Active-passive load balancing

[incogni996]

Hi folks, we have a situation where we would need to route traffic to a higher availability static page, whenever our primary on-prem server is down due to power outage or any physical hardware hiccups.

AFAIK, Kong's load balancing leans more on the active-active load balancing, where each target on an upstream can be set to some arbitrary weight. Surfing around the internet, especially in the topic discussed here https://discuss.konghq.com/t/failover-api-handling/1341/19, it seems to suggest that a way to achieve this is to basically hack the weight to a very minimum weight but with the drawback that even if the active pool is up, some traffic might be routed to the passive pool. Another solution that I can think of is again hacking our way through "blue-green deployment" https://developer.konghq.com/gateway/traffic-control/blue-green-deployments, but this would involve a manual switch from blue to green, vice-versa.

My question is:

1. Is this not supported by Kong OOTB (seems to me that it is not)
2. What are some other ideas that we can use to try and mimic this behaviour?

We have implemented this in the edge LB in CloudFlare (https://developers.cloudflare.com/load-balancing/load-balancers/common-configurations/#active---passive-failover), but there are some cases where Kong is up but its upstream is not.

Thanks 🙏

[incogni996]

Eventually we made use of the Post-Plugin Function plugin, and add something like this to be triggered during Header Filter phase:

if  kong.response.get_status() > 500 then
    kong.response.set_headers({
        ["Location"] = "<insert-link>"
    })
    return kong.response.exit(302, "<insert-message>")
end