partner-down state transition when max-unacked-clients reached
Suppose the server lost the connection with its partner. The server begins the failover procedure by checking whether or not the partner responds to the DHCP queries. The max-unacked-clients
setting controls how many different clients should retry getting the lease with the increased value of the secs
field before the server considers partner dead. One would expect the server to make partner-down
transition as soon as the number of unacked clients reaches the configured number. In fact, the state transitions are generally performed when the server completes a heartbeat or a lease update. It is possible that under heavy traffic there will be much larger number of unacked clients and the server still sits in the normal state (e.g. hot-standby), waiting for the heartbeat trigger. Assuming the heartbeat interval is reasonable, it should probably be fine. However, we may consider starting the transition as soon as the number of unacked clients reaches the configured maximum.