//
// Get the txnid from the packet if the packet is a ProposalMsg or CommitMsg.
//
func (l *LeaderSyncProxy) getPacketTxnId(packet common.Packet) common.Txnid {
txid := common.BOOTSTRAP_LAST_LOGGED_TXID
if packet != nil {
switch request := packet.(type) {
case ProposalMsg:
txid = common.Txnid(request.GetTxnid())
case CommitMsg:
txid = common.Txnid(request.GetTxnid())
}
}
return txid
}
func (w *watcher) LogProposal(p protocol.ProposalMsg) error {
w.mutex.Lock()
defer w.mutex.Unlock()
msg := w.factory.CreateLogEntry(p.GetTxnid(), p.GetOpCode(), p.GetKey(), p.GetContent())
w.pendings[common.Txnid(p.GetTxnid())] = msg
handle, ok := w.pendingReqs[p.GetReqId()]
if ok {
delete(w.pendingReqs, p.GetReqId())
w.loggedReqs[common.Txnid(p.GetTxnid())] = handle
}
return nil
}
// Get value from iterator
func (i *TransientLogIterator) Next() (txnid common.Txnid, op common.OpCode, key string, content []byte, err error) {
if i.iter == nil {
return 0, common.OPCODE_INVALID, "", nil, fdb.RESULT_ITERATOR_FAIL
}
if i.curError != nil {
return 0, common.OPCODE_INVALID, "", nil, i.curError
}
key = i.curKey
content = i.curContent
txnid = i.curTxnid
i.curTxnid = common.Txnid(uint64(i.curTxnid) + 1)
i.curKey, i.curContent, i.curError = i.iter.Next()
if i.curError == nil {
// it is not the last entry. Does not matter what is the actual txnid as long as it is
// smaller than the snapshot's txnid (TransientLogIterator.txnid).
return txnid, common.OPCODE_SET, key, content, nil
}
// last entry : use the txnid matching the snapshot
return i.txnid, common.OPCODE_SET, key, content, nil
}
//
// handle accept message from follower
//
func (l *Leader) handleAccept(msg AcceptMsg) error {
// If this Ack is on an old proposal, then ignore.
// This indicates that the follower may be slower
// than others. Therefore, the proposal may be
// committed, before the follower can Ack.
mtxid := common.Txnid(msg.GetTxnid())
if l.lastCommitted >= mtxid {
// cleanup. l.quorums should not have mtxid.
// This is just in case since we will never commit
// this proposal.
_, ok := l.quorums[mtxid]
if ok {
delete(l.quorums, mtxid)
delete(l.proposals, mtxid)
}
return nil
}
// update quorum
l.updateQuorum(mtxid, msg.GetFid())
if l.hasQuorum(mtxid) {
// proposal has quorum. Now commit. If cannot commit, then return error
// which will cause the leader to re-election. Just to handle
// case where there is hardware failure or repository corruption.
err := l.commit(mtxid)
if err != nil {
return err
}
}
return nil
}
//
// Send the entries in the committed log to the follower. Termination condition:
// 1) There is no more entry in commit log
// 2) The entry in commit log matches the first entry in the observer queue
// This function returns the txid of the last entry sent from the log. Return 0 if nothing is sent from commit log.
