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Merge pull request #461 from xiangli-cmu/stream_watcher

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feat(stream watchers) add stream watcher support
This commit is contained in:
Ben Johnson 2014-01-10 08:42:31 -08:00
commit c64c739fab
7 changed files with 143 additions and 65 deletions
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2
server/v1/watch_key_handler.go
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@ -25,7 +25,7 @@ func WatchKeyHandler(w http.ResponseWriter, req *http.Request, s Server) error {
}
// Start the watcher on the store.
watcher, err := s.Store().Watch(key, false, sinceIndex)
watcher, err := s.Store().Watch(key, false, false, sinceIndex)
if err != nil {
return etcdErr.NewError(500, key, s.Store().Index())
}

115
server/v2/get_handler.go
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@ -9,15 +9,11 @@ import (
etcdErr "github.com/coreos/etcd/error"
"github.com/coreos/etcd/log"
"github.com/coreos/etcd/store"
"github.com/coreos/raft"
"github.com/gorilla/mux"
)
func GetHandler(w http.ResponseWriter, req *http.Request, s Server) error {
var err error
var event *store.Event
vars := mux.Vars(req)
key := "/" + vars["key"]
@ -40,52 +36,91 @@ func GetHandler(w http.ResponseWriter, req *http.Request, s Server) error {
}
recursive := (req.FormValue("recursive") == "true")
sorted := (req.FormValue("sorted") == "true")
sort := (req.FormValue("sorted") == "true")
waitIndex := req.FormValue("waitIndex")
stream := (req.FormValue("stream") == "true")
if req.FormValue("wait") == "true" { // watch
// Create a command to watch from a given index (default 0).
var sinceIndex uint64 = 0
if req.FormValue("wait") == "true" {
return handleWatch(key, recursive, stream, waitIndex, w, s)
}
waitIndex := req.FormValue("waitIndex")
if waitIndex != "" {
sinceIndex, err = strconv.ParseUint(string(req.FormValue("waitIndex")), 10, 64)
if err != nil {
return etcdErr.NewError(etcdErr.EcodeIndexNaN, "Watch From Index", s.Store().Index())
}
}
return handleGet(key, recursive, sort, w, s)
}
// Start the watcher on the store.
watcher, err := s.Store().Watch(key, recursive, sinceIndex)
func handleWatch(key string, recursive, stream bool, waitIndex string, w http.ResponseWriter, s Server) error {
// Create a command to watch from a given index (default 0).
var sinceIndex uint64 = 0
var err error
if waitIndex != "" {
sinceIndex, err = strconv.ParseUint(waitIndex, 10, 64)
if err != nil {
return err
}
cn, _ := w.(http.CloseNotifier)
closeChan := cn.CloseNotify()
select {
case <-closeChan:
watcher.Remove()
return nil
case event = <-watcher.EventChan:
}
} else { //get
// Retrieve the key from the store.
event, err = s.Store().Get(key, recursive, sorted)
if err != nil {
return err
return etcdErr.NewError(etcdErr.EcodeIndexNaN, "Watch From Index", s.Store().Index())
}
}
watcher, err := s.Store().Watch(key, recursive, stream, sinceIndex)
if err != nil {
return err
}
cn, _ := w.(http.CloseNotifier)
closeChan := cn.CloseNotify()
writeHeaders(w, s)
if stream {
// watcher hub will not help to remove stream watcher
// so we need to remove here
defer watcher.Remove()
for {
select {
case <-closeChan:
return nil
case event, ok := <-watcher.EventChan:
if !ok {
// If the channel is closed this may be an indication of
// that notifications are much more than we are able to
// send to the client in time. Then we simply end streaming.
return nil
}
b, _ := json.Marshal(event)
_, err := w.Write(b)
if err != nil {
return nil
}
w.(http.Flusher).Flush()
}
}
}
select {
case <-closeChan:
watcher.Remove()
case event := <-watcher.EventChan:
b, _ := json.Marshal(event)
w.Write(b)
}
return nil
}
func handleGet(key string, recursive, sort bool, w http.ResponseWriter, s Server) error {
event, err := s.Store().Get(key, recursive, sort)
if err != nil {
return err
}
writeHeaders(w, s)
b, _ := json.Marshal(event)
w.Write(b)
return nil
}
func writeHeaders(w http.ResponseWriter, s Server) {
w.Header().Set("Content-Type", "application/json")
w.Header().Add("X-Etcd-Index", fmt.Sprint(s.Store().Index()))
w.Header().Add("X-Raft-Index", fmt.Sprint(s.CommitIndex()))
w.Header().Add("X-Raft-Term", fmt.Sprint(s.Term()))
w.WriteHeader(http.StatusOK)
b, _ := json.Marshal(event)
w.Write(b)
return nil
}

8
store/store.go
View File

@ -53,7 +53,7 @@ type Store interface {
Delete(nodePath string, recursive, dir bool) (*Event, error)
CompareAndDelete(nodePath string, prevValue string, prevIndex uint64) (*Event, error)
Watch(prefix string, recursive bool, sinceIndex uint64) (*Watcher, error)
Watch(prefix string, recursive, stream bool, sinceIndex uint64) (*Watcher, error)
Save() ([]byte, error)
Recovery(state []byte) error
@ -340,7 +340,7 @@ func (s *store) CompareAndDelete(nodePath string, prevValue string, prevIndex ui
return e, nil
}
func (s *store) Watch(key string, recursive bool, sinceIndex uint64) (*Watcher, error) {
func (s *store) Watch(key string, recursive, stream bool, sinceIndex uint64) (*Watcher, error) {
key = path.Clean(path.Join("/", key))
nextIndex := s.CurrentIndex + 1
@ -351,10 +351,10 @@ func (s *store) Watch(key string, recursive bool, sinceIndex uint64) (*Watcher,
var err *etcdErr.Error
if sinceIndex == 0 {
w, err = s.WatcherHub.watch(key, recursive, nextIndex)
w, err = s.WatcherHub.watch(key, recursive, stream, nextIndex)
} else {
w, err = s.WatcherHub.watch(key, recursive, sinceIndex)
w, err = s.WatcherHub.watch(key, recursive, stream, sinceIndex)
}
if err != nil {

