Blue Green Deployment Strategy

Blue/Green is a Deployment StrategyDeployment Strategy
Deployment strategies describe how we handle the release of the new code to an environment. Each has it's different use case, pros and cons.

Here is a (non-definitive) list of deployment strategie... where version B is deployed alongside version A, after which the traffic is switched from A to B.

How it works

  • before we start, we have 2 instances of A running and serving traffic
  • we deploy 2 instances of B alongside them, which are still not serving any traffic
  • we confirm that version B deployment looks good
  • we switch traffic flow from version A to version B on Load Balancer side

Tradeoffs

Pros:

  • zero downtime
  • instant rollout and rollback
  • entire application is changed in one go, no different api versions running at the same time

Cons:

  • it expects us to run 2 identical environments alongside one another, which can be expensive
  • it doesn't make much sense to run two databases, so you have to figure out how to run both versions connected to a single database (backwards-compatible db updates, decoupled db migrations from application deployment)

Status: #💡

References: