https://github.com/coreos/etcd
Tip revision: 946a5a6f25c3b6b89408ab447852731bde6e6289 authored by Sam Batschelet on 15 June 2021, 21:34:52 UTC
version: 3.5.0
version: 3.5.0
Tip revision: 946a5a6
lease.go
// 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 clientv3
import (
"context"
"sync"
"time"
pb "go.etcd.io/etcd/api/v3/etcdserverpb"
"go.etcd.io/etcd/api/v3/v3rpc/rpctypes"
"go.uber.org/zap"
"google.golang.org/grpc"
"google.golang.org/grpc/metadata"
)
type (
LeaseRevokeResponse pb.LeaseRevokeResponse
LeaseID int64
)
// LeaseGrantResponse wraps the protobuf message LeaseGrantResponse.
type LeaseGrantResponse struct {
*pb.ResponseHeader
ID LeaseID
TTL int64
Error string
}
// LeaseKeepAliveResponse wraps the protobuf message LeaseKeepAliveResponse.
type LeaseKeepAliveResponse struct {
*pb.ResponseHeader
ID LeaseID
TTL int64
}
// LeaseTimeToLiveResponse wraps the protobuf message LeaseTimeToLiveResponse.
type LeaseTimeToLiveResponse struct {
*pb.ResponseHeader
ID LeaseID `json:"id"`
// TTL is the remaining TTL in seconds for the lease; the lease will expire in under TTL+1 seconds. Expired lease will return -1.
TTL int64 `json:"ttl"`
// GrantedTTL is the initial granted time in seconds upon lease creation/renewal.
GrantedTTL int64 `json:"granted-ttl"`
// Keys is the list of keys attached to this lease.
Keys [][]byte `json:"keys"`
}
// LeaseStatus represents a lease status.
type LeaseStatus struct {
ID LeaseID `json:"id"`
// TODO: TTL int64
}
// LeaseLeasesResponse wraps the protobuf message LeaseLeasesResponse.
type LeaseLeasesResponse struct {
*pb.ResponseHeader
Leases []LeaseStatus `json:"leases"`
}
const (
// defaultTTL is the assumed lease TTL used for the first keepalive
// deadline before the actual TTL is known to the client.
defaultTTL = 5 * time.Second
// NoLease is a lease ID for the absence of a lease.
NoLease LeaseID = 0
// retryConnWait is how long to wait before retrying request due to an error
retryConnWait = 500 * time.Millisecond
)
// LeaseResponseChSize is the size of buffer to store unsent lease responses.
// WARNING: DO NOT UPDATE.
// Only for testing purposes.
var LeaseResponseChSize = 16
// ErrKeepAliveHalted is returned if client keep alive loop halts with an unexpected error.
//
// This usually means that automatic lease renewal via KeepAlive is broken, but KeepAliveOnce will still work as expected.
type ErrKeepAliveHalted struct {
Reason error
}
func (e ErrKeepAliveHalted) Error() string {
s := "etcdclient: leases keep alive halted"
if e.Reason != nil {
s += ": " + e.Reason.Error()
}
return s
}
type Lease interface {
// Grant creates a new lease.
Grant(ctx context.Context, ttl int64) (*LeaseGrantResponse, error)
// Revoke revokes the given lease.
Revoke(ctx context.Context, id LeaseID) (*LeaseRevokeResponse, error)
// TimeToLive retrieves the lease information of the given lease ID.
TimeToLive(ctx context.Context, id LeaseID, opts ...LeaseOption) (*LeaseTimeToLiveResponse, error)
// Leases retrieves all leases.
Leases(ctx context.Context) (*LeaseLeasesResponse, error)
// KeepAlive attempts to keep the given lease alive forever. If the keepalive responses posted
// to the channel are not consumed promptly the channel may become full. When full, the lease
// client will continue sending keep alive requests to the etcd server, but will drop responses
// until there is capacity on the channel to send more responses.
//
// If client keep alive loop halts with an unexpected error (e.g. "etcdserver: no leader") or
// canceled by the caller (e.g. context.Canceled), KeepAlive returns a ErrKeepAliveHalted error
// containing the error reason.
//
// The returned "LeaseKeepAliveResponse" channel closes if underlying keep
// alive stream is interrupted in some way the client cannot handle itself;
// given context "ctx" is canceled or timed out.
