[VOL-4291] OfAgent changes for gRPC migration
Change-Id: I8da1db6df49d478ef24ec8f9bd719e9692f48a7f
diff --git a/vendor/github.com/coreos/etcd/raft/node.go b/vendor/github.com/coreos/etcd/raft/node.go
new file mode 100644
index 0000000..33a9db8
--- /dev/null
+++ b/vendor/github.com/coreos/etcd/raft/node.go
@@ -0,0 +1,539 @@
+// Copyright 2015 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package raft
+
+import (
+ "context"
+ "errors"
+
+ pb "github.com/coreos/etcd/raft/raftpb"
+)
+
+type SnapshotStatus int
+
+const (
+ SnapshotFinish SnapshotStatus = 1
+ SnapshotFailure SnapshotStatus = 2
+)
+
+var (
+ emptyState = pb.HardState{}
+
+ // ErrStopped is returned by methods on Nodes that have been stopped.
+ ErrStopped = errors.New("raft: stopped")
+)
+
+// SoftState provides state that is useful for logging and debugging.
+// The state is volatile and does not need to be persisted to the WAL.
+type SoftState struct {
+ Lead uint64 // must use atomic operations to access; keep 64-bit aligned.
+ RaftState StateType
+}
+
+func (a *SoftState) equal(b *SoftState) bool {
+ return a.Lead == b.Lead && a.RaftState == b.RaftState
+}
+
+// Ready encapsulates the entries and messages that are ready to read,
+// be saved to stable storage, committed or sent to other peers.
+// All fields in Ready are read-only.
+type Ready struct {
+ // The current volatile state of a Node.
+ // SoftState will be nil if there is no update.
+ // It is not required to consume or store SoftState.
+ *SoftState
+
+ // The current state of a Node to be saved to stable storage BEFORE
+ // Messages are sent.
+ // HardState will be equal to empty state if there is no update.
+ pb.HardState
+
+ // ReadStates can be used for node to serve linearizable read requests locally
+ // when its applied index is greater than the index in ReadState.
+ // Note that the readState will be returned when raft receives msgReadIndex.
+ // The returned is only valid for the request that requested to read.
+ ReadStates []ReadState
+
+ // Entries specifies entries to be saved to stable storage BEFORE
+ // Messages are sent.
+ Entries []pb.Entry
+
+ // Snapshot specifies the snapshot to be saved to stable storage.
+ Snapshot pb.Snapshot
+
+ // CommittedEntries specifies entries to be committed to a
+ // store/state-machine. These have previously been committed to stable
+ // store.
+ CommittedEntries []pb.Entry
+
+ // Messages specifies outbound messages to be sent AFTER Entries are
+ // committed to stable storage.
+ // If it contains a MsgSnap message, the application MUST report back to raft
+ // when the snapshot has been received or has failed by calling ReportSnapshot.
+ Messages []pb.Message
+
+ // MustSync indicates whether the HardState and Entries must be synchronously
+ // written to disk or if an asynchronous write is permissible.
+ MustSync bool
+}
+
+func isHardStateEqual(a, b pb.HardState) bool {
+ return a.Term == b.Term && a.Vote == b.Vote && a.Commit == b.Commit
+}
+
+// IsEmptyHardState returns true if the given HardState is empty.
+func IsEmptyHardState(st pb.HardState) bool {
+ return isHardStateEqual(st, emptyState)
+}
+
+// IsEmptySnap returns true if the given Snapshot is empty.
+func IsEmptySnap(sp pb.Snapshot) bool {
+ return sp.Metadata.Index == 0
+}
+
+func (rd Ready) containsUpdates() bool {
+ return rd.SoftState != nil || !IsEmptyHardState(rd.HardState) ||
+ !IsEmptySnap(rd.Snapshot) || len(rd.Entries) > 0 ||
+ len(rd.CommittedEntries) > 0 || len(rd.Messages) > 0 || len(rd.ReadStates) != 0
+}
+
+// Node represents a node in a raft cluster.
+type Node interface {
+ // Tick increments the internal logical clock for the Node by a single tick. Election
+ // timeouts and heartbeat timeouts are in units of ticks.
+ Tick()
+ // Campaign causes the Node to transition to candidate state and start campaigning to become leader.
+ Campaign(ctx context.Context) error
+ // Propose proposes that data be appended to the log.
+ Propose(ctx context.Context, data []byte) error
+ // ProposeConfChange proposes config change.
+ // At most one ConfChange can be in the process of going through consensus.
+ // Application needs to call ApplyConfChange when applying EntryConfChange type entry.
+ ProposeConfChange(ctx context.Context, cc pb.ConfChange) error
+ // Step advances the state machine using the given message. ctx.Err() will be returned, if any.
+ Step(ctx context.Context, msg pb.Message) error
+
+ // Ready returns a channel that returns the current point-in-time state.
