Move deps from _workspace/ to vendor/

godep restore
pushd $GOPATH/src/github.com/appc/spec
git co master
popd
go get go4.org/errorutil
rm -rf Godeps
godep save ./...
git add vendor
git add -f $(git ls-files --other vendor/)
git co -- Godeps/LICENSES Godeps/.license_file_state Godeps/OWNERS

vendor/github.com/coreos/etcd/lease/leasehttp/http.go

@@ -0,0 +1,112 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// 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 leasehttp
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"time"
+
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	"github.com/coreos/etcd/lease"
+)
+
+// NewHandler returns an http Handler for lease renewals
+func NewHandler(l lease.Lessor) http.Handler {
+	return &leaseHandler{l}
+}
+
+type leaseHandler struct{ l lease.Lessor }
+
+func (h *leaseHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "POST" {
+		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	b, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		http.Error(w, "error reading body", http.StatusBadRequest)
+		return
+	}
+
+	lreq := pb.LeaseKeepAliveRequest{}
+	if err := lreq.Unmarshal(b); err != nil {
+		http.Error(w, "error unmarshalling request", http.StatusBadRequest)
+		return
+	}
+
+	ttl, err := h.l.Renew(lease.LeaseID(lreq.ID))
+	if err != nil {
+		if err == lease.ErrLeaseNotFound {
+			http.Error(w, err.Error(), http.StatusNotFound)
+			return
+		}
+
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	// TODO: fill out ResponseHeader
+	resp := &pb.LeaseKeepAliveResponse{ID: lreq.ID, TTL: ttl}
+	v, err := resp.Marshal()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/protobuf")
+	w.Write(v)
+}
+
+// RenewHTTP renews a lease at a given primary server.
+// TODO: Batch request in future?
+func RenewHTTP(id lease.LeaseID, url string, rt http.RoundTripper, timeout time.Duration) (int64, error) {
+	// will post lreq protobuf to leader
+	lreq, err := (&pb.LeaseKeepAliveRequest{ID: int64(id)}).Marshal()
+	if err != nil {
+		return -1, err
+	}
+
+	cc := &http.Client{Transport: rt, Timeout: timeout}
+	resp, err := cc.Post(url, "application/protobuf", bytes.NewReader(lreq))
+	if err != nil {
+		// TODO detect if leader failed and retry?
+		return -1, err
+	}
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return -1, err
+	}
+
+	if resp.StatusCode == http.StatusNotFound {
+		return -1, lease.ErrLeaseNotFound
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return -1, fmt.Errorf("lease: unknown error(%s)", string(b))
+	}
+
+	lresp := &pb.LeaseKeepAliveResponse{}
+	if err := lresp.Unmarshal(b); err != nil {
+		return -1, fmt.Errorf(`lease: %v. data = "%s"`, err, string(b))
+	}
+	if lresp.ID != int64(id) {
+		return -1, fmt.Errorf("lease: renew id mismatch")
+	}
+	return lresp.TTL, nil
+}

vendor/github.com/coreos/etcd/lease/leasepb/lease.pb.go

@@ -0,0 +1,314 @@
+// Code generated by protoc-gen-gogo.
+// source: lease.proto
+// DO NOT EDIT!
+
+/*
+	Package leasepb is a generated protocol buffer package.
