Merge pull request #4868 from heyitsanthony/api-quota

etcdserver: storage quotas

alarm/alarms.go

@@ -0,0 +1,144 @@
+// 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 alarm manages health status alarms in etcd.
+package alarm
+
+import (
+	"sync"
+
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	"github.com/coreos/etcd/pkg/types"
+	"github.com/coreos/etcd/storage/backend"
+	"github.com/coreos/pkg/capnslog"
+)
+
+var (
+	alarmBucketName = []byte("alarm")
+	plog            = capnslog.NewPackageLogger("github.com/coreos/etcd", "alarm")
+)
+
+type BackendGetter interface {
+	Backend() backend.Backend
+}
+
+type alarmSet map[types.ID]*pb.AlarmMember
+
+// AlarmStore persists alarms to the backend.
+type AlarmStore struct {
+	mu    sync.Mutex
+	types map[pb.AlarmType]alarmSet
+
+	bg BackendGetter
+}
+
+func NewAlarmStore(bg BackendGetter) (*AlarmStore, error) {
+	ret := &AlarmStore{types: make(map[pb.AlarmType]alarmSet), bg: bg}
+	err := ret.restore()
+	return ret, err
+}
+
+func (a *AlarmStore) Activate(id types.ID, at pb.AlarmType) *pb.AlarmMember {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	newAlarm := &pb.AlarmMember{MemberID: uint64(id), Alarm: at}
+	if m := a.addToMap(newAlarm); m != newAlarm {
+		return m
+	}
+
+	v, err := newAlarm.Marshal()
+	if err != nil {
+		plog.Panicf("failed to marshal alarm member")
+	}
+
+	b := a.bg.Backend()
+	b.BatchTx().Lock()
+	b.BatchTx().UnsafePut(alarmBucketName, v, nil)
+	b.BatchTx().Unlock()
+
+	return newAlarm
+}
+
+func (a *AlarmStore) Deactivate(id types.ID, at pb.AlarmType) *pb.AlarmMember {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	t := a.types[at]
+	if t == nil {
+		t = make(alarmSet)
+		a.types[at] = t
+	}
+	m := t[id]
+	if m == nil {
+		return nil
+	}
+
+	delete(t, id)
+
+	v, err := m.Marshal()
+	if err != nil {
+		plog.Panicf("failed to marshal alarm member")
+	}
+
+	b := a.bg.Backend()
+	b.BatchTx().Lock()
+	b.BatchTx().UnsafeDelete(alarmBucketName, v)
+	b.BatchTx().Unlock()
+
+	return m
+}
+
+func (a *AlarmStore) Get(at pb.AlarmType) (ret []*pb.AlarmMember) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	for _, m := range a.types[at] {
+		ret = append(ret, m)
+	}
+	return ret
+}
+
+func (a *AlarmStore) restore() error {
+	b := a.bg.Backend()
+	tx := b.BatchTx()
+
+	tx.Lock()
+	tx.UnsafeCreateBucket(alarmBucketName)
+	err := tx.UnsafeForEach(alarmBucketName, func(k, v []byte) error {
+		var m pb.AlarmMember
+		if err := m.Unmarshal(k); err != nil {
+			return err
+		}
+		a.addToMap(&m)
+		return nil
+	})
+	tx.Unlock()
+
+	b.ForceCommit()
+	return err
+}
+
+func (a *AlarmStore) addToMap(newAlarm *pb.AlarmMember) *pb.AlarmMember {
+	t := a.types[newAlarm.Alarm]
+	if t == nil {
+		t = make(alarmSet)
+		a.types[newAlarm.Alarm] = t
+	}
+	m := t[types.ID(newAlarm.MemberID)]
+	if m != nil {
+		return m
+	}
+	t[types.ID(newAlarm.MemberID)] = newAlarm
+	return newAlarm
+}

etcdserver/api/v3rpc/grpc.go

@@ -30,9 +30,9 @@ func Server(s *etcdserver.EtcdServer, tls *tls.Config) *grpc.Server {
 	}
 
 	grpcServer := grpc.NewServer(opts...)
-	pb.RegisterKVServer(grpcServer, NewKVServer(s))
+	pb.RegisterKVServer(grpcServer, NewQuotaKVServer(s))
 	pb.RegisterWatchServer(grpcServer, NewWatchServer(s))
-	pb.RegisterLeaseServer(grpcServer, NewLeaseServer(s))
+	pb.RegisterLeaseServer(grpcServer, NewQuotaLeaseServer(s))
 	pb.RegisterClusterServer(grpcServer, NewClusterServer(s))
 	pb.RegisterAuthServer(grpcServer, NewAuthServer(s))
 	pb.RegisterMaintenanceServer(grpcServer, NewMaintenanceServer(s))

etcdserver/api/v3rpc/key.go

@@ -297,6 +297,8 @@ func togRPCError(err error) error {
 	// TODO: handle error from raft and timeout
 	case etcdserver.ErrRequestTooLarge:
 		return rpctypes.ErrRequestTooLarge
+	case etcdserver.ErrNoSpace:
+		return rpctypes.ErrNoSpace
 	default:
 		return grpc.Errorf(codes.Internal, err.Error())
 	}

etcdserver/api/v3rpc/maintenance.go

@@ -25,12 +25,17 @@ type BackendGetter interface {
 	Backend() backend.Backend
 }
 
+type Alarmer interface {
+	Alarm(ctx context.Context, ar *pb.AlarmRequest) (*pb.AlarmResponse, error)
+}
+
 type maintenanceServer struct {
 	bg BackendGetter
+	a  Alarmer
 }
 
 func NewMaintenanceServer(s *etcdserver.EtcdServer) pb.MaintenanceServer {
-	return &maintenanceServer{bg: s}
+	return &maintenanceServer{bg: s, a: s}
 }
 
 func (ms *maintenanceServer) Defragment(ctx context.Context, sr *pb.DefragmentRequest) (*pb.DefragmentResponse, error) {
@@ -43,3 +48,8 @@ func (ms *maintenanceServer) Defragment(ctx context.Context, sr *pb.DefragmentRe
 	plog.Noticef("finished defragmenting the storage backend")
 	return &pb.DefragmentResponse{}, nil
 }
+
+func (ms *maintenanceServer) Alarm(ctx context.Context, ar *pb.AlarmRequest) (*pb.AlarmResponse, error) {
+	plog.Warningf("alarming %+v", ar)
+	return ms.a.Alarm(ctx, ar)
+}

etcdserver/api/v3rpc/quota.go

@@ -0,0 +1,89 @@
+// 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 v3rpc
+
+import (
+	"github.com/coreos/etcd/etcdserver"
+	"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	"github.com/coreos/etcd/pkg/types"
+	"golang.org/x/net/context"
+)
+
+type quotaKVServer struct {
+	pb.KVServer
+	qa quotaAlarmer
+}
+
+type quotaAlarmer struct {
+	q  etcdserver.Quota
+	a  Alarmer
+	id types.ID
+}
+
+// check whether request satisfies the quota. If there is not enough space,
+// ignore request and raise the free space alarm.
+func (qa *quotaAlarmer) check(ctx context.Context, r interface{}) error {
+	if qa.q.Available(r) {
+		return nil
+	}
+	req := &pb.AlarmRequest{
+		MemberID: int64(qa.id),
+		Action:   pb.AlarmRequest_ACTIVATE,
+		Alarm:    pb.AlarmType_NOSPACE,
+	}
+	qa.a.Alarm(ctx, req)
+	return rpctypes.ErrNoSpace
+}
+
+func NewQuotaKVServer(s *etcdserver.EtcdServer) pb.KVServer {
+	return &quotaKVServer{
+		NewKVServer(s),
+		quotaAlarmer{etcdserver.NewBackendQuota(s), s, s.ID()},
+	}
+}
+
+func (s *quotaKVServer) Put(ctx context.Context, r *pb.PutRequest) (*pb.PutResponse, error) {
+	if err := s.qa.check(ctx, r); err != nil {
+		return nil, err
+	}
+	return s.KVServer.Put(ctx, r)
+}
+
+func (s *quotaKVServer) Txn(ctx context.Context, r *pb.TxnRequest) (*pb.TxnResponse, error) {
+	if err := s.qa.check(ctx, r); err != nil {
+		return nil, err
+	}
+	return s.KVServer.Txn(ctx, r)
+}
+
+type quotaLeaseServer struct {
+	pb.LeaseServer
+	qa quotaAlarmer
+}
+
+func (s *quotaLeaseServer) LeaseCreate(ctx context.Context, cr *pb.LeaseCreateRequest) (*pb.LeaseCreateResponse, error) {
+	if err := s.qa.check(ctx, cr); err != nil {
+		return nil, err
+	}
+	return s.LeaseServer.LeaseCreate(ctx, cr)
+}
+
+func NewQuotaLeaseServer(s *etcdserver.EtcdServer) pb.LeaseServer {
+	return &quotaLeaseServer{
+		NewLeaseServer(s),
+		quotaAlarmer{etcdserver.NewBackendQuota(s), s, s.ID()},
+	}
+}

etcdserver/api/v3rpc/rpctypes/error.go

@@ -25,6 +25,7 @@ var (
 	ErrDuplicateKey = grpc.Errorf(codes.InvalidArgument, "etcdserver: duplicate key given in txn request")
 	ErrCompacted    = grpc.Errorf(codes.OutOfRange, "etcdserver: storage: required revision has been compacted")
 	ErrFutureRev    = grpc.Errorf(codes.OutOfRange, "etcdserver: storage: required revision is a future revision")
+	ErrNoSpace      = grpc.Errorf(codes.ResourceExhausted, "etcdserver: storage: database space exceeded")
 
