private void askWhoIsTheLeader() {
logger.info("Node " + conf.getNodeId() + " is searching for the leader");
MgmtHeader.Builder mhb = MgmtHeader.newBuilder();
mhb.setOriginator(conf.getNodeId());
mhb.setTime(System.currentTimeMillis());
mhb.setSecurityCode(-999); // TODO add security
VectorClock.Builder rpb = VectorClock.newBuilder();
rpb.setNodeId(conf.getNodeId());
rpb.setTime(mhb.getTime());
rpb.setVersion(termId);
mhb.addPath(rpb);
LeaderElection.Builder elb = LeaderElection.newBuilder();
elb.setTermId(termId);
elb.setLastLogIndex(lastLogIndex);
elb.setAction(ElectAction.WHOISTHELEADER);
elb.setDesc("Node " + this.leaderNode + " is asking who the leader is");
elb.setCandidateId(-1);
elb.setExpires(-1);
Management.Builder mb = Management.newBuilder();
mb.setHeader(mhb.build());
mb.setElection(elb.build());
// now send it to the requester
ConnectionManager.broadcast(mb.build());
}
private boolean updateCurrent(LeaderElection req) {
boolean isNew = false;
if (current == null) {
current = new ElectionState();
isNew = true;
} else {
if (req.getExpires() > current.maxDuration) {
isNew = false; // If this election was started after the current election, dont do anything!
logger.info("Ignoring this election - older election already in progress! Not voting!");
return isNew;
} else {
isNew = true;
}
}
if (req.getCandidateId() == this.nodeId) {
// logger.info("Updating election details in RAFT Election");
isNew = false;
}
current.electionID = req.getElectId();
current.candidate = req.getCandidateId();
current.desc = req.getDesc();
current.maxDuration = req.getExpires();
current.startedOn = System.currentTimeMillis();
current.state = req.getAction();
current.id = -1; // TODO me or sender?
current.active = true;
return isNew;
}
// gives back the current leader if the node is aware of who the leader is // else responds I do
// not know who the leader is/
private void respondToWhoIsTheLeader(Management mgmt) {
if (this.leaderNode == null) {
logger.info("----> I cannot respond to who the leader is! I don't know!");
return;
}
logger.info(
"Node "
+ conf.getNodeId()
+ " is replying to "
+ mgmt.getHeader().getOriginator()
+ "'s request who the leader is. Its Node "
+ this.leaderNode);
MgmtHeader.Builder mhb = MgmtHeader.newBuilder();
mhb.setOriginator(conf.getNodeId());
mhb.setTime(System.currentTimeMillis());
mhb.setSecurityCode(-999);
VectorClock.Builder rpb = VectorClock.newBuilder();
rpb.setNodeId(conf.getNodeId());
rpb.setTime(mhb.getTime());
rpb.setVersion(termId);
mhb.addPath(rpb);
LeaderElection.Builder elb = LeaderElection.newBuilder();
elb.setTermId(termId);
elb.setLastLogIndex(lastLogIndex);
elb.setAction(ElectAction.THELEADERIS);
elb.setDesc("Node " + this.leaderNode + " is the leader");
elb.setCandidateId(this.leaderNode);
elb.setExpires(-1);
Management.Builder mb = Management.newBuilder();
mb.setHeader(mhb.build());
mb.setElection(elb.build());
// now send it to the requester
try {
ConnectionManager.getConnection(mgmt.getHeader().getOriginator(), true).write(mb.build());
} catch (Exception ex) {
ex.printStackTrace();
}
}
/** @param args */
public void processRequest(Management mgmt) {
if (!mgmt.hasElection()) return;
LeaderElection req = mgmt.getElection();
// when a new node joins the network it will want to know who the leader
// is - we kind of ram this request-response in the process request
// though there has to be a better place for it
if (req.getAction().getNumber() == LeaderElection.ElectAction.WHOISTHELEADER_VALUE) {
respondToWhoIsTheLeader(mgmt);
return;
} else if (req.getAction().getNumber() == LeaderElection.ElectAction.THELEADERIS_VALUE) {
logger.info(
"Node "
+ conf.getNodeId()
+ " got an answer on who the leader is. Its Node "
+ req.getCandidateId());
this.leaderNode = req.getCandidateId();
this.termId = req.getTermId();
// the current term id
// TODO Last log index to be synced
return;
}
// else fall through to an election
// if the time has expired, an election is initiated.
if (req.hasExpires()) {
long ct = System.currentTimeMillis();
if (ct > req.getExpires()) {
// ran out of time so the election is over
if (election != null) election.clear();
return;
}
}
Management rtn = electionInstance().process(mgmt);
if (rtn != null) ConnectionManager.broadcast(rtn);
}
/**
* initiate an election from within the server - most likely scenario is the heart beat manager
* detects a failure of the leader and calls this method.
