Feature request: streaming/SSE updates to avoid full environment-document polling

[adamvialpando]

Is your feature request related to a problem?

The Edge Proxy polls /api/v1/environment-document/ on a fixed interval. Deployments running many proxy instances with short poll intervals results in an unnecessary amount of API requests to the Core API. Since this was implemented, the load caused by these requests is fairly low since the environment rarely changes in relation to the polling interval, but the requests could be redundant nonetheless.

The time taken for a change to a flag to be reflected in the API served by each Edge Proxy instance is also therefore dependent on the polling interval. When using longer polling intervals (to optimise API requests for example), a change could take up to one full polling interval to be reflected in the API served by the Edge Proxy.

Describe the solution you would like

A streaming or push based update channel (for example SSE) for environment updates, so a proxy is notified when an environment changes rather than polling the Core API.

Additional context

Most relevant for high instance count deployments.

[matthewelwell]

Note: the issue body here isn't quite correct, although the feature request is still valid. Since this was implemented, the document itself is only sent in response if the environment has actually changed.

Edit: Updated the body of the issue to correctly reflect the current situation.