 	ErrLeaseNotFound = grpc.Errorf(codes.NotFound, "etcdserver: requested lease not found")
 	ErrLeaseExist    = grpc.Errorf(codes.FailedPrecondition, "etcdserver: lease already exists")

etcdserver/apply.go

@@ -0,0 +1,587 @@
+// 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 etcdserver
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	"github.com/coreos/etcd/lease"
+	"github.com/coreos/etcd/pkg/types"
+	dstorage "github.com/coreos/etcd/storage"
+	"github.com/coreos/etcd/storage/storagepb"
+	"github.com/gogo/protobuf/proto"
+)
+
+const (
+	// noTxn is an invalid txn ID.
+	// To apply with independent Range, Put, Delete, you can pass noTxn
+	// to apply functions instead of a valid txn ID.
+	noTxn = -1
+)
+
+type applyResult struct {
+	resp proto.Message
+	err  error
+}
+
+// applierV3 is the interface for processing V3 raft messages
+type applierV3 interface {
+	Put(txnID int64, p *pb.PutRequest) (*pb.PutResponse, error)
+	Range(txnID int64, r *pb.RangeRequest) (*pb.RangeResponse, error)
+	DeleteRange(txnID int64, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error)
+	Txn(rt *pb.TxnRequest) (*pb.TxnResponse, error)
+	Compaction(compaction *pb.CompactionRequest) (*pb.CompactionResponse, error)
+	LeaseCreate(lc *pb.LeaseCreateRequest) (*pb.LeaseCreateResponse, error)
+	LeaseRevoke(lc *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error)
+	Alarm(*pb.AlarmRequest) (*pb.AlarmResponse, error)
+	AuthEnable() (*pb.AuthEnableResponse, error)
+	UserAdd(ua *pb.UserAddRequest) (*pb.UserAddResponse, error)
+}
+
+type applierV3backend struct {
+	s *EtcdServer
+}
+
+func (s *EtcdServer) applyV3Request(r *pb.InternalRaftRequest) *applyResult {
+	ar := &applyResult{}
+	switch {
+	case r.Range != nil:
+		ar.resp, ar.err = s.applyV3.Range(noTxn, r.Range)
+	case r.Put != nil:
+		ar.resp, ar.err = s.applyV3.Put(noTxn, r.Put)
+	case r.DeleteRange != nil:
+		ar.resp, ar.err = s.applyV3.DeleteRange(noTxn, r.DeleteRange)
+	case r.Txn != nil:
+		ar.resp, ar.err = s.applyV3.Txn(r.Txn)
+	case r.Compaction != nil:
+		ar.resp, ar.err = s.applyV3.Compaction(r.Compaction)
+	case r.LeaseCreate != nil:
+		ar.resp, ar.err = s.applyV3.LeaseCreate(r.LeaseCreate)
+	case r.LeaseRevoke != nil:
+		ar.resp, ar.err = s.applyV3.LeaseRevoke(r.LeaseRevoke)
+	case r.Alarm != nil:
+		ar.resp, ar.err = s.applyV3.Alarm(r.Alarm)
+	case r.AuthEnable != nil:
+		ar.resp, ar.err = s.applyV3.AuthEnable()
+	case r.UserAdd != nil:
+		ar.resp, ar.err = s.applyV3.UserAdd(r.UserAdd)
+	default:
+		panic("not implemented")
+	}
+	return ar
+}
+
+func (a *applierV3backend) Put(txnID int64, p *pb.PutRequest) (*pb.PutResponse, error) {
+	resp := &pb.PutResponse{}
+	resp.Header = &pb.ResponseHeader{}
+	var (
+		rev int64
+		err error
+	)
+	if txnID != noTxn {
+		rev, err = a.s.getKV().TxnPut(txnID, p.Key, p.Value, lease.LeaseID(p.Lease))
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		leaseID := lease.LeaseID(p.Lease)
+		if leaseID != lease.NoLease {
+			if l := a.s.lessor.Lookup(leaseID); l == nil {
+				return nil, lease.ErrLeaseNotFound
+			}
+		}
+		rev = a.s.getKV().Put(p.Key, p.Value, leaseID)
+	}
+	resp.Header.Revision = rev
+	return resp, nil
+}
+
+func (a *applierV3backend) DeleteRange(txnID int64, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
+	resp := &pb.DeleteRangeResponse{}
+	resp.Header = &pb.ResponseHeader{}
+
+	var (
+		n   int64
+		rev int64
+		err error
+	)
+
+	if isGteRange(dr.RangeEnd) {
+		dr.RangeEnd = []byte{}
+	}
+
+	if txnID != noTxn {
+		n, rev, err = a.s.getKV().TxnDeleteRange(txnID, dr.Key, dr.RangeEnd)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		n, rev = a.s.getKV().DeleteRange(dr.Key, dr.RangeEnd)
+	}
+
+	resp.Deleted = n
+	resp.Header.Revision = rev
+	return resp, nil
+}
+
+func (a *applierV3backend) Range(txnID int64, r *pb.RangeRequest) (*pb.RangeResponse, error) {
+	resp := &pb.RangeResponse{}
+	resp.Header = &pb.ResponseHeader{}
+
+	var (
+		kvs []storagepb.KeyValue
+		rev int64
+		err error
+	)
+
+	if isGteRange(r.RangeEnd) {
+		r.RangeEnd = []byte{}
+	}
+
+	limit := r.Limit
+	if r.SortOrder != pb.RangeRequest_NONE {
+		// fetch everything; sort and truncate afterwards
+		limit = 0
+	}
+	if limit > 0 {
+		// fetch one extra for 'more' flag
+		limit = limit + 1
+	}
+
+	if txnID != noTxn {
+		kvs, rev, err = a.s.getKV().TxnRange(txnID, r.Key, r.RangeEnd, limit, r.Revision)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		kvs, rev, err = a.s.getKV().Range(r.Key, r.RangeEnd, limit, r.Revision)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if r.SortOrder != pb.RangeRequest_NONE {
+		var sorter sort.Interface
+		switch {
+		case r.SortTarget == pb.RangeRequest_KEY:
+			sorter = &kvSortByKey{&kvSort{kvs}}
+		case r.SortTarget == pb.RangeRequest_VERSION:
+			sorter = &kvSortByVersion{&kvSort{kvs}}
+		case r.SortTarget == pb.RangeRequest_CREATE:
+			sorter = &kvSortByCreate{&kvSort{kvs}}
+		case r.SortTarget == pb.RangeRequest_MOD:
+			sorter = &kvSortByMod{&kvSort{kvs}}
+		case r.SortTarget == pb.RangeRequest_VALUE:
+			sorter = &kvSortByValue{&kvSort{kvs}}
+		}
+		switch {
+		case r.SortOrder == pb.RangeRequest_ASCEND:
+			sort.Sort(sorter)
+		case r.SortOrder == pb.RangeRequest_DESCEND:
+			sort.Sort(sort.Reverse(sorter))
+		}
+	}
+
+	if r.Limit > 0 && len(kvs) > int(r.Limit) {
+		kvs = kvs[:r.Limit]
+		resp.More = true
+	}
+
+	resp.Header.Revision = rev
+	for i := range kvs {
+		resp.Kvs = append(resp.Kvs, &kvs[i])
+	}
+	return resp, nil
+}
+
+func (a *applierV3backend) Txn(rt *pb.TxnRequest) (*pb.TxnResponse, error) {
+	var revision int64
+
+	ok := true
+	for _, c := range rt.Compare {
+		if revision, ok = a.applyCompare(c); !ok {
+			break
+		}
+	}
+
+	var reqs []*pb.RequestUnion
+	if ok {
+		reqs = rt.Success
+	} else {
+		reqs = rt.Failure
+	}
+
+	if err := a.checkRequestLeases(reqs); err != nil {
+		return nil, err
+	}
+	if err := a.checkRequestRange(reqs); err != nil {
+		return nil, err
+	}
+
+	// When executing the operations of txn, we need to hold the txn lock.
+	// So the reader will not see any intermediate results.
+	txnID := a.s.getKV().TxnBegin()
+	defer func() {
+		err := a.s.getKV().TxnEnd(txnID)
+		if err != nil {
+			panic(fmt.Sprint("unexpected error when closing txn", txnID))
+		}
+	}()
+
+	resps := make([]*pb.ResponseUnion, len(reqs))
+	for i := range reqs {
+		resps[i] = a.applyUnion(txnID, reqs[i])
+	}
+
+	if len(resps) != 0 {
+		revision += 1
+	}
+
+	txnResp := &pb.TxnResponse{}
+	txnResp.Header = &pb.ResponseHeader{}
+	txnResp.Header.Revision = revision
+	txnResp.Responses = resps
+	txnResp.Succeeded = ok
+	return txnResp, nil
+}
+
+// applyCompare applies the compare request.
+// It returns the revision at which the comparison happens. If the comparison
+// succeeds, the it returns true. Otherwise it returns false.
+func (a *applierV3backend) applyCompare(c *pb.Compare) (int64, bool) {
+	ckvs, rev, err := a.s.getKV().Range(c.Key, nil, 1, 0)
+	if err != nil {
+		if err == dstorage.ErrTxnIDMismatch {
+			panic("unexpected txn ID mismatch error")
+		}
+		return rev, false
+	}
+	var ckv storagepb.KeyValue
+	if len(ckvs) != 0 {
+		ckv = ckvs[0]
+	} else {
+		// Use the zero value of ckv normally. However...
+		if c.Target == pb.Compare_VALUE {
+			// Always fail if we're comparing a value on a key that doesn't exist.
+			// We can treat non-existence as the empty set explicitly, such that
+			// even a key with a value of length 0 bytes is still a real key
+			// that was written that way
+			return rev, false
+		}
+	}
+
+	// -1 is less, 0 is equal, 1 is greater
+	var result int
+	switch c.Target {
+	case pb.Compare_VALUE:
+		tv, _ := c.TargetUnion.(*pb.Compare_Value)
+		if tv != nil {
+			result = bytes.Compare(ckv.Value, tv.Value)
+		}
+	case pb.Compare_CREATE:
+		tv, _ := c.TargetUnion.(*pb.Compare_CreateRevision)
+		if tv != nil {
+			result = compareInt64(ckv.CreateRevision, tv.CreateRevision)
+		}
+
+	case pb.Compare_MOD:
+		tv, _ := c.TargetUnion.(*pb.Compare_ModRevision)
+		if tv != nil {
+			result = compareInt64(ckv.ModRevision, tv.ModRevision)
+		}
+	case pb.Compare_VERSION:
+		tv, _ := c.TargetUnion.(*pb.Compare_Version)
+		if tv != nil {
+			result = compareInt64(ckv.Version, tv.Version)
+		}
+	}
+
+	switch c.Result {
+	case pb.Compare_EQUAL:
+		if result != 0 {
+			return rev, false
+		}
+	case pb.Compare_GREATER:
+		if result != 1 {
+			return rev, false
+		}
+	case pb.Compare_LESS:
+		if result != -1 {
+			return rev, false
+		}
+	}
+	return rev, true
+}
+
+func (a *applierV3backend) applyUnion(txnID int64, union *pb.RequestUnion) *pb.ResponseUnion {
+	switch tv := union.Request.(type) {
+	case *pb.RequestUnion_RequestRange:
+		if tv.RequestRange != nil {
+			resp, err := a.Range(txnID, tv.RequestRange)
+			if err != nil {
+				panic("unexpected error during txn")
+			}
+			return &pb.ResponseUnion{Response: &pb.ResponseUnion_ResponseRange{ResponseRange: resp}}
+		}
+	case *pb.RequestUnion_RequestPut:
+		if tv.RequestPut != nil {
+			resp, err := a.Put(txnID, tv.RequestPut)
+			if err != nil {
+				panic("unexpected error during txn")
+			}
+			return &pb.ResponseUnion{Response: &pb.ResponseUnion_ResponsePut{ResponsePut: resp}}
+		}
+	case *pb.RequestUnion_RequestDeleteRange:
+		if tv.RequestDeleteRange != nil {
+			resp, err := a.DeleteRange(txnID, tv.RequestDeleteRange)
+			if err != nil {
+				panic("unexpected error during txn")
+			}
+			return &pb.ResponseUnion{Response: &pb.ResponseUnion_ResponseDeleteRange{ResponseDeleteRange: resp}}
+		}
+	default:
+		// empty union
+		return nil
+	}
+	return nil
+
+}
+
+func (a *applierV3backend) Compaction(compaction *pb.CompactionRequest) (*pb.CompactionResponse, error) {
+	resp := &pb.CompactionResponse{}
+	resp.Header = &pb.ResponseHeader{}
+	err := a.s.getKV().Compact(compaction.Revision)
+	if err != nil {
+		return nil, err
+	}
+	// get the current revision. which key to get is not important.
+	_, resp.Header.Revision, _ = a.s.getKV().Range([]byte("compaction"), nil, 1, 0)
+	return resp, err
+}
+
+func (a *applierV3backend) LeaseCreate(lc *pb.LeaseCreateRequest) (*pb.LeaseCreateResponse, error) {
+	l, err := a.s.lessor.Grant(lease.LeaseID(lc.ID), lc.TTL)
+	resp := &pb.LeaseCreateResponse{}
+	if err == nil {
+		resp.ID = int64(l.ID)
+		resp.TTL = l.TTL
+	}
+	return resp, err
+}
+
+func (a *applierV3backend) LeaseRevoke(lc *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error) {
+	err := a.s.lessor.Revoke(lease.LeaseID(lc.ID))
+	return &pb.LeaseRevokeResponse{}, err
+}
+
+func (a *applierV3backend) Alarm(ar *pb.AlarmRequest) (*pb.AlarmResponse, error) {
+	resp := &pb.AlarmResponse{}
+	switch ar.Action {
+	case pb.AlarmRequest_GET:
+		resp.Alarms = a.s.alarmStore.Get(ar.Alarm)
+	case pb.AlarmRequest_ACTIVATE:
+		m := a.s.alarmStore.Activate(types.ID(ar.MemberID), ar.Alarm)
+		if m == nil {
+			break
+		}
+		resp.Alarms = append(resp.Alarms, m)
+		switch m.Alarm {
+		case pb.AlarmType_NOSPACE:
+			if len(a.s.alarmStore.Get(m.Alarm)) == 1 {
+				a.s.applyV3 = newApplierV3Capped(a)
+			}
+		default:
+			plog.Warningf("unimplemented alarm activation (%+v)", m)
+		}
+	case pb.AlarmRequest_DEACTIVATE:
+		m := a.s.alarmStore.Deactivate(types.ID(ar.MemberID), ar.Alarm)
+		if m == nil {
+			break
+		}
+		resp.Alarms = append(resp.Alarms, m)
+		if m.Alarm == pb.AlarmType_NOSPACE && len(a.s.alarmStore.Get(ar.Alarm)) == 0 {
+			a.s.applyV3 = newQuotaApplierV3(a.s, &applierV3backend{a.s})
+		}
+	default:
+		return nil, nil
+	}
+	return resp, nil
+}
+
+type applierV3Capped struct {
+	applierV3
+	q backendQuota
+}
+
+// newApplierV3Capped creates an applyV3 that will reject Puts and transactions
+// with Puts so that the number of keys in the store is capped.
+func newApplierV3Capped(base applierV3) applierV3 { return &applierV3Capped{applierV3: base} }
+
+func (a *applierV3Capped) Put(txnID int64, p *pb.PutRequest) (*pb.PutResponse, error) {
+	return nil, ErrNoSpace
+}
+
+func (a *applierV3Capped) Txn(r *pb.TxnRequest) (*pb.TxnResponse, error) {
+	if a.q.Cost(r) > 0 {
+		return nil, ErrNoSpace
+	}
+	return a.applierV3.Txn(r)
+}
+
+func (a *applierV3Capped) LeaseCreate(lc *pb.LeaseCreateRequest) (*pb.LeaseCreateResponse, error) {
+	return nil, ErrNoSpace
+}
+
+func (a *applierV3backend) AuthEnable() (*pb.AuthEnableResponse, error) {
+	a.s.AuthStore().AuthEnable()
+	return &pb.AuthEnableResponse{}, nil
+}
+
+func (a *applierV3backend) UserAdd(r *pb.UserAddRequest) (*pb.UserAddResponse, error) {
+	return a.s.AuthStore().UserAdd(r)
+}
+
+type quotaApplierV3 struct {
+	applierV3
+	q Quota
+}
+
+func newQuotaApplierV3(s *EtcdServer, app applierV3) applierV3 {
+	return &quotaApplierV3{app, NewBackendQuota(s)}
+}
+
+func (a *quotaApplierV3) Put(txnID int64, p *pb.PutRequest) (*pb.PutResponse, error) {
+	ok := a.q.Available(p)
+	resp, err := a.applierV3.Put(txnID, p)
+	if err == nil && !ok {
+		err = ErrNoSpace
+	}
+	return resp, err
+}
+
+func (a *quotaApplierV3) Txn(rt *pb.TxnRequest) (*pb.TxnResponse, error) {
+	ok := a.q.Available(rt)
+	resp, err := a.applierV3.Txn(rt)
+	if err == nil && !ok {
+		err = ErrNoSpace
+	}
+	return resp, err
+}
+
+func (a *quotaApplierV3) LeaseCreate(lc *pb.LeaseCreateRequest) (*pb.LeaseCreateResponse, error) {
+	ok := a.q.Available(lc)
+	resp, err := a.applierV3.LeaseCreate(lc)
+	if err == nil && !ok {
+		err = ErrNoSpace
+	}
+	return resp, err
+}
+
+type kvSort struct{ kvs []storagepb.KeyValue }
+
+func (s *kvSort) Swap(i, j int) {
+	t := s.kvs[i]
+	s.kvs[i] = s.kvs[j]
+	s.kvs[j] = t
+}
+func (s *kvSort) Len() int { return len(s.kvs) }
+
+type kvSortByKey struct{ *kvSort }
+
+func (s *kvSortByKey) Less(i, j int) bool {
+	return bytes.Compare(s.kvs[i].Key, s.kvs[j].Key) < 0
+}
+
+type kvSortByVersion struct{ *kvSort }
+
+func (s *kvSortByVersion) Less(i, j int) bool {
+	return (s.kvs[i].Version - s.kvs[j].Version) < 0
+}
+
+type kvSortByCreate struct{ *kvSort }
+
+func (s *kvSortByCreate) Less(i, j int) bool {
+	return (s.kvs[i].CreateRevision - s.kvs[j].CreateRevision) < 0
+}
+
+type kvSortByMod struct{ *kvSort }
+
+func (s *kvSortByMod) Less(i, j int) bool {
+	return (s.kvs[i].ModRevision - s.kvs[j].ModRevision) < 0
+}
+
+type kvSortByValue struct{ *kvSort }
+
+func (s *kvSortByValue) Less(i, j int) bool {
+	return bytes.Compare(s.kvs[i].Value, s.kvs[j].Value) < 0
+}
+
+func (a *applierV3backend) checkRequestLeases(reqs []*pb.RequestUnion) error {
+	for _, requ := range reqs {
+		tv, ok := requ.Request.(*pb.RequestUnion_RequestPut)
+		if !ok {
+			continue
+		}
+		preq := tv.RequestPut
+		if preq == nil || lease.LeaseID(preq.Lease) == lease.NoLease {
+			continue
+		}
+		if l := a.s.lessor.Lookup(lease.LeaseID(preq.Lease)); l == nil {
+			return lease.ErrLeaseNotFound
+		}
+	}
+	return nil
+}
+
+func (a *applierV3backend) checkRequestRange(reqs []*pb.RequestUnion) error {
+	for _, requ := range reqs {
+		tv, ok := requ.Request.(*pb.RequestUnion_RequestRange)
+		if !ok {
+			continue
+		}
+		greq := tv.RequestRange
+		if greq == nil || greq.Revision == 0 {
+			continue
+		}
+
+		if greq.Revision > a.s.getKV().Rev() {
+			return dstorage.ErrFutureRev
+		}
+		if greq.Revision < a.s.getKV().FirstRev() {
+			return dstorage.ErrCompacted
+		}
+	}
+	return nil
+}
+
+func compareInt64(a, b int64) int {
+	switch {
+	case a < b:
+		return -1
+	case a > b:
+		return 1
+	default:
+		return 0
+	}
+}
+
+// isGteRange determines if the range end is a >= range. This works around grpc
+// sending empty byte strings as nil; >= is encoded in the range end as '\0'.
+func isGteRange(rangeEnd []byte) bool {
+	return len(rangeEnd) == 1 && rangeEnd[0] == 0
+}