+
+	It is generated from these files:
+		lease.proto
+
+	It has these top-level messages:
+		Lease
+*/
+package leasepb
+
+import (
+	"fmt"
+
+	proto "github.com/gogo/protobuf/proto"
+
+	math "math"
+)
+
+import io "io"
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+type Lease struct {
+	ID  int64 `protobuf:"varint,1,opt,name=ID,proto3" json:"ID,omitempty"`
+	TTL int64 `protobuf:"varint,2,opt,name=TTL,proto3" json:"TTL,omitempty"`
+}
+
+func (m *Lease) Reset()         { *m = Lease{} }
+func (m *Lease) String() string { return proto.CompactTextString(m) }
+func (*Lease) ProtoMessage()    {}
+
+func init() {
+	proto.RegisterType((*Lease)(nil), "leasepb.Lease")
+}
+func (m *Lease) 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 *Lease) MarshalTo(data []byte) (int, error) {
+	var i int
+	_ = i
+	var l int
+	_ = l
+	if m.ID != 0 {
+		data[i] = 0x8
+		i++
+		i = encodeVarintLease(data, i, uint64(m.ID))
+	}
+	if m.TTL != 0 {
+		data[i] = 0x10
+		i++
+		i = encodeVarintLease(data, i, uint64(m.TTL))
+	}
+	return i, nil
+}
+
+func encodeFixed64Lease(data []byte, offset int, v uint64) int {
+	data[offset] = uint8(v)
+	data[offset+1] = uint8(v >> 8)
+	data[offset+2] = uint8(v >> 16)
+	data[offset+3] = uint8(v >> 24)
+	data[offset+4] = uint8(v >> 32)
+	data[offset+5] = uint8(v >> 40)
+	data[offset+6] = uint8(v >> 48)
+	data[offset+7] = uint8(v >> 56)
+	return offset + 8
+}
+func encodeFixed32Lease(data []byte, offset int, v uint32) int {
+	data[offset] = uint8(v)
+	data[offset+1] = uint8(v >> 8)
+	data[offset+2] = uint8(v >> 16)
+	data[offset+3] = uint8(v >> 24)
+	return offset + 4
+}
+func encodeVarintLease(data []byte, offset int, v uint64) int {
+	for v >= 1<<7 {
+		data[offset] = uint8(v&0x7f | 0x80)
+		v >>= 7
+		offset++
+	}
+	data[offset] = uint8(v)
+	return offset + 1
+}
+func (m *Lease) Size() (n int) {
+	var l int
+	_ = l
+	if m.ID != 0 {
+		n += 1 + sovLease(uint64(m.ID))
+	}
+	if m.TTL != 0 {
+		n += 1 + sovLease(uint64(m.TTL))
+	}
+	return n
+}
+
+func sovLease(x uint64) (n int) {
+	for {
+		n++
+		x >>= 7
+		if x == 0 {
+			break
+		}
+	}
+	return n
+}
+func sozLease(x uint64) (n int) {
+	return sovLease(uint64((x << 1) ^ uint64((int64(x) >> 63))))
+}
+func (m *Lease) 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 ErrIntOverflowLease
+			}
+			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: Lease: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: Lease: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		case 1:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field ID", wireType)
+			}
+			m.ID = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowLease
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.ID |= (int64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 2:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field TTL", wireType)
+			}
+			m.TTL = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowLease
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.TTL |= (int64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		default:
+			iNdEx = preIndex
+			skippy, err := skipLease(data[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthLease
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
+func skipLease(data []byte) (n int, err error) {
+	l := len(data)
+	iNdEx := 0
+	for iNdEx < l {
+		var wire uint64
+		for shift := uint(0); ; shift += 7 {
+			if shift >= 64 {
+				return 0, ErrIntOverflowLease
+			}
+			if iNdEx >= l {
+				return 0, io.ErrUnexpectedEOF
+			}
+			b := data[iNdEx]
+			iNdEx++
+			wire |= (uint64(b) & 0x7F) << shift
+			if b < 0x80 {
+				break
+			}
+		}
+		wireType := int(wire & 0x7)
+		switch wireType {
+		case 0:
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return 0, ErrIntOverflowLease
+				}
+				if iNdEx >= l {
+					return 0, io.ErrUnexpectedEOF
+				}
+				iNdEx++
+				if data[iNdEx-1] < 0x80 {
+					break
+				}
+			}
+			return iNdEx, nil
+		case 1:
+			iNdEx += 8
+			return iNdEx, nil
+		case 2:
+			var length int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return 0, ErrIntOverflowLease
+				}
