CS 551: Distributed Operating Systems
Token Ring Election Algorithm Example


Token Ring Election Algorithm Example

We start with 6 processes,
    connected in a logical ring.
Process 6 is the leader,
    as it has the highest number.

Process 6 fails.

Process 3 notices that Process 6 does not respond
    So it starts an election,
        sending a message containing its id
    to the next node in the ring.

Process 5 passes the message on,
    adding its own id to the message.

Process 0 passes the message on,
    adding its own id to the message.

Process 1 passes the message on,
    adding its own id to the message.

Process 4 passes the message on,
    adding its own id to the message.

When Process 3 receives the message back,
    it knows the message has gone around the ring,
        as its own id is in the list.
Picking the highest id in the list,
    it starts the coordinator message
        "5 is the leader" around the ring.

Process 5 passes on the coordinator message.

Process 0 passes on the coordinator message.

Process 1 passes on the coordinator message.

Process 4 passes on the coordinator message.

Process 3 receives the coordinator message,
    and stops it.



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