Push Terror

I first experienced “Push Terror” in 2012. At the time I was starting my career as an engineer, at Yelp. Yelp was (probably still is) powered by a gigantic Python monolith called “yelp-main”. To support releasing new yelp-main versions a set of engineers known as “pushmasters” were dedicated to the task of gathering dev branches, merge them into a release branch, and shepherd it to production, multiple times a day.

Push Terror describes what happens right after the final “Return” key is pressed; right after a new yelp-main deployment is launched. Off we go, folks! Now what? Push Terror. Pushmasters and pushees wait, anxiously. They prepare, meticulously. The release hits production, slowly. 1%, 2%, 5%, 10%…sweating yet? Time to prep rollback commands, pull up dashboards, tail error logs, have one more look at prod configs, just in case.

Experienced pushmasters would learn to vet individual changes, build a rough mental map of what could go wrong, and ask pointed questions to new pushees. Will this be safe to rollback? Did you remember to translate this? What about your testing plan here?

Experienced pushees would figure out, over time, which pushmaster to lean on when a risky change had to be deployed. Risky changes go out in the morning push to minimize blast radius. Safe ones during main business hours. Maybe we need a custom deployment for this because it’s more risky than usual.

In the years I spent at Yelp I’ve dealt with Push Terror both as a pushmaster and a pushee. It has taught me a few important, hard-to-teach skills. Let’s cover a couple of them.

The first one is preparation. As in: preparing my code and thinking through how it’s going to make it to production. How do I minimize Push Terror? Logging, good error handling, feature toggles, a plan when database structure needs to change, and some tickets to configure the different environments are a good start. Oh and: a testing plan! You do not want to be figuring out which commands to run or where to click while Push Terror is lowering your IQ by a couple dozen points.

Second: embrace risk. I’ve seen a comment update cause a site-wide outage when deployed to production. “How on Earth”, you ask? Unicode + Python 2 ≠ Good Times. But that’s besides the point. The point is: some amount of Push Terror is healthy. You can’t aim to feel 100% confident before deploying code. You’ll probably never get there because there’s always a chance something will go wrong. Deployments should feel risky, because they are. Embrace this feeling and execute on what you’ve prepared: pull up logs, dashboards, and pre-written plans. Click around in the production app once your new code is live. “Do we still have a website/app?” should be a question on your mind. Don’t take this for granted! Did anything regress? Is your feature looking good? Is your bug actually fixed? Did anything slow down? Did error rates spike up? And what else?

Push Terror has served me well. It’s shaped my instincts about preparation and risks over time. I hope reading this will instill a healthy dose of Push Terror during your next production deployment. Godspeed!

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