lease: process renew request via raft

Previously, the renew request can only be processed by the leader.
If a follower receives the renew request, it just forwards the
request to the leader via a internal http channel. This isn't
accurate because the leader may change during the process.

When a leader receives the renew request, the previous implementation
follows a three stage workflow: pre-raft, raft and post-raft. It's
too complicated and error prone, and the raft is more like just a
network transport channel instead of a concensus mechanism in this
case.

So we process the renew request via raft directly, it can greatly
simplify the code.

Signed-off-by: Benjamin Wang <wachao@vmware.com>

server/etcdserver/api/v3rpc/lease.go

@@ -123,26 +123,11 @@ func (ls *LeaseServer) leaseKeepAlive(stream pb.Lease_LeaseKeepAliveServer) erro
 			return err
 		}
 
-		// Create header before we sent out the renew request.
-		// This can make sure that the revision is strictly smaller or equal to
-		// when the keepalive happened at the local server (when the local server is the leader)
-		// or remote leader.
-		// Without this, a lease might be revoked at rev 3 but client can see the keepalive succeeded
-		// at rev 4.
-		resp := &pb.LeaseKeepAliveResponse{ID: req.ID, Header: &pb.ResponseHeader{}}
-		ls.hdr.fill(resp.Header)
-
-		ttl, err := ls.le.LeaseRenew(stream.Context(), lease.LeaseID(req.ID))
-		if err == lease.ErrLeaseNotFound {
-			err = nil
-			ttl = 0
-		}
-
+		resp, err := ls.le.LeaseRenew(stream.Context(), req)
 		if err != nil {
 			return togRPCError(err)
 		}
 
-		resp.TTL = ttl
 		err = stream.Send(resp)
 		if err != nil {
 			if isClientCtxErr(stream.Context().Err(), err) {

server/etcdserver/apply/apply.go

@@ -79,6 +79,7 @@ type applierV3 interface {
 
 	LeaseGrant(lc *pb.LeaseGrantRequest) (*pb.LeaseGrantResponse, error)
 	LeaseRevoke(lc *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error)
+	LeaseRenew(lc *pb.LeaseKeepAliveRequest) (*pb.LeaseKeepAliveResponse, error)
 
 	LeaseCheckpoint(lc *pb.LeaseCheckpointRequest) (*pb.LeaseCheckpointResponse, error)
 
@@ -207,6 +208,11 @@ func (a *applierV3backend) LeaseRevoke(lc *pb.LeaseRevokeRequest) (*pb.LeaseRevo
 	return &pb.LeaseRevokeResponse{Header: a.newHeader()}, err
 }
 
+func (a *applierV3backend) LeaseRenew(lc *pb.LeaseKeepAliveRequest) (*pb.LeaseKeepAliveResponse, error) {
+	ttl, err := a.lessor.Renew(lease.LeaseID(lc.ID))
+	return &pb.LeaseKeepAliveResponse{Header: a.newHeader(), ID: lc.ID, TTL: ttl}, err
+}
+
 func (a *applierV3backend) LeaseCheckpoint(lc *pb.LeaseCheckpointRequest) (*pb.LeaseCheckpointResponse, error) {
 	for _, c := range lc.Checkpoints {
 		err := a.lessor.Checkpoint(lease.LeaseID(c.ID), c.Remaining_TTL)

server/etcdserver/apply/corrupt.go

@@ -56,3 +56,7 @@ func (a *applierV3Corrupt) LeaseGrant(_ *pb.LeaseGrantRequest) (*pb.LeaseGrantRe
 func (a *applierV3Corrupt) LeaseRevoke(_ *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error) {
 	return nil, errors.ErrCorrupt
 }
+
+func (a *applierV3Corrupt) LeaseRenew(lc *pb.LeaseKeepAliveRequest) (*pb.LeaseKeepAliveResponse, error) {
+	return nil, errors.ErrCorrupt
+}

