forked from etcd-io/etcd
/
watch.go
380 lines (336 loc) · 9.38 KB
/
watch.go
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// Copyright 2015 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 v3rpc
import (
"io"
"sync"
"time"
"golang.org/x/net/context"
"github.com/coreos/etcd/etcdserver"
"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
"github.com/coreos/etcd/mvcc"
"github.com/coreos/etcd/mvcc/mvccpb"
)
type watchServer struct {
clusterID int64
memberID int64
raftTimer etcdserver.RaftTimer
watchable mvcc.WatchableKV
}
func NewWatchServer(s *etcdserver.EtcdServer) pb.WatchServer {
return &watchServer{
clusterID: int64(s.Cluster().ID()),
memberID: int64(s.ID()),
raftTimer: s,
watchable: s.Watchable(),
}
}
var (
// External test can read this with GetProgressReportInterval()
// and change this to a small value to finish fast with
// SetProgressReportInterval().
progressReportInterval = 10 * time.Minute
progressReportIntervalMu sync.RWMutex
)
func GetProgressReportInterval() time.Duration {
progressReportIntervalMu.RLock()
defer progressReportIntervalMu.RUnlock()
return progressReportInterval
}
func SetProgressReportInterval(newTimeout time.Duration) {
progressReportIntervalMu.Lock()
defer progressReportIntervalMu.Unlock()
progressReportInterval = newTimeout
}
const (
// We send ctrl response inside the read loop. We do not want
// send to block read, but we still want ctrl response we sent to
// be serialized. Thus we use a buffered chan to solve the problem.
// A small buffer should be OK for most cases, since we expect the
// ctrl requests are infrequent.
ctrlStreamBufLen = 16
)
// serverWatchStream is an etcd server side stream. It receives requests
// from client side gRPC stream. It receives watch events from mvcc.WatchStream,
// and creates responses that forwarded to gRPC stream.
// It also forwards control message like watch created and canceled.
type serverWatchStream struct {
clusterID int64
memberID int64
raftTimer etcdserver.RaftTimer
watchable mvcc.WatchableKV
gRPCStream pb.Watch_WatchServer
watchStream mvcc.WatchStream
ctrlStream chan *pb.WatchResponse
// mu protects progress, prevKV
mu sync.Mutex
// progress tracks the watchID that stream might need to send
// progress to.
// TODO: combine progress and prevKV into a single struct?
progress map[mvcc.WatchID]bool
prevKV map[mvcc.WatchID]bool
// closec indicates the stream is closed.
closec chan struct{}
// wg waits for the send loop to complete
wg sync.WaitGroup
}
func (ws *watchServer) Watch(stream pb.Watch_WatchServer) (err error) {
sws := serverWatchStream{
clusterID: ws.clusterID,
memberID: ws.memberID,
raftTimer: ws.raftTimer,
watchable: ws.watchable,
gRPCStream: stream,
watchStream: ws.watchable.NewWatchStream(),
// chan for sending control response like watcher created and canceled.
ctrlStream: make(chan *pb.WatchResponse, ctrlStreamBufLen),
progress: make(map[mvcc.WatchID]bool),
prevKV: make(map[mvcc.WatchID]bool),
closec: make(chan struct{}),
}
sws.wg.Add(1)
go func() {
sws.sendLoop()
sws.wg.Done()
}()
errc := make(chan error, 1)
// Ideally recvLoop would also use sws.wg to signal its completion
// but when stream.Context().Done() is closed, the stream's recv
// may continue to block since it uses a different context, leading to
// deadlock when calling sws.close().
go func() { errc <- sws.recvLoop() }()
select {
case err = <-errc:
case <-stream.Context().Done():
err = stream.Context().Err()
// the only server-side cancellation is noleader for now.
if err == context.Canceled {
err = rpctypes.ErrGRPCNoLeader
}
}
sws.close()
return err
}
func (sws *serverWatchStream) recvLoop() error {
defer close(sws.ctrlStream)
for {
req, err := sws.gRPCStream.Recv()
if err == io.EOF {
return nil
}
if err != nil {
return err
}
switch uv := req.RequestUnion.(type) {
case *pb.WatchRequest_CreateRequest:
if uv.CreateRequest == nil {
break
}
creq := uv.CreateRequest
if len(creq.Key) == 0 {
// \x00 is the smallest key
creq.Key = []byte{0}
}
if len(creq.RangeEnd) == 1 && creq.RangeEnd[0] == 0 {
// support >= key queries
creq.RangeEnd = []byte{}
}
filters := FiltersFromRequest(creq)
wsrev := sws.watchStream.Rev()
rev := creq.StartRevision
if rev == 0 {
rev = wsrev + 1
}
id := sws.watchStream.Watch(creq.Key, creq.RangeEnd, rev, filters...)