etcdserver/errors.go

@@ -35,6 +35,7 @@ var (
 	ErrNotEnoughStartedMembers    = errors.New("etcdserver: re-configuration failed due to not enough started members")
 	ErrNoLeader                   = errors.New("etcdserver: no leader")
 	ErrRequestTooLarge            = errors.New("etcdserver: request is too large")
+	ErrNoSpace                    = errors.New("etcdserver: no space")
 )
 
 func isKeyNotFound(err error) bool {

etcdserver/etcdserverpb/etcdserver.pb.go

@@ -52,6 +52,9 @@
 		MemberListResponse
 		DefragmentRequest
 		DefragmentResponse
+		AlarmRequest
+		AlarmMember
+		AlarmResponse
 		AuthEnableRequest
 		AuthDisableRequest
 		AuthenticateRequest

etcdserver/etcdserverpb/raft_internal.pb.go

@@ -33,6 +33,7 @@ type InternalRaftRequest struct {
 	LeaseRevoke *LeaseRevokeRequest `protobuf:"bytes,9,opt,name=lease_revoke" json:"lease_revoke,omitempty"`
 	AuthEnable  *AuthEnableRequest  `protobuf:"bytes,10,opt,name=auth_enable" json:"auth_enable,omitempty"`
 	UserAdd     *UserAddRequest     `protobuf:"bytes,11,opt,name=user_add" json:"user_add,omitempty"`
+	Alarm       *AlarmRequest       `protobuf:"bytes,12,opt,name=alarm" json:"alarm,omitempty"`
 }
 
 func (m *InternalRaftRequest) Reset()         { *m = InternalRaftRequest{} }
@@ -170,6 +171,16 @@ func (m *InternalRaftRequest) MarshalTo(data []byte) (int, error) {
 		}
 		i += n10
 	}
+	if m.Alarm != nil {
+		data[i] = 0x62
+		i++
+		i = encodeVarintRaftInternal(data, i, uint64(m.Alarm.Size()))
+		n11, err := m.Alarm.MarshalTo(data[i:])
+		if err != nil {
+			return 0, err
+		}
+		i += n11
+	}
 	return i, nil
 }
 