server/etcdserver/apply/uber_applier.go

@@ -172,6 +172,9 @@ func (a *uberApplier) dispatch(ctx context.Context, r *pb.InternalRaftRequest, s
 	case r.LeaseRevoke != nil:
 		op = "LeaseRevoke"
 		ar.Resp, ar.Err = a.applyV3.LeaseRevoke(r.LeaseRevoke)
+	case r.LeaseRenew != nil:
+		op = "LeaseRenew"
+		ar.Resp, ar.Err = a.applyV3.LeaseRenew(r.LeaseRenew)
 	case r.LeaseCheckpoint != nil:
 		op = "LeaseCheckpoint"
 		ar.Resp, ar.Err = a.applyV3.LeaseCheckpoint(r.LeaseCheckpoint)

server/etcdserver/v3_server.go

@@ -68,9 +68,8 @@ type Lessor interface {
 	// LeaseRevoke sends LeaseRevoke request to raft and toApply it after committed.
 	LeaseRevoke(ctx context.Context, r *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error)
 
-	// LeaseRenew renews the lease with given ID. The renewed TTL is returned. Or an error
-	// is returned.
-	LeaseRenew(ctx context.Context, id lease.LeaseID) (int64, error)
+	// LeaseRenew renews the lease.
+	LeaseRenew(ctx context.Context, r *pb.LeaseKeepAliveRequest) (*pb.LeaseKeepAliveResponse, error)
 
 	// LeaseTimeToLive retrieves lease information.
 	LeaseTimeToLive(ctx context.Context, r *pb.LeaseTimeToLiveRequest) (*pb.LeaseTimeToLiveResponse, error)
@@ -276,13 +275,13 @@ func (s *EtcdServer) LeaseRevoke(ctx context.Context, r *pb.LeaseRevokeRequest)
 	return resp.(*pb.LeaseRevokeResponse), nil
 }
 
-func (s *EtcdServer) LeaseRenew(ctx context.Context, id lease.LeaseID) (int64, error) {
+func (s *EtcdServer) LeaseRenewV2(ctx context.Context, id lease.LeaseID) (int64, error) {
 	if s.isLeader() {
 		if err := s.waitAppliedIndex(); err != nil {
 			return 0, err
 		}
 
-		ttl, err := s.lessor.Renew(id)
+		ttl, err := s.lessor.RenewV2(id)
 		if err == nil { // already requested to primary lessor(leader)
 			return ttl, nil
 		}
@@ -317,6 +316,14 @@ func (s *EtcdServer) LeaseRenew(ctx context.Context, id lease.LeaseID) (int64, e
 	return -1, errors.ErrCanceled
 }
 
+func (s *EtcdServer) LeaseRenew(ctx context.Context, r *pb.LeaseKeepAliveRequest) (*pb.LeaseKeepAliveResponse, error) {
+	resp, err := s.raftRequestOnce(ctx, pb.InternalRaftRequest{LeaseRenew: r})
+	if err != nil {
+		return nil, err
+	}
+	return resp.(*pb.LeaseKeepAliveResponse), err
+}
+
 func (s *EtcdServer) LeaseTimeToLive(ctx context.Context, r *pb.LeaseTimeToLiveRequest) (*pb.LeaseTimeToLiveResponse, error) {
 	if s.isLeader() {
 		if err := s.waitAppliedIndex(); err != nil {

server/lease/lessor.go

@@ -119,8 +119,13 @@ type Lessor interface {
 	// 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.
+	// RenewV2 renews a lease with given ID. It returns the renewed TTL.
+	// If the ID does not exist, an error will be returned.
+	// TODO(ahrtr): remove this legacy method in 3.7.
+	RenewV2(id LeaseID) (int64, error)
+
+	// Renew renews a lease with given ID. It returns the renewed TTL.
+	// If the given lease does not exist, an error will be returned.
 	Renew(id LeaseID) (int64, error)
 