if id != -1 {
sws.mu.Lock()
if creq.ProgressNotify {
sws.progress[id] = true
}
if creq.PrevKv {
sws.prevKV[id] = true
}
sws.mu.Unlock()
}
wr := &pb.WatchResponse{
Header: sws.newResponseHeader(wsrev),
WatchId: int64(id),
Created: true,
Canceled: id == -1,
}
select {
case sws.ctrlStream <- wr:
case <-sws.closec:
return nil
}
case *pb.WatchRequest_CancelRequest:
if uv.CancelRequest != nil {
id := uv.CancelRequest.WatchId
err := sws.watchStream.Cancel(mvcc.WatchID(id))
if err == nil {
sws.ctrlStream <- &pb.WatchResponse{
Header: sws.newResponseHeader(sws.watchStream.Rev()),
WatchId: id,
Canceled: true,
}
sws.mu.Lock()
delete(sws.progress, mvcc.WatchID(id))
delete(sws.prevKV, mvcc.WatchID(id))
sws.mu.Unlock()
}
}
default:
// we probably should not shutdown the entire stream when
// receive an valid command.
// so just do nothing instead.
continue
}
}
}
func (sws *serverWatchStream) sendLoop() {
// watch ids that are currently active
ids := make(map[mvcc.WatchID]struct{})
// watch responses pending on a watch id creation message
pending := make(map[mvcc.WatchID][]*pb.WatchResponse)
interval := GetProgressReportInterval()
progressTicker := time.NewTicker(interval)
defer func() {
progressTicker.Stop()
// drain the chan to clean up pending events
for ws := range sws.watchStream.Chan() {
mvcc.ReportEventReceived(len(ws.Events))
}
for _, wrs := range pending {
for _, ws := range wrs {
mvcc.ReportEventReceived(len(ws.Events))
}
}
}()
for {
select {
case wresp, ok := <-sws.watchStream.Chan():
if !ok {
return
}
// TODO: evs is []mvccpb.Event type
// either return []*mvccpb.Event from the mvcc package
// or define protocol buffer with []mvccpb.Event.
evs := wresp.Events
events := make([]*mvccpb.Event, len(evs))
sws.mu.Lock()
needPrevKV := sws.prevKV[wresp.WatchID]
sws.mu.Unlock()
for i := range evs {
events[i] = &evs[i]
if needPrevKV {
opt := mvcc.RangeOptions{Rev: evs[i].Kv.ModRevision - 1}
r, err := sws.watchable.Range(evs[i].Kv.Key, nil, opt)
if err == nil && len(r.KVs) != 0 {
events[i].PrevKv = &(r.KVs[0])
}
}
}
wr := &pb.WatchResponse{
Header: sws.newResponseHeader(wresp.Revision),
WatchId: int64(wresp.WatchID),
Events: events,
CompactRevision: wresp.CompactRevision,
}
if _, hasId := ids[wresp.WatchID]; !hasId {
// buffer if id not yet announced
wrs := append(pending[wresp.WatchID], wr)
pending[wresp.WatchID] = wrs
continue
}
mvcc.ReportEventReceived(len(evs))
if err := sws.gRPCStream.Send(wr); err != nil {
return
}
sws.mu.Lock()
if len(evs) > 0 && sws.progress[wresp.WatchID] {
// elide next progress update if sent a key update
sws.progress[wresp.WatchID] = false
}
sws.mu.Unlock()
case c, ok := <-sws.ctrlStream:
if !ok {
return
}
if err := sws.gRPCStream.Send(c); err != nil {
return
}
// track id creation
wid := mvcc.WatchID(c.WatchId)
if c.Canceled {
delete(ids, wid)
continue
}
if c.Created {
// flush buffered events
ids[wid] = struct{}{}
for _, v := range pending[wid] {
mvcc.ReportEventReceived(len(v.Events))
if err := sws.gRPCStream.Send(v); err != nil {
return
}
}
delete(pending, wid)
}
case <-progressTicker.C:
sws.mu.Lock()
for id, ok := range sws.progress {
if ok {
sws.watchStream.RequestProgress(id)
}
sws.progress[id] = true
}
sws.mu.Unlock()
case <-sws.closec:
return
}
}
}
func (sws *serverWatchStream) close() {
sws.watchStream.Close()
close(sws.closec)
sws.wg.Wait()
}
func (sws *serverWatchStream) newResponseHeader(rev int64) *pb.ResponseHeader {
return &pb.ResponseHeader{
ClusterId: uint64(sws.clusterID),
MemberId: uint64(sws.memberID),
Revision: rev,
RaftTerm: sws.raftTimer.Term(),
}
}
func filterNoDelete(e mvccpb.Event) bool {
return e.Type == mvccpb.DELETE
}
func filterNoPut(e mvccpb.Event) bool {
return e.Type == mvccpb.PUT
}
func FiltersFromRequest(creq *pb.WatchCreateRequest) []mvcc.FilterFunc {
filters := make([]mvcc.FilterFunc, 0, len(creq.Filters))
for _, ft := range creq.Filters {
switch ft {
case pb.WatchCreateRequest_NOPUT:
filters = append(filters, filterNoPut)
case pb.WatchCreateRequest_NODELETE:
filters = append(filters, filterNoDelete)
default:
}
}
return filters
}