/**
* Once connected to the leader, perform the handshake protocol to establish a following /
* observing connection.
*
* @param pktType
* @return the zxid the Leader sends for synchronization purposes.
* @throws IOException
*/
protected long registerWithLeader(int pktType) throws IOException {
/*
* Send follower info, including last zxid and sid
*/
long lastLoggedZxid = self.getLastLoggedZxid();
QuorumPacket qp = new QuorumPacket();
qp.setType(pktType);
qp.setZxid(ZxidUtils.makeZxid(self.getAcceptedEpoch(), 0));
/*
* Add sid to payload
*/
LearnerInfo li = new LearnerInfo(self.getId(), 0x10000);
ByteArrayOutputStream bsid = new ByteArrayOutputStream();
BinaryOutputArchive boa = BinaryOutputArchive.getArchive(bsid);
boa.writeRecord(li, "LearnerInfo");
qp.setData(bsid.toByteArray());
writePacket(qp, true);
readPacket(qp);
final long newEpoch = ZxidUtils.getEpochFromZxid(qp.getZxid());
if (qp.getType() == Leader.LEADERINFO) {
// we are connected to a 1.0 server so accept the new epoch and read
// the next packet
leaderProtocolVersion = ByteBuffer.wrap(qp.getData()).getInt();
byte epochBytes[] = new byte[4];
final ByteBuffer wrappedEpochBytes = ByteBuffer.wrap(epochBytes);
if (newEpoch > self.getAcceptedEpoch()) {
wrappedEpochBytes.putInt((int) self.getCurrentEpoch());
self.setAcceptedEpoch(newEpoch);
} else if (newEpoch == self.getAcceptedEpoch()) {
// since we have already acked an epoch equal to the leaders, we
// cannot ack
// again, but we still need to send our lastZxid to the leader
// so that we can
// sync with it if it does assume leadership of the epoch.
// the -1 indicates that this reply should not count as an ack
// for the new epoch
wrappedEpochBytes.putInt(-1);
} else {
throw new IOException(
"Leaders epoch, "
+ newEpoch
+ " is less than accepted epoch, "
+ self.getAcceptedEpoch());
}
QuorumPacket ackNewEpoch =
new QuorumPacket(Leader.ACKEPOCH, lastLoggedZxid, epochBytes); // 发送ack
writePacket(ackNewEpoch, true);
return ZxidUtils.makeZxid(newEpoch, 0);
} else {
if (newEpoch > self.getAcceptedEpoch()) {
self.setAcceptedEpoch(newEpoch);
}
if (qp.getType() != Leader.NEWLEADER) {
LOG.error("First packet should have been NEWLEADER");
throw new IOException("First packet should have been NEWLEADER");
}
return qp.getZxid();
}
}