 	// Lookup gives the lease at a given lease id, if any
@@ -364,7 +369,10 @@ func (le *lessor) Revoke(id LeaseID) error {
 func (le *lessor) Checkpoint(id LeaseID, remainingTTL int64) error {
 	le.mu.Lock()
 	defer le.mu.Unlock()
+	return le.checkpoint(id, remainingTTL)
+}
 
+func (le *lessor) checkpoint(id LeaseID, remainingTTL int64) error {
 	if l, ok := le.leaseMap[id]; ok {
 		// when checkpointing, we only update the remainingTTL, Promote is responsible for applying this to lease expiry
 		l.remainingTTL = remainingTTL
@@ -388,9 +396,10 @@ func greaterOrEqual(first, second semver.Version) bool {
 	return !version.LessThan(first, second)
 }
 
-// Renew renews an existing lease. If the given lease does not exist or
+// RenewV2 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) {
+// TODO(ahrtr): remove the legacy method in 3.7
+func (le *lessor) RenewV2(id LeaseID) (int64, error) {
 	le.mu.RLock()
 	if !le.isPrimary() {
 		// forward renew request to primary instead of returning error.
@@ -442,6 +451,31 @@ func (le *lessor) Renew(id LeaseID) (int64, error) {
 	return l.ttl, nil
 }
 
+func (le *lessor) Renew(id LeaseID) (int64, error) {
+	le.mu.Lock()
+	defer le.mu.Unlock()
+
+	l := le.leaseMap[id]
+	if l == nil {
+		return -1, ErrLeaseNotFound
+	}
+
+	if !le.isPrimary() {
+		if l.remainingTTL > 0 {
+			le.checkpoint(id, 0)
+		}
+		return l.ttl, nil
+	}
+
+	le.checkpoint(id, 0)
+	l.refresh(0)
+	item := &LeaseWithTime{id: l.ID, time: l.expiry}
+	le.leaseExpiredNotifier.RegisterOrUpdate(item)
+
+	leaseRenewed.Inc()
+	return l.ttl, nil
+}
+
 func (le *lessor) Lookup(id LeaseID) *Lease {
 	le.mu.RLock()
 	defer le.mu.RUnlock()
@@ -842,6 +876,8 @@ func (fl *FakeLessor) Promote(extend time.Duration) {}
 
 func (fl *FakeLessor) Demote() {}
 
+func (fl *FakeLessor) RenewV2(id LeaseID) (int64, error) { return 10, nil }
+
 func (fl *FakeLessor) Renew(id LeaseID) (int64, error) { return 10, nil }
 
 func (fl *FakeLessor) Lookup(id LeaseID) *Lease { return nil }

server/lease/lessor_test.go

@@ -426,7 +426,8 @@ func TestLessorRecover(t *testing.T) {
 	}
 }
 
-func TestLessorExpire(t *testing.T) {
+// TODO(ahrtr): remove this test case when the legacy `RenewV2` is removed.
+func TestLessorExpireV2(t *testing.T) {
 	lg := zap.NewNop()
 	dir, be := NewTestBackend(t)
 	defer os.RemoveAll(dir)
@@ -455,7 +456,7 @@ func TestLessorExpire(t *testing.T) {
 	donec := make(chan struct{}, 1)
 	go func() {
 		// expired lease cannot be renewed
-		if _, err := le.Renew(l.ID); err != ErrLeaseNotFound {
+		if _, err := le.RenewV2(l.ID); err != ErrLeaseNotFound {
 			t.Errorf("unexpected renew")
 		}
 		donec <- struct{}{}
@@ -479,7 +480,49 @@ func TestLessorExpire(t *testing.T) {
 	}
 }
 
