raft: introduce protos for joint quorums

raft/raftpb/raft.pb.go

@@ -15,6 +15,8 @@
 		HardState
 		ConfState
 		ConfChange
+		ConfChangeSingle
+		ConfChangeV2
 */
 package raftpb
 
@@ -44,17 +46,20 @@ const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
 type EntryType int32
 
 const (
-	EntryNormal     EntryType = 0
-	EntryConfChange EntryType = 1
+	EntryNormal       EntryType = 0
+	EntryConfChange   EntryType = 1
+	EntryConfChangeV2 EntryType = 2
 )
 
 var EntryType_name = map[int32]string{
 	0: "EntryNormal",
 	1: "EntryConfChange",
+	2: "EntryConfChangeV2",
 }
 var EntryType_value = map[string]int32{
-	"EntryNormal":     0,
-	"EntryConfChange": 1,
+	"EntryNormal":       0,
+	"EntryConfChange":   1,
+	"EntryConfChangeV2": 2,
 }
 
 func (x EntryType) Enum() *EntryType {
@@ -160,6 +165,51 @@ func (x *MessageType) UnmarshalJSON(data []byte) error {
 }
 func (MessageType) EnumDescriptor() ([]byte, []int) { return fileDescriptorRaft, []int{1} }
 
+// ConfChangeTransition specifies the behavior of a configuration change with
+// respect to joint consensus.
+type ConfChangeTransition int32
+
+const (
+	// Automatically use the simple protocol if possible, otherwise fall back
+	// to ConfChangeJointImplicit.
+	ConfChangeTransitionAuto ConfChangeTransition = 0
+	// Use joint consensus, but transition out of the joint configuration
+	// automatically by proposing a no-op configuration change.
+	ConfChangeTransitionJointImplicit ConfChangeTransition = 1
+	// Use joint consensus and remain in the joint configuration until the
+	// application proposes a no-op configuration change.
+	ConfChangeTransitionJointExplicit ConfChangeTransition = 2
+)
+
+var ConfChangeTransition_name = map[int32]string{
+	0: "ConfChangeTransitionAuto",
+	1: "ConfChangeTransitionJointImplicit",
+	2: "ConfChangeTransitionJointExplicit",
+}
+var ConfChangeTransition_value = map[string]int32{
+	"ConfChangeTransitionAuto":          0,
+	"ConfChangeTransitionJointImplicit": 1,
+	"ConfChangeTransitionJointExplicit": 2,
+}
+
+func (x ConfChangeTransition) Enum() *ConfChangeTransition {
+	p := new(ConfChangeTransition)
+	*p = x
+	return p
+}
+func (x ConfChangeTransition) String() string {
+	return proto.EnumName(ConfChangeTransition_name, int32(x))
+}
+func (x *ConfChangeTransition) UnmarshalJSON(data []byte) error {
+	value, err := proto.UnmarshalJSONEnum(ConfChangeTransition_value, data, "ConfChangeTransition")
+	if err != nil {
+		return err
+	}
+	*x = ConfChangeTransition(value)
+	return nil
+}
+func (ConfChangeTransition) EnumDescriptor() ([]byte, []int) { return fileDescriptorRaft, []int{2} }
+
 type ConfChangeType int32
 
 const (
@@ -198,7 +248,7 @@ func (x *ConfChangeType) UnmarshalJSON(data []byte) error {
 	*x = ConfChangeType(value)
 	return nil
 }
-func (ConfChangeType) EnumDescriptor() ([]byte, []int) { return fileDescriptorRaft, []int{2} }
+func (ConfChangeType) EnumDescriptor() ([]byte, []int) { return fileDescriptorRaft, []int{3} }
 
 type Entry struct {
 	Term             uint64    `protobuf:"varint,2,opt,name=Term" json:"Term"`
@@ -271,7 +321,10 @@ func (*HardState) Descriptor() ([]byte, []int) { return fileDescriptorRaft, []in
 
 type ConfState struct {
 	Nodes            []uint64 `protobuf:"varint,1,rep,name=nodes" json:"nodes,omitempty"`
+	NodesJoint       []uint64 `protobuf:"varint,3,rep,name=nodes_joint,json=nodesJoint" json:"nodes_joint,omitempty"`
 	Learners         []uint64 `protobuf:"varint,2,rep,name=learners" json:"learners,omitempty"`
+	LearnersNext     []uint64 `protobuf:"varint,4,rep,name=learners_next,json=learnersNext" json:"learners_next,omitempty"`
+	AutoLeave        bool     `protobuf:"varint,5,opt,name=auto_leave,json=autoLeave" json:"auto_leave"`
 	XXX_unrecognized []byte   `json:"-"`
 }
 