@@ -264,6 +275,10 @@ func (m *InternalRaftRequest) Size() (n int) {
 		l = m.UserAdd.Size()
 		n += 1 + l + sovRaftInternal(uint64(l))
 	}
+	if m.Alarm != nil {
+		l = m.Alarm.Size()
+		n += 1 + l + sovRaftInternal(uint64(l))
+	}
 	return n
 }
 
@@ -664,6 +679,39 @@ func (m *InternalRaftRequest) Unmarshal(data []byte) error {
 				return err
 			}
 			iNdEx = postIndex
+		case 12:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Alarm", wireType)
+			}
+			var msglen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaftInternal
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				msglen |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if msglen < 0 {
+				return ErrInvalidLengthRaftInternal
+			}
+			postIndex := iNdEx + msglen
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			if m.Alarm == nil {
+				m.Alarm = &AlarmRequest{}
+			}
+			if err := m.Alarm.Unmarshal(data[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
 			skippy, err := skipRaftInternal(data[iNdEx:])

etcdserver/etcdserverpb/raft_internal.proto

@@ -27,6 +27,8 @@ message InternalRaftRequest {
 
   AuthEnableRequest auth_enable = 10;
   UserAddRequest user_add = 11;
+
+  AlarmRequest alarm = 12;
 }
 
 message EmptyResponse {

etcdserver/etcdserverpb/rpc.pb.go

@@ -26,6 +26,26 @@ var _ = proto.Marshal
 var _ = fmt.Errorf
 var _ = math.Inf
 
+type AlarmType int32
+
+const (
+	AlarmType_NONE    AlarmType = 0
+	AlarmType_NOSPACE AlarmType = 1
+)
+
+var AlarmType_name = map[int32]string{
+	0: "NONE",
+	1: "NOSPACE",
+}
+var AlarmType_value = map[string]int32{
+	"NONE":    0,
+	"NOSPACE": 1,
+}
+
+func (x AlarmType) String() string {
+	return proto.EnumName(AlarmType_name, int32(x))
+}
+
 type RangeRequest_SortOrder int32
 
 const (
@@ -127,6 +147,29 @@ func (x Compare_CompareTarget) String() string {
 	return proto.EnumName(Compare_CompareTarget_name, int32(x))
 }
 
+type AlarmRequest_AlarmAction int32
+
+const (
+	AlarmRequest_GET        AlarmRequest_AlarmAction = 0
+	AlarmRequest_ACTIVATE   AlarmRequest_AlarmAction = 1
+	AlarmRequest_DEACTIVATE AlarmRequest_AlarmAction = 2
+)
+
+var AlarmRequest_AlarmAction_name = map[int32]string{
+	0: "GET",
+	1: "ACTIVATE",
+	2: "DEACTIVATE",
+}
+var AlarmRequest_AlarmAction_value = map[string]int32{
+	"GET":        0,
+	"ACTIVATE":   1,
+	"DEACTIVATE": 2,
+}
+
+func (x AlarmRequest_AlarmAction) String() string {
+	return proto.EnumName(AlarmRequest_AlarmAction_name, int32(x))
+}
+
 type ResponseHeader struct {
 	ClusterId uint64 `protobuf:"varint,1,opt,name=cluster_id,proto3" json:"cluster_id,omitempty"`
 	MemberId  uint64 `protobuf:"varint,2,opt,name=member_id,proto3" json:"member_id,omitempty"`
@@ -1159,6 +1202,49 @@ func (m *DefragmentResponse) GetHeader() *ResponseHeader {
 	return nil
 }
 
+type AlarmRequest struct {
+	Action AlarmRequest_AlarmAction `protobuf:"varint,1,opt,name=action,proto3,enum=etcdserverpb.AlarmRequest_AlarmAction" json:"action,omitempty"`
+	// MemberID is the member raising the alarm request
+	MemberID int64     `protobuf:"varint,2,opt,name=memberID,proto3" json:"memberID,omitempty"`
+	Alarm    AlarmType `protobuf:"varint,3,opt,name=alarm,proto3,enum=etcdserverpb.AlarmType" json:"alarm,omitempty"`
+}
+
+func (m *AlarmRequest) Reset()         { *m = AlarmRequest{} }
+func (m *AlarmRequest) String() string { return proto.CompactTextString(m) }
+func (*AlarmRequest) ProtoMessage()    {}
+
+type AlarmMember struct {
+	MemberID uint64    `protobuf:"varint,1,opt,name=memberID,proto3" json:"memberID,omitempty"`
+	Alarm    AlarmType `protobuf:"varint,2,opt,name=alarm,proto3,enum=etcdserverpb.AlarmType" json:"alarm,omitempty"`
+}
+
+func (m *AlarmMember) Reset()         { *m = AlarmMember{} }
+func (m *AlarmMember) String() string { return proto.CompactTextString(m) }
+func (*AlarmMember) ProtoMessage()    {}
+
+type AlarmResponse struct {
+	Header *ResponseHeader `protobuf:"bytes,1,opt,name=header" json:"header,omitempty"`
+	Alarms []*AlarmMember  `protobuf:"bytes,2,rep,name=alarms" json:"alarms,omitempty"`
+}
+
+func (m *AlarmResponse) Reset()         { *m = AlarmResponse{} }
+func (m *AlarmResponse) String() string { return proto.CompactTextString(m) }
+func (*AlarmResponse) ProtoMessage()    {}
+
+func (m *AlarmResponse) GetHeader() *ResponseHeader {
+	if m != nil {
+		return m.Header
+	}
+	return nil
+}
+
+func (m *AlarmResponse) GetAlarms() []*AlarmMember {
+	if m != nil {
+		return m.Alarms
+	}
+	return nil
+}
+
 type AuthEnableRequest struct {
 }
 
@@ -1507,6 +1593,9 @@ func init() {
 	proto.RegisterType((*MemberListResponse)(nil), "etcdserverpb.MemberListResponse")
 	proto.RegisterType((*DefragmentRequest)(nil), "etcdserverpb.DefragmentRequest")
 	proto.RegisterType((*DefragmentResponse)(nil), "etcdserverpb.DefragmentResponse")
+	proto.RegisterType((*AlarmRequest)(nil), "etcdserverpb.AlarmRequest")
+	proto.RegisterType((*AlarmMember)(nil), "etcdserverpb.AlarmMember")
+	proto.RegisterType((*AlarmResponse)(nil), "etcdserverpb.AlarmResponse")
 	proto.RegisterType((*AuthEnableRequest)(nil), "etcdserverpb.AuthEnableRequest")
 	proto.RegisterType((*AuthDisableRequest)(nil), "etcdserverpb.AuthDisableRequest")
 	proto.RegisterType((*AuthenticateRequest)(nil), "etcdserverpb.AuthenticateRequest")
@@ -1535,10 +1624,12 @@ func init() {
 	proto.RegisterType((*RoleDeleteResponse)(nil), "etcdserverpb.RoleDeleteResponse")
 	proto.RegisterType((*RoleGrantResponse)(nil), "etcdserverpb.RoleGrantResponse")
 	proto.RegisterType((*RoleRevokeResponse)(nil), "etcdserverpb.RoleRevokeResponse")
+	proto.RegisterEnum("etcdserverpb.AlarmType", AlarmType_name, AlarmType_value)
 	proto.RegisterEnum("etcdserverpb.RangeRequest_SortOrder", RangeRequest_SortOrder_name, RangeRequest_SortOrder_value)
 	proto.RegisterEnum("etcdserverpb.RangeRequest_SortTarget", RangeRequest_SortTarget_name, RangeRequest_SortTarget_value)
 	proto.RegisterEnum("etcdserverpb.Compare_CompareResult", Compare_CompareResult_name, Compare_CompareResult_value)
 	proto.RegisterEnum("etcdserverpb.Compare_CompareTarget", Compare_CompareTarget_name, Compare_CompareTarget_value)
+	proto.RegisterEnum("etcdserverpb.AlarmRequest_AlarmAction", AlarmRequest_AlarmAction_name, AlarmRequest_AlarmAction_value)
 }
 
 // Reference imports to suppress errors if they are not otherwise used.
@@ -2185,6 +2276,8 @@ var _Cluster_serviceDesc = grpc.ServiceDesc{
 type MaintenanceClient interface {
 	// TODO: move Hash from kv to Maintenance
 	Defragment(ctx context.Context, in *DefragmentRequest, opts ...grpc.CallOption) (*DefragmentResponse, error)
+	// Alarm activates, deactivates, and queries alarms regarding cluster health.
+	Alarm(ctx context.Context, in *AlarmRequest, opts ...grpc.CallOption) (*AlarmResponse, error)
 }
 
 type maintenanceClient struct {
@@ -2204,11 +2297,22 @@ func (c *maintenanceClient) Defragment(ctx context.Context, in *DefragmentReques
 	return out, nil
 }
 
+func (c *maintenanceClient) Alarm(ctx context.Context, in *AlarmRequest, opts ...grpc.CallOption) (*AlarmResponse, error) {
+	out := new(AlarmResponse)
+	err := grpc.Invoke(ctx, "/etcdserverpb.Maintenance/Alarm", in, out, c.cc, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // Server API for Maintenance service
 
 type MaintenanceServer interface {
 	// TODO: move Hash from kv to Maintenance
 	Defragment(context.Context, *DefragmentRequest) (*DefragmentResponse, error)
+	// Alarm activates, deactivates, and queries alarms regarding cluster health.
+	Alarm(context.Context, *AlarmRequest) (*AlarmResponse, error)
 }
 
 func RegisterMaintenanceServer(s *grpc.Server, srv MaintenanceServer) {
@@ -2227,6 +2331,18 @@ func _Maintenance_Defragment_Handler(srv interface{}, ctx context.Context, dec f
 	return out, nil
 }
 
+func _Maintenance_Alarm_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error) (interface{}, error) {
+	in := new(AlarmRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	out, err := srv.(MaintenanceServer).Alarm(ctx, in)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 var _Maintenance_serviceDesc = grpc.ServiceDesc{
 	ServiceName: "etcdserverpb.Maintenance",
 	HandlerType: (*MaintenanceServer)(nil),
@@ -2235,6 +2351,10 @@ var _Maintenance_serviceDesc = grpc.ServiceDesc{
 			MethodName: "Defragment",
 			Handler:    _Maintenance_Defragment_Handler,
 		},
+		{
+			MethodName: "Alarm",
+			Handler:    _Maintenance_Alarm_Handler,
+		},
 	},
 	Streams: []grpc.StreamDesc{},
 }
@@ -4115,6 +4235,107 @@ func (m *DefragmentResponse) MarshalTo(data []byte) (int, error) {
 	return i, nil
 }
 
