lease: Use monotonic time in lease

lease uses monotimer to calculate its expiration. In this way, changing system time won't affect in lease expiration.

FIX #6700

lease/lessor.go

@@ -24,6 +24,7 @@ import (
 
 	"github.com/coreos/etcd/lease/leasepb"
 	"github.com/coreos/etcd/mvcc/backend"
+	"github.com/coreos/etcd/pkg/monotime"
 )
 
 const (
@@ -33,9 +34,9 @@ const (
 
 var (
 	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)
+
+	monoTimer = monotime.New()
+	forever   = time.Duration(1>>63 - 1)
 
 	ErrNotPrimary    = errors.New("not a primary lessor")
 	ErrLeaseNotFound = errors.New("lease not found")
@@ -504,8 +505,8 @@ type Lease struct {
 	ttl int64 // time to live in seconds
 
 	itemSet map[LeaseItem]struct{}
-	// expiry time in unixnano
-	expiry  time.Time
+	// expiry is time when lease should expire
+	expiry  time.Duration
 	revokec chan struct{}
 }
 
@@ -534,7 +535,7 @@ func (l *Lease) TTL() int64 {
 
 // refresh refreshes the expiry of the lease.
 func (l *Lease) refresh(extend time.Duration) {
-	l.expiry = time.Now().Add(extend + time.Second*time.Duration(l.ttl))
+	l.expiry = extend + monoTimer.SinceBegining() + time.Duration(l.ttl)*time.Second
 }
 
 // forever sets the expiry of lease to be forever.
@@ -551,7 +552,7 @@ func (l *Lease) Keys() []string {
 
 // Remaining returns the remaining time of the lease.
 func (l *Lease) Remaining() time.Duration {
-	return l.expiry.Sub(time.Now())
+	return l.expiry - monoTimer.SinceBegining()
 }
 
 type LeaseItem struct {

lease/lessor_test.go

@@ -26,7 +26,10 @@ import (
 	"github.com/coreos/etcd/mvcc/backend"
 )
 
-const minLeaseTTL = int64(5)
+const (
+	minLeaseTTL         = int64(5)
+	minLeaseTTLDuration = time.Duration(minLeaseTTL) * time.Second
+)
 
 // TestLessorGrant ensures Lessor can grant wanted lease.
 // The granted lease should have a unique ID with a term
@@ -48,8 +51,8 @@ func TestLessorGrant(t *testing.T) {
 	if !reflect.DeepEqual(gl, l) {
 		t.Errorf("lease = %v, want %v", gl, l)
 	}
-	if l.expiry.Sub(time.Now()) < time.Duration(minLeaseTTL)*time.Second-time.Second {
-		t.Errorf("term = %v, want at least %v", l.expiry.Sub(time.Now()), time.Duration(minLeaseTTL)*time.Second-time.Second)
+	if l.Remaining() < minLeaseTTLDuration-time.Second {
+		t.Errorf("term = %v, want at least %v", l.Remaining(), minLeaseTTLDuration-time.Second)
 	}
 
 	nl, err := le.Grant(1, 1)
@@ -152,7 +155,7 @@ func TestLessorRenew(t *testing.T) {
 	}
 
 	l = le.Lookup(l.ID)
-	if l.expiry.Sub(time.Now()) < 9*time.Second {
+	if l.Remaining() < 9*time.Second {
 		t.Errorf("failed to renew the lease")
 	}
 }

pkg/monotime/issue15006.s

@@ -0,0 +1,6 @@
+// Copyright (C) 2016  Arista Networks, Inc.
+// Use of this source code is governed by the Apache License 2.0
+// that can be found in the COPYING file.
+
+// This file is intentionally empty.
+// It's a workaround for https://github.com/golang/go/issues/15006

pkg/monotime/monotime.go

@@ -0,0 +1,49 @@
+// Copyright 2016 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package monotime
+
+import (
+	"time"
+)
+
+type Timer interface {
+	// Since returns duration between two points of time
+	Since(uint64) time.Duration
+	// SinceBegining returns duration between now and when timer is created
+	SinceBegining() time.Duration
+	// Now returns the current time in nanoseconds
+	Now() uint64
+}
+
+func New() Timer {
+	return &monoTimer{
+		begin: Now(),
+	}
+}
+
+type monoTimer struct {
+	begin uint64
+}
+
+func (t *monoTimer) Now() uint64 {
+	return Now()
+}
+
+func (t *monoTimer) Since(start uint64) time.Duration {
+	return time.Duration(Now() - start)
+}
+
+func (t *monoTimer) SinceBegining() time.Duration {
+	return t.Since(t.begin)
+}

pkg/monotime/nanotime.go

@@ -0,0 +1,24 @@
+// Copyright (C) 2016  Arista Networks, Inc.
+// Use of this source code is governed by the Apache License 2.0
+// that can be found in the COPYING file.
+
+// Package monotime provides a fast monotonic clock source.
+package monotime
+
+import (
+	_ "unsafe" // required to use //go:linkname
+)
+
+//go:noescape
+//go:linkname nanotime runtime.nanotime
+func nanotime() int64
+
+// Now returns the current time in nanoseconds from a monotonic clock.
+// The time returned is based on some arbitrary platform-specific point in the
+// past.  The time returned is guaranteed to increase monotonically at a
+// constant rate, unlike time.Now() from the Go standard library, which may
+// slow down, speed up, jump forward or backward, due to NTP activity or leap
+// seconds.
+func Now() uint64 {
+	return uint64(nanotime())
+}

pkg/monotime/nanotime_test.go

@@ -0,0 +1,23 @@
+// Copyright (C) 2016  Arista Networks, Inc.
+// Use of this source code is governed by the Apache License 2.0
+// that can be found in the COPYING file.
+
+// Package monotime provides a fast monotonic clock source.
+
+package monotime
+
+import (
+	"testing"
+)
+
+func TestNow(t *testing.T) {
+	for i := 0; i < 100; i++ {
+		t1 := Now()
+		t2 := Now()
+		// I honestly thought that we needed >= here, but in some environments
+		// two consecutive calls can return the same value!
+		if t1 > t2 {
+			t.Fatalf("t1=%d should have been less than or equal to t2=%d", t1, t2)
+		}
+	}
+}