lease.go
package clientv3
import (
"sync"
"time"
"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
"golang.org/x/net/context"
"google.golang.org/grpc"
)
type (
LeaseRevokeResponse pb.LeaseRevokeResponse
LeaseID int64
)
// LeaseGrantResponse is used to convert the protobuf grant response.
type LeaseGrantResponse struct {
*pb.ResponseHeader
ID LeaseID
TTL int64
Error string
}
// LeaseKeepAliveResponse is used to convert the protobuf keepalive response.
type LeaseKeepAliveResponse struct {
*pb.ResponseHeader
ID LeaseID
TTL int64
}
// LeaseTimeToLiveResponse is used to convert the protobuf lease timetolive response.
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.
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"`
}
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
// a small buffer to store unsent lease responses.
leaseResponseChSize = 16
// NoLease is a lease ID for the absence of a lease.
NoLease LeaseID = 0
)
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)
// KeepAlive keeps the given lease alive forever.
KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error)
// KeepAliveOnce renews the lease once. 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 when recvKeepAliveLoop stops
donec chan struct{}
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
}
// 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 {
l := &lessor{
donec: make(chan struct{}),
keepAlives: make(map[LeaseID]*keepAlive),
remote: RetryLeaseClient(c),
firstKeepAliveTimeout: c.cfg.DialTimeout + time.Second,
}
if l.firstKeepAliveTimeout == time.Second {
l.firstKeepAliveTimeout = defaultTTL
}
l.stopCtx, l.stopCancel = context.WithCancel(context.Background())
go l.recvKeepAliveLoop()
go l.deadlineLoop()
return l
}
func (l *lessor) Grant(ctx context.Context, ttl int64) (*LeaseGrantResponse, error) {
cctx, cancel := context.WithCancel(ctx)
done := cancelWhenStop(cancel, l.stopCtx.Done())
defer close(done)
for {
r := &pb.LeaseGrantRequest{TTL: ttl}
resp, err := l.remote.LeaseGrant(cctx, r)
if err == nil {
gresp := &LeaseGrantResponse{
ResponseHeader: resp.GetHeader(),
ID: LeaseID(resp.ID),
TTL: resp.TTL,
Error: resp.Error,
}
return gresp, nil
}
if isHaltErr(cctx, err) {
return nil, toErr(cctx, err)
}
if nerr := l.newStream(); nerr != nil {
return nil, nerr
}
}
}
func (l *lessor) Revoke(ctx context.Context, id LeaseID) (*LeaseRevokeResponse, error) {
cctx, cancel := context.WithCancel(ctx)
done := cancelWhenStop(cancel, l.stopCtx.Done())
defer close(done)
for {
r := &pb.LeaseRevokeRequest{ID: int64(id)}
resp, err := l.remote.LeaseRevoke(cctx, r)
if err == nil {
return (*LeaseRevokeResponse)(resp), nil
}
if isHaltErr(ctx, err) {
return nil, toErr(ctx, err)
}
if nerr := l.newStream(); nerr != nil {
return nil, nerr
}
}
}
func (l *lessor) TimeToLive(ctx context.Context, id LeaseID, opts ...LeaseOption) (*LeaseTimeToLiveResponse, error) {
cctx, cancel := context.WithCancel(ctx)
done := cancelWhenStop(cancel, l.stopCtx.Done())
defer close(done)
for {
r := toLeaseTimeToLiveRequest(id, opts...)
