. Choose the obvious path forward, and if you don’t see one, find someone who does.”

# 27th September 2023, 4:34 am / ab-testing, david-cramer, sentry

The first ever commit to Sentry (via) This is fascinating: the first 70 lines of code that started the Sentry error tracking project. It’s a straight-forward Django process_exception() middleware method that collects the traceback and the exception class and saves them to a database. The trick of using the md5 hash of the traceback message to de-dupe errors has been there from the start, and remains one of my favourite things about the design of Sentry.

# 6th November 2019, 11:08 pm / django, sentry

How Sentry Receives 20 Billion Events Per Month While Preparing To Handle Twice That. RabbitMQ federation, nginx and HAProxy, Riak as a key/value store, data processing is still mainly Python with a little bit of Rust. As of July 2017 it’s all hosted on Google Cloud Platform.

# 8th November 2017, 11:32 pm / scaling, rust, sentry

Try hosting on PyPy by simonw. I had a go at hosting my blog on PyPy. Thanks to the combination of Travis CI, Sentry and Heroku it was pretty easy to give it a go—I had to swap psycopg2 for psycopg2cffi and switch to the currently undocumented pypy3-5.8.0 Heroku runtime (pypy3-5.5.0 is only compatible with Python 3.3, which Django 2.0 does not support). I ran it in production for a few minutes and didn’t get any Sentry errors but did end up using more Heroku dyno memory than I’m comfortable with—see the graph I posted in a comment. I’m going to stick with CPython 3.6 for the moment. Amusingly I did almost all of the work on this on my phone! Travis CI means it’s easy to create and test a branch through GitHub’s web UI, and deploying a tested branch to Heroku is then just a button click.

# 5th November 2017, 7:17 pm / pypy, python, heroku, travis, sentry