In the README.md file, they compare it with a ClusterIP service, but not with a Headless on "ClusterIP: None".
The advantages of using Kuberesolver are that you do not need to change DNS refresh and cache settings. However, I think this is preferable to the application calling the Kubernetes API.
The code in question was: https://github.com/grpc/grpc-go/blob/b597a8e1d0ce3f63ef8a7b6...
That meant that deploying a service which drained in less than 30s would have a little mini-outage for that service until the in-process DNS cache expired, with of course no way to configure it.
Kuberesolver streams updates, and thus lets clients talk to new pods almost immediately.
I think things are a little better now, but based on my reading of https://github.com/grpc/grpc/issues/12295, it looks like the dns resolver still might not resolve new pod names quickly in some cases.
It feels like it would solve all the requirement that they laid out, is fully client side, and doesn't require real time updates for the host list via discovery.
From the recent grpConf ( https://www.youtube.com/playlist?list=PLj6h78yzYM2On4kCcnWjl... ) it seems gRPC as a standard is also moving in this "proxyless" model - gRPC will read xDS itself.
https://nginx.org/en/docs/http/ngx_http_upstream_module.html...
this is "partially" true.
if you're using ipvs, you can configure the scheduler to just about anything ipvs supports (including wrr). they removed the validation for the scheduler name quite a while back.
kubernetes itself though doesn't "understand" (i.e., can NOT represent) the nuances (e.g., weights per endpoint with wrr), which is the problem.
the "impact" can be reduced by configuring an overall connection-ttl, so it takes some time when new pods come up but it works out over time.
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that said, i'm not surprised that even a company as large as databricks feels that adding a service mesh is going to add operational complexity.
looks like they've taken the best parts (endpoint watch, sync to clients with xDS) and moved it client-side. compared to the failure mode of a service mesh, this seems better.
that seems like the tail wagging the dog