+				if iNdEx >= l {
+					return 0, io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				length |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			iNdEx += length
+			if length < 0 {
+				return 0, ErrInvalidLengthLease
+			}
+			return iNdEx, nil
+		case 3:
+			for {
+				var innerWire uint64
+				var start int = iNdEx
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return 0, ErrIntOverflowLease
+					}
+					if iNdEx >= l {
+						return 0, io.ErrUnexpectedEOF
+					}
+					b := data[iNdEx]
+					iNdEx++
+					innerWire |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				innerWireType := int(innerWire & 0x7)
+				if innerWireType == 4 {
+					break
+				}
+				next, err := skipLease(data[start:])
+				if err != nil {
+					return 0, err
+				}
+				iNdEx = start + next
+			}
+			return iNdEx, nil
+		case 4:
+			return iNdEx, nil
+		case 5:
+			iNdEx += 4
+			return iNdEx, nil
+		default:
+			return 0, fmt.Errorf("proto: illegal wireType %d", wireType)
+		}
+	}
+	panic("unreachable")
+}
+
+var (
+	ErrInvalidLengthLease = fmt.Errorf("proto: negative length found during unmarshaling")
+	ErrIntOverflowLease   = fmt.Errorf("proto: integer overflow")
+)

vendor/github.com/coreos/etcd/lease/leasepb/lease.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+package leasepb;
+
+import "gogoproto/gogo.proto";
+
+option (gogoproto.marshaler_all) = true;
+option (gogoproto.sizer_all) = true;
+option (gogoproto.unmarshaler_all) = true;
+option (gogoproto.goproto_getters_all) = false;
+option (gogoproto.goproto_enum_prefix_all) = false;
+
+message Lease {
+  int64 ID = 1;
+  int64 TTL = 2;
+}

vendor/github.com/coreos/etcd/lease/lessor.go

@@ -0,0 +1,507 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// 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 lease
+
+import (
+	"encoding/binary"
+	"errors"
+	"math"
+	"sync"
+	"time"
+
+	"github.com/coreos/etcd/lease/leasepb"
+	"github.com/coreos/etcd/storage/backend"
+)
+
+const (
+	// NoLease is a special LeaseID representing the absence of a lease.
+	NoLease = LeaseID(0)
+)
+
+var (
+	minLeaseTTL = int64(5)
+
+	leaseBucketName = []byte("lease")
+	// do not use maxInt64 since it can overflow time which will add
+	// the offset of unix time (1970yr to seconds).
+	forever = time.Unix(math.MaxInt64>>1, 0)
+
+	ErrNotPrimary    = errors.New("not a primary lessor")
+	ErrLeaseNotFound = errors.New("lease not found")
+	ErrLeaseExists   = errors.New("lease already exists")
+)
+
+type LeaseID int64
+
+// RangeDeleter defines an interface with DeleteRange method.
+// We define this interface only for lessor to limit the number
+// of methods of storage.KV to what lessor actually needs.
+//
+// Having a minimum interface makes testing easy.
+type RangeDeleter interface {
+	DeleteRange(key, end []byte) (int64, int64)
+}
+
+// A Lessor is the owner of leases. It can grant, revoke, renew and modify leases for lessee.
+type Lessor interface {
+	// SetRangeDeleter sets the RangeDeleter to the Lessor.
+	// Lessor deletes the items in the revoked or expired lease from the
+	// the set RangeDeleter.
+	SetRangeDeleter(dr RangeDeleter)
+
+	// Grant grants a lease that expires at least after TTL seconds.
+	Grant(id LeaseID, ttl int64) (*Lease, error)
+	// Revoke revokes a lease with given ID. The item attached to the
+	// given lease will be removed. If the ID does not exist, an error
+	// will be returned.
+	Revoke(id LeaseID) error
+
+	// Attach attaches given leaseItem to the lease with given LeaseID.
+	// If the lease does not exist, an error will be returned.
+	Attach(id LeaseID, items []LeaseItem) error
+
+	// Detach detaches given leaseItem from the lease with given LeaseID.
+	// If the lease does not exist, an error will be returned.
+	Detach(id LeaseID, items []LeaseItem) error
+
+	// Promote promotes the lessor to be the primary lessor. Primary lessor manages
+	// the expiration and renew of leases.
+	// Newly promoted lessor renew the TTL of all lease to extend + previous TTL.
+	Promote(extend time.Duration)
+
+	// Demote demotes the lessor from being the primary lessor.