@@ -281,11 +334,14 @@ func (*ConfState) ProtoMessage()               {}
 func (*ConfState) Descriptor() ([]byte, []int) { return fileDescriptorRaft, []int{5} }
 
 type ConfChange struct {
-	ID               uint64         `protobuf:"varint,1,opt,name=ID" json:"ID"`
-	Type             ConfChangeType `protobuf:"varint,2,opt,name=Type,enum=raftpb.ConfChangeType" json:"Type"`
-	NodeID           uint64         `protobuf:"varint,3,opt,name=NodeID" json:"NodeID"`
-	Context          []byte         `protobuf:"bytes,4,opt,name=Context" json:"Context,omitempty"`
-	XXX_unrecognized []byte         `json:"-"`
+	Type    ConfChangeType `protobuf:"varint,2,opt,name=type,enum=raftpb.ConfChangeType" json:"type"`
+	NodeID  uint64         `protobuf:"varint,3,opt,name=node_id,json=nodeId" json:"node_id"`
+	Context []byte         `protobuf:"bytes,4,opt,name=context" json:"context,omitempty"`
+	// NB: this is used only by etcd to thread through a unique identifier.
+	// Ideally it should really use the Context instead. No counterpart to
+	// this field exists in ConfChangeV2.
+	ID               uint64 `protobuf:"varint,1,opt,name=id" json:"id"`
+	XXX_unrecognized []byte `json:"-"`
 }
 
 func (m *ConfChange) Reset()                    { *m = ConfChange{} }
@@ -293,6 +349,63 @@ func (m *ConfChange) String() string            { return proto.CompactTextString
 func (*ConfChange) ProtoMessage()               {}
 func (*ConfChange) Descriptor() ([]byte, []int) { return fileDescriptorRaft, []int{6} }
 
