Upgrade to grpc 1.30.0

[pracucci]

We're using the etcd clientv3 in the Cortex project. We're currently blocked from upgrading some dependencies (ie. Prometheus) because of a breaking change introduced in grpc 1.30.0: the deprecated naming package (in grpc) has been removed.

What's the feeling about upgrading etcd to grpc 1.30.0?

[pracucci]

To better understand how widespread the issue is in etcd, I've upgraded to grpc 1.30 forking the naming package:
master...pracucci:upgrade-to-grpc-1.30

[pracucci]

Handling the removal of naming package looks relative easy. However, grpc 1.30.0 has also moved Balancer and Picker to V2 (and deleted the old one) in grpc/grpc-go#3431.

[pracucci]

We should be able to solve this issue in Cortex using the replace directive in go.mod, but considering upgrading etcd to grpc 1.30 would be great.

[beorn7]

Sadly, the replace directive doesn't work to downgrade because grpc 1.30 is in a multi-module repo, but 1.29 is in a mono-module repo. The new example module that sprang into existence with 1.30 is incompatible with the old example subdir in 1.29, and we haven't found a way to replace a module with a subdir…

[xiegeo]

Duplicate of #12124

[pracucci]

Closing because it's a duplicate of #12124.