resp, err := l.remote.LeaseTimeToLive(cctx, r, grpc.FailFast(false))
if err == nil {
gresp := &LeaseTimeToLiveResponse{
ResponseHeader: resp.GetHeader(),
ID: LeaseID(resp.ID),
TTL: resp.TTL,
GrantedTTL: resp.GrantedTTL,
Keys: resp.Keys,
}
return gresp, nil
}
if isHaltErr(cctx, err) {
return nil, toErr(cctx, err)
}
}
}
func (l *lessor) KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error) {
ch := make(chan *LeaseKeepAliveResponse, leaseResponseChSize)
l.mu.Lock()
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(id, ctx, ka.donec)
return ch, nil
}
func (l *lessor) KeepAliveOnce(ctx context.Context, id LeaseID) (*LeaseKeepAliveResponse, error) {
cctx, cancel := context.WithCancel(ctx)
done := cancelWhenStop(cancel, l.stopCtx.Done())
defer close(done)
for {
resp, err := l.keepAliveOnce(cctx, id)
if err == nil {
if resp.TTL == 0 {
err = rpctypes.ErrLeaseNotFound
}
return resp, err
}
if isHaltErr(ctx, err) {
return nil, toErr(ctx, err)
}
if nerr := l.newStream(); nerr != nil {
return nil, nerr
}
}
}
func (l *lessor) Close() error {
l.stopCancel()
<-l.donec
return nil
}
func (l *lessor) keepAliveCtxCloser(id LeaseID, ctx context.Context, 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)
}
}
func (l *lessor) keepAliveOnce(ctx context.Context, id LeaseID) (*LeaseKeepAliveResponse, error) {
cctx, cancel := context.WithCancel(ctx)
defer cancel()
stream, err := l.remote.LeaseKeepAlive(cctx, grpc.FailFast(false))
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() {
defer func() {
l.mu.Lock()
close(l.donec)
for _, ka := range l.keepAlives {
ka.Close()
}
l.keepAlives = make(map[LeaseID]*keepAlive)
l.mu.Unlock()
}()
stream, serr := l.resetRecv()
for serr == nil {
resp, err := stream.Recv()
if err != nil {
if isHaltErr(l.stopCtx, err) {
return
}
stream, serr = l.resetRecv()
continue
}
l.recvKeepAlive(resp)
}
}
// resetRecv opens a new lease stream and starts sending LeaseKeepAliveRequests
func (l *lessor) resetRecv() (pb.Lease_LeaseKeepAliveClient, error) {
if err := l.newStream(); err != nil {
return nil, err
}
stream := l.getKeepAliveStream()
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(1 + time.Duration(karesp.TTL/3)*time.Second)
ka.deadline = time.Now().Add(time.Duration(karesp.TTL) * time.Second)
for _, ch := range ka.chs {
select {
case ch <- karesp:
ka.nextKeepAlive = nextKeepAlive
default:
}
}
}
// 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 LeaseKeepAliveRequests for the lifetime of a lease stream
func (l *lessor) sendKeepAliveLoop(stream pb.Lease_LeaseKeepAliveClient) {
for {
select {
case <-time.After(500 * time.Millisecond):
case <-stream.Context().Done():
return
case <-l.donec:
return
case <-l.stopCtx.Done():
return
}
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
}
}
}
}
func (l *lessor) getKeepAliveStream() pb.Lease_LeaseKeepAliveClient {
l.mu.Lock()
defer l.mu.Unlock()
return l.stream
}
func (l *lessor) newStream() error {
sctx, cancel := context.WithCancel(l.stopCtx)
stream, err := l.remote.LeaseKeepAlive(sctx, grpc.FailFast(false))
if err != nil {
cancel()
return toErr(sctx, err)
}
l.mu.Lock()
defer l.mu.Unlock()
if l.stream != nil && l.streamCancel != nil {
l.stream.CloseSend()
l.streamCancel()
}
l.streamCancel = cancel
l.stream = stream
return nil
}
func (ka *keepAlive) Close() {
close(ka.donec)
for _, ch := range ka.chs {
close(ch)
}
}
// cancelWhenStop calls cancel when the given stopc fires. It returns a done chan. done
// should be closed when the work is finished. When done fires, cancelWhenStop will release
// its internal resource.
func cancelWhenStop(cancel context.CancelFunc, stopc <-chan struct{}) chan<- struct{} {
done := make(chan struct{}, 1)
go func() {
select {
case <-stopc:
case <-done:
}
cancel()
}()
return done
}
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