+ // Users of the Node must call Advance after retrieving the state returned by Ready.
+ //
+ // NOTE: No committed entries from the next Ready may be applied until all committed entries
+ // and snapshots from the previous one have finished.
+ Ready() <-chan Ready
+
+ // Advance notifies the Node that the application has saved progress up to the last Ready.
+ // It prepares the node to return the next available Ready.
+ //
+ // The application should generally call Advance after it applies the entries in last Ready.
+ //
+ // However, as an optimization, the application may call Advance while it is applying the
+ // commands. For example. when the last Ready contains a snapshot, the application might take
+ // a long time to apply the snapshot data. To continue receiving Ready without blocking raft
+ // progress, it can call Advance before finishing applying the last ready.
+ Advance()
+ // ApplyConfChange applies config change to the local node.
+ // Returns an opaque ConfState protobuf which must be recorded
+ // in snapshots. Will never return nil; it returns a pointer only
+ // to match MemoryStorage.Compact.
+ ApplyConfChange(cc pb.ConfChange) *pb.ConfState
+
+ // TransferLeadership attempts to transfer leadership to the given transferee.
+ TransferLeadership(ctx context.Context, lead, transferee uint64)
+
+ // ReadIndex request a read state. The read state will be set in the ready.
+ // Read state has a read index. Once the application advances further than the read
+ // index, any linearizable read requests issued before the read request can be
+ // processed safely. The read state will have the same rctx attached.
+ ReadIndex(ctx context.Context, rctx []byte) error
+
+ // Status returns the current status of the raft state machine.
+ Status() Status
+ // ReportUnreachable reports the given node is not reachable for the last send.
+ ReportUnreachable(id uint64)
+ // ReportSnapshot reports the status of the sent snapshot.
+ ReportSnapshot(id uint64, status SnapshotStatus)
+ // Stop performs any necessary termination of the Node.
+ Stop()
+}
+
+type Peer struct {
+ ID uint64
+ Context []byte
+}
+
+// StartNode returns a new Node given configuration and a list of raft peers.
+// It appends a ConfChangeAddNode entry for each given peer to the initial log.
+func StartNode(c *Config, peers []Peer) Node {
+ r := newRaft(c)
+ // become the follower at term 1 and apply initial configuration
+ // entries of term 1
+ r.becomeFollower(1, None)
+ for _, peer := range peers {
+ cc := pb.ConfChange{Type: pb.ConfChangeAddNode, NodeID: peer.ID, Context: peer.Context}
+ d, err := cc.Marshal()
+ if err != nil {
+ panic("unexpected marshal error")
+ }
+ e := pb.Entry{Type: pb.EntryConfChange, Term: 1, Index: r.raftLog.lastIndex() + 1, Data: d}
+ r.raftLog.append(e)
+ }
+ // Mark these initial entries as committed.
+ // TODO(bdarnell): These entries are still unstable; do we need to preserve
+ // the invariant that committed < unstable?
+ r.raftLog.committed = r.raftLog.lastIndex()
+ // Now apply them, mainly so that the application can call Campaign
+ // immediately after StartNode in tests. Note that these nodes will
+ // be added to raft twice: here and when the application's Ready
+ // loop calls ApplyConfChange. The calls to addNode must come after
+ // all calls to raftLog.append so progress.next is set after these
+ // bootstrapping entries (it is an error if we try to append these
+ // entries since they have already been committed).
+ // We do not set raftLog.applied so the application will be able
+ // to observe all conf changes via Ready.CommittedEntries.
+ for _, peer := range peers {
+ r.addNode(peer.ID)
+ }
+
+ n := newNode()
+ n.logger = c.Logger
+ go n.run(r)
+ return &n
+}
+
+// RestartNode is similar to StartNode but does not take a list of peers.
+// The current membership of the cluster will be restored from the Storage.
+// If the caller has an existing state machine, pass in the last log index that
+// has been applied to it; otherwise use zero.
+func RestartNode(c *Config) Node {
+ r := newRaft(c)
+
+ n := newNode()
+ n.logger = c.Logger
+ go n.run(r)
+ return &n
+}
+
+// node is the canonical implementation of the Node interface
+type node struct {
+ propc chan pb.Message
+ recvc chan pb.Message
+ confc chan pb.ConfChange
+ confstatec chan pb.ConfState
+ readyc chan Ready
+ advancec chan struct{}
+ tickc chan struct{}
+ done chan struct{}
+ stop chan struct{}
+ status chan chan Status
+
+ logger Logger
+}
+
+func newNode() node {
+ return node{
+ propc: make(chan pb.Message),
+ recvc: make(chan pb.Message),
+ confc: make(chan pb.ConfChange),
+ confstatec: make(chan pb.ConfState),
+ readyc: make(chan Ready),
+ advancec: make(chan struct{}),
+ // make tickc a buffered chan, so raft node can buffer some ticks when the node
+ // is busy processing raft messages. Raft node will resume process buffered
+ // ticks when it becomes idle.