+func (m *AlarmRequest) 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 *AlarmRequest) MarshalTo(data []byte) (int, error) {
+	var i int
+	_ = i
+	var l int
+	_ = l
+	if m.Action != 0 {
+		data[i] = 0x8
+		i++
+		i = encodeVarintRpc(data, i, uint64(m.Action))
+	}
+	if m.MemberID != 0 {
+		data[i] = 0x10
+		i++
+		i = encodeVarintRpc(data, i, uint64(m.MemberID))
+	}
+	if m.Alarm != 0 {
+		data[i] = 0x18
+		i++
+		i = encodeVarintRpc(data, i, uint64(m.Alarm))
+	}
+	return i, nil
+}
+
+func (m *AlarmMember) 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 *AlarmMember) MarshalTo(data []byte) (int, error) {
+	var i int
+	_ = i
+	var l int
+	_ = l
+	if m.MemberID != 0 {
+		data[i] = 0x8
+		i++
+		i = encodeVarintRpc(data, i, uint64(m.MemberID))
+	}
+	if m.Alarm != 0 {
+		data[i] = 0x10
+		i++
+		i = encodeVarintRpc(data, i, uint64(m.Alarm))
+	}
+	return i, nil
+}
+
+func (m *AlarmResponse) 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 *AlarmResponse) MarshalTo(data []byte) (int, error) {
+	var i int
+	_ = i
+	var l int
+	_ = l
+	if m.Header != nil {
+		data[i] = 0xa
+		i++
+		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
+		n29, err := m.Header.MarshalTo(data[i:])
+		if err != nil {
+			return 0, err
+		}
+		i += n29
+	}
+	if len(m.Alarms) > 0 {
+		for _, msg := range m.Alarms {
+			data[i] = 0x12
+			i++
+			i = encodeVarintRpc(data, i, uint64(msg.Size()))
+			n, err := msg.MarshalTo(data[i:])
+			if err != nil {
+				return 0, err
+			}
+			i += n
+		}
+	}
+	return i, nil
+}
+
 func (m *AuthEnableRequest) Marshal() (data []byte, err error) {
 	size := m.Size()
 	data = make([]byte, size)
@@ -4398,11 +4619,11 @@ func (m *AuthEnableResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n29, err := m.Header.MarshalTo(data[i:])
+		n30, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n29
+		i += n30
 	}
 	return i, nil
 }
@@ -4426,11 +4647,11 @@ func (m *AuthDisableResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n30, err := m.Header.MarshalTo(data[i:])
+		n31, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n30
+		i += n31
 	}
 	return i, nil
 }
@@ -4454,11 +4675,11 @@ func (m *AuthenticateResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n31, err := m.Header.MarshalTo(data[i:])
+		n32, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n31
+		i += n32
 	}
 	return i, nil
 }
@@ -4482,11 +4703,11 @@ func (m *UserAddResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n32, err := m.Header.MarshalTo(data[i:])
+		n33, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n32
+		i += n33
 	}
 	return i, nil
 }
@@ -4510,11 +4731,11 @@ func (m *UserGetResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n33, err := m.Header.MarshalTo(data[i:])
+		n34, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n33
+		i += n34
 	}
 	return i, nil
 }
@@ -4538,11 +4759,11 @@ func (m *UserDeleteResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n34, err := m.Header.MarshalTo(data[i:])
+		n35, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n34
+		i += n35
 	}
 	return i, nil
 }
@@ -4566,11 +4787,11 @@ func (m *UserChangePasswordResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n35, err := m.Header.MarshalTo(data[i:])
+		n36, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n35
+		i += n36
 	}
 	return i, nil
 }
@@ -4594,11 +4815,11 @@ func (m *UserGrantResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n36, err := m.Header.MarshalTo(data[i:])
+		n37, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n36
+		i += n37
 	}
 	return i, nil
 }
@@ -4622,11 +4843,11 @@ func (m *UserRevokeResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n37, err := m.Header.MarshalTo(data[i:])
+		n38, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n37
+		i += n38
 	}
 	return i, nil
 }
@@ -4650,11 +4871,11 @@ func (m *RoleAddResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n38, err := m.Header.MarshalTo(data[i:])
+		n39, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n38
+		i += n39
 	}
 	return i, nil
 }
@@ -4678,11 +4899,11 @@ func (m *RoleGetResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n39, err := m.Header.MarshalTo(data[i:])
+		n40, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n39
+		i += n40
 	}
 	return i, nil
 }
@@ -4706,11 +4927,11 @@ func (m *RoleDeleteResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n40, err := m.Header.MarshalTo(data[i:])
+		n41, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n40
+		i += n41
 	}
 	return i, nil
 }
@@ -4734,11 +4955,11 @@ func (m *RoleGrantResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n41, err := m.Header.MarshalTo(data[i:])
+		n42, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n41
+		i += n42
 	}
 	return i, nil
 }
@@ -4762,11 +4983,11 @@ func (m *RoleRevokeResponse) MarshalTo(data []byte) (int, error) {
 		data[i] = 0xa
 		i++
 		i = encodeVarintRpc(data, i, uint64(m.Header.Size()))
-		n42, err := m.Header.MarshalTo(data[i:])
+		n43, err := m.Header.MarshalTo(data[i:])
 		if err != nil {
 			return 0, err
 		}
-		i += n42
+		i += n43
 	}
 	return i, nil
 }
@@ -5431,6 +5652,49 @@ func (m *DefragmentResponse) Size() (n int) {
 	return n
 }
 
+func (m *AlarmRequest) Size() (n int) {
+	var l int
+	_ = l
+	if m.Action != 0 {
+		n += 1 + sovRpc(uint64(m.Action))
+	}
+	if m.MemberID != 0 {
+		n += 1 + sovRpc(uint64(m.MemberID))
+	}
+	if m.Alarm != 0 {
+		n += 1 + sovRpc(uint64(m.Alarm))
+	}
+	return n
+}
+
+func (m *AlarmMember) Size() (n int) {
+	var l int
+	_ = l
+	if m.MemberID != 0 {
+		n += 1 + sovRpc(uint64(m.MemberID))
+	}
+	if m.Alarm != 0 {
+		n += 1 + sovRpc(uint64(m.Alarm))
+	}
+	return n
+}
+
+func (m *AlarmResponse) Size() (n int) {
+	var l int
+	_ = l
+	if m.Header != nil {
+		l = m.Header.Size()
+		n += 1 + l + sovRpc(uint64(l))
+	}
+	if len(m.Alarms) > 0 {
+		for _, e := range m.Alarms {
+			l = e.Size()
+			n += 1 + l + sovRpc(uint64(l))
+		}
+	}
+	return n
+}
+
 func (m *AuthEnableRequest) Size() (n int) {
 	var l int
 	_ = l
@@ -9761,6 +10025,315 @@ func (m *DefragmentResponse) Unmarshal(data []byte) error {
 	}
 	return nil
 }
+func (m *AlarmRequest) 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 ErrIntOverflowRpc
+			}
+			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: AlarmRequest: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: AlarmRequest: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		case 1:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Action", wireType)
+			}
+			m.Action = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.Action |= (AlarmRequest_AlarmAction(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 2:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field MemberID", wireType)
+			}
+			m.MemberID = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.MemberID |= (int64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 3:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Alarm", wireType)
+			}
+			m.Alarm = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.Alarm |= (AlarmType(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		default:
+			iNdEx = preIndex
+			skippy, err := skipRpc(data[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthRpc
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
+func (m *AlarmMember) 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 ErrIntOverflowRpc
+			}
+			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: AlarmMember: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: AlarmMember: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		case 1:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field MemberID", wireType)
+			}
+			m.MemberID = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.MemberID |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		case 2:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Alarm", wireType)
+			}
+			m.Alarm = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.Alarm |= (AlarmType(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+		default:
+			iNdEx = preIndex
+			skippy, err := skipRpc(data[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthRpc
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
+func (m *AlarmResponse) 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 ErrIntOverflowRpc
+			}
+			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: AlarmResponse: wiretype end group for non-group")
+		}
+		if fieldNum <= 0 {
+			return fmt.Errorf("proto: AlarmResponse: illegal tag %d (wire type %d)", fieldNum, wire)
+		}
+		switch fieldNum {
+		case 1:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Header", wireType)
+			}
+			var msglen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				msglen |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if msglen < 0 {
+				return ErrInvalidLengthRpc
+			}
+			postIndex := iNdEx + msglen
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			if m.Header == nil {
+				m.Header = &ResponseHeader{}
+			}
+			if err := m.Header.Unmarshal(data[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
+		case 2:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Alarms", wireType)
+			}
+			var msglen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRpc
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				msglen |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if msglen < 0 {
+				return ErrInvalidLengthRpc
+			}
+			postIndex := iNdEx + msglen
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.Alarms = append(m.Alarms, &AlarmMember{})
+			if err := m.Alarms[len(m.Alarms)-1].Unmarshal(data[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
+		default:
+			iNdEx = preIndex
+			skippy, err := skipRpc(data[iNdEx:])
+			if err != nil {
+				return err
+			}
+			if skippy < 0 {
+				return ErrInvalidLengthRpc
+			}
+			if (iNdEx + skippy) > l {
+				return io.ErrUnexpectedEOF
+			}
+			iNdEx += skippy
+		}
+	}
+
+	if iNdEx > l {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}
 func (m *AuthEnableRequest) Unmarshal(data []byte) error {
 	l := len(data)
 	iNdEx := 0

etcdserver/etcdserverpb/rpc.proto

@@ -79,6 +79,9 @@ service Cluster {
 service Maintenance {
   // TODO: move Hash from kv to Maintenance
   rpc Defragment(DefragmentRequest) returns (DefragmentResponse) {}
+
+  // Alarm activates, deactivates, and queries alarms regarding cluster health.
+  rpc Alarm(AlarmRequest) returns (AlarmResponse) {}
 }
 
 service Auth {
@@ -438,6 +441,33 @@ message DefragmentResponse {
   ResponseHeader header = 1;
 }
 
