High Availability recovery strategy for failed servers
The recovery strategy dictates how Load Balancer behaves when one Dispatcher machine fails and there is another configured as a backup.
Two Dispatcher machines are configured: the primary machine, and a second machine called the backup. At startup, the primary machine sends all the connection data to the backup machine until that machine is synchronized. The primary machine becomes active, that is, it begins load balancing. The backup machine, meanwhile, monitors the status of the primary machine, and is said to be in standby state.
If the backup Load Balancer machine detects that the primary machine has failed, it performs a takeover load balancing functions and becomes the active machine. After the primary machine has once again become operational, the machines respond according to how the recovery strategy has been configured by the user.
- Automatic - The primary machine resumes routing packets as soon as it becomes operational again.
- Manual - intervention is required to return the primary machine to active state and reset the backup machine to standby. The manual recovery strategy allows you to force the routing of packets to a particular machine, using the takeover command. Manual recovery is useful when maintenance is being performed on the other machine