+// ConfChangeSingle is an individual configuration change operation. Multiple
+// such operations can be carried out atomically via a ConfChangeV2.
+type ConfChangeSingle struct {
+	Type             ConfChangeType `protobuf:"varint,1,opt,name=type,enum=raftpb.ConfChangeType" json:"type"`
+	NodeID           uint64         `protobuf:"varint,2,opt,name=node_id,json=nodeId" json:"node_id"`
+	XXX_unrecognized []byte         `json:"-"`
+}
+
+func (m *ConfChangeSingle) Reset()                    { *m = ConfChangeSingle{} }
+func (m *ConfChangeSingle) String() string            { return proto.CompactTextString(m) }
+func (*ConfChangeSingle) ProtoMessage()               {}
+func (*ConfChangeSingle) Descriptor() ([]byte, []int) { return fileDescriptorRaft, []int{7} }
+
+// ConfChangeV2 messages initiate configuration changes. They support both the
+// simple "one at a time" membership change protocol and full Joint Consensus
+// allowing for arbitrary changes in membership.
+//
+// The supplied context is treated as an opaque payload and can be used to
+// attach an action on the state machine to the application of the config change
+// proposal. Note that contrary to Joint Consensus as outlined in the Raft
+// paper[1], configuration changes become active when they are *applied* to the
+// state machine (not when they are appended to the log).
+//
+// The simple protocol can be used whenever only a single change is made.
+//
+// Non-simple changes require the use of Joint Consensus, for which two
+// configuration changes are run. The first configuration change specifies the
+// desired changes and transitions the Raft group into the joint configuration,
+// in which quorum requires a majority of both the pre-changes and post-changes
+// configuration. Joint Consensus avoids entering fragile intermediate
+// configurations that could compromise survivability. For example, without the
+// use of Joint Consensus and running across three availability zones with a
+// replication factor of three, it is not possible to replace a voter without
+// entering an intermediate configuration that does not survive the outage of
+// one availability zone.
+//
+// The provided ConfChangeTransition specifies how (and whether) Joint Consensus
+// is used, and assigns the task of leaving the joint configuration either to
+// Raft or the application. Leaving the joint configuration is accomplished by
+// proposing a ConfChangeV2 with only and optionally the Context field
+// populated.
+//
+// For details on Raft membership changes, see:
+//
+// [1]: https://github.com/ongardie/dissertation/blob/master/online-trim.pdf
+type ConfChangeV2 struct {
+	Transition       ConfChangeTransition `protobuf:"varint,1,opt,name=transition,enum=raftpb.ConfChangeTransition" json:"transition"`
+	Changes          []ConfChangeSingle   `protobuf:"bytes,2,rep,name=changes" json:"changes"`
+	Context          []byte               `protobuf:"bytes,3,opt,name=context" json:"context,omitempty"`
+	XXX_unrecognized []byte               `json:"-"`
+}
+
+func (m *ConfChangeV2) Reset()                    { *m = ConfChangeV2{} }
+func (m *ConfChangeV2) String() string            { return proto.CompactTextString(m) }
+func (*ConfChangeV2) ProtoMessage()               {}
+func (*ConfChangeV2) Descriptor() ([]byte, []int) { return fileDescriptorRaft, []int{8} }
+
 func init() {
 	proto.RegisterType((*Entry)(nil), "raftpb.Entry")
 	proto.RegisterType((*SnapshotMetadata)(nil), "raftpb.SnapshotMetadata")
@@ -301,8 +414,11 @@ func init() {
 	proto.RegisterType((*HardState)(nil), "raftpb.HardState")
 	proto.RegisterType((*ConfState)(nil), "raftpb.ConfState")
 	proto.RegisterType((*ConfChange)(nil), "raftpb.ConfChange")
+	proto.RegisterType((*ConfChangeSingle)(nil), "raftpb.ConfChangeSingle")
+	proto.RegisterType((*ConfChangeV2)(nil), "raftpb.ConfChangeV2")
 	proto.RegisterEnum("raftpb.EntryType", EntryType_name, EntryType_value)
 	proto.RegisterEnum("raftpb.MessageType", MessageType_name, MessageType_value)
+	proto.RegisterEnum("raftpb.ConfChangeTransition", ConfChangeTransition_name, ConfChangeTransition_value)
 	proto.RegisterEnum("raftpb.ConfChangeType", ConfChangeType_name, ConfChangeType_value)
 }
 func (m *Entry) Marshal() (dAtA []byte, err error) {
@@ -549,6 +665,28 @@ func (m *ConfState) MarshalTo(dAtA []byte) (int, error) {
 			i = encodeVarintRaft(dAtA, i, uint64(num))
 		}
 	}
+	if len(m.NodesJoint) > 0 {
+		for _, num := range m.NodesJoint {
+			dAtA[i] = 0x18
+			i++
+			i = encodeVarintRaft(dAtA, i, uint64(num))
+		}
+	}
+	if len(m.LearnersNext) > 0 {
+		for _, num := range m.LearnersNext {
+			dAtA[i] = 0x20
+			i++
+			i = encodeVarintRaft(dAtA, i, uint64(num))
+		}
+	}
+	dAtA[i] = 0x28
+	i++
+	if m.AutoLeave {
+		dAtA[i] = 1
+	} else {
+		dAtA[i] = 0
+	}
+	i++
 	if m.XXX_unrecognized != nil {
 		i += copy(dAtA[i:], m.XXX_unrecognized)
 	}
@@ -591,6 +729,75 @@ func (m *ConfChange) MarshalTo(dAtA []byte) (int, error) {
 	return i, nil
 }
 
