pseudocode

模拟器提供了一个简单易用的平台

handle cluster refresh () ====>

if (I dont think this pkt src is in this cluster) {
  ignore it
  return
}

define s = pkt src
update s refresh info in the appropriate agent info

case 1: // I am the root

  if (s thinks its the root) {

    if (s is doing root transfer to me) {
      /* then I rule ... I will maintain status quo */
      absorb all members from s unknown to me
      if (s doing cluster remove)
        remove it
      (this might cause cluster split etc)
      return
    }

    if (s is doing root transfer to p, where p <> me)
      define y = p
    else
      define y = s
    /* Root challenge should always be sent to s, root transfer
     * will be sent to y
     */

    s_max = dist of s from its farthest known member
    my_max = dist of me from my farthest known member
    /* memberset(x) defined as set of members with known dists */
    if (memberset(s) == memberset(mine)) {
      if ( (my_max < s_max) ||
           ( (my_max == s_max) && (my->id < s->id) ) ) { // i.e. I win
        absorb all members unknown to me from s
        send root-challenge to s iff y == s (what about to y, for y <> s)
        return
      }
      else { // I lose
        send root-transfer to y
        return
      }
    }
    else if (memberset(s) is a superset of memberset(mine)) {
      send root-transfer to y
      return
    }
    else if (memberset(mine) is a superset of memberset(s)) {
        absorb all members unknown to me from s
        send root-challenge to s iff y == s
        return
    }
    else { // each has some members in memberset unknown to the other
      if (my id < s->id) {
        absorb all members unknown to me from s
        send root-challenge to s iff y == s
        return
	/* Root-challenge: send him an immediate cluster refresh */
        /* note: if s was doing a root-transfer to someone else, and
         *    if p was not in my cluster, I should add p ?
         * automatically taken care of, since p in s cluster
         */
      }
      else { /* my id > s->id, and so I lose */
        send root-transfer to y
        return
      }
    }
  }
  else { // s does not think it is the root
  }

case 2: // I am not the root

  if (s thinks it is the root) {
    if (I also think s is the root) {
      update info of the cluster as suggested by s
    }
    else (I think someone else is the root) {
      // do nothing, just stay put
    }
  }

end handle-cluster-refresh <=======

cluster-refresh-timeout () ========>

purge all members that are dead

if (i am root and cluster size too small/too large) {
  do appropriate repair
  if (delay cluster repair flag set) {
    clear it
  }
  return
}
  
if (root is dead) {

  select a new root,r, based on local dist info
  if (r == me) {

    if (cluster size is too small/too lare) {
      set a delay cluster repair flag
      /* cluster will be repaired in next timeout */
    }
    send appropriate new cluster refresh to all members
  }
end cluster-refresh-timeout <========

/* Note, in regular cluster-refresh, the leader will repair
 * the cluster only if its too large/too small, if the delay
 * cluster repair flag is not set.
 * Alternative: Cluster repair done only at cluster repair
 * timeouts
 */