In distributed computing, 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 ID number from amongst the non-failed processes is selected as the coordinator. Assumptions The algorithm assumes that: the system is synchronous. processes may fail at any time, including during execution of the algorithm. a process fails by stopping and returns from failure by restarting. there is a failure detector which detects failed processes. message delivery between processes is reliable. each process knows its own process id and address, and that of every other process. Algorithm The algorithm uses the following message types: Election Message: Sent to announce election. Answer (Alive) Message: Responds to the Election message. Coordinator (Victory) Message: Sent by winner of the election to announce victory. When a process recovers from failure, or the failure detector indicates that the current coordinator has failed, performs the following actions: If has the highest process ID, it sends a Victory message to all other processes and becomes the new Coordinator. Otherwise, broadcasts an Election message to all other processes with higher process IDs than itself. If receives no Answer after sending an Election message, then it broadcasts a Victory message to all other processes and becomes the Coordinator. If receives an Answer from a process with a higher ID, it sends no further messages for this election and waits for a Victory message. (If there is no Victory message after a period of time, it restarts the process at the beginning.) If receives an Election message from another process with a lower ID it sends an Answer message back and if it has not already started an election, it starts the election process at the beginning, by sending an Election message to higher-numbered processes. If receives a Coordinator message, it treats the sender as the coordinator. Analysis Safety The safety property expected of leader election protocols is that every non-faulty process either elects a process , or elects none at all. Note that all processes that elect a leader must decide on the same process as the leader. The Bully algorithm satisfies this property (under the system model specified), and at no point in time is it possible for two processes in the group to have a conflicting view of who the leader is, except during an election. This is true because