Bully algorithm

The bully algorithm is a method for dynamically electing a coordinator, or leader, from a group of distributed computer processes. The process with the highest process identifier among the processes that have not failed becomes the coordinator. The algorithm assumes a synchronous system, processes that fail by stopping and may later restart, a failure detector, reliable message delivery, and that every process knows the identifier and address of every other process. It uses three message types: election, answer and coordinator. A process that notices the coordinator has failed sends election messages to all processes with higher identifiers. If none answers, it announces itself as coordinator. If one answers, it waits for that process to finish the election. A recovering process with the highest identifier simply takes over. The algorithm is safe, since two processes can never both announce victory, and live in the synchronous crash-recovery model. In the worst case the message count grows quadratically with the number of processes.