*
* <p>Depending upon the algo. used (bully, flood, lcr, hs) the manager.startElection() will
* create the algo class instance and forward processing to it. If there was an election in
* progress and the election ID is not the same, the new election will supplant the current
* (older) election. This should only be triggered from nodes that share an edge with the leader.
*/
public void startElection() {
System.out.println("Inside start election");
this.state = RState.Candidate;
this.termId = electionInstance().createTermId();
LeaderElection.Builder elb = LeaderElection.newBuilder();
elb.setTermId(this.termId);
elb.setLastLogIndex(this.lastLogIndex);
elb.setAction(ElectAction.DECLAREELECTION);
elb.setDesc("Node " + conf.getNodeId() + " detects no leader. Election!");
elb.setCandidateId(conf.getNodeId()); // promote self
elb.setExpires(2 * 60 * 1000 + System.currentTimeMillis()); // 1 minute
// bias the voting with my number of votes (for algos that use vote
// counting)
// TODO use voting int votes = conf.getNumberOfElectionVotes();
MgmtHeader.Builder mhb = MgmtHeader.newBuilder();
mhb.setOriginator(conf.getNodeId());
mhb.setTime(System.currentTimeMillis());
mhb.setSecurityCode(-999); // TODO add security
VectorClock.Builder rpb = VectorClock.newBuilder();
rpb.setNodeId(conf.getNodeId());
rpb.setTime(mhb.getTime());
rpb.setVersion(termId);
mhb.addPath(rpb);
Management.Builder mb = Management.newBuilder();
mb.setHeader(mhb.build());
mb.setElection(elb.build());
// now send it out to all my edges
logger.info("Election started by node " + conf.getNodeId());
ConnectionManager.broadcast(mb.build());
}
/*
* (non-Javadoc)
*
* @see poke.server.election.Election#process(eye.Comm.LeaderElection)
*
* @return The Management instance returned represents the message to send
* on. If null, no action is required. Not a great choice to convey to the
* caller; can be improved upon easily.
*/
@Override
public Management process(Management mgmt) {
if (!mgmt.hasElection()) return null;
LeaderElection req = mgmt.getElection();
if (req.getExpires() <= System.currentTimeMillis()) {
// election has expired without a conclusion?
}
Management rtn = null;
if (req.getAction().getNumber() == ElectAction.DECLAREELECTION_VALUE) {
// an election is declared!
// required to eliminate duplicate messages - on a declaration,
// should not happen if the network does not have cycles
List<VectorClock> rtes = mgmt.getHeader().getPathList();
for (VectorClock rp : rtes) {
if (rp.getNodeId() == this.nodeId) {
// message has already been sent to me, don't use and
// forward
return null;
}
}
// I got here because the election is unknown to me
// this 'if debug is on' should cover the below dozen or so
// println()s. It is here to help with seeing when an election
// occurs.
if (logger.isDebugEnabled()) {}
System.out.println("\n\n*********************************************************");
System.out.println(" RAFT ELECTION: Election declared");
System.out.println(" Election ID: " + req.getElectId());
System.out.println(" Rcv from: Node " + mgmt.getHeader().getOriginator());
System.out.println(" Expires: " + new Date(req.getExpires()));
System.out.println(" Nominates: Node " + req.getCandidateId());
System.out.println(" Desc: " + req.getDesc());
System.out.print(" Routing tbl: [");
for (VectorClock rp : rtes)
System.out.print(
"Node " + rp.getNodeId() + " (" + rp.getVersion() + "," + rp.getTime() + "), ");
System.out.println("]");
System.out.println("*********************************************************\n\n");
// sync master IDs to current election
ElectionIDGenerator.setMasterID(req.getElectId());
/**
* a new election can be declared over an existing election.
*
* <p>TODO need to have an monotonically increasing ID that we can test
*/
boolean isNew = updateCurrent(req);
rtn = castVote(mgmt, isNew);
} else if (req.getAction().getNumber() == ElectAction.DECLAREVOID_VALUE) {
// no one was elected, I am dropping into standby mode
logger.info("TODO: no one was elected, I am dropping into standby mode");
this.clear();
notify(false, null);
} else if (req.getAction().getNumber() == ElectAction.DECLAREWINNER_VALUE) {
// some node declared itself the leader
logger.info(
"Election "
+ req.getElectId()
+ ": Node "
+ req.getCandidateId()
+ " is declared the leader");
updateCurrent(mgmt.getElection());
current.active = false; // it's over
notify(true, req.getCandidateId());
} else if (req.getAction().getNumber() == ElectAction.ABSTAIN_VALUE) {
// for some reason, a node declines to vote - therefore, do nothing
} else if (req.getAction().getNumber() == ElectAction.NOMINATE_VALUE) {
boolean isNew = updateCurrent(mgmt.getElection());
rtn = castVote(mgmt, isNew);
} else {
// this is me!