+func (m *ConfChangeSingle) Marshal() (dAtA []byte, err error) {
+	size := m.Size()
+	dAtA = make([]byte, size)
+	n, err := m.MarshalTo(dAtA)
+	if err != nil {
+		return nil, err
+	}
+	return dAtA[:n], nil
+}
+
+func (m *ConfChangeSingle) MarshalTo(dAtA []byte) (int, error) {
+	var i int
+	_ = i
+	var l int
+	_ = l
+	dAtA[i] = 0x8
+	i++
+	i = encodeVarintRaft(dAtA, i, uint64(m.Type))
+	dAtA[i] = 0x10
+	i++
+	i = encodeVarintRaft(dAtA, i, uint64(m.NodeID))
+	if m.XXX_unrecognized != nil {
+		i += copy(dAtA[i:], m.XXX_unrecognized)
+	}
+	return i, nil
+}
+
+func (m *ConfChangeV2) Marshal() (dAtA []byte, err error) {
+	size := m.Size()
+	dAtA = make([]byte, size)
+	n, err := m.MarshalTo(dAtA)
+	if err != nil {
+		return nil, err
+	}
+	return dAtA[:n], nil
+}
+
+func (m *ConfChangeV2) MarshalTo(dAtA []byte) (int, error) {
+	var i int
+	_ = i
+	var l int
+	_ = l
+	dAtA[i] = 0x8
+	i++
+	i = encodeVarintRaft(dAtA, i, uint64(m.Transition))
+	if len(m.Changes) > 0 {
+		for _, msg := range m.Changes {
+			dAtA[i] = 0x12
+			i++
+			i = encodeVarintRaft(dAtA, i, uint64(msg.Size()))
+			n, err := msg.MarshalTo(dAtA[i:])
+			if err != nil {
+				return 0, err
+			}
+			i += n
+		}
+	}
+	if m.Context != nil {
+		dAtA[i] = 0x1a
+		i++
+		i = encodeVarintRaft(dAtA, i, uint64(len(m.Context)))
+		i += copy(dAtA[i:], m.Context)
+	}
+	if m.XXX_unrecognized != nil {
+		i += copy(dAtA[i:], m.XXX_unrecognized)
+	}
+	return i, nil
+}
+
 func encodeVarintRaft(dAtA []byte, offset int, v uint64) int {
 	for v >= 1<<7 {
 		dAtA[offset] = uint8(v&0x7f | 0x80)
@@ -699,6 +906,17 @@ func (m *ConfState) Size() (n int) {
 			n += 1 + sovRaft(uint64(e))
 		}
 	}
+	if len(m.NodesJoint) > 0 {
+		for _, e := range m.NodesJoint {
+			n += 1 + sovRaft(uint64(e))
+		}
+	}
+	if len(m.LearnersNext) > 0 {
+		for _, e := range m.LearnersNext {
+			n += 1 + sovRaft(uint64(e))
+		}
+	}
+	n += 2
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -721,6 +939,37 @@ func (m *ConfChange) Size() (n int) {
 	return n
 }
 