+	Demote()
+
+	// Renew renews a lease with given ID. It returns the renewed TTL. If the ID does not exist,
+	// an error will be returned.
+	Renew(id LeaseID) (int64, error)
+
+	// Lookup gives the lease at a given lease id, if any
+	Lookup(id LeaseID) *Lease
+
+	// ExpiredLeasesC returns a chan that is used to receive expired leases.
+	ExpiredLeasesC() <-chan []*Lease
+
+	// Recover recovers the lessor state from the given backend and RangeDeleter.
+	Recover(b backend.Backend, rd RangeDeleter)
+
+	// Stop stops the lessor for managing leases. The behavior of calling Stop multiple
+	// times is undefined.
+	Stop()
+}
+
+// lessor implements Lessor interface.
+// TODO: use clockwork for testability.
+type lessor struct {
+	mu sync.Mutex
+
+	// primary indicates if this lessor is the primary lessor. The primary
+	// lessor manages lease expiration and renew.
+	//
+	// in etcd, raft leader is the primary. Thus there might be two primary
+	// leaders at the same time (raft allows concurrent leader but with different term)
+	// for at most a leader election timeout.
+	// The old primary leader cannot affect the correctness since its proposal has a
+	// smaller term and will not be committed.
+	//
+	// TODO: raft follower do not forward lease management proposals. There might be a
+	// very small window (within second normally which depends on go scheduling) that
+	// a raft follow is the primary between the raft leader demotion and lessor demotion.
+	// Usually this should not be a problem. Lease should not be that sensitive to timing.
+	primary bool
+
+	// TODO: probably this should be a heap with a secondary
+	// id index.
+	// Now it is O(N) to loop over the leases to find expired ones.
+	// We want to make Grant, Revoke, and findExpiredLeases all O(logN) and
+	// Renew O(1).
+	// findExpiredLeases and Renew should be the most frequent operations.
+	leaseMap map[LeaseID]*Lease
+
+	// When a lease expires, the lessor will delete the
+	// leased range (or key) by the RangeDeleter.
+	rd RangeDeleter
+
+	// backend to persist leases. We only persist lease ID and expiry for now.
+	// The leased items can be recovered by iterating all the keys in kv.
+	b backend.Backend
+
+	expiredC chan []*Lease
+	// stopC is a channel whose closure indicates that the lessor should be stopped.
+	stopC chan struct{}
+	// doneC is a channel whose closure indicates that the lessor is stopped.
+	doneC chan struct{}
+}
+
+func NewLessor(b backend.Backend) Lessor {
+	return newLessor(b)
+}
+
+func newLessor(b backend.Backend) *lessor {
+	l := &lessor{
+		leaseMap: make(map[LeaseID]*Lease),
+		b:        b,
+		// expiredC is a small buffered chan to avoid unnecessary blocking.
+		expiredC: make(chan []*Lease, 16),
+		stopC:    make(chan struct{}),
+		doneC:    make(chan struct{}),
+	}
+	l.initAndRecover()
+
+	go l.runLoop()
+
+	return l
+}
+
+func (le *lessor) SetRangeDeleter(rd RangeDeleter) {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	le.rd = rd
+}
+
+// TODO: when lessor is under high load, it should give out lease
+// with longer TTL to reduce renew load.
+func (le *lessor) Grant(id LeaseID, ttl int64) (*Lease, error) {
+	if id == NoLease {
+		return nil, ErrLeaseNotFound
+	}
+
+	l := &Lease{ID: id, TTL: ttl, itemSet: make(map[LeaseItem]struct{})}
+
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	if _, ok := le.leaseMap[id]; ok {
+		return nil, ErrLeaseExists
+	}
+
+	if le.primary {
+		l.refresh(0)
+	} else {
+		l.forever()
+	}
+
+	le.leaseMap[id] = l
+	l.persistTo(le.b)
+
+	return l, nil
+}
+
+func (le *lessor) Revoke(id LeaseID) error {
+	le.mu.Lock()
+
+	l := le.leaseMap[id]
+	if l == nil {
+		le.mu.Unlock()
+		return ErrLeaseNotFound
+	}
+	// unlock before doing external work
+	le.mu.Unlock()
+
+	if le.rd != nil {
+		for item := range l.itemSet {
+			le.rd.DeleteRange([]byte(item.Key), nil)
+		}
+	}
+
+	le.mu.Lock()
+	defer le.mu.Unlock()
+	delete(le.leaseMap, l.ID)
+	l.removeFrom(le.b)
+
+	return nil
+}
+
+// Renew renews an existing lease. If the given lease does not exist or
+// has expired, an error will be returned.
