sky

@agentzh Thank you, I've learned. It's really flexible, so that we can achieve some business logic in the upstream module using balancer_by_lua is more simpler :).

@agentzh thanks for CR, Im update code style and some logic, now they support load balance algorithm: ip_hash, round_robin or least_conn.

@aledbf As agentzh put it. dynamic manage upstream clould use `balancer_by_lua*` and it's very flexible. Now our internal using `lua-upstream-nginx-module` provide atomic rest http about dynamic manage upstream. Using consul/etcd...

I'm also meet the same issue: https://dev.azure.com/cncf/envoy/_build/results?buildId=121458&view=logs&j=bbe4b42d-86e6-5e9c-8a0b-fea01d818a24&t=e00c5a13-c6dc-5e9a-6104-69976170e881&l=224