This alert as shown below is issued when an etcd member node does not have a leader or cannot reach its leader:
As documented here https://github.com/etcd-io/etcd/blob/master/Documentation/metrics.md, metric `has_leader`:
If a member does not have a leader, it is totally unavailable. If all the members in the cluster do not have any leader, the entire cluster is totally unavailable.
The metric etcd_server_has_leader is obtained from the etcd
/metrics HTTP endpoint.