Paxos Pseudocode

Paxos.txt

--- Paxos Proposer ---
proposer(v):
  choose n > n_p
  send prepare(n) to all servers including self
  if prepare_ok(n, n_a, v_a) from majority:
    v’ = v_a with highest n_a; choose own v otherwise
    send accept(n, v’) to all
    if accept_ok(n) from majority:
      send decided(v’) to all
      
--- Paxos Acceptor ---
acceptor state on each node (persistent):
  n_p --- highest prepare seen
  n_a, v_a --- highest accept seen

acceptor’s prepare(n) handler:
  if n > n_p
    n_p = n
    reply prepare_ok(n, n_a, v_a)

acceptor’s accept(n, v) handler:
  if n >= n_p
    n_p = n
    n_a = n
    v_a = v
    reply accept_ok(n)