-func TestLessorExpireAndDemote(t *testing.T) {
+func TestLessorExpire(t *testing.T) {
+	lg := zap.NewNop()
+	dir, be := NewTestBackend(t)
+	defer os.RemoveAll(dir)
+	defer be.Close()
+
+	testMinTTL := int64(1)
+
+	le := newLessor(lg, be, clusterLatest(), LessorConfig{MinLeaseTTL: testMinTTL})
+	defer le.Stop()
+
+	le.Promote(1 * time.Second)
+	l, err := le.Grant(1, testMinTTL)
+	if err != nil {
+		t.Fatalf("failed to create lease: %v", err)
+	}
+
+	select {
+	case el := <-le.ExpiredLeasesC():
+		if el[0].ID != l.ID {
+			t.Fatalf("expired id = %x, want %x", el[0].ID, l.ID)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatalf("failed to receive expired lease")
+	}
+
+	if _, err := le.Renew(l.ID); err != nil {
+		t.Errorf("unexpected renew")
+	}
+
+	// expired lease can be revoked
+	if err := le.Revoke(l.ID); err != nil {
+		t.Fatalf("failed to revoke expired lease: %v", err)
+	}
+
+	// revoked lease can't be renewed
+	if _, err := le.Renew(l.ID); err != ErrLeaseNotFound {
+		t.Errorf("unexpected renew")
+	}
+}
+
+// TODO(ahrtr): remove this test case when the legacy `RenewV2` is removed.
+func TestLessorExpireAndDemoteV2(t *testing.T) {
 	lg := zap.NewNop()
 	dir, be := NewTestBackend(t)
 	defer os.RemoveAll(dir)
@@ -508,7 +551,7 @@ func TestLessorExpireAndDemote(t *testing.T) {
 	donec := make(chan struct{}, 1)
 	go func() {
 		// expired lease cannot be renewed
-		if _, err := le.Renew(l.ID); err != ErrNotPrimary {
+		if _, err := le.RenewV2(l.ID); err != ErrNotPrimary {
 			t.Errorf("unexpected renew: %v", err)
 		}
 		donec <- struct{}{}
@@ -520,7 +563,7 @@ func TestLessorExpireAndDemote(t *testing.T) {
 	case <-time.After(50 * time.Millisecond):
 	}
 
-	// demote will cause the renew request to fail with ErrNotPrimary
+	// demote will cause the renewV2 request to fail with ErrNotPrimary
 	le.Demote()
 
 	select {
@@ -530,6 +573,44 @@ func TestLessorExpireAndDemote(t *testing.T) {
 	}
 }
 
+func TestLessorExpireAndDemote(t *testing.T) {
+	lg := zap.NewNop()
+	dir, be := NewTestBackend(t)
+	defer os.RemoveAll(dir)
+	defer be.Close()
+
+	testMinTTL := int64(1)
+
+	le := newLessor(lg, be, clusterLatest(), LessorConfig{MinLeaseTTL: testMinTTL})
+	defer le.Stop()
+
+	le.Promote(1 * time.Second)
+	l, err := le.Grant(1, testMinTTL)
+	if err != nil {
+		t.Fatalf("failed to create lease: %v", err)
+	}
+
+	select {
+	case el := <-le.ExpiredLeasesC():
+		if el[0].ID != l.ID {
+			t.Fatalf("expired id = %x, want %x", el[0].ID, l.ID)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatalf("failed to receive expired lease")
+	}
+
+	if _, err := le.Renew(l.ID); err != nil {
+		t.Errorf("unexpected renew: %v", err)
+	}
+
+	le.Demote()
+
+	// renew should work after demote.
+	if _, err := le.Renew(l.ID); err != nil {
+		t.Errorf("unexpected renew: %v", err)
+	}
+}
+
 func TestLessorMaxTTL(t *testing.T) {
 	lg := zap.NewNop()
 	dir, be := NewTestBackend(t)

tests/integration/v3_lease_test.go

@@ -747,7 +747,7 @@ func TestV3LeaseFailover(t *testing.T) {
 
 	// send keep alive to old leader until the old leader starts
 	// to drop lease request.
-	var expectedExp time.Time
+	expectedExp := time.Now().Add(time.Duration(lresp.TTL) * time.Second)
 	for {
 		if err = lac.Send(lreq); err != nil {
 			break