Xiang Li
commit
3e74ff7ad4
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// Copyright 2015 CoreOS, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package lease
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import (
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"fmt"
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"sync"
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"time"
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"github.com/coreos/etcd/pkg/idutil"
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)
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var (
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minLeaseTerm = 5 * time.Second
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)
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// a lessor is the owner of leases. It can grant, revoke,
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// renew and modify leases for lessee.
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// TODO: persist lease on to stable backend for failure recovery.
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// TODO: use clockwork for testability.
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type lessor struct {
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mu sync.Mutex
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// TODO: probably this should be a heap with a secondary
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// id index.
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// Now it is O(N) to loop over the leases to find expired ones.
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// We want to make Grant, Revoke, and FindExpired all O(logN) and
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// Renew O(1).
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// FindExpired and Renew should be the most frequent operations.
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leaseMap map[uint64]*lease
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idgen *idutil.Generator
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}
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func NewLessor(lessorID uint8) *lessor {
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return &lessor{
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leaseMap: make(map[uint64]*lease),
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idgen: idutil.NewGenerator(lessorID, time.Now()),
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}
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}
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// Grant grants a lease that expires at least at the given expiry
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// time.
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// TODO: when leassor is under highload, it should give out lease
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// with longer term to reduce renew load.
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func (le *lessor) Grant(expiry time.Time) *lease {
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expiry = minExpiry(time.Now(), expiry)
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id := le.idgen.Next()
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le.mu.Lock()
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defer le.mu.Unlock()
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l := &lease{id: id, expiry: expiry}
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if _, ok := le.leaseMap[id]; ok {
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panic("lease: unexpected duplicate ID!")
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}
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le.leaseMap[id] = l
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return l
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}
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// Revoke revokes a lease with given ID. The item attached to the
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// given lease will be removed. If the ID does not exist, an error
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// will be returned.
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func (le *lessor) Revoke(id uint64) error {
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le.mu.Lock()
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defer le.mu.Unlock()
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l := le.leaseMap[id]
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if l == nil {
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return fmt.Errorf("lease: cannot find lease %x", id)
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}
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delete(le.leaseMap, l.id)
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// TODO: remove attached items
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return nil
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}
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// Renew renews an existing lease with at least the given expiry.
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// If the given lease does not exist or has expired, an error will
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// be returned.
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func (le *lessor) Renew(id uint64, expiry time.Time) error {
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le.mu.Lock()
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defer le.mu.Unlock()
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l := le.leaseMap[id]
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if l == nil {
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return fmt.Errorf("lease: cannot find lease %x", id)
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}
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l.expiry = minExpiry(time.Now(), expiry)
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return nil
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}
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// Attach attaches items to the lease with given ID. When the lease
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// expires, the attached items will be automatically removed.
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// If the given lease does not exist, an error will be returned.
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func (le *lessor) Attach(id uint64, items []leaseItem) error {
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le.mu.Lock()
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defer le.mu.Unlock()
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l := le.leaseMap[id]
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if l == nil {
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return fmt.Errorf("lease: cannot find lease %x", id)
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}
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for _, it := range items {
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l.itemSet[it] = struct{}{}
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}
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return nil
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}
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// findExpiredLeases loops all the leases in the leaseMap and returns the expired
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// leases that needed to be revoked.
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func (le *lessor) findExpiredLeases() []*lease {
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le.mu.Lock()
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defer le.mu.Unlock()
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leases := make([]*lease, 0, 16)
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now := time.Now()
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for _, l := range le.leaseMap {
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if l.expiry.Sub(now) <= 0 {
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leases = append(leases, l)
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}
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}
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return leases
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}
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// get gets the lease with given id.
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// get is a helper fucntion for testing, at least for now.
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func (le *lessor) get(id uint64) *lease {
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le.mu.Lock()
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defer le.mu.Unlock()
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return le.leaseMap[id]
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}
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type lease struct {
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id uint64
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itemSet map[leaseItem]struct{}
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// expiry time in unixnano
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expiry time.Time
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}
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type leaseItem struct {
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key string
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endRange string
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}
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// minExpiry returns a minimal expiry. A minimal expiry is the larger on
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// between now + minLeaseTerm and the given expectedExpiry.
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func minExpiry(now time.Time, expectedExpiry time.Time) time.Time {
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minExpiry := time.Now().Add(minLeaseTerm)
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if expectedExpiry.Sub(minExpiry) < 0 {
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expectedExpiry = minExpiry
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}
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return expectedExpiry
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}
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@ -0,0 +1,75 @@
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// Copyright 2015 CoreOS, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package lease
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import (
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"reflect"
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"testing"
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"time"
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)
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// TestLessorGrant ensures Lessor can grant wanted lease.
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// The granted lease should have a unique ID with a term
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// that is greater than minLeaseTerm.
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func TestLessorGrant(t *testing.T) {
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le := NewLessor(1)
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l := le.Grant(time.Now().Add(time.Second))
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gl := le.get(l.id)
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if !reflect.DeepEqual(gl, l) {
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t.Errorf("lease = %v, want %v", gl, l)
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}
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if l.expiry.Sub(time.Now()) < minLeaseTerm-time.Second {
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t.Errorf("term = %v, want at least %v", l.expiry.Sub(time.Now()), minLeaseTerm-time.Second)
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}
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nl := le.Grant(time.Now().Add(time.Second))
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if nl.id == l.id {
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t.Errorf("new lease.id = %x, want != %x", nl.id, l.id)
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}
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}
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// TestLessorRevoke ensures Lessor can revoke a lease.
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// The revoked lease cannot be got from Lessor again.
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func TestLessorRevoke(t *testing.T) {
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le := NewLessor(1)
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// grant a lease with long term (100 seconds) to
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// avoid early termination during the test.
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l := le.Grant(time.Now().Add(100 * time.Second))
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err := le.Revoke(l.id)
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if err != nil {
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t.Fatal("failed to revoke lease:", err)
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}
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if le.get(l.id) != nil {
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t.Errorf("got revoked lease %x", l.id)
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}
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}
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// TestLessorRenew ensures Lessor can renew an existing lease.
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func TestLessorRenew(t *testing.T) {
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le := NewLessor(1)
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l := le.Grant(time.Now().Add(5 * time.Second))
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le.Renew(l.id, time.Now().Add(100*time.Second))
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l = le.get(l.id)
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if l.expiry.Sub(time.Now()) < 95*time.Second {
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t.Errorf("failed to renew the lease for 100 seconds")
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}
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}
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