+func (m *ConfChangeSingle) Size() (n int) {
+	var l int
+	_ = l
+	n += 1 + sovRaft(uint64(m.Type))
+	n += 1 + sovRaft(uint64(m.NodeID))
+	if m.XXX_unrecognized != nil {
+		n += len(m.XXX_unrecognized)
+	}
+	return n
+}
+
+func (m *ConfChangeV2) Size() (n int) {
+	var l int
+	_ = l
+	n += 1 + sovRaft(uint64(m.Transition))
+	if len(m.Changes) > 0 {
+		for _, e := range m.Changes {
+			l = e.Size()
+			n += 1 + l + sovRaft(uint64(l))
+		}
+	}
+	if m.Context != nil {
+		l = len(m.Context)
+		n += 1 + l + sovRaft(uint64(l))
+	}
+	if m.XXX_unrecognized != nil {
+		n += len(m.XXX_unrecognized)
+	}
+	return n
+}
+
 func sovRaft(x uint64) (n int) {
 	for {
 		n++
@@ -1680,6 +1929,150 @@ func (m *ConfState) Unmarshal(dAtA []byte) error {
 			} else {
 				return fmt.Errorf("proto: wrong wireType = %d for field Learners", wireType)
 			}
+		case 3:
+			if wireType == 0 {
+				var v uint64
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowRaft
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					v |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				m.NodesJoint = append(m.NodesJoint, v)
+			} else if wireType == 2 {
+				var packedLen int
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowRaft
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					packedLen |= (int(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				if packedLen < 0 {
+					return ErrInvalidLengthRaft
+				}
+				postIndex := iNdEx + packedLen
+				if postIndex > l {
+					return io.ErrUnexpectedEOF
+				}
+				for iNdEx < postIndex {
+					var v uint64
+					for shift := uint(0); ; shift += 7 {
+						if shift >= 64 {
+							return ErrIntOverflowRaft
+						}
+						if iNdEx >= l {
+							return io.ErrUnexpectedEOF
+						}
+						b := dAtA[iNdEx]
+						iNdEx++
+						v |= (uint64(b) & 0x7F) << shift
+						if b < 0x80 {
+							break
+						}
+					}
+					m.NodesJoint = append(m.NodesJoint, v)
+				}
+			} else {
+				return fmt.Errorf("proto: wrong wireType = %d for field NodesJoint", wireType)
+			}
+		case 4:
+			if wireType == 0 {
+				var v uint64
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowRaft
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					v |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				m.LearnersNext = append(m.LearnersNext, v)
+			} else if wireType == 2 {
+				var packedLen int
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowRaft
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					packedLen |= (int(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				if packedLen < 0 {
+					return ErrInvalidLengthRaft
+				}
+				postIndex := iNdEx + packedLen
+				if postIndex > l {
+					return io.ErrUnexpectedEOF
+				}
+				for iNdEx < postIndex {
+					var v uint64
+					for shift := uint(0); ; shift += 7 {
+						if shift >= 64 {
+							return ErrIntOverflowRaft
+						}
+						if iNdEx >= l {
+							return io.ErrUnexpectedEOF
+						}
+						b := dAtA[iNdEx]
+						iNdEx++
+						v |= (uint64(b) & 0x7F) << shift
+						if b < 0x80 {
+							break
+						}
+					}
+					m.LearnersNext = append(m.LearnersNext, v)
+				}
+			} else {
+				return fmt.Errorf("proto: wrong wireType = %d for field LearnersNext", wireType)
+			}
+		case 5:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field AutoLeave", wireType)
+			}
+			var v int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaft
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				v |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			m.AutoLeave = bool(v != 0)
 		default:
 			iNdEx = preIndex
 			skippy, err := skipRaft(dAtA[iNdEx:])
@@ -1841,6 +2234,227 @@ func (m *ConfChange) Unmarshal(dAtA []byte) error {
 	}
 	return nil
 }
+func (m *ConfChangeSingle) Unmarshal(dAtA []byte) error {
+	l := len(dAtA)
+	iNdEx := 0
+	for iNdEx < l {
+		preIndex := iNdEx
+		var wire uint64
+		for shift := uint(0); ; shift += 7 {
+			if shift >= 64 {
+				return ErrIntOverflowRaft
+			}
+			if iNdEx >= l {
+				return io.ErrUnexpectedEOF
+			}
+			b := dAtA[iNdEx]
+			iNdEx++
+			wire |= (uint64(b) & 0x7F) << shift
+			if b < 0x80 {
+				break
+			}
+		}
+		fieldNum := int32(wire >> 3)
+		wireType := int(wire & 0x7)
+		if wireType == 4 {
+			return fmt.Errorf("proto: ConfChangeSingle: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: ConfChangeSingle: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		case 1:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Type", wireType)
+			}
+			m.Type = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaft
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				m.Type |= (ConfChangeType(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 2:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field NodeID", wireType)
+			}
+			m.NodeID = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaft
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				m.NodeID |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		default:
+			iNdEx = preIndex
+			skippy, err := skipRaft(dAtA[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthRaft
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.XXX_unrecognized = append(m.XXX_unrecognized, dAtA[iNdEx:iNdEx+skippy]...)
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
+func (m *ConfChangeV2) Unmarshal(dAtA []byte) error {
+	l := len(dAtA)
+	iNdEx := 0
+	for iNdEx < l {
+		preIndex := iNdEx
+		var wire uint64
+		for shift := uint(0); ; shift += 7 {
+			if shift >= 64 {
+				return ErrIntOverflowRaft
+			}
+			if iNdEx >= l {
+				return io.ErrUnexpectedEOF
+			}
+			b := dAtA[iNdEx]
+			iNdEx++
+			wire |= (uint64(b) & 0x7F) << shift
+			if b < 0x80 {
+				break
+			}
+		}
+		fieldNum := int32(wire >> 3)
+		wireType := int(wire & 0x7)
+		if wireType == 4 {
+			return fmt.Errorf("proto: ConfChangeV2: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: ConfChangeV2: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		case 1:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Transition", wireType)
+			}
+			m.Transition = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaft
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				m.Transition |= (ConfChangeTransition(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 2:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Changes", wireType)
+			}
+			var msglen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaft
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				msglen |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if msglen < 0 {
+				return ErrInvalidLengthRaft
+			}
+			postIndex := iNdEx + msglen
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.Changes = append(m.Changes, ConfChangeSingle{})
+			if err := m.Changes[len(m.Changes)-1].Unmarshal(dAtA[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
+		case 3:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Context", wireType)
+			}
+			var byteLen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaft
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				byteLen |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if byteLen < 0 {
+				return ErrInvalidLengthRaft
+			}
+			postIndex := iNdEx + byteLen
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.Context = append(m.Context[:0], dAtA[iNdEx:postIndex]...)
+			if m.Context == nil {
+				m.Context = []byte{}
+			}
+			iNdEx = postIndex
+		default:
+			iNdEx = preIndex
+			skippy, err := skipRaft(dAtA[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthRaft
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.XXX_unrecognized = append(m.XXX_unrecognized, dAtA[iNdEx:iNdEx+skippy]...)
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
 func skipRaft(dAtA []byte) (n int, err error) {
 	l := len(dAtA)
 	iNdEx := 0
@@ -1949,56 +2563,68 @@ var (
 func init() { proto.RegisterFile("raft.proto", fileDescriptorRaft) }
 