+func (le *lessor) Renew(id LeaseID) (int64, error) {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	if !le.primary {
+		// forward renew request to primary instead of returning error.
+		return -1, ErrNotPrimary
+	}
+
+	l := le.leaseMap[id]
+	if l == nil {
+		return -1, ErrLeaseNotFound
+	}
+
+	l.refresh(0)
+	return l.TTL, nil
+}
+
+func (le *lessor) Lookup(id LeaseID) *Lease {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+	if l, ok := le.leaseMap[id]; ok {
+		return l
+	}
+	return nil
+}
+
+func (le *lessor) Promote(extend time.Duration) {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	le.primary = true
+
+	// refresh the expiries of all leases.
+	for _, l := range le.leaseMap {
+		l.refresh(extend)
+	}
+}
+
+func (le *lessor) Demote() {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	// set the expiries of all leases to forever
+	for _, l := range le.leaseMap {
+		l.forever()
+	}
+
+	le.primary = false
+}
+
+// Attach attaches items to the lease with given ID. When the lease
+// expires, the attached items will be automatically removed.
+// If the given lease does not exist, an error will be returned.
+func (le *lessor) Attach(id LeaseID, items []LeaseItem) error {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	l := le.leaseMap[id]
+	if l == nil {
+		return ErrLeaseNotFound
+	}
+
+	for _, it := range items {
+		l.itemSet[it] = struct{}{}
+	}
+	return nil
+}
+
+// Detach detaches items from the lease with given ID.
+// If the given lease does not exist, an error will be returned.
+func (le *lessor) Detach(id LeaseID, items []LeaseItem) error {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	l := le.leaseMap[id]
+	if l == nil {
+		return ErrLeaseNotFound
+	}
+
+	for _, it := range items {
+		delete(l.itemSet, it)
+	}
+	return nil
+}
+
+func (le *lessor) Recover(b backend.Backend, rd RangeDeleter) {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	le.b = b
+	le.rd = rd
+	le.leaseMap = make(map[LeaseID]*Lease)
+
+	le.initAndRecover()
+}
+
+func (le *lessor) ExpiredLeasesC() <-chan []*Lease {
+	return le.expiredC
+}
+
+func (le *lessor) Stop() {
+	close(le.stopC)
+	<-le.doneC
+}
+
+func (le *lessor) runLoop() {
+	defer close(le.doneC)
+
+	for {
+		var ls []*Lease
+
+		le.mu.Lock()
+		if le.primary {
+			ls = le.findExpiredLeases()
+		}
+		le.mu.Unlock()
+
+		if len(ls) != 0 {
+			select {
+			case <-le.stopC:
+				return
+			case le.expiredC <- ls:
+			default:
+				// the receiver of expiredC is probably busy handling
+				// other stuff
+				// let's try this next time after 500ms
+			}
+		}
+
+		select {
+		case <-time.After(500 * time.Millisecond):
+		case <-le.stopC:
+			return
+		}
+	}
+}
+
+// findExpiredLeases loops all the leases in the leaseMap and returns the expired
+// leases that needed to be revoked.
+func (le *lessor) findExpiredLeases() []*Lease {
+	leases := make([]*Lease, 0, 16)
+	now := time.Now()
+
+	for _, l := range le.leaseMap {
+		// TODO: probably should change to <= 100-500 millisecond to
+		// make up committing latency.
+		if l.expiry.Sub(now) <= 0 {
+			leases = append(leases, l)
+		}
+	}
+
+	return leases
+}
+
+// get gets the lease with given id.
+// get is a helper function for testing, at least for now.