+enum AlarmType {
+	NONE = 0; // default, used to query if any alarm is active
+	NOSPACE = 1;
+}
+
+message AlarmRequest {
+  enum AlarmAction {
+	GET = 0;
+	ACTIVATE = 1;
+	DEACTIVATE = 2;
+  }
+  AlarmAction action = 1;
+  // MemberID is the member raising the alarm request
+  int64 memberID = 2;
+  AlarmType alarm = 3;
+}
+
+message AlarmMember {
+	uint64	memberID = 1;
+	AlarmType alarm = 2;
+}
+
+message AlarmResponse {
+  ResponseHeader header = 1;
+  repeated AlarmMember alarms = 2;
+}
+
 message AuthEnableRequest {
 }
 

etcdserver/quota.go

@@ -0,0 +1,95 @@
+// 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 etcdserver
+
+import (
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	"github.com/coreos/etcd/storage/backend"
+)
+
+// Quota represents an arbitrary quota against arbitrary requests. Each request
+// costs some charge; if there is not enough remaining charge, then there are
+// too few resources available within the quota to apply the request.
+type Quota interface {
+	// Available judges whether the given request fits within the quota.
+	Available(req interface{}) bool
+	// Cost computes the charge against the quota for a given request.
+	Cost(req interface{}) int
+	// Remaining is the amount of charge left for the quota.
+	Remaining() int64
+}
+
+type backendQuota struct {
+	s               *EtcdServer
+	maxBackendBytes int64
+}
+
+const (
+	// leaseOverhead is an estimate for the cost of storing a lease
+	leaseOverhead = 64
+	// kvOverhead is an estimate for the cost of storing a key's metadata
+	kvOverhead = 256
+)
+
+func NewBackendQuota(s *EtcdServer) Quota {
+	return &backendQuota{s, backend.InitialMmapSize}
+}
+
+func (b *backendQuota) Available(v interface{}) bool {
+	// TODO: maybe optimize backend.Size()
+	return b.s.Backend().Size()+int64(b.Cost(v)) < b.maxBackendBytes
+}
+
+func (b *backendQuota) Cost(v interface{}) int {
+	switch r := v.(type) {
+	case *pb.PutRequest:
+		return costPut(r)
+	case *pb.TxnRequest:
+		return costTxn(r)
+	case *pb.LeaseCreateRequest:
+		return leaseOverhead
+	default:
+		panic("unexpected cost")
+	}
+}
+
+func costPut(r *pb.PutRequest) int { return kvOverhead + len(r.Key) + len(r.Value) }
+
+func costTxnReq(u *pb.RequestUnion) int {
+	r := u.GetRequestPut()
+	if r == nil {
+		return 0
+	}
+	return costPut(r)
+}
+
+func costTxn(r *pb.TxnRequest) int {
+	sizeSuccess := 0
+	for _, u := range r.Success {
+		sizeSuccess += costTxnReq(u)
+	}
+	sizeFailure := 0
+	for _, u := range r.Failure {
+		sizeFailure += costTxnReq(u)
+	}
+	if sizeFailure > sizeSuccess {
+		return sizeFailure
+	}
+	return sizeSuccess
+}
+
+func (b *backendQuota) Remaining() int64 {
+	return b.maxBackendBytes - b.s.Backend().Size()
+}

etcdserver/server.go

@@ -27,6 +27,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/coreos/etcd/alarm"
 	"github.com/coreos/etcd/auth"
 	"github.com/coreos/etcd/compactor"
 	"github.com/coreos/etcd/discovery"
@@ -172,11 +173,13 @@ type EtcdServer struct {
 
 	store store.Store
 
-	kv        dstorage.ConsistentWatchableKV
-	lessor    lease.Lessor
-	bemu      sync.Mutex
-	be        backend.Backend
-	authStore auth.AuthStore
+	applyV3    applierV3
+	kv         dstorage.ConsistentWatchableKV
+	lessor     lease.Lessor
+	bemu       sync.Mutex
+	be         backend.Backend
+	authStore  auth.AuthStore
+	alarmStore *alarm.AlarmStore
 
 	stats  *stats.ServerStats
 	lstats *stats.LeaderStats
@@ -374,6 +377,10 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 		srv.compactor.Run()
 	}
 
+	if err := srv.restoreAlarms(); err != nil {
+		return nil, err
+	}
+
 	// TODO: move transport initialization near the definition of remote
 	tr := &rafthttp.Transport{
 		TLSInfo:     cfg.PeerTLSInfo,
@@ -613,6 +620,10 @@ func (s *EtcdServer) applySnapshot(ep *etcdProgress, apply *apply) {
 		s.lessor.Recover(newbe, s.kv)
 	}
 
+	if err := s.restoreAlarms(); err != nil {
+		plog.Panicf("restore alarms error: %v", err)
+	}
+
 	if s.authStore != nil {
 		s.authStore.Recover(newbe)
 	}
@@ -1005,14 +1016,26 @@ func (s *EtcdServer) apply(es []raftpb.Entry, confState *raftpb.ConfState) (uint
 				var r pb.Request
 				pbutil.MustUnmarshal(&r, e.Data)
 				s.w.Trigger(r.ID, s.applyRequest(r))
+			} else if raftReq.V2 != nil {
+				req := raftReq.V2
+				s.w.Trigger(req.ID, s.applyRequest(*req))
 			} else {
-				switch {
-				case raftReq.V2 != nil:
-					req := raftReq.V2
-					s.w.Trigger(req.ID, s.applyRequest(*req))
-				default:
-					s.w.Trigger(raftReq.ID, s.applyV3Request(&raftReq))
+				ar := s.applyV3Request(&raftReq)
+				if ar.err != ErrNoSpace || len(s.alarmStore.Get(pb.AlarmType_NOSPACE)) > 0 {
+					s.w.Trigger(raftReq.ID, ar)
+					break
 				}
+				plog.Errorf("applying raft message exceeded backend quota")
+				go func() {
+					a := &pb.AlarmRequest{
+						MemberID: int64(s.ID()),
+						Action:   pb.AlarmRequest_ACTIVATE,
+						Alarm:    pb.AlarmType_NOSPACE,
+					}
+					r := pb.InternalRaftRequest{Alarm: a}
+					s.processInternalRaftRequest(context.TODO(), r)
+					s.w.Trigger(raftReq.ID, ar)
+				}()
 			}
 		case raftpb.EntryConfChange:
 			var cc raftpb.ConfChange
@@ -1319,3 +1342,17 @@ func (s *EtcdServer) Backend() backend.Backend {
 }
 
 func (s *EtcdServer) AuthStore() auth.AuthStore { return s.authStore }
+
+func (s *EtcdServer) restoreAlarms() error {
+	s.applyV3 = newQuotaApplierV3(s, &applierV3backend{s})
+
+	as, err := alarm.NewAlarmStore(s)
+	if err != nil {
+		return err
+	}
+	s.alarmStore = as
+	if len(as.Get(pb.AlarmType_NOSPACE)) > 0 {
+		s.applyV3 = newApplierV3Capped(s.applyV3)
+	}
+	return nil
+}

etcdserver/v3demo_server.go

@@ -15,17 +15,12 @@
 package etcdserver
 
 import (
-	"bytes"
-	"fmt"
-	"sort"
 	"time"
 
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/lease"
 	"github.com/coreos/etcd/lease/leasehttp"
 	dstorage "github.com/coreos/etcd/storage"
-	"github.com/coreos/etcd/storage/storagepb"
-	"github.com/gogo/protobuf/proto"
 	"golang.org/x/net/context"
 )
 
@@ -64,7 +59,7 @@ type Authenticator interface {
 
 func (s *EtcdServer) Range(ctx context.Context, r *pb.RangeRequest) (*pb.RangeResponse, error) {
 	if r.Serializable {
-		return applyRange(noTxn, s.kv, r)
+		return s.applyV3.Range(noTxn, r)
 	}
 
 	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Range: r})
@@ -178,6 +173,14 @@ func (s *EtcdServer) LeaseRenew(id lease.LeaseID) (int64, error) {
 	return ttl, err
 }
 
+func (s *EtcdServer) Alarm(ctx context.Context, r *pb.AlarmRequest) (*pb.AlarmResponse, error) {
+	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Alarm: r})
+	if err != nil {
+		return nil, err
+	}
+	return result.resp.(*pb.AlarmResponse), result.err
+}
+
 func (s *EtcdServer) AuthEnable(ctx context.Context, r *pb.AuthEnableRequest) (*pb.AuthEnableResponse, error) {
 	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{AuthEnable: r})
 	if err != nil {
@@ -194,11 +197,6 @@ func (s *EtcdServer) UserAdd(ctx context.Context, r *pb.UserAddRequest) (*pb.Use
 	return result.resp.(*pb.UserAddResponse), result.err
 }
 
-type applyResult struct {
-	resp proto.Message
-	err  error
-}
-
 func (s *EtcdServer) processInternalRaftRequest(ctx context.Context, r pb.InternalRaftRequest) (*applyResult, error) {
 	r.ID = s.reqIDGen.Next()
 
