IPVS state synchronization

[SpComb]

clusterf-ipvs should support configuring the in-kernel IPVS sync daemon for supporting failover between IPVS routers, as done with keepalived lvs_sync_daemon_interface.

This needs support for the IPVS_CMD_*_DAEMON commands and IPVS_DAEMON_ATTR_*struct in the ipvs package.

The kernel has both master and backup daemons. Can we use both for symmetric active-active sync, or does clusterf-ipvs need to learn which node is actually the master processing traffic?

Note: sync apparently doesn't work with mixed-family services?
http://lxr.free-electrons.com/source/net/netfilter/ipvs/ip_vs_ctl.c?v=4.6#L3426

[SpComb]

keepalived configures the sync daemon master/backup state based on the VRRP state: vrrp_state_become_master calls ipvs_syncd_master and vrrp_state_leave_master calls ipvs_syncd_backup.

Ideal case would be for keepalived to handle the IPVS sync daemon while leaving the services/backends to clusterf... clusterf does not really know about the VRRP state.

[SpComb]

Marking as wontfix since clusterf should not really be configuring any frontend master/slave state unless it is also managing the frontend vip routing.

The IPVS sync stuff could probably just be managed using ipvsadm calls from e.g. keepalived VRRP hooks.

Unless IPVS sync can be used in a master-master configuration, whereupon it would be convenient for clusterf-ipvs to be able to configure that.

Pending close on investigation of how IPVS sync actually works 😎