}
return rtn;
}
/**
* cast a vote based on what I know (my ID) and where the message has traveled.
*
* <p>This is not a pretty piece of code, nor is the problem as we cannot ensure consistent
* behavior.
*
* @param mgmt
* @param isNew
* @return
*/
private synchronized Management castVote(Management mgmt, boolean isNew) {
ElectionState st = new ElectionState();
if (!mgmt.hasElection()) return null;
if (current == null || !current.isActive()) {
return null;
}
LeaderElection req = mgmt.getElection();
if (req.getExpires() <= System.currentTimeMillis()) {
logger.info("Node " + this.nodeId + " says election expired - not voting");
return null;
}
logger.info("casting vote in election " + req.getElectId());
// DANGER! If we return because this node ID is in the list, we have a
// high chance an election will not converge as the maxHops determines
// if the graph has been traversed!
boolean allowCycles = true;
if (!allowCycles) {
List<VectorClock> rtes = mgmt.getHeader().getPathList();
for (VectorClock rp : rtes) {
if (rp.getNodeId() == this.nodeId) {
// logger.info("Node " + this.nodeId +
// " already in the routing path - not voting");
return null;
}
}
}
// okay, the message is new (to me) so I want to determine if I should
// nominate myself
LeaderElection.Builder elb = LeaderElection.newBuilder();
MgmtHeader.Builder mhb = MgmtHeader.newBuilder();
mhb.setTime(System.currentTimeMillis());
mhb.setSecurityCode(-999); // TODO add security
// reversing path. If I'm the farthest a message can travel, reverse the
// sending
if (elb.getHops() == 0) mhb.clearPath();
else mhb.addAllPath(mgmt.getHeader().getPathList());
mhb.setOriginator(mgmt.getHeader().getOriginator());
elb.setElectId(req.getElectId());
elb.setAction(ElectAction.NOMINATE);
elb.setDesc(req.getDesc());
elb.setExpires(req.getExpires());
elb.setCandidateId(req.getCandidateId());
// my vote
if (req.getCandidateId() == this.nodeId) {
// if I am not in the list and the candidate is myself, I can
// declare myself to be the leader.
//
// this is non-deterministic as it assumes the message has
// reached all nodes in the network (because we know the
// diameter or the number of nodes).
//
// can end up with a partitioned graph of leaders if hops <
// diameter!
// this notify goes out to on-node listeners and will arrive before
// the other nodes receive notice.
// notify(true, this.nodeId);
current.incrementVoteCount();
// System.out.println("Candidate:"+current.getVoteCount());
if (current.getVoteCount() > (ConnectionManager.getNumMgmtConnections()) / 2) {
elb.setAction(ElectAction.DECLAREWINNER);
elb.setHops(mgmt.getHeader().getPathCount());
} else {
System.out.println("No majority");
// ElectionManager.getInstance().leaderNode=null;
return null;
}
logger.info("Node " + this.nodeId + " is declaring itself the leader");
ElectionManager.getInstance().leaderNode = this.nodeId;
} else {
current.incrementVoteCount();
// System.out.println("Follower"+current.getVoteCount());
if (req.getHops() == -1) elb.setHops(-1);
else elb.setHops(req.getHops() - 1);
if (elb.getHops() == 0) {
// reverse travel of the message to ensure it gets back to
// the originator
elb.setHops(mgmt.getHeader().getPathCount());
// no clear winner, send back the candidate with the highest
// known ID. So, if a candidate sees itself, it will
// declare itself to be the winner (see above).
} else {
// forwarding the message on so, keep the history where the
// message has been
mhb.addAllPath(mgmt.getHeader().getPathList());
}
}
// add myself (may allow duplicate entries, if cycling is allowed)
VectorClock.Builder rpb = VectorClock.newBuilder();
rpb.setNodeId(this.nodeId);
rpb.setTime(System.currentTimeMillis());
rpb.setVersion(req.getElectId());
mhb.addPath(rpb);
Management.Builder mb = Management.newBuilder();
mb.setHeader(mhb.build());
mb.setElection(elb.build());
return mb.build();
}