Feature Flags

[ripienaar]

Proposed change

We should develop a pattern and framework for having feature flags in the server.

There could be features we want to enable on just core behaviours but also some that are JetStream specific such as write behaviour changes etc.

The problem here is that, generally, the entire cluster should or shouldn't have a flag set and so as clusters form the fact that a flag is set tends to need to propagate in the INFO headers and only if the entire cluster supports it should it enable. Like recent NRG traffic changes.

So we might need to support a few approaches here and under the cover different types of flag implementation

Use case

Ability for users to opt-in to high impact but higher risk changes and enable us to release behaviour changes more frequently

Contribution

No response