//
func (l *LeaderSyncProxy) sendEntriesInCommittedLog(startTxid, endTxid common.Txnid, o *observer) (common.Txnid, error) {
log.Current.Debugf("LeaderSyncProxy.sendEntriesInCommittedLog(): startTxid %d endTxid %d observer first txid %d",
startTxid, endTxid, l.firstTxnIdInObserver(o))
var lastSeen common.Txnid = common.BOOTSTRAP_LAST_LOGGED_TXID
logChan, errChan, killch, err := l.handler.GetCommitedEntries(startTxid, endTxid)
if logChan == nil || errChan == nil || err != nil {
return lastSeen, err
}
for {
select {
case entry, ok := <-logChan:
if !ok {
killch <- true
return lastSeen, nil // no more data
}
// send the entry to follower
err = send(entry, l.follower)
if err != nil {
// lastSeen can be 0 if there is no new entry in repo
killch <- true
return lastSeen, err
}
lastSeen = common.Txnid(entry.GetTxnid())
// we found the committed entries matches what's in observer queue
if l.hasSeenEntryInObserver(o, common.Txnid(entry.GetTxnid())) {
killch <- true
return lastSeen, nil
}
case err := <-errChan:
if err != nil {
return lastSeen, err
}
break
}
}
return lastSeen, nil
}
func (a *ServerAction) LogProposal(p protocol.ProposalMsg) error {
if a.notifier != nil {
tnxid, op, key, content := p.GetTxnid(), p.GetOpCode(), p.GetKey(), p.GetContent()
if err := a.notifier.OnNewProposal(common.Txnid(tnxid), common.OpCode(op), key, content); err != nil {
return err
}
}
err := a.appendCommitLog(common.Txnid(p.GetTxnid()), common.OpCode(p.GetOpCode()), p.GetKey(), p.GetContent())
if err != nil {
return err
}
a.server.UpdateStateOnNewProposal(p)
return nil
}
//
// Bootstrp
//
func (s *Coordinator) bootstrap(config string) (err error) {
s.state.mutex.Lock()
defer s.state.mutex.Unlock()
if s.state.done {
return
}
s.env, err = newEnv(config)
if err != nil {
return err
}
// Initialize server state
s.state.resetCoordinatorState()
// Initialize various callback facility for leader election and
// voting protocol.
s.factory = message.NewConcreteMsgFactory()
s.skillch = make(chan bool, 1) // make it buffered to unblock sender
s.site = nil
// Create and initialize new txn state.
s.txn = common.NewTxnState()
// Initialize the state to enable voting
repoName := filepath.Join(s.basepath, COORDINATOR_CONFIG_STORE)
s.configRepo, err = r.OpenRepositoryWithName(repoName, s.idxMgr.GetMemoryQuota())
if err != nil {
return err
}
s.config = r.NewServerConfig(s.configRepo)
lastLoggedTxid, err := s.config.GetLastLoggedTxnId()
if err != nil {
return err
}
s.txn.InitCurrentTxnid(common.Txnid(lastLoggedTxid))
// Need to start the peer listener before election. A follower may
// finish its election before a leader finishes its election. Therefore,
// a follower node can request a connection to the leader node before that
// node knows it is a leader. By starting the listener now, it allows the
// follower to establish the connection and let the leader handles this
// connection at a later time (when it is ready to be a leader).
s.listener, err = common.StartPeerListener(s.getHostTCPAddr())
if err != nil {
return NewError(ERROR_COOR_LISTENER_FAIL, NORMAL, COORDINATOR, err,
fmt.Sprintf("Index Coordinator : Fail to start PeerListener"))
}
// tell boostrap is ready
s.markReady()
return nil
}
//
// Handle a new proposal
//
func (l *Leader) newProposal(proposal ProposalMsg) error {
// Call out to log the proposal. Always do this first before
// sending to followers.
err := l.handler.LogProposal(proposal)
if err != nil {
if _, ok := err.(*common.RecoverableError); ok {
/// update the last committed to advacne the txnid.
l.lastCommitted = common.Txnid(proposal.GetTxnid())
l.sendAbort(proposal.GetFid(), proposal.GetReqId(), err.Error())
return nil
}
// If fails to log the proposal, return the error.
// This can cause the leader to re-elect. Just to handle
// case where there is hardware failure or repository
// corruption.
return err
}
// The leader votes for itself
l.updateQuorum(common.Txnid(proposal.GetTxnid()), l.GetFollowerId())
// remember this proposal so I can commmit it later
l.proposals[common.Txnid(proposal.GetTxnid())] = proposal
// Send the proposal to follower
l.sendProposal(proposal)
// check if proposal has quorum (if ensembleSize <= 2). Make sure that this
// is after sendProposal() so that we can still send proposal to follower BEFORE
// we send the commit message.
if l.hasQuorum(common.Txnid(proposal.GetTxnid())) {
// proposal has quorum. Now commit. If cannot commit, then return error
// which will cause the leader to re-election. Just to handle
// case where there is hardware failure or repository corruption.
err := l.commit(common.Txnid(proposal.GetTxnid()))
if err != nil {
return err
}
}
return nil
}
//
// Add a follower and starts a listener for the follower.
