@Override
public void handleAccepted(PaxosMessage proposal) {
ensureSize(chosen, proposal.getInstanceNum() + 1); // Prevent NPE
if (chosen.get(proposal.getInstanceNum()) != null)
return; // Something has already been chosen so I dont care anymore.
List<PaxosMessage> acceptedVotes = proposalAcceptedVotes.get(proposal.getInstanceNum());
if (acceptedVotes == null) {
acceptedVotes = new ArrayList<PaxosMessage>();
acceptedVotes.add(proposal);
proposalAcceptedVotes.put(proposal.getInstanceNum(), acceptedVotes);
} else {
for (PaxosMessage acceptedVote : acceptedVotes) {
if (proposal.getProposerId() == acceptedVote.getProposerId())
return; // This person is reaffirming their acceptance of this instances proposal.
}
acceptedVotes.add(proposal);
proposalAcceptedVotes.put(proposal.getInstanceNum(), acceptedVotes);
}
// handle being chosen
if (proposalAcceptedVotes.get(proposal.getInstanceNum()).size() >= serverSet.getQuorumSize()) {
onChosen(proposal);
}
}
/**
* Work through the chosen messages sending what we have left and stopping once we get to an
* unfilled slot or the end of the array.
*/
private void onChosen(PaxosMessage proposal) {
chosen.set(proposal.getInstanceNum(), (ChatMessage) proposal.getValue());
if (proposal.getInstanceNum() >= nextInstance) nextInstance = proposal.getInstanceNum() + 1;
while (lastSent + 1 < chosen.size()) {
ChatMessage toSend = chosen.get(lastSent + 1);
if (toSend != null) {
if (nodeIsLeader()) sendToClients(toSend);
lastSent++;
} else {
break; // There is still a missing slot.
}
}
}
@Override
public void handlePropose(PaxosMessage proposal) {
if (preparedFor > proposal.getProposeNum()) return;
ensureSize(accepted, proposal.getInstanceNum() + 1);
ensureSize(chosen, proposal.getInstanceNum() + 1);
accepted.set(proposal.getInstanceNum(), (ChatMessage) proposal.getValue());
// Send accept to all
/* sendAllMessage(new DefaultPaxosMessage(proposal.getInstanceNum(),
proposal.getProposeNum(),
id,
PaxosMessageType.ACCEPTED,
proposal.getValue())); */
// Silently accept proposals
}
@Override
public void handlePrepareResponse(PaxosMessage response) {
if (!prepareResponseFrom.contains(response.getProposerId()))
prepareResponseFrom.add(
response.getProposerId()); // This is a new server accepted our prepare request.
List<ChatMessage> remoteAccepted = (List<ChatMessage>) response.getValue();
for (int i = 0; i < remoteAccepted.size(); i++) {
if (chosen.size() > i && chosen.get(i) != null) continue;
if (remoteAccepted.get(i) != null) {
propose(
new DefaultPaxosMessage(
i, nextPropose, id, PaxosMessageType.PROPOSE, remoteAccepted.get(i)));
if (i > nextInstance) nextInstance = i;
}
}
}
private void handleRecoveryResponse(PaxosMessage recoveryResponse) {
ArrayList<ChatMessage> newChosen = (ArrayList<ChatMessage>) recoveryResponse.getValue();
ensureSize(chosen, newChosen.size());
for (int i = 0; i < newChosen.size(); i++) {
if (chosen.get(i) == null) {
chosen.set(i, newChosen.get(i));
} else if (!chosen.get(i).equals(newChosen.get(i))) {
System.out.println("We have an error, two servers conflict in their chosen values.");
}
}
}
public void messageReceived(IoSession ioSession, Object message) throws Exception {
if (message instanceof DefaultPaxosMessage) {
PaxosMessage paxosMessage = (DefaultPaxosMessage) message;
switch (paxosMessage.getType()) {
case PROPOSE:
handlePropose(paxosMessage);
break;
case ACCEPTED:
handleAccepted(paxosMessage);
break;
case PREPARE:
handlePrepare(
(Integer) paxosMessage.getValue(),
paxosMessage.getProposerId()); // PSN and consensus instance dont matter
break;
case PREPARE_RESP:
handlePrepareResponse(paxosMessage);
break;
case RECOVERY:
handleRecovery(paxosMessage);
break;
case RECOVERY_RESP:
handleRecoveryResponse(paxosMessage);
break;
case PING:
if (paxosMessage.getProposerId() == getLeader()) // Leaders HeartBeat
leaderLastHeard = new Date();
else if (((Integer) paxosMessage.getValue())
> preparedFor) { // I came alive and the leader is not who I thought.
preparedFor = ((Integer) paxosMessage.getValue());
handlePrepare(preparedFor, getLeader());
sendRecovery();
}
break;
default:
throw new Exception(
"received PaxosMessage of unknown type" + paxosMessage.getType().name());
}
} else if (message instanceof ChatMessage) { // Some client sent or some server forwarded.
if (nodeIsLeader()) {
propose(
new DefaultPaxosMessage(
nextInstance, nextPropose, id, PaxosMessageType.PROPOSE, (ChatMessage) message));
nextInstance++;
} else {
sendToLeader((ChatMessage) message);
}
} else {
throw new Exception("Unknown message type:" + message.getClass().getSimpleName());
}
}
private void handleRecovery(PaxosMessage recoveryRequest) {
PaxosMessage recoveryResponse =
new DefaultPaxosMessage(-1, -1, id, PaxosMessageType.RECOVERY_RESP, chosen);
sendMessage(recoveryResponse, recoveryRequest.getProposerId());
}