//
// TODO(v4.0): post errors to last keep alive message before closing
// (see https://github.com/etcd-io/etcd/pull/7866)
KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error)
// KeepAliveOnce renews the lease once. The response corresponds to the
// first message from calling KeepAlive. If the response has a recoverable
// error, KeepAliveOnce will retry the RPC with a new keep alive message.
//
// In most of the cases, Keepalive should be used instead of KeepAliveOnce.
KeepAliveOnce(ctx context.Context, id LeaseID) (*LeaseKeepAliveResponse, error)
// Close releases all resources Lease keeps for efficient communication
// with the etcd server.
Close() error
}
type lessor struct {
mu sync.Mutex // guards all fields
// donec is closed and loopErr is set when recvKeepAliveLoop stops
donec chan struct{}
loopErr error
remote pb.LeaseClient
stream pb.Lease_LeaseKeepAliveClient
streamCancel context.CancelFunc
stopCtx context.Context
stopCancel context.CancelFunc
keepAlives map[LeaseID]*keepAlive
// firstKeepAliveTimeout is the timeout for the first keepalive request
// before the actual TTL is known to the lease client
firstKeepAliveTimeout time.Duration
// firstKeepAliveOnce ensures stream starts after first KeepAlive call.
firstKeepAliveOnce sync.Once
callOpts []grpc.CallOption
lg *zap.Logger
}
// keepAlive multiplexes a keepalive for a lease over multiple channels
type keepAlive struct {
chs []chan<- *LeaseKeepAliveResponse
ctxs []context.Context
// deadline is the time the keep alive channels close if no response
deadline time.Time
// nextKeepAlive is when to send the next keep alive message
nextKeepAlive time.Time
// donec is closed on lease revoke, expiration, or cancel.
donec chan struct{}
}
func NewLease(c *Client) Lease {
return NewLeaseFromLeaseClient(RetryLeaseClient(c), c, c.cfg.DialTimeout+time.Second)
}
func NewLeaseFromLeaseClient(remote pb.LeaseClient, c *Client, keepAliveTimeout time.Duration) Lease {
l := &lessor{
donec: make(chan struct{}),
keepAlives: make(map[LeaseID]*keepAlive),
remote: remote,
firstKeepAliveTimeout: keepAliveTimeout,
lg: c.lg,
}
if l.firstKeepAliveTimeout == time.Second {
l.firstKeepAliveTimeout = defaultTTL
}
if c != nil {
l.callOpts = c.callOpts
}
reqLeaderCtx := WithRequireLeader(context.Background())
l.stopCtx, l.stopCancel = context.WithCancel(reqLeaderCtx)
return l
}
func (l *lessor) Grant(ctx context.Context, ttl int64) (*LeaseGrantResponse, error) {
r := &pb.LeaseGrantRequest{TTL: ttl}
resp, err := l.remote.LeaseGrant(ctx, r, l.callOpts...)
if err == nil {
gresp := &LeaseGrantResponse{
ResponseHeader: resp.GetHeader(),
ID: LeaseID(resp.ID),
TTL: resp.TTL,
Error: resp.Error,
}
return gresp, nil
}
return nil, toErr(ctx, err)
}
func (l *lessor) Revoke(ctx context.Context, id LeaseID) (*LeaseRevokeResponse, error) {
r := &pb.LeaseRevokeRequest{ID: int64(id)}
resp, err := l.remote.LeaseRevoke(ctx, r, l.callOpts...)
if err == nil {
return (*LeaseRevokeResponse)(resp), nil
}
return nil, toErr(ctx, err)
}
func (l *lessor) TimeToLive(ctx context.Context, id LeaseID, opts ...LeaseOption) (*LeaseTimeToLiveResponse, error) {
r := toLeaseTimeToLiveRequest(id, opts...)
resp, err := l.remote.LeaseTimeToLive(ctx, r, l.callOpts...)
if err != nil {
return nil, toErr(ctx, err)
}
gresp := &LeaseTimeToLiveResponse{
ResponseHeader: resp.GetHeader(),
ID: LeaseID(resp.ID),
TTL: resp.TTL,
GrantedTTL: resp.GrantedTTL,
Keys: resp.Keys,
}
return gresp, nil
}
func (l *lessor) Leases(ctx context.Context) (*LeaseLeasesResponse, error) {
resp, err := l.remote.LeaseLeases(ctx, &pb.LeaseLeasesRequest{}, l.callOpts...)
