In order to enable swarm networking following tutorial ( https://docs.docker.com/swarm/networking/) says to start docker engine on all nodes of swarm cluster (masters and minions) like this:
docker engine sysconfig:
OPTIONS="–cluster-advertise “NODE_IP”:12376 --cluster-store etcd://“ETCD_IP”:12379 --cluster-store-opt kv.cacertfile=/var/lib/docker/discovery_certs/ca.pem --cluster-store-opt kv.certfile=/var/lib/docker/discovery_certs/cert.pem --cluster-store-opt kv.keyfile=/var/lib/docker/discovery_certs/key.pem"
This works fine when you run just one swarm master. However if I create another UCP master replica (docker run --rm -it -v /var/run/docker.sock:/var/run/docker.sock --name ucp dockerorca/ucp join --replica -i) this installs its own copy of etcd K/V store.
Lets assume that master fails with its own etcd. Replica becomes master. Now, i have concern how swarm minions can connect to replica’s etcd K/V
IP address of etcd K/V is static and pointing to failed master: --cluster-store etcd://“ETCD_IP”:12379
There is no such thing like cluster IP.