 var fileDescriptorRaft = []byte{
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+	0x9f, 0xfc, 0xfc, 0xc3, 0x5c, 0xc8, 0x79, 0x88, 0x1b, 0xba, 0xec, 0x61, 0xe2, 0x9b, 0x0b, 0x9a,
+	0x72, 0x79, 0xca, 0x99, 0xc7, 0x25, 0xde, 0xb0, 0xa7, 0x2f, 0x82, 0x90, 0x8b, 0xb9, 0x3a, 0x13,
+	0xbf, 0xe0, 0xa6, 0x35, 0x33, 0xe2, 0xcc, 0x33, 0x3f, 0x2e, 0xbc, 0x69, 0xcd, 0x2c, 0x10, 0x63,
+	0x06, 0xdb, 0x7a, 0x5f, 0x4a, 0x6e, 0x4a, 0xdc, 0xb2, 0x59, 0xed, 0xde, 0x68, 0xc8, 0xde, 0xef,
+	0x08, 0x5a, 0x4f, 0x8d, 0x07, 0xd9, 0x01, 0xfa, 0x14, 0x7e, 0x30, 0x57, 0x02, 0x17, 0xc8, 0xe7,
+	0xf0, 0xc9, 0x53, 0xac, 0x79, 0xf5, 0x83, 0x30, 0x9e, 0x05, 0x93, 0x40, 0x5f, 0xc5, 0x87, 0x64,
+	0x2f, 0x6e, 0xad, 0xcc, 0xd9, 0xbb, 0x83, 0xe6, 0xea, 0xa3, 0xd0, 0xcd, 0x58, 0x22, 0x07, 0x9e,
+	0xa7, 0xc7, 0x1f, 0x17, 0x08, 0xcd, 0x9b, 0x1d, 0xf1, 0x50, 0xdc, 0x70, 0xc3, 0xa0, 0x55, 0xe6,
+	0x55, 0xec, 0x31, 0x95, 0x32, 0xce, 0x6a, 0x21, 0x07, 0x9e, 0x77, 0x9a, 0x7e, 0x7b, 0x0c, 0x5b,
+	0x3c, 0xa4, 0xf7, 0xef, 0xdb, 0x85, 0xb7, 0xef, 0xdb, 0x85, 0xfb, 0x87, 0x36, 0x7a, 0xfb, 0xd0,
+	0x46, 0xff, 0x3c, 0xb4, 0xd1, 0x1f, 0xff, 0xb6, 0x0b, 0xff, 0x05, 0x00, 0x00, 0xff, 0xff, 0x39,
+	0x56, 0x89, 0xed, 0xa5, 0x08, 0x00, 0x00,
 }

raft/raftpb/raft.proto

@@ -10,8 +10,9 @@ option (gogoproto.goproto_getters_all) = false;
 option (gogoproto.goproto_enum_prefix_all) = false;
 
 enum EntryType {
-	EntryNormal     = 0;
-	EntryConfChange = 1;
+	EntryNormal       = 0;
+	EntryConfChange   = 1; // corresponds to pb.ConfChange
+	EntryConfChangeV2 = 2; // corresponds to pb.ConfChangeV2
 }
 
 message Entry {
@@ -75,9 +76,41 @@ message HardState {
 	optional uint64 commit = 3 [(gogoproto.nullable) = false];
 }
 
