[RFC] Scaling and Failover features

[willrstern]

Some features that help with scaling and failover:

• add /health route to default server (allows services like AWS ELB to monitor health)
• add ability to filter containers by node tag with NGINX_NODE_TAGS env var
  • this allows a single service to scale across multiple AZ/regions, while LB's only balance containers in their own AZ/region
  • e.g. a single web service can deploy 20 containers across all regions, but us-west-1 LB won't balance us-east-1 containers.

cc @ericclemmons @EvanK

[EvanK]

This looks fantastic! The only thing it may need is an example of NGINX_NODE_TAGS usage on the Readme

[ericclemmons]

Dunno if this is still a need based on Rancher today?