No silver bullets exist (yet). A couple of things I can recommend:
1. GitLab's experience of changing schema without downtime and maintaining backward compatibility – they have open documentation and a lot of things solved and documented
- check their migration_helpers.rb, plenty of useful things there
2. What my team and I are doing with respect to database migration testing: https://postgres.ai/. We created Database Lab Engine, an open-source tool to clone databases of any size in seconds and test, manually or automatically in CI, anything you want using "full-size" databases. It can help you catch and block dangerous changes leading to downtime, as well as (if you have a well-maintained set of tests for CI) enforce the backward compability.
I wonder if I could garner some of the wealth of experience on this group:
Our current application deployments (every 3 weeks) require about 30min downtime. We are now tasked of making this 0 downtime.
From all the reading I have done, we have solutions for the infrastructure and code deploy, but with regards to the DB the main issue seems to be keeping the new deploy backwards compatible – functions/tables/fields – all of it.
That seems like quite a large management task and would require careful reviews of changes. Is there any type of framework that already manages this type of capability? Or are there aspects of PG that we should be using in this regard?