@@ -230,448 +228,3 @@ func (s *EtcdServer) processInternalRaftRequest(ctx context.Context, r pb.Intern
 func (s *EtcdServer) Watchable() dstorage.Watchable {
 	return s.getKV()
 }
-
-const (
-	// noTxn is an invalid txn ID.
-	// To apply with independent Range, Put, Delete, you can pass noTxn
-	// to apply functions instead of a valid txn ID.
-	noTxn = -1
-)
-
-func (s *EtcdServer) applyV3Request(r *pb.InternalRaftRequest) interface{} {
-	kv := s.getKV()
-	le := s.lessor
-
-	ar := &applyResult{}
-
-	switch {
-	case r.Range != nil:
-		ar.resp, ar.err = applyRange(noTxn, kv, r.Range)
-	case r.Put != nil:
-		ar.resp, ar.err = applyPut(noTxn, kv, le, r.Put)
-	case r.DeleteRange != nil:
-		ar.resp, ar.err = applyDeleteRange(noTxn, kv, r.DeleteRange)
-	case r.Txn != nil:
-		ar.resp, ar.err = applyTxn(kv, le, r.Txn)
-	case r.Compaction != nil:
-		ar.resp, ar.err = applyCompaction(kv, r.Compaction)
-	case r.LeaseCreate != nil:
-		ar.resp, ar.err = applyLeaseCreate(le, r.LeaseCreate)
-	case r.LeaseRevoke != nil:
-		ar.resp, ar.err = applyLeaseRevoke(le, r.LeaseRevoke)
-	case r.AuthEnable != nil:
-		ar.resp, ar.err = applyAuthEnable(s)
-	case r.UserAdd != nil:
-		ar.resp, ar.err = applyUserAdd(s, r.UserAdd)
-	default:
-		panic("not implemented")
-	}
-
-	return ar
-}
-
-func applyPut(txnID int64, kv dstorage.KV, le lease.Lessor, p *pb.PutRequest) (*pb.PutResponse, error) {
-	resp := &pb.PutResponse{}
-	resp.Header = &pb.ResponseHeader{}
-	var (
-		rev int64
-		err error
-	)
-	if txnID != noTxn {
-		rev, err = kv.TxnPut(txnID, p.Key, p.Value, lease.LeaseID(p.Lease))
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		leaseID := lease.LeaseID(p.Lease)
-		if leaseID != lease.NoLease {
-			if l := le.Lookup(leaseID); l == nil {
-				return nil, lease.ErrLeaseNotFound
-			}
-		}
-		rev = kv.Put(p.Key, p.Value, leaseID)
-	}
-	resp.Header.Revision = rev
-	return resp, nil
-}
-
-type kvSort struct{ kvs []storagepb.KeyValue }
-
-func (s *kvSort) Swap(i, j int) {
-	t := s.kvs[i]
-	s.kvs[i] = s.kvs[j]
-	s.kvs[j] = t
-}
-func (s *kvSort) Len() int { return len(s.kvs) }
-
-type kvSortByKey struct{ *kvSort }
-
-func (s *kvSortByKey) Less(i, j int) bool {
-	return bytes.Compare(s.kvs[i].Key, s.kvs[j].Key) < 0
-}
-
-type kvSortByVersion struct{ *kvSort }
-
-func (s *kvSortByVersion) Less(i, j int) bool {
-	return (s.kvs[i].Version - s.kvs[j].Version) < 0
-}
-
-type kvSortByCreate struct{ *kvSort }
-
-func (s *kvSortByCreate) Less(i, j int) bool {
-	return (s.kvs[i].CreateRevision - s.kvs[j].CreateRevision) < 0
-}
-
-type kvSortByMod struct{ *kvSort }
-
-func (s *kvSortByMod) Less(i, j int) bool {
-	return (s.kvs[i].ModRevision - s.kvs[j].ModRevision) < 0
-}
-
-type kvSortByValue struct{ *kvSort }
-
-func (s *kvSortByValue) Less(i, j int) bool {
-	return bytes.Compare(s.kvs[i].Value, s.kvs[j].Value) < 0
-}
-
-func applyRange(txnID int64, kv dstorage.KV, r *pb.RangeRequest) (*pb.RangeResponse, error) {
-	resp := &pb.RangeResponse{}
-	resp.Header = &pb.ResponseHeader{}
-
-	var (
-		kvs []storagepb.KeyValue
-		rev int64
-		err error
-	)
-
-	if isGteRange(r.RangeEnd) {
-		r.RangeEnd = []byte{}
-	}
-
-	limit := r.Limit
-	if r.SortOrder != pb.RangeRequest_NONE {
-		// fetch everything; sort and truncate afterwards
-		limit = 0
-	}
-	if limit > 0 {
-		// fetch one extra for 'more' flag
-		limit = limit + 1
-	}
-
-	if txnID != noTxn {
-		kvs, rev, err = kv.TxnRange(txnID, r.Key, r.RangeEnd, limit, r.Revision)
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		kvs, rev, err = kv.Range(r.Key, r.RangeEnd, limit, r.Revision)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	if r.SortOrder != pb.RangeRequest_NONE {
-		var sorter sort.Interface
-		switch {
-		case r.SortTarget == pb.RangeRequest_KEY:
-			sorter = &kvSortByKey{&kvSort{kvs}}
-		case r.SortTarget == pb.RangeRequest_VERSION:
-			sorter = &kvSortByVersion{&kvSort{kvs}}
-		case r.SortTarget == pb.RangeRequest_CREATE:
-			sorter = &kvSortByCreate{&kvSort{kvs}}
-		case r.SortTarget == pb.RangeRequest_MOD:
-			sorter = &kvSortByMod{&kvSort{kvs}}
-		case r.SortTarget == pb.RangeRequest_VALUE:
-			sorter = &kvSortByValue{&kvSort{kvs}}
-		}
-		switch {
-		case r.SortOrder == pb.RangeRequest_ASCEND:
-			sort.Sort(sorter)
-		case r.SortOrder == pb.RangeRequest_DESCEND:
-			sort.Sort(sort.Reverse(sorter))
-		}
-	}
-
-	if r.Limit > 0 && len(kvs) > int(r.Limit) {
-		kvs = kvs[:r.Limit]
-		resp.More = true
-	}
-
-	resp.Header.Revision = rev
-	for i := range kvs {
-		resp.Kvs = append(resp.Kvs, &kvs[i])
-	}
-	return resp, nil
-}
-
-func applyDeleteRange(txnID int64, kv dstorage.KV, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
-	resp := &pb.DeleteRangeResponse{}
-	resp.Header = &pb.ResponseHeader{}
-
-	var (
-		n   int64
-		rev int64
-		err error
-	)
-
-	if isGteRange(dr.RangeEnd) {
-		dr.RangeEnd = []byte{}
-	}
-
-	if txnID != noTxn {
-		n, rev, err = kv.TxnDeleteRange(txnID, dr.Key, dr.RangeEnd)
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		n, rev = kv.DeleteRange(dr.Key, dr.RangeEnd)
-	}
-
-	resp.Deleted = n
-	resp.Header.Revision = rev
-	return resp, nil
-}
-
-func checkRequestLeases(le lease.Lessor, reqs []*pb.RequestUnion) error {
-	for _, requ := range reqs {
-		tv, ok := requ.Request.(*pb.RequestUnion_RequestPut)
-		if !ok {
-			continue
-		}
-		preq := tv.RequestPut
-		if preq == nil || lease.LeaseID(preq.Lease) == lease.NoLease {
-			continue
-		}
-		if l := le.Lookup(lease.LeaseID(preq.Lease)); l == nil {
-			return lease.ErrLeaseNotFound
-		}
-	}
-	return nil
-}
-
-func checkRequestRange(kv dstorage.KV, reqs []*pb.RequestUnion) error {
-	for _, requ := range reqs {
-		tv, ok := requ.Request.(*pb.RequestUnion_RequestRange)
-		if !ok {
-			continue
-		}
-		greq := tv.RequestRange
-		if greq == nil || greq.Revision == 0 {
-			continue
-		}
-
-		if greq.Revision > kv.Rev() {
-			return dstorage.ErrFutureRev
-		}
-		if greq.Revision < kv.FirstRev() {
-			return dstorage.ErrCompacted
-		}
-	}
-	return nil
-}
-
-func applyTxn(kv dstorage.KV, le lease.Lessor, rt *pb.TxnRequest) (*pb.TxnResponse, error) {
-	var revision int64
-
-	ok := true
-	for _, c := range rt.Compare {
-		if revision, ok = applyCompare(kv, c); !ok {
-			break
-		}
-	}
-
-	var reqs []*pb.RequestUnion
-	if ok {
-		reqs = rt.Success
-	} else {
-		reqs = rt.Failure
-	}
-
-	if err := checkRequestLeases(le, reqs); err != nil {
-		return nil, err
-	}
-	if err := checkRequestRange(kv, reqs); err != nil {
-		return nil, err
-	}
-
-	// When executing the operations of txn, we need to hold the txn lock.
-	// So the reader will not see any intermediate results.
-	txnID := kv.TxnBegin()
-	defer func() {
-		err := kv.TxnEnd(txnID)
-		if err != nil {
-			panic(fmt.Sprint("unexpected error when closing txn", txnID))
-		}
-	}()
-
-	resps := make([]*pb.ResponseUnion, len(reqs))
-	for i := range reqs {
-		resps[i] = applyUnion(txnID, kv, reqs[i])
-	}
-
-	if len(resps) != 0 {
-		revision += 1
-	}
-
-	txnResp := &pb.TxnResponse{}
-	txnResp.Header = &pb.ResponseHeader{}
-	txnResp.Header.Revision = revision
-	txnResp.Responses = resps
-	txnResp.Succeeded = ok
-	return txnResp, nil
-}
-
-func applyCompaction(kv dstorage.KV, compaction *pb.CompactionRequest) (*pb.CompactionResponse, error) {
-	resp := &pb.CompactionResponse{}
-	resp.Header = &pb.ResponseHeader{}
-	err := kv.Compact(compaction.Revision)
-	if err != nil {
-		return nil, err
-	}
-	// get the current revision. which key to get is not important.
-	_, resp.Header.Revision, _ = kv.Range([]byte("compaction"), nil, 1, 0)
-	return resp, err
-}
-
-func applyUnion(txnID int64, kv dstorage.KV, union *pb.RequestUnion) *pb.ResponseUnion {
-	switch tv := union.Request.(type) {
-	case *pb.RequestUnion_RequestRange:
-		if tv.RequestRange != nil {
-			resp, err := applyRange(txnID, kv, tv.RequestRange)
-			if err != nil {
-				panic("unexpected error during txn")
-			}
-			return &pb.ResponseUnion{Response: &pb.ResponseUnion_ResponseRange{ResponseRange: resp}}
-		}
-	case *pb.RequestUnion_RequestPut:
-		if tv.RequestPut != nil {
-			resp, err := applyPut(txnID, kv, nil, tv.RequestPut)
-			if err != nil {
-				panic("unexpected error during txn")
-			}
-			return &pb.ResponseUnion{Response: &pb.ResponseUnion_ResponsePut{ResponsePut: resp}}
-		}
-	case *pb.RequestUnion_RequestDeleteRange:
-		if tv.RequestDeleteRange != nil {
-			resp, err := applyDeleteRange(txnID, kv, tv.RequestDeleteRange)
-			if err != nil {
-				panic("unexpected error during txn")
-			}
-			return &pb.ResponseUnion{Response: &pb.ResponseUnion_ResponseDeleteRange{ResponseDeleteRange: resp}}
-		}
-	default:
-		// empty union
-		return nil
-	}
-	return nil
-}
-
-// applyCompare applies the compare request.
-// It returns the revision at which the comparison happens. If the comparison
-// succeeds, the it returns true. Otherwise it returns false.
-func applyCompare(kv dstorage.KV, c *pb.Compare) (int64, bool) {
-	ckvs, rev, err := kv.Range(c.Key, nil, 1, 0)
-	if err != nil {
-		if err == dstorage.ErrTxnIDMismatch {
-			panic("unexpected txn ID mismatch error")
-		}
-		return rev, false
-	}
-	var ckv storagepb.KeyValue
-	if len(ckvs) != 0 {
-		ckv = ckvs[0]
-	} else {
-		// Use the zero value of ckv normally. However...
-		if c.Target == pb.Compare_VALUE {
-			// Always fail if we're comparing a value on a key that doesn't exist.
-			// We can treat non-existence as the empty set explicitly, such that
-			// even a key with a value of length 0 bytes is still a real key
-			// that was written that way
-			return rev, false
-		}
-	}
-
-	// -1 is less, 0 is equal, 1 is greater
-	var result int
-	switch c.Target {
-	case pb.Compare_VALUE:
-		tv, _ := c.TargetUnion.(*pb.Compare_Value)
-		if tv != nil {
-			result = bytes.Compare(ckv.Value, tv.Value)
-		}
-	case pb.Compare_CREATE:
-		tv, _ := c.TargetUnion.(*pb.Compare_CreateRevision)
-		if tv != nil {
-			result = compareInt64(ckv.CreateRevision, tv.CreateRevision)
-		}
-
-	case pb.Compare_MOD:
-		tv, _ := c.TargetUnion.(*pb.Compare_ModRevision)
-		if tv != nil {
-			result = compareInt64(ckv.ModRevision, tv.ModRevision)
-		}
-	case pb.Compare_VERSION:
-		tv, _ := c.TargetUnion.(*pb.Compare_Version)
-		if tv != nil {
-			result = compareInt64(ckv.Version, tv.Version)
-		}
-	}
-
-	switch c.Result {
-	case pb.Compare_EQUAL:
-		if result != 0 {
-			return rev, false
-		}
-	case pb.Compare_GREATER:
-		if result != 1 {
-			return rev, false
-		}
-	case pb.Compare_LESS:
-		if result != -1 {
-			return rev, false
-		}
-	}
-	return rev, true
-}
-
-func applyLeaseCreate(le lease.Lessor, lc *pb.LeaseCreateRequest) (*pb.LeaseCreateResponse, error) {
-	l, err := le.Grant(lease.LeaseID(lc.ID), lc.TTL)
-	resp := &pb.LeaseCreateResponse{}
-	if err == nil {
-		resp.ID = int64(l.ID)
-		resp.TTL = l.TTL
-	}
-	return resp, err
-}
-
-func applyLeaseRevoke(le lease.Lessor, lc *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error) {
-	err := le.Revoke(lease.LeaseID(lc.ID))
-
-	return &pb.LeaseRevokeResponse{}, err
-}
-
-func compareInt64(a, b int64) int {
-	switch {
-	case a < b:
-		return -1
-	case a > b:
-		return 1
-	default:
-		return 0
-	}
-}
-
-// isGteRange determines if the range end is a >= range. This works around grpc
-// sending empty byte strings as nil; >= is encoded in the range end as '\0'.
-func isGteRange(rangeEnd []byte) bool {
-	return len(rangeEnd) == 1 && rangeEnd[0] == 0
-}
-
-func applyAuthEnable(s *EtcdServer) (*pb.AuthEnableResponse, error) {
-	s.AuthStore().AuthEnable()
-	return &pb.AuthEnableResponse{}, nil
-}
-
-func applyUserAdd(s *EtcdServer, r *pb.UserAddRequest) (*pb.UserAddResponse, error) {
-	return s.AuthStore().UserAdd(r)
-}

