Jeongseok Kang

LGTM. Maybe we can discuss replacing `--status=ALL` with `--all` in a further issue.

It seems that [Etcd Election API](https://etcd.io/docs/v3.3/dev-guide/api_concurrency_reference_v3/#service-election-etcdserverapiv3electionv3electionpbv3electionproto) is only for their own cluster. Therefore, I wrote [aioraft-ng](https://github.com/lablup/aioraft-ng) which can run in standalone mode and can be attached to our `backend.ai` manager.

@Dreamsorcerer Deeply appreciated your feedback! I made some changes following your advice. Also, I found that Redis supports async context manager, it resets and releases a connection when `__aexit__` is...

When running a cluster with 5 nodes, it tolerates up to 2 failures. Also, a GlobalTimer joins when its process becomes a leader and leaves when it steps down. https://user-images.githubusercontent.com/14137676/188081676-2f0d7204-a936-455c-b7a7-b258b95e3ec8.mov

Need to find a way to transfer `RootContext` and `PrivateContext` objects to the leader process using Redis.

Please link this PR to the corresponding issue using one of these keywords, `["resolves", "closes", ...]` (e.g. `closes #ISSUE`). This will close the linked issue automatically when this PR is...

@bdehamer Hi! May I kindly request your review for these changes? Thank you!