+func (le *lessor) get(id LeaseID) *Lease {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	return le.leaseMap[id]
+}
+
+func (le *lessor) initAndRecover() {
+	tx := le.b.BatchTx()
+	tx.Lock()
+
+	tx.UnsafeCreateBucket(leaseBucketName)
+	_, vs := tx.UnsafeRange(leaseBucketName, int64ToBytes(0), int64ToBytes(math.MaxInt64), 0)
+	// TODO: copy vs and do decoding outside tx lock if lock contention becomes an issue.
+	for i := range vs {
+		var lpb leasepb.Lease
+		err := lpb.Unmarshal(vs[i])
+		if err != nil {
+			tx.Unlock()
+			panic("failed to unmarshal lease proto item")
+		}
+		ID := LeaseID(lpb.ID)
+		le.leaseMap[ID] = &Lease{
+			ID:  ID,
+			TTL: lpb.TTL,
+			// itemSet will be filled in when recover key-value pairs
+			// set expiry to forever, refresh when promoted
+			itemSet: make(map[LeaseItem]struct{}),
+			expiry:  forever,
+		}
+	}
+	tx.Unlock()
+
+	le.b.ForceCommit()
+}
+
+type Lease struct {
+	ID  LeaseID
+	TTL int64 // time to live in seconds
+
+	itemSet map[LeaseItem]struct{}
+	// expiry time in unixnano
+	expiry time.Time
+}
+
+func (l Lease) persistTo(b backend.Backend) {
+	key := int64ToBytes(int64(l.ID))
+
+	lpb := leasepb.Lease{ID: int64(l.ID), TTL: int64(l.TTL)}
+	val, err := lpb.Marshal()
+	if err != nil {
+		panic("failed to marshal lease proto item")
+	}
+
+	b.BatchTx().Lock()
+	b.BatchTx().UnsafePut(leaseBucketName, key, val)
+	b.BatchTx().Unlock()
+}
+
+func (l Lease) removeFrom(b backend.Backend) {
+	key := int64ToBytes(int64(l.ID))
+
+	b.BatchTx().Lock()
+	b.BatchTx().UnsafeDelete(leaseBucketName, key)
+	b.BatchTx().Unlock()
+}
+
+// refresh refreshes the expiry of the lease. It extends the expiry at least
+// minLeaseTTL second.
+func (l *Lease) refresh(extend time.Duration) {
+	if l.TTL < minLeaseTTL {
+		l.TTL = minLeaseTTL
+	}
+	l.expiry = time.Now().Add(extend + time.Second*time.Duration(l.TTL))
+}
+
+// forever sets the expiry of lease to be forever.
+func (l *Lease) forever() {
+	if l.TTL < minLeaseTTL {
+		l.TTL = minLeaseTTL
+	}
+	l.expiry = forever
+}
+
+type LeaseItem struct {
+	Key string
+}
+
+func int64ToBytes(n int64) []byte {
+	bytes := make([]byte, 8)
+	binary.BigEndian.PutUint64(bytes, uint64(n))
+	return bytes
+}
+
+// FakeLessor is a fake implementation of Lessor interface.
+// Used for testing only.
+type FakeLessor struct{}
+
+func (fl *FakeLessor) SetRangeDeleter(dr RangeDeleter) {}
+
+func (fl *FakeLessor) Grant(id LeaseID, ttl int64) (*Lease, error) { return nil, nil }
+
+func (fl *FakeLessor) Revoke(id LeaseID) error { return nil }
+
+func (fl *FakeLessor) Attach(id LeaseID, items []LeaseItem) error { return nil }
+
+func (fl *FakeLessor) Detach(id LeaseID, items []LeaseItem) error { return nil }
+
+func (fl *FakeLessor) Promote(extend time.Duration) {}
+
+func (fl *FakeLessor) Demote() {}
+
+func (fl *FakeLessor) Renew(id LeaseID) (int64, error) { return 10, nil }
+
+func (le *FakeLessor) Lookup(id LeaseID) *Lease { return nil }
+
+func (fl *FakeLessor) ExpiredLeasesC() <-chan []*Lease { return nil }
+
+func (fl *FakeLessor) Recover(b backend.Backend, rd RangeDeleter) {}
+
+func (fl *FakeLessor) Stop() {}