+// ConfChangeTransition specifies the behavior of a configuration change with
+// respect to joint consensus.
+enum ConfChangeTransition {
+	// Automatically use the simple protocol if possible, otherwise fall back
+	// to ConfChangeJointImplicit. Most applications will want to use this.
+	ConfChangeTransitionAuto          = 0;
+	// Use joint consensus unconditionally, and transition out of them
+	// automatically (by proposing a zero configuration change).
+	//
+	// This option is suitable for applications that want to minimize the time
+	// spent in the joint configuration and do not store the joint configuration
+	// in the state machine (outside of InitialState).
+	ConfChangeTransitionJointImplicit = 1;
+	// Use joint consensus and remain in the joint configuration until the
+	// application proposes a no-op configuration change. This is suitable for
+	// applications that want to explicitly control the transitions, for example
+	// to use a custom payload (via the Context field).
+	ConfChangeTransitionJointExplicit = 2;
+}
+
 message ConfState {
-	repeated uint64 nodes    = 1;
-	repeated uint64 learners = 2;
+	// The voters in the incoming config. (If the configuration is not joint,
+	// then the outgoing config is empty).
+	repeated uint64 nodes          = 1;
+	// The voters in the outgoing config.
+	repeated uint64 nodes_joint    = 3;
+	// The learners in the incoming config.
+	repeated uint64 learners       = 2;
+	// The nodes that will become learners when the outgoing config is removed.
+	// These nodes are necessarily currently in nodes_joint (or they would have
+	// been added to the incoming config right away).
+	repeated uint64 learners_next  = 4;
+	// If set, the config is joint and Raft will automatically transition into
+	// the final config (i.e. remove the outgoing config) when this is safe.
+	optional bool   auto_leave     = 5 [(gogoproto.nullable) = false];
 }
 
 enum ConfChangeType {
@@ -88,8 +121,57 @@ enum ConfChangeType {
 }
 
 message ConfChange {
-	optional uint64          ID      = 1 [(gogoproto.nullable) = false];
-	optional ConfChangeType  Type    = 2 [(gogoproto.nullable) = false];
-	optional uint64          NodeID  = 3 [(gogoproto.nullable) = false];
-	optional bytes           Context = 4;
+	optional ConfChangeType  type    = 2 [(gogoproto.nullable) = false];
+	optional uint64          node_id = 3 [(gogoproto.nullable) = false, (gogoproto.customname) = "NodeID" ];
+	optional bytes           context = 4;
+
+	// NB: this is used only by etcd to thread through a unique identifier.
+	// Ideally it should really use the Context instead. No counterpart to
+	// this field exists in ConfChangeV2.
+	optional uint64          id      = 1 [(gogoproto.nullable) = false, (gogoproto.customname) = "ID" ];
+}
+
+// ConfChangeSingle is an individual configuration change operation. Multiple
+// such operations can be carried out atomically via a ConfChangeV2.
+message ConfChangeSingle {
+	optional ConfChangeType  type    = 1 [(gogoproto.nullable) = false];
+	optional uint64          node_id = 2 [(gogoproto.nullable) = false, (gogoproto.customname) = "NodeID"];
+}
+
+// ConfChangeV2 messages initiate configuration changes. They support both the
+// simple "one at a time" membership change protocol and full Joint Consensus
+// allowing for arbitrary changes in membership.
+//
+// The supplied context is treated as an opaque payload and can be used to
+// attach an action on the state machine to the application of the config change
+// proposal. Note that contrary to Joint Consensus as outlined in the Raft
+// paper[1], configuration changes become active when they are *applied* to the
+// state machine (not when they are appended to the log).
+//
+// The simple protocol can be used whenever only a single change is made.
+//
+// Non-simple changes require the use of Joint Consensus, for which two
+// configuration changes are run. The first configuration change specifies the
+// desired changes and transitions the Raft group into the joint configuration,
+// in which quorum requires a majority of both the pre-changes and post-changes
+// configuration. Joint Consensus avoids entering fragile intermediate
+// configurations that could compromise survivability. For example, without the
+// use of Joint Consensus and running across three availability zones with a
+// replication factor of three, it is not possible to replace a voter without
+// entering an intermediate configuration that does not survive the outage of
+// one availability zone.
+//
+// The provided ConfChangeTransition specifies how (and whether) Joint Consensus
+// is used, and assigns the task of leaving the joint configuration either to
+// Raft or the application. Leaving the joint configuration is accomplished by
+// proposing a ConfChangeV2 with only and optionally the Context field
+// populated.
+//
+// For details on Raft membership changes, see:
+//
+// [1]: https://github.com/ongardie/dissertation/blob/master/online-trim.pdf
+message ConfChangeV2 {
+	optional ConfChangeTransition transition = 1 [(gogoproto.nullable) = false];
+	repeated ConfChangeSingle     changes =    2 [(gogoproto.nullable) = false];
+	optional bytes                context =    3;
 }