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Do your routine backend code releases require downtime? (lemm.ee)

submitted 1 year ago by [email protected] to c/[email protected]

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Curious to know how many people do zero-downtime deployment of backend code and how many people regularly take their service down, even if very briefly, to roll out new code.

Zero-downtime deployment is valuable in some applications and a complete waste of effort in others, of course, but that doesn't mean people do it when they should and skip it when it's not useful.

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[–] [email protected] 0 points 1 year ago (1 children)

Zero downtime deployments can get very complex for heavy usage apps, such as blue-green deployment.

We decided to avoid the complexity with some practical workarounds.

Most deployments happen at 4am. "develop" branch merges deploy at 4am, and "master" branch merges deploy immediately.
We force browser refresh if the front end detects the back end has had breaking changes. We attempt to re-populate form field values.
During database migrations, we send 503 with Retry-After header in response to POSTs. Our client code knows to wait for that time and try again. If the time is too long, the user gets a friendly message that it will try again in X seconds. GETs are handled by an available read-replica, if possible.

[–] [email protected] 1 points 1 year ago (1 children)

We force browser refresh if the front end detects the back end has had breaking changes. We attempt to re-populate form field values.

Do users not find this disruptive?

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago)

Yes, but it's a very rare event. Maintaining state (form fields) makes it less of an issue. As I said, most deploys are at 4am at extremely low usage (usu zero), and even then a refresh is only needed if the backend has had breaking changes. A severe bug requires a mid-day deploy, but in my experience most severe bug fixes are only a few lines and therefore aren't a breaking change so don't require a refresh.

Our way wouldn't work well if you had 24 hours of heavy load, but most apps I've written have been US-only with low nightly usage (HR, K-12 admin, power grid, medical).