// If the leader is terminated, the pipe between leader
// and follower will also be closed.
//
func (l *Leader) AddFollower(fid string,
peer *common.PeerPipe,
o *observer) {
l.mutex.Lock()
defer l.mutex.Unlock()
// AddFollower requires holding the mutex such that the leader thread
// will not be sending new proposal or commit (see sendProposal() and
// sendCommit()) to followers. This allow this function to copy the
// proposals and commits from the observer queue into the pipe, before
// the leader has a chance to send new messages.
for packet := o.getNext(); packet != nil; packet = o.getNext() {
switch request := packet.(type) {
case ProposalMsg:
txid := common.Txnid(request.GetTxnid())
log.Current.Debugf("Leader.AddFollower() : send observer's packet %s, txid %d", packet.Name(), txid)
case CommitMsg:
txid := common.Txnid(request.GetTxnid())
log.Current.Debugf("Leader.AddFollower() : send observer's packet %s, txid %d", packet.Name(), txid)
}
peer.Send(packet)
}
// Rememeber the old message listener and start a new one.
oldListener, ok := l.followers[fid]
listener := newListener(fid, peer, l)
l.followers[fid] = listener
go listener.start()
// kill the old message listener
if ok && oldListener != nil {
log.Current.Debugf("Leader.AddFollower() : old Listener found for follower %s. Terminating old listener", fid)
oldListener.terminate()
} else {
// notify a brand new follower (not just replacing an existing one)
l.changech <- true
}
}
//
// Bootstrp
//
func (s *Server) bootstrap() (err error) {
// Initialize server state
s.state = newServerState()
// Initialize repository service
s.repo, err = r.OpenRepository()
if err != nil {
return err
}
s.log = r.NewCommitLog(s.repo)
s.srvConfig = r.NewServerConfig(s.repo)
// Create and initialize new txn state.
s.txn = common.NewTxnState()
// initialize the current transaction id to the lastLoggedTxid. This
// is the txid that this node has seen so far. If this node becomes
// the leader, a new epoch will be used and new current txid will
// be generated. So no need to initialize the epoch at this point.
lastLoggedTxid, err := s.srvConfig.GetLastLoggedTxnId()
if err != nil {
return err
}
s.txn.InitCurrentTxnid(common.Txnid(lastLoggedTxid))
// Initialize various callback facility for leader election and
// voting protocol.
s.factory = message.NewConcreteMsgFactory()
s.handler = action.NewServerAction(s.repo, s.log, s.srvConfig, s, s.txn, s.factory, s)
s.skillch = make(chan bool, 1) // make it buffered to unblock sender
s.site = nil
// Need to start the peer listener before election. A follower may
// finish its election before a leader finishes its election. Therefore,
// a follower node can request a connection to the leader node before that
// node knows it is a leader. By starting the listener now, it allows the
// follower to establish the connection and let the leader handles this
// connection at a later time (when it is ready to be a leader).
s.listener, err = common.StartPeerListener(GetHostTCPAddr())
if err != nil {
return common.WrapError(common.SERVER_ERROR, "Fail to start PeerListener.", err)
}
// Start a request listener.
