You've done everything right: you have a continuous deployment pipeline, you have a commit stage with great unit tests, a pre-prod stage with fully automated deployment, robust end-to-end tests as well as some performance & security checks, and once all your quality gates are passed, your stream of changes march confidently towards production - but then somehow, someway, somewhy, production still blows up!
Continuous delivery is awesome, but the devil is in the details, and there's a decent chance you've been bitten by one of the biggest challenges - the safe management of contract changes.
Contracts can be obvious and public such as APIs (URL structure & schema), or obvious and private, such as database schemas, or non-obvious, such as the schema of in-flight messages in a queue, or dependency on specific timing expectations.
This talk demonstrates with real deployments the fundamental principle that underlies all safe contract changes - the 3 step model:
1. expand - introduce the change in a backwards and forwards compatible way
2. change - ensure all instances of the component and all dependants are using the new definition
3. contract - retire the obsolete compatibility elements
The good news is, with continuous delivery we can often do all three steps in quick succession!
Chris Simon
Chris Simon - Technology Coaching & Advisory
Chris is a technology coach & advisor empowering technology teams to drive business success. He has a particular focus on helping startups realise their vision and new CTOs flourish in their roles. He also supports executives & boards with strategic technology advice, and engineering teams with training, mentoring and consulting in architecture, quality, domain-driven design and test driven development.
He is a regular meetup & conference speaker (NDC, KanDDDinsky, Serverless Days ANZ) and to support teams using Domain-Driven Design, he recently launched & co-founded the DDD Australia meetup.
He is the technical co-founder of, home of Australian Fintech success stories and (recently acquired by NAB).