+ tickc: make(chan struct{}, 128),
+ done: make(chan struct{}),
+ stop: make(chan struct{}),
+ status: make(chan chan Status),
+ }
+}
+
+func (n *node) Stop() {
+ select {
+ case n.stop <- struct{}{}:
+ // Not already stopped, so trigger it
+ case <-n.done:
+ // Node has already been stopped - no need to do anything
+ return
+ }
+ // Block until the stop has been acknowledged by run()
+ <-n.done
+}
+
+func (n *node) run(r *raft) {
+ var propc chan pb.Message
+ var readyc chan Ready
+ var advancec chan struct{}
+ var prevLastUnstablei, prevLastUnstablet uint64
+ var havePrevLastUnstablei bool
+ var prevSnapi uint64
+ var rd Ready
+
+ lead := None
+ prevSoftSt := r.softState()
+ prevHardSt := emptyState
+
+ for {
+ if advancec != nil {
+ readyc = nil
+ } else {
+ rd = newReady(r, prevSoftSt, prevHardSt)
+ if rd.containsUpdates() {
+ readyc = n.readyc
+ } else {
+ readyc = nil
+ }
+ }
+
+ if lead != r.lead {
+ if r.hasLeader() {
+ if lead == None {
+ r.logger.Infof("raft.node: %x elected leader %x at term %d", r.id, r.lead, r.Term)
+ } else {
+ r.logger.Infof("raft.node: %x changed leader from %x to %x at term %d", r.id, lead, r.lead, r.Term)
+ }
+ propc = n.propc
+ } else {
+ r.logger.Infof("raft.node: %x lost leader %x at term %d", r.id, lead, r.Term)
+ propc = nil
+ }
+ lead = r.lead
+ }
+
+ select {
+ // TODO: maybe buffer the config propose if there exists one (the way
+ // described in raft dissertation)
+ // Currently it is dropped in Step silently.
+ case m := <-propc:
+ m.From = r.id
+ r.Step(m)
+ case m := <-n.recvc:
+ // filter out response message from unknown From.
+ if pr := r.getProgress(m.From); pr != nil || !IsResponseMsg(m.Type) {
+ r.Step(m) // raft never returns an error
+ }
+ case cc := <-n.confc:
+ if cc.NodeID == None {
+ r.resetPendingConf()
+ select {
+ case n.confstatec <- pb.ConfState{Nodes: r.nodes()}:
+ case <-n.done:
+ }
+ break
+ }
+ switch cc.Type {
+ case pb.ConfChangeAddNode:
+ r.addNode(cc.NodeID)
+ case pb.ConfChangeAddLearnerNode:
+ r.addLearner(cc.NodeID)
+ case pb.ConfChangeRemoveNode:
+ // block incoming proposal when local node is
+ // removed
+ if cc.NodeID == r.id {
+ propc = nil
+ }
+ r.removeNode(cc.NodeID)
+ case pb.ConfChangeUpdateNode:
+ r.resetPendingConf()
+ default:
+ panic("unexpected conf type")
+ }
+ select {
+ case n.confstatec <- pb.ConfState{Nodes: r.nodes()}:
+ case <-n.done:
+ }
+ case <-n.tickc:
+ r.tick()
+ case readyc <- rd:
+ if rd.SoftState != nil {
+ prevSoftSt = rd.SoftState
+ }
+ if len(rd.Entries) > 0 {
+ prevLastUnstablei = rd.Entries[len(rd.Entries)-1].Index
+ prevLastUnstablet = rd.Entries[len(rd.Entries)-1].Term
+ havePrevLastUnstablei = true
+ }
+ if !IsEmptyHardState(rd.HardState) {
+ prevHardSt = rd.HardState
+ }
+ if !IsEmptySnap(rd.Snapshot) {
+ prevSnapi = rd.Snapshot.Metadata.Index
+ }
+
+ r.msgs = nil
+ r.readStates = nil
+ advancec = n.advancec
+ case <-advancec:
+ if prevHardSt.Commit != 0 {
+ r.raftLog.appliedTo(prevHardSt.Commit)
+ }
+ if havePrevLastUnstablei {
+ r.raftLog.stableTo(prevLastUnstablei, prevLastUnstablet)
+ havePrevLastUnstablei = false
+ }
+ r.raftLog.stableSnapTo(prevSnapi)
+ advancec = nil
+ case c := <-n.status:
+ c <- getStatus(r)
+ case <-n.stop:
+ close(n.done)
+ return
+ }
+ }
+}
+
+// Tick increments the internal logical clock for this Node. Election timeouts
+// and heartbeat timeouts are in units of ticks.