s.reqListener, err = StartRequestListener(GetHostRequestAddr(), s)
if err != nil {
return common.WrapError(common.SERVER_ERROR, "Fail to start RequestListener.", err)
}
return nil
}
func (r *Repository) AcquireSnapshot(kind RepoKind) (common.Txnid, *RepoIterator, error) {
r.mutex.Lock()
defer r.mutex.Unlock()
if len(r.snapshots[kind]) == 0 {
return common.Txnid(0), nil, nil
}
snapshot := r.snapshots[kind][len(r.snapshots[kind])-1]
snapshot.count++
// Create a snaphsot for iteration
var FORESTDB_INMEMSEQ = fdb.SeqNum(math.MaxUint64)
kvstore, err := snapshot.snapshot.SnapshotOpen(FORESTDB_INMEMSEQ)
iter, err := kvstore.IteratorInit(nil, nil, fdb.ITR_NO_DELETES)
if err != nil {
return common.Txnid(0), nil, err
}
return snapshot.txnid, &RepoIterator{iter: iter, store: kvstore}, nil
}
//
// Create a new iterator. This is used by LeaderSyncProxy to replicate log
// entries to a folower/watcher. txid1 is last logged commited txid from follower/watcher.
// txid2 is the txid of the first packet in the observer queue for this follower/watcher.
// If the observer queue is empty, then txid2 is 0.
//
// For any LogEntry returned form the iterator, the following condition must be satisifed:
// 1) The txid of any LogEntry returned from the iterator must be greater than or equal to txid1.
// 2) The last LogEntry must have txid >= txid2. In other words, the iterator can gaurantee
// that it will cover any mutation by txid2, but cannot guarantee that it stops at txid2.
//
// Since TransientCommitLog does not keep track of history, it only supports the following case:
// 1) the beginning txid (txid1) is 0 (sending the full repository)
//
func (r *TransientCommitLog) NewIterator(txid1, txid2 common.Txnid) (CommitLogIterator, error) {
if txid1 != 0 {
return nil, common.NewError(common.REPO_ERROR, "TransientLCommitLog.NewIterator: cannot support beginning txid > 0")
}
// iter can be nil if nothing has been logged
retry := true
retryLabel:
txnid, iter, err := r.repo.AcquireSnapshot(MAIN)
if err != nil {
return nil, err
}
// The snapshot txnid must be at least match the ending txid (txid2). If not, it will retry.
// This is to ensure that it takes care race condition in which the first msg in an observer's
// queue is a commit, and the caller asks for the state of the repository which is at least as
// recent as that commit msg (txid2). If retry fails, return an error.
if txnid < txid2 {
if retry {
time.Sleep(common.XACT_COMMIT_WAIT_TIME)
retry = false
goto retryLabel
}
return nil, common.NewError(common.REPO_ERROR,
fmt.Sprintf("TransientLCommitLog.NewIterator: cannot support ending txid > %d", txnid))
}
result := &TransientLogIterator{
iter: iter,
txnid: txnid,
repo: r.repo,
curTxnid: common.Txnid(txid1 + 1),
curKey: "",
curContent: nil,
curError: nil}
if result.iter != nil {
result.curKey, result.curContent, result.curError = result.iter.Next()
}
return result, nil
}
//
// Callback when a new proposal arrives
//
func (s *Server) UpdateStateOnNewProposal(proposal protocol.ProposalMsg) {
fid := proposal.GetFid()
reqId := proposal.GetReqId()
txnid := proposal.GetTxnid()
// If this host is the one that sends the request to the leader
if fid == s.handler.GetFollowerId() {
s.state.mutex.Lock()
defer s.state.mutex.Unlock()
// look up the request handle from the pending list and
// move it to the proposed list
handle, ok := s.state.pendings[reqId]
if ok {
delete(s.state.pendings, reqId)
s.state.proposals[common.Txnid(txnid)] = handle
}
}
}
// Get value from iterator
func (i *LogIterator) Next() (txnid common.Txnid, op common.OpCode, key string, content []byte, err error) {
// TODO: Check if fdb and iterator is closed
key, content, err = i.iter.Next()
if err != nil {
return 0, common.OPCODE_INVALID, "", nil, err
}
// Since actual data is stored in the same repository, make sure
// we don't read them.
