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The Principle of Flow

Published: Mar 2020
Updated: Mar 2021

Podcast Episode

The process used to write code and deploy it production is biggest contributor to your team’s velocity. You’ve probably been in the situation where something is seriously broken in production and you need deploy a fix right now. You may have even tried to circumvent the existing process to deploy it out faster. Simply put, the faster your team can write and deploy code to production the better. This is the principal of flow or the “first way” of DevOps.

The DevOps Handbook provides a two step process for achieving fast flow from development to production.

  • Step 1: use trunk-based development and continuous integration
  • Step 2: use continuous delivery

You’ve like heard these terms before. They’re thrown around and often used incorrectly. Continuous integration is a prime example. I’ll do my best to clarify the right and proper way to achieve fast flow from development to production.

The goal at the end of each development cycle is produce production-ready builds from master that been verified in a production-like environment and validated with automated tests. That’s continuous delivery in a nutshell. Continuous deployment takes it one step further by automatically pushing code to production but that’s a topic for another episode. For now let’s start at with trunk-based development.

I bet the mere mention of “trunk” makes some of you shudder. Some of you may even be thinking: “trunk what is madman talking about SVN for? We use git so what’s the point?” Well the point is reducing cycle times from development to production. Trunk-based development optimizes for team productivity instead of individual productivity.

The trunk-based development boils down to keeping branches small and maintaining an incremental straight line of development. Branches should be merged to trunk (or master) at the end of the day. They must be covered by automated tests so it’s clear which commits are broken. This is the origin of continuous integration (and they’re a lot of “continuous” things in DevOps). This practices ensures commits are smaller, thus easier to write, test, and deploy to production hence improving times from development to production.

I can hear some of you saying: “Adam-wait, what the hell are you talking about? How does this make any sense? What am I supposed to do with my feature branches? What about our epic branches that are open for weeks?” The answers to that question lies in a perspective shift regarding individual roles and what a team values, but I want to put these questions another way.

Would you rather work in your topic branch for as long as possible or would rather get your code out the door and into production? I choose production and you should too. Anyways, I don’t want to get into the weeds on this topic because it’s somewhat controversial so check the show notes for more links on the topic. Let’s move forward to continuous delivery.

The idea here is connect commits from trunk/master to an automated deployment pipeline that verifies builds are fit for production. Naturally this requires varying levels of tests and automation. Now don’t get lost in the statements from the blogosphere that you need Docker or microservices to do this. These proclamations miss the point that technical practices like infrastructure as code and automated testing are more important than specific technologies. There’s no prescriptive solution but I’ll provide you an outline:

  1. Deploy code to a staging environment
  2. Run a smoke test against staging
  3. Deploy code to production, Ideally using a blue/green or canary deploy
  4. Run smoke tests against production
  5. All good? You’re done. If not, rollback.

Expand out to more pre-production environments as necessary. You may have a dedicated performance testing environments, a manual QA environment, or whatever floats your boat. Honestly, it doesn’t matter how many environments you have as long as promotion and verification is automated as much as possible. However, your number of environments will grow over time as your deployment pipeline becomes more rigorous.

Alright, that’s enough for this batch. The principal of flow covers reducing cycle times from development to production. Trunk-based development backed continuous integration and continuous delivery is the best way to do that.

The book Accelerate provides two metrics to measure flow: lead time and deployment frequency. Lead time is how long it takes go from commit to production. Deployment frequency is simply how often deploys happens. Accelerate also breaks down these metrics into tiers.

Top tier lead times are under an hour. This means a developer can start working on, and deliver completed code to production in under an hour. Mid their lead times range between a week and a month. How does your team stack up?

Anyways, that’s a wrap on episode. Head over to the podcasts’ website smallbatches.dev for a transcript, show notes, and links to my review and further analysis on both the DevOps Handbook and Accelerate.

Until the next one, good luck out there and happing shipping.