func (lp *libpaxos) ReceivePrepare(args *paxosrpc.ReceivePrepareArgs, reply *paxosrpc.ReceivePrepareReply) error {
if lp.interruptFunc != nil {
lp.interruptFunc(lp.myNode.ID, Prepare, lp.slotBox.nextUnknownSlotNumber)
}
lp.dataMutex.Lock()
lp.slotBoxMutex.Lock()
slot := lp.slotBox.Get(args.CommandSlotNumber)
lp.slotBoxMutex.Unlock()
if slot != nil {
// The Proposer will suggest a slot number for its proposal. If that slot
// number has already been decided upon, tell the Proposer, and give it
// the decided value, so it can update its own slot box and choose a
// different slot number.
reply.Status = paxosrpc.DecidedValueExists
reply.DecidedSlotNumber = slot.Number
reply.DecidedValue = *slot.Value
} else if lp.highestProposalNumberSeen != nil && args.ProposalNumber.LessThan(lp.highestProposalNumberSeen) {
// If the proposal number is not highest, reject automatically.
reply.Status = paxosrpc.Reject
} else {
// If the proposal number is highest, then OK it, but also send back
// any accepted proposals.
lp.highestProposalNumberSeen = &args.ProposalNumber
reply.Status = paxosrpc.OK
if lp.highestAcceptedProposal != nil {
reply.HasAcceptedProposal = true
reply.AcceptedProposal = *lp.highestAcceptedProposal
} else {
reply.HasAcceptedProposal = false
}
}
lp.dataMutex.Unlock()
return nil
}