log.Current.Debugf("CommitLog.Next() : Iterator read key %s", key)
entry, err := unmarshall(content)
if err != nil {
return 0, common.OPCODE_INVALID, "", nil, err
}
return common.Txnid(entry.GetTxnid()),
common.GetOpCodeFromInt(entry.GetOpCode()),
entry.GetKey(), entry.GetContent(), nil
}
func (s *watcher) UpdateStateOnNewProposal(proposal protocol.ProposalMsg) {
s.mutex.Lock()
defer s.mutex.Unlock()
opCode := common.OpCode(proposal.GetOpCode())
logging.Debugf("Watcher.UpdateStateOnNewProposal(): receive proposal on metadata kind %d", findTypeFromKey(proposal.GetKey()))
// register the event for notification
var evtType EventType = EVENT_NONE
switch opCode {
case common.OPCODE_ADD:
metaType := findTypeFromKey(proposal.GetKey())
if metaType == KIND_INDEX_DEFN {
evtType = EVENT_CREATE_INDEX
} else if metaType == KIND_TOPOLOGY {
evtType = EVENT_UPDATE_TOPOLOGY
}
case common.OPCODE_SET:
metaType := findTypeFromKey(proposal.GetKey())
if metaType == KIND_INDEX_DEFN {
evtType = EVENT_CREATE_INDEX
} else if metaType == KIND_TOPOLOGY {
evtType = EVENT_UPDATE_TOPOLOGY
}
case common.OPCODE_DELETE:
if findTypeFromKey(proposal.GetKey()) == KIND_INDEX_DEFN {
evtType = EVENT_DROP_INDEX
}
default:
logging.Debugf("Watcher.UpdateStateOnNewProposal(): recieve proposal with opcode %d. Skip convert proposal to event.", opCode)
}
logging.Debugf("Watcher.UpdateStateOnNewProposal(): convert metadata type to event %d", evtType)
if evtType != EVENT_NONE {
logging.Debugf("Watcher.UpdateStateOnNewProposal(): register event for txid %d", proposal.GetTxnid())
s.notifications[common.Txnid(proposal.GetTxnid())] =
newNotificationHandle(proposal.GetKey(), evtType, proposal.GetContent())
}
}
func (l *LeaderSyncProxy) updateCurrentEpochAfterQuorum() error {
log.Current.Debugf("LeaderSyncProxy.updateCurrentEpochAfterQuorum()")
// Get my follower's vote for the epoch ack
packet, err := listen("EpochAck", l.follower)
if err != nil {
return err
}
// Get epoch from follower message
// TODO : Validate follower epoch
info := packet.(EpochAckMsg)
l.followerState.currentEpoch = info.GetCurrentEpoch()
l.followerState.lastLoggedTxid = common.Txnid(info.GetLastLoggedTxid())
// update my vote and wait for quorum of ack from followers
ok := l.state.voteEpochAck(l.GetFid(), l.followerState.voting)
if !ok {
return common.NewError(common.ELECTION_ERROR,
"LeaderSyncProxy.updateCurrentEpochAfterQuorum(): Fail to reach quorum on current epoch (EpochAck)")
}
// update the current epock after quorum of followers have ack'ed
epoch, err := l.handler.GetAcceptedEpoch()
if err != nil {
return err
}
// update the current epoch based on the quorum result. This function
// will perform update only if the new epoch is larger than existing value.
err = l.handler.NotifyNewCurrentEpoch(epoch)
if err != nil {
return err
}
return nil
}
//
// Update the request upon new proposal.
