In some cases when load is high you may observe the following error in vrrp logs (docker logs vrrp).
Tue Nov 17 02:26:36 2020: (nas) Receive advertisement timeout Tue Nov 17 02:26:36 2020: (nas) Entering MASTER STATE Tue Nov 17 02:26:36 2020: (nas) setting VIPs. Tue Nov 17 02:26:36 2020: (nas) Sending/queueing gratuitous ARPs on eth0 for 18.104.22.168
In this case an unintended VRRP state change is occurring for service nas because instance in BACKUP state has detected that MASTER instance is no longer responding. This situation may be caused by high load on MASTER node and also connectivity issues between instances. BACKUP instance waits 3 intervals to initiate switchover, by default this is 3x1 seconds - 3 seconds.
Now this timer value can be adjusted with configuration. To set interval to 3 seconds, run the following:
ntk cfg set vrrp.services.nas.pulse_interval 3 ntk vrrp restart
Now the timeout for master failure detection will be 3x3 seconds - 9 seconds. This value should be the same on all nodes that serve this service using VRRP.
Remember to replace service name (in this case nas) with your service name, if using custom services.