if err == nil {
leases := make([]LeaseStatus, len(resp.Leases))
for i := range resp.Leases {
leases[i] = LeaseStatus{ID: LeaseID(resp.Leases[i].ID)}
}
return &LeaseLeasesResponse{ResponseHeader: resp.GetHeader(), Leases: leases}, nil
}
return nil, toErr(ctx, err)
}
func (l *lessor) KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error) {
ch := make(chan *LeaseKeepAliveResponse, LeaseResponseChSize)
l.mu.Lock()
// ensure that recvKeepAliveLoop is still running
select {
case <-l.donec:
err := l.loopErr
l.mu.Unlock()
close(ch)
return ch, ErrKeepAliveHalted{Reason: err}
default:
}
ka, ok := l.keepAlives[id]
if !ok {
// create fresh keep alive
ka = &keepAlive{
chs: []chan<- *LeaseKeepAliveResponse{ch},
ctxs: []context.Context{ctx},
deadline: time.Now().Add(l.firstKeepAliveTimeout),
nextKeepAlive: time.Now(),
donec: make(chan struct{}),
}
l.keepAlives[id] = ka
} else {
// add channel and context to existing keep alive
ka.ctxs = append(ka.ctxs, ctx)
ka.chs = append(ka.chs, ch)
}
l.mu.Unlock()
go l.keepAliveCtxCloser(ctx, id, ka.donec)
l.firstKeepAliveOnce.Do(func() {
go l.recvKeepAliveLoop()
go l.deadlineLoop()
})
return ch, nil
}
func (l *lessor) KeepAliveOnce(ctx context.Context, id LeaseID) (*LeaseKeepAliveResponse, error) {
for {
resp, err := l.keepAliveOnce(ctx, id)
if err == nil {
if resp.TTL <= 0 {
err = rpctypes.ErrLeaseNotFound
}
return resp, err
}
if isHaltErr(ctx, err) {
return nil, toErr(ctx, err)
}
}
}
func (l *lessor) Close() error {
l.stopCancel()
// close for synchronous teardown if stream goroutines never launched
l.firstKeepAliveOnce.Do(func() { close(l.donec) })
<-l.donec
return nil
}
func (l *lessor) keepAliveCtxCloser(ctx context.Context, id LeaseID, donec <-chan struct{}) {
select {
case <-donec:
return
case <-l.donec:
return
case <-ctx.Done():
}
l.mu.Lock()
defer l.mu.Unlock()
ka, ok := l.keepAlives[id]
if !ok {
return
}
// close channel and remove context if still associated with keep alive
for i, c := range ka.ctxs {
if c == ctx {
close(ka.chs[i])
ka.ctxs = append(ka.ctxs[:i], ka.ctxs[i+1:]...)
ka.chs = append(ka.chs[:i], ka.chs[i+1:]...)
break
}
}
// remove if no one more listeners
if len(ka.chs) == 0 {
delete(l.keepAlives, id)
}
}
// closeRequireLeader scans keepAlives for ctxs that have require leader
// and closes the associated channels.
func (l *lessor) closeRequireLeader() {
l.mu.Lock()
defer l.mu.Unlock()
for _, ka := range l.keepAlives {
reqIdxs := 0
// find all required leader channels, close, mark as nil
for i, ctx := range ka.ctxs {
md, ok := metadata.FromOutgoingContext(ctx)
if !ok {
continue
}
ks := md[rpctypes.MetadataRequireLeaderKey]
if len(ks) < 1 || ks[0] != rpctypes.MetadataHasLeader {
continue
}
close(ka.chs[i])
ka.chs[i] = nil
reqIdxs++
}
if reqIdxs == 0 {
continue
}
// remove all channels that required a leader from keepalive
newChs := make([]chan<- *LeaseKeepAliveResponse, len(ka.chs)-reqIdxs)
newCtxs := make([]context.Context, len(newChs))
newIdx := 0
for i := range ka.chs {
if ka.chs[i] == nil {
continue
}
newChs[newIdx], newCtxs[newIdx] = ka.chs[i], ka.ctxs[newIdx]
newIdx++
}
ka.chs, ka.ctxs = newChs, newCtxs
}
}
func (l *lessor) keepAliveOnce(ctx context.Context, id LeaseID) (*LeaseKeepAliveResponse, error) {
cctx, cancel := context.WithCancel(ctx)
defer cancel()
stream, err := l.remote.LeaseKeepAlive(cctx, l.callOpts...)