//
func (c *Coordinator) updateRequestOnNewProposal(proposal protocol.ProposalMsg) {
fid := proposal.GetFid()
reqId := proposal.GetReqId()
txnid := proposal.GetTxnid()
logging.Debugf("Coorindator.updateRequestOnNewProposal(): recieve proposal. Txnid %d, follower id %s, coorindator fid %s",
txnid, fid, c.GetFollowerId())
// If this host is the one that sends the request to the leader
if fid == c.GetFollowerId() {
c.state.mutex.Lock()
defer c.state.mutex.Unlock()
// look up the request handle from the pending list and
// move it to the proposed list
handle, ok := c.state.pendings[reqId]
if ok {
delete(c.state.pendings, reqId)
c.state.proposals[common.Txnid(txnid)] = handle
}
}
}
func (l *FollowerSyncProxy) syncReceive() error {
log.Current.Tracef("FollowerSyncProxy.syncReceive()")
lastCommittedFromLeader := common.BOOTSTRAP_LAST_COMMITTED_TXID
pendingCommit := make([]LogEntryMsg, 0, common.MAX_PROPOSALS)
for {
packet, err := listen("LogEntry", l.leader)
if err != nil {
return err
}
entry := packet.(LogEntryMsg)
lastTxnid := common.Txnid(entry.GetTxnid())
// If this is the first one, skip
if entry.GetOpCode() == uint32(common.OPCODE_STREAM_BEGIN_MARKER) {
log.Current.Debugf("LeaderSyncProxy.syncReceive(). Receive stream_begin. Txid : %d", lastTxnid)
lastCommittedFromLeader = lastTxnid
continue
}
// If this is the last one, then flush the pending log entry as well. The streamEnd
// message has a more recent lastCommitedTxid from the leader which is retreievd after
// the last log entry is sent.
if entry.GetOpCode() == uint32(common.OPCODE_STREAM_END_MARKER) {
log.Current.Debugf("LeaderSyncProxy.syncReceive(). Receive stream_end. Txid : %d", lastTxnid)
lastCommittedFromLeader = lastTxnid
// write any log entry that has not been logged.
for _, entry := range pendingCommit {
toCommit := entry.GetTxnid() <= uint64(lastCommittedFromLeader)
if err := l.handler.LogAndCommit(common.Txnid(entry.GetTxnid()),
entry.GetOpCode(),
entry.GetKey(),
entry.GetContent(),
toCommit); err != nil {
return err
}
}
return nil
}
// write the new log entry. If the txid is less than the last known committed txid
// from the leader, then commit the entry. Otherwise, keep it in a pending list.
toCommit := lastTxnid <= lastCommittedFromLeader
if toCommit {
// This call needs to be atomic to ensure that the commit log and the data store
// are updated transactionally. This ensures that if the follower crashes, the
// repository as a while remains in a consistent state.
if err := l.handler.LogAndCommit(common.Txnid(entry.GetTxnid()),
entry.GetOpCode(),
entry.GetKey(),
entry.GetContent(),
true); err != nil {
return err
}
} else {
pendingCommit = append(pendingCommit, entry)
}
}
return nil
}
func (l *FollowerSyncProxy) receiveAndUpdateAcceptedEpoch() error {
log.Current.Debugf("FollowerSyncProxy.receiveAndUpdateAcceptedEpoch()")
// Get the accepted epoch from the leader. This epoch
// is already being voted on by multiple followers (the highest
// epoch among the quorum of followers).
packet, err := listen("LeaderInfo", l.leader)
if err != nil {
return err
}
// Get epoch from leader message
info := packet.(LeaderInfoMsg)
epoch := info.GetAcceptedEpoch()
if err != nil {
return err
}
acceptedEpoch, err := l.handler.GetAcceptedEpoch()
if err != nil {
return err
}
if epoch > acceptedEpoch {
// Update the accepted epoch based on the quorum result. This function
// will perform update only if the new epoch is larger than existing value.
// Once the accepted epoch is updated, it will not be reset even if the
// sychornization with the leader fails. Therefore, the follower will always
// remember the largest accepted epoch known to it, such that it can be used
// in the next round of voting. Note that the leader derives this new accepted
// epoch only after it has polled from a quorum of followers. So even if sync fails,
// it is unlikey that in the next sync, the leader will give a new accepted epoch smaller
// than what is being stored now.
err = l.handler.NotifyNewAcceptedEpoch(epoch)
if err != nil {
return err
}
} else if epoch == acceptedEpoch {
// In ZK, if the local epoch (acceptedEpoch) == leader's epoch (epoch), it will replly an EpochAck with epoch = -1.
