Bully algorithm: Difference between revisions

Revision as of 14:09, 18 May 2017

Revision as of 14:11, 18 May 2017

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* Election Message: Sent to announce faster election

* Answer Message: Respond to the election message

* Coordinator (Victory) Message: Sent to announce the identity of the elected process

When a process P determines that the current coordinator is down because of message timeouts or failure of the coordinator to initiate a handshake, it performs the following sequence of actions:

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# If P hears from no process with a higher process ID, then it wins the election and broadcasts victory.

# If P hears from a process with a higher ID, P waits a certain amount of time for any process with a higher ID to broadcast itself as the leader. If it does not receive this message in time, it re-broadcasts the election message.

# If P gets an election message (inquiry) from another process with a lower ID it sends an "I am alive" message back and starts a new electionselection.

Note that if P receives a victory message from a process with a lower ID number, it immediately initiates a new election. This is how the algorithm gets its name – a process with a higher ID number will bully a lower ID process out of the coordinator position as soon as it comes online.