Re: What is the way to implement failover where DDBOOST IFGroup is configured?
There is no reason why you can't add the resilient interface/IP to the ifgroup too.
It's allocated to ifgroup membership as a "designated" interface/IP not a "dedicated" interface/IP.
If you wanted to create a failover virtual port of your 10gbe interfaces, you could also create an alias (or VLAN tagged interface) IP on veth0.
That way you could keep the management/resolved IP and the 'data' IP (for ifgroup) separate but still using the same resilient underlying 10Gbe ports. I would expect that this is needed in most environments with different subnet/LAN config/criteria for management vs replication vs data etc...
ifgroup members don't need to resolve to DNS, they're just IP's.