epoch and hash

cas.js

// by default ballot has a form of a tuple (tick, node_id)

// so in this piece of code

appeal = casCmd.apply(function(state) {
    if (state.epoch == epoch) {
        state.requests = requests;
        state.epoch += 1;
    }
    return state;
});

// even if a proposer has stale epoch it still compete for the register
// and potentially causes up to date proposers to retry
// we may include epoch into the ballot number to cut off the stale
// proposers: (epoch, tick, node_id)

// the next step is to reduce competition between proposers for the same epoch
// we'll achieve it if use hash of data (requests) instead of node_id: (epoch, tick, hash(requests))

// during a prepare phase a proposer may discover a competitor for the same epoch with greater hash
// in that case it picks up the competitor's request and executes prepare / accept using it. Since it uses
// the same ballot, the same value and the current epoch doesn't depends on the value of the previous epoch
// the concurrent requests don't cancel each other and the system faster achieves consensus