integration/cluster.go

@@ -757,6 +757,8 @@ type grpcAPI struct {
 	Lease pb.LeaseClient
 	// Watch is the watch API for the client's connection.
 	Watch pb.WatchClient
+	// Maintenance is the maintenance API for the client's connection.
+	Maintenance pb.MaintenanceClient
 }
 
 func toGRPC(c *clientv3.Client) grpcAPI {
@@ -765,5 +767,6 @@ func toGRPC(c *clientv3.Client) grpcAPI {
 		pb.NewKVClient(c.ActiveConnection()),
 		pb.NewLeaseClient(c.ActiveConnection()),
 		pb.NewWatchClient(c.ActiveConnection()),
+		pb.NewMaintenanceClient(c.ActiveConnection()),
 	}
 }

integration/v3_grpc_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/pkg/testutil"
+	"github.com/coreos/etcd/storage/backend"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 )
@@ -455,6 +456,142 @@ func TestV3Hash(t *testing.T) {
 	}
 }
 
+// TestV3StorageQuotaAPI tests the V3 server respects quotas at the API layer
+func TestV3StorageQuotaAPI(t *testing.T) {
+	oldSize := backend.InitialMmapSize
+	defer func() {
+		backend.InitialMmapSize = oldSize
+		testutil.AfterTest(t)
+	}()
+
+	backend.InitialMmapSize = 64 * 1024
+	clus := NewClusterV3(t, &ClusterConfig{Size: 3})
+	defer clus.Terminate(t)
+	kvc := toGRPC(clus.RandClient()).KV
+
+	key := []byte("abc")
+
+	// test small put that fits in quota
+	smallbuf := make([]byte, 512)
+	if _, err := kvc.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf}); err != nil {
+		t.Fatal(err)
+	}
+
+	// test big put
+	bigbuf := make([]byte, 64*1024)
+	_, err := kvc.Put(context.TODO(), &pb.PutRequest{Key: key, Value: bigbuf})
+	if err == nil || err != rpctypes.ErrNoSpace {
+		t.Fatalf("big put got %v, expected %v", err, rpctypes.ErrNoSpace)
+	}
+
+	// test big txn
+	puttxn := &pb.RequestUnion{
+		Request: &pb.RequestUnion_RequestPut{
+			RequestPut: &pb.PutRequest{
+				Key:   key,
+				Value: bigbuf,
+			},
+		},
+	}
+	txnreq := &pb.TxnRequest{}
+	txnreq.Success = append(txnreq.Success, puttxn)
+	_, txnerr := kvc.Txn(context.TODO(), txnreq)
+	if txnerr == nil || err != rpctypes.ErrNoSpace {
+		t.Fatalf("big txn got %v, expected %v", err, rpctypes.ErrNoSpace)
+	}
+}
+
+// TestV3StorageQuotaApply tests the V3 server respects quotas during apply
+func TestV3StorageQuotaApply(t *testing.T) {
+	oldSize := backend.InitialMmapSize
+	defer func() {
+		backend.InitialMmapSize = oldSize
+		testutil.AfterTest(t)
+	}()
+
+	clus := NewClusterV3(t, &ClusterConfig{Size: 2})
+	defer clus.Terminate(t)
+	kvc0 := toGRPC(clus.Client(0)).KV
+	kvc1 := toGRPC(clus.Client(1)).KV
+
+	// force a node to have a different quota
+	backend.InitialMmapSize = 64 * 1024
+	clus.Members[0].Stop(t)
+	clus.Members[0].Restart(t)
+	clus.waitLeader(t, clus.Members)
+
+	key := []byte("abc")
+
+	// test small put still works
+	smallbuf := make([]byte, 1024)
+	_, serr := kvc0.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf})
+	if serr != nil {
+		t.Fatal(serr)
+	}
+
+	// test big put
+	bigbuf := make([]byte, 64*1024)
+	_, err := kvc1.Put(context.TODO(), &pb.PutRequest{Key: key, Value: bigbuf})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// small quota machine should reject put
+	// first, synchronize with the cluster via quorum get
+	kvc0.Range(context.TODO(), &pb.RangeRequest{Key: []byte("foo")})
+	if _, err := kvc0.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf}); err == nil {
+		t.Fatalf("past-quota instance should reject put")
+	}
+
+	// large quota machine should reject put
+	if _, err := kvc1.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf}); err == nil {
+		t.Fatalf("past-quota instance should reject put")
+	}
+
+	// reset large quota node to ensure alarm persisted
+	backend.InitialMmapSize = oldSize
+	clus.Members[1].Stop(t)
+	clus.Members[1].Restart(t)
+	clus.waitLeader(t, clus.Members)
+
+	if _, err := kvc1.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf}); err == nil {
+		t.Fatalf("alarmed instance should reject put after reset")
+	}
+}
+
+// TestV3AlarmDeactivate ensures that space alarms can be deactivated so puts go through.
+func TestV3AlarmDeactivate(t *testing.T) {
+	clus := NewClusterV3(t, &ClusterConfig{Size: 3})
+	defer clus.Terminate(t)
+	kvc := toGRPC(clus.RandClient()).KV
+	mt := toGRPC(clus.RandClient()).Maintenance
+
+	alarmReq := &pb.AlarmRequest{
+		MemberID: 123,
+		Action:   pb.AlarmRequest_ACTIVATE,
+		Alarm:    pb.AlarmType_NOSPACE,
+	}
+	if _, err := mt.Alarm(context.TODO(), alarmReq); err != nil {
+		t.Fatal(err)
+	}
+
+	key := []byte("abc")
+	smallbuf := make([]byte, 512)
+	_, err := kvc.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf})
+	if err == nil && err != rpctypes.ErrNoSpace {
+		t.Fatalf("put got %v, expected %v", err, rpctypes.ErrNoSpace)
+	}
+
+	alarmReq.Action = pb.AlarmRequest_DEACTIVATE
+	if _, err = mt.Alarm(context.TODO(), alarmReq); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err = kvc.Put(context.TODO(), &pb.PutRequest{Key: key, Value: smallbuf}); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestV3RangeRequest(t *testing.T) {
 	defer testutil.AfterTest(t)
 	tests := []struct {

storage/backend/batch_tx.go

@@ -31,6 +31,7 @@ type BatchTx interface {
 	UnsafeSeqPut(bucketName []byte, key []byte, value []byte)
 	UnsafeRange(bucketName []byte, key, endKey []byte, limit int64) (keys [][]byte, vals [][]byte)
 	UnsafeDelete(bucketName []byte, key []byte)
+	UnsafeForEach(bucketName []byte, visitor func(k, v []byte) error) error
 	Commit()
 	CommitAndStop()
 }
@@ -122,6 +123,11 @@ func (t *batchTx) UnsafeDelete(bucketName []byte, key []byte) {
 	t.pending++
 }
 
+// UnsafeForEach must be called holding the lock on the tx.
+func (t *batchTx) UnsafeForEach(bucketName []byte, visitor func(k, v []byte) error) error {
+	return t.tx.Bucket(bucketName).ForEach(visitor)
+}
+
 // Commit commits a previous tx and begins a new writable one.
 func (t *batchTx) Commit() {
 	t.Lock()

storage/kvstore_test.go

@@ -584,6 +584,9 @@ func (b *fakeBatchTx) UnsafeRange(bucketName []byte, key, endKey []byte, limit i
 func (b *fakeBatchTx) UnsafeDelete(bucketName []byte, key []byte) {
 	b.Recorder.Record(testutil.Action{Name: "delete", Params: []interface{}{bucketName, key}})
 }
+func (b *fakeBatchTx) UnsafeForEach(bucketName []byte, visitor func(k, v []byte) error) error {
+	return nil
+}
 func (b *fakeBatchTx) Commit()        {}
 func (b *fakeBatchTx) CommitAndStop() {}
 

test

@@ -21,7 +21,7 @@ TESTABLE_AND_FORMATTABLE="client clientv3 discovery error etcdctl/ctlv2 etcdctl/
 # TODO: add it to race testing when the issue is resolved
 # https://github.com/golang/go/issues/9946
 NO_RACE_TESTABLE="rafthttp"
-FORMATTABLE="$TESTABLE_AND_FORMATTABLE $NO_RACE_TESTABLE *.go etcdctl/ integration clientv3/integration e2e"
+FORMATTABLE="$TESTABLE_AND_FORMATTABLE $NO_RACE_TESTABLE *.go etcdctl/ integration clientv3/integration e2e alarm"
 
 # user has not provided PKG override
 if [ -z "$PKG" ]; then