// This is to tell the leader that it should not count this EpockAck when computing quorum of EpochAck.
// This is to ensure that this follower does not "double ack" to the leader (e.g. when this follower rejoins a
// stable ensemble). In our implementation for ConsentState, it should not be affected by double ack from the same host.
} else {
return common.NewError(common.PROTOCOL_ERROR, "Accepted Epoch from leader is smaller or equal to my epoch.")
}
// Notify the leader that I have accepted the epoch. Send
// the last logged txid and current epoch to the leader.
txid, err := l.handler.GetLastLoggedTxid()
if err != nil {
return err
}
currentEpoch, err := l.handler.GetCurrentEpoch()
if err != nil {
return err
}
l.state.lastLoggedTxid = common.Txnid(txid)
l.state.currentEpoch = currentEpoch
packet = l.factory.CreateEpochAck(uint64(txid), currentEpoch)
return send(packet, l.leader)
}
func (w *watcher) GetLastCommittedTxid() (common.Txnid, error) {
return common.Txnid(0), nil
}
func (c *Coordinator) GetLastCommittedTxid() (common.Txnid, error) {
val, err := c.config.GetLastCommittedTxnId()
return common.Txnid(val), err
}
func (a *ServerAction) GetLastCommittedTxid() (common.Txnid, error) {
val, err := a.config.GetLastCommittedTxnId()
return common.Txnid(val), err
}
//
// Bootstrp
//
func (s *EmbeddedServer) bootstrap() (err error) {
defer func() {
r := recover()
if r != nil {
log.Current.Errorf("panic in EmbeddedServer.bootstrap() : %s\n", r)
log.Current.Errorf("%s", log.Current.StackTrace())
}
if err != nil || r != nil {
common.SafeRun("EmbeddedServer.bootstrap()",
func() {
s.cleanupState()
})
}
}()
// Initialize server state
s.state = newServerState()
// Create and initialize new txn state.
s.txn = common.NewTxnState()
// Initialize repository service
s.repo, err = r.OpenRepositoryWithName(s.repoName, s.quota)
if err != nil {
return err
}
// Initialize server config
s.srvConfig = r.NewServerConfig(s.repo)
// initialize the current transaction id to the lastLoggedTxid. This
// is the txid that this node has seen so far. If this node becomes
// the leader, a new epoch will be used and new current txid will
// be generated. So no need to initialize the epoch at this point.
lastLoggedTxid, err := s.srvConfig.GetLastLoggedTxnId()
if err != nil {
return err
}
s.txn.InitCurrentTxnid(common.Txnid(lastLoggedTxid))
// Initialize commit log
lastCommittedTxid, err := s.srvConfig.GetLastCommittedTxnId()
if err != nil {
return err
}
s.log, err = r.NewTransientCommitLog(s.repo, lastCommittedTxid)
if err != nil {
return err
}
// Initialize various callback facility for leader election and
// voting protocol.
s.factory = message.NewConcreteMsgFactory()
s.handler = action.NewServerActionWithNotifier(s.repo, s.log, s.srvConfig, s, s.notifier, s.txn, s.factory, s)
s.skillch = make(chan bool, 1) // make it buffered to unblock sender
// Need to start the peer listener before election. A follower may
// finish its election before a leader finishes its election. Therefore,
// a follower node can request a connection to the leader node before that
// node knows it is a leader. By starting the listener now, it allows the
// follower to establish the connection and let the leader handles this
// connection at a later time (when it is ready to be a leader).
s.listener, err = common.StartPeerListener(s.msgAddr)
if err != nil {
err = common.WrapError(common.SERVER_ERROR, "Fail to start PeerListener. err = %v", err)
return
}
return nil
}
func (r *ServerConfig) GetLastCommittedTxnId() (common.Txnid, error) {
value, err := r.GetInt(common.CONFIG_LAST_COMMITTED_TXID)
return common.Txnid(value), err
}