etcdctl: fix member add (again...)

[jingyih]

I just realized we could simply use the members information in member add response, which is guaranteed to be up to date.

We tried to fix etcdctl member add in #11194. But it does not solve the problem if the client balancer is provided with 2 endpoints and balancer is doing round robin.

Fixes #11554

[jingyih]

cc @gyuho @jpbetz

[jpbetz]

LGTM

[eselvam]

{"level":"warn","ts":"2020-07-15T05:45:40.089+0100","caller":"clientv3/retry_interceptor.go:61","msg":"retrying of unary invoker failed","target":"passthrough:///https://ipmasked:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}

It is happening when we add stacked kubernetes masters based on instruction at kubernetes.io. It is a second master node.

The etcdctl member status and list are showing correctly with node 1 as master and node 2 as false however when we down the master 1, the entire cluster is going downe.

Kubernetes version 1.18.5 and etcd version: 3.4.3

+------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| ENDPOINT | ID | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| master1:2379 | 16cf629ee72c2590 | 3.4.3 | 3.2 MB | false | false | 6 | 3637096 | 3637096 | |
| master2:2379 | 448a38484560a13c | 3.4.3 | 3.2 MB | true | false | 6 | 3637096 | 3637096 | |
+------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+

[jingyih]

@eselvam I am not sure I follow you comment. Are you trying to add a new node to a 2-node cluster with 1 of the nodes down?