+func (n *node) Tick() {
+ select {
+ case n.tickc <- struct{}{}:
+ case <-n.done:
+ default:
+ n.logger.Warningf("A tick missed to fire. Node blocks too long!")
+ }
+}
+
+func (n *node) Campaign(ctx context.Context) error { return n.step(ctx, pb.Message{Type: pb.MsgHup}) }
+
+func (n *node) Propose(ctx context.Context, data []byte) error {
+ return n.step(ctx, pb.Message{Type: pb.MsgProp, Entries: []pb.Entry{{Data: data}}})
+}
+
+func (n *node) Step(ctx context.Context, m pb.Message) error {
+ // ignore unexpected local messages receiving over network
+ if IsLocalMsg(m.Type) {
+ // TODO: return an error?
+ return nil
+ }
+ return n.step(ctx, m)
+}
+
+func (n *node) ProposeConfChange(ctx context.Context, cc pb.ConfChange) error {
+ data, err := cc.Marshal()
+ if err != nil {
+ return err
+ }
+ return n.Step(ctx, pb.Message{Type: pb.MsgProp, Entries: []pb.Entry{{Type: pb.EntryConfChange, Data: data}}})
+}
+
+// Step advances the state machine using msgs. The ctx.Err() will be returned,
+// if any.
+func (n *node) step(ctx context.Context, m pb.Message) error {
+ ch := n.recvc
+ if m.Type == pb.MsgProp {
+ ch = n.propc
+ }
+
+ select {
+ case ch <- m:
+ return nil
+ case <-ctx.Done():
+ return ctx.Err()
+ case <-n.done:
+ return ErrStopped
+ }
+}
+
+func (n *node) Ready() <-chan Ready { return n.readyc }
+
+func (n *node) Advance() {
+ select {
+ case n.advancec <- struct{}{}:
+ case <-n.done:
+ }
+}
+
+func (n *node) ApplyConfChange(cc pb.ConfChange) *pb.ConfState {
+ var cs pb.ConfState
+ select {
+ case n.confc <- cc:
+ case <-n.done:
+ }
+ select {
+ case cs = <-n.confstatec:
+ case <-n.done:
+ }
+ return &cs
+}
+
+func (n *node) Status() Status {
+ c := make(chan Status)
+ select {
+ case n.status <- c:
+ return <-c
+ case <-n.done:
+ return Status{}
+ }
+}
+
+func (n *node) ReportUnreachable(id uint64) {
+ select {
+ case n.recvc <- pb.Message{Type: pb.MsgUnreachable, From: id}:
+ case <-n.done:
+ }
+}
+
+func (n *node) ReportSnapshot(id uint64, status SnapshotStatus) {
+ rej := status == SnapshotFailure
+
+ select {
+ case n.recvc <- pb.Message{Type: pb.MsgSnapStatus, From: id, Reject: rej}:
+ case <-n.done:
+ }
+}
+
+func (n *node) TransferLeadership(ctx context.Context, lead, transferee uint64) {
+ select {
+ // manually set 'from' and 'to', so that leader can voluntarily transfers its leadership
+ case n.recvc <- pb.Message{Type: pb.MsgTransferLeader, From: transferee, To: lead}:
+ case <-n.done:
+ case <-ctx.Done():
+ }
+}
+
+func (n *node) ReadIndex(ctx context.Context, rctx []byte) error {
+ return n.step(ctx, pb.Message{Type: pb.MsgReadIndex, Entries: []pb.Entry{{Data: rctx}}})
+}
+
+func newReady(r *raft, prevSoftSt *SoftState, prevHardSt pb.HardState) Ready {
+ rd := Ready{
+ Entries: r.raftLog.unstableEntries(),
+ CommittedEntries: r.raftLog.nextEnts(),
+ Messages: r.msgs,
+ }
+ if softSt := r.softState(); !softSt.equal(prevSoftSt) {
+ rd.SoftState = softSt
+ }
+ if hardSt := r.hardState(); !isHardStateEqual(hardSt, prevHardSt) {
+ rd.HardState = hardSt
+ }
+ if r.raftLog.unstable.snapshot != nil {
+ rd.Snapshot = *r.raftLog.unstable.snapshot
+ }
+ if len(r.readStates) != 0 {
+ rd.ReadStates = r.readStates
+ }
+ rd.MustSync = MustSync(rd.HardState, prevHardSt, len(rd.Entries))
+ return rd
+}
+
+// MustSync returns true if the hard state and count of Raft entries indicate
+// that a synchronous write to persistent storage is required.
+func MustSync(st, prevst pb.HardState, entsnum int) bool {
+ // Persistent state on all servers:
+ // (Updated on stable storage before responding to RPCs)
+ // currentTerm
+ // votedFor
+ // log entries[]
+ return entsnum != 0 || st.Vote != prevst.Vote || st.Term != prevst.Term
+}