if err != nil {
return nil, toErr(ctx, err)
}
err = stream.Send(&pb.LeaseKeepAliveRequest{ID: int64(id)})
if err != nil {
return nil, toErr(ctx, err)
}
resp, rerr := stream.Recv()
if rerr != nil {
return nil, toErr(ctx, rerr)
}
karesp := &LeaseKeepAliveResponse{
ResponseHeader: resp.GetHeader(),
ID: LeaseID(resp.ID),
TTL: resp.TTL,
}
return karesp, nil
}
func (l *lessor) recvKeepAliveLoop() (gerr error) {
defer func() {
l.mu.Lock()
close(l.donec)
l.loopErr = gerr
for _, ka := range l.keepAlives {
ka.close()
}
l.keepAlives = make(map[LeaseID]*keepAlive)
l.mu.Unlock()
}()
for {
stream, err := l.resetRecv()
if err != nil {
if canceledByCaller(l.stopCtx, err) {
return err
}
} else {
for {
resp, err := stream.Recv()
if err != nil {
if canceledByCaller(l.stopCtx, err) {
return err
}
if toErr(l.stopCtx, err) == rpctypes.ErrNoLeader {
l.closeRequireLeader()
}
break
}
l.recvKeepAlive(resp)
}
}
select {
case <-time.After(retryConnWait):
case <-l.stopCtx.Done():
return l.stopCtx.Err()
}
}
}
// resetRecv opens a new lease stream and starts sending keep alive requests.
func (l *lessor) resetRecv() (pb.Lease_LeaseKeepAliveClient, error) {
sctx, cancel := context.WithCancel(l.stopCtx)
stream, err := l.remote.LeaseKeepAlive(sctx, append(l.callOpts, withMax(0))...)
if err != nil {
cancel()
return nil, err
}
l.mu.Lock()
defer l.mu.Unlock()
if l.stream != nil && l.streamCancel != nil {
l.streamCancel()
}
l.streamCancel = cancel
l.stream = stream
go l.sendKeepAliveLoop(stream)
return stream, nil
}
// recvKeepAlive updates a lease based on its LeaseKeepAliveResponse
func (l *lessor) recvKeepAlive(resp *pb.LeaseKeepAliveResponse) {
karesp := &LeaseKeepAliveResponse{
ResponseHeader: resp.GetHeader(),
ID: LeaseID(resp.ID),
TTL: resp.TTL,
}
l.mu.Lock()
defer l.mu.Unlock()
ka, ok := l.keepAlives[karesp.ID]
if !ok {
return
}
if karesp.TTL <= 0 {
// lease expired; close all keep alive channels
delete(l.keepAlives, karesp.ID)
ka.close()
return
}
// send update to all channels
nextKeepAlive := time.Now().Add((time.Duration(karesp.TTL) * time.Second) / 3.0)
ka.deadline = time.Now().Add(time.Duration(karesp.TTL) * time.Second)
for _, ch := range ka.chs {
select {
case ch <- karesp:
default:
if l.lg != nil {
l.lg.Warn("lease keepalive response queue is full; dropping response send",
zap.Int("queue-size", len(ch)),
zap.Int("queue-capacity", cap(ch)),
)
}
}
// still advance in order to rate-limit keep-alive sends
ka.nextKeepAlive = nextKeepAlive
}
}
// deadlineLoop reaps any keep alive channels that have not received a response
// within the lease TTL
func (l *lessor) deadlineLoop() {
for {
select {
case <-time.After(time.Second):
case <-l.donec:
return
}
now := time.Now()
l.mu.Lock()
for id, ka := range l.keepAlives {
if ka.deadline.Before(now) {
// waited too long for response; lease may be expired
ka.close()
delete(l.keepAlives, id)
}
}
l.mu.Unlock()
}
}
// sendKeepAliveLoop sends keep alive requests for the lifetime of the given stream.
func (l *lessor) sendKeepAliveLoop(stream pb.Lease_LeaseKeepAliveClient) {
for {
var tosend []LeaseID
now := time.Now()
l.mu.Lock()
for id, ka := range l.keepAlives {
if ka.nextKeepAlive.Before(now) {
tosend = append(tosend, id)
}
}
l.mu.Unlock()
for _, id := range tosend {
r := &pb.LeaseKeepAliveRequest{ID: int64(id)}
if err := stream.Send(r); err != nil {
// TODO do something with this error?
return
}
}
select {
case <-time.After(retryConnWait):
case <-stream.Context().Done():
return
case <-l.donec:
return
case <-l.stopCtx.Done():
return
}
}
}
func (ka *keepAlive) close() {
close(ka.donec)
for _, ch := range ka.chs {
close(ch)
}
}