42
store/store_test.go
View File

@ -489,7 +489,7 @@ func TestStoreCompareAndSwapPrevIndexFailsIfNotMatch(t *testing.T) {
// Ensure that the store can watch for key creation.
func TestStoreWatchCreate(t *testing.T) {
s := newStore()
w, _ := s.Watch("/foo", false, 0)
w, _ := s.Watch("/foo", false, false, 0)
c := w.EventChan
s.Create("/foo", false, "bar", false, Permanent)
e := nbselect(c)
@ -502,7 +502,7 @@ func TestStoreWatchCreate(t *testing.T) {
// Ensure that the store can watch for recursive key creation.
func TestStoreWatchRecursiveCreate(t *testing.T) {
s := newStore()
w, _ := s.Watch("/foo", true, 0)
w, _ := s.Watch("/foo", true, false, 0)
s.Create("/foo/bar", false, "baz", false, Permanent)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "create", "")
@ -513,7 +513,7 @@ func TestStoreWatchRecursiveCreate(t *testing.T) {
func TestStoreWatchUpdate(t *testing.T) {
s := newStore()
s.Create("/foo", false, "bar", false, Permanent)
w, _ := s.Watch("/foo", false, 0)
w, _ := s.Watch("/foo", false, false, 0)
s.Update("/foo", "baz", Permanent)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "update", "")
@ -524,7 +524,7 @@ func TestStoreWatchUpdate(t *testing.T) {
func TestStoreWatchRecursiveUpdate(t *testing.T) {
s := newStore()
s.Create("/foo/bar", false, "baz", false, Permanent)
w, _ := s.Watch("/foo", true, 0)
w, _ := s.Watch("/foo", true, false, 0)
s.Update("/foo/bar", "baz", Permanent)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "update", "")
@ -535,7 +535,7 @@ func TestStoreWatchRecursiveUpdate(t *testing.T) {
func TestStoreWatchDelete(t *testing.T) {
s := newStore()
s.Create("/foo", false, "bar", false, Permanent)
w, _ := s.Watch("/foo", false, 0)
w, _ := s.Watch("/foo", false, false, 0)
s.Delete("/foo", false, false)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "delete", "")
@ -546,7 +546,7 @@ func TestStoreWatchDelete(t *testing.T) {
func TestStoreWatchRecursiveDelete(t *testing.T) {
s := newStore()
s.Create("/foo/bar", false, "baz", false, Permanent)
w, _ := s.Watch("/foo", true, 0)
w, _ := s.Watch("/foo", true, false, 0)
s.Delete("/foo/bar", false, false)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "delete", "")
@ -557,7 +557,7 @@ func TestStoreWatchRecursiveDelete(t *testing.T) {
func TestStoreWatchCompareAndSwap(t *testing.T) {
s := newStore()
s.Create("/foo", false, "bar", false, Permanent)
w, _ := s.Watch("/foo", false, 0)
w, _ := s.Watch("/foo", false, false, 0)
s.CompareAndSwap("/foo", "bar", 0, "baz", Permanent)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "compareAndSwap", "")
@ -568,7 +568,7 @@ func TestStoreWatchCompareAndSwap(t *testing.T) {
func TestStoreWatchRecursiveCompareAndSwap(t *testing.T) {
s := newStore()
s.Create("/foo/bar", false, "baz", false, Permanent)
w, _ := s.Watch("/foo", true, 0)
w, _ := s.Watch("/foo", true, false, 0)
s.CompareAndSwap("/foo/bar", "baz", 0, "bat", Permanent)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "compareAndSwap", "")
@ -588,7 +588,7 @@ func TestStoreWatchExpire(t *testing.T) {
s.Create("/foo", false, "bar", false, time.Now().Add(500*time.Millisecond))
s.Create("/foofoo", false, "barbarbar", false, time.Now().Add(500*time.Millisecond))
w, _ := s.Watch("/", true, 0)
w, _ := s.Watch("/", true, false, 0)
c := w.EventChan
e := nbselect(c)
assert.Nil(t, e, "")
@ -596,12 +596,34 @@ func TestStoreWatchExpire(t *testing.T) {
e = nbselect(c)
assert.Equal(t, e.Action, "expire", "")
assert.Equal(t, e.Node.Key, "/foo", "")
w, _ = s.Watch("/", true, 4)
w, _ = s.Watch("/", true, false, 4)
e = nbselect(w.EventChan)
assert.Equal(t, e.Action, "expire", "")
assert.Equal(t, e.Node.Key, "/foofoo", "")
}
// Ensure that the store can watch in streaming mode.
func TestStoreWatchStream(t *testing.T) {
s := newStore()
w, _ := s.Watch("/foo", false, true, 0)
// first modification
s.Create("/foo", false, "bar", false, Permanent)
e := nbselect(w.EventChan)
assert.Equal(t, e.Action, "create", "")
assert.Equal(t, e.Node.Key, "/foo", "")
assert.Equal(t, e.Node.Value, "bar", "")
e = nbselect(w.EventChan)
assert.Nil(t, e, "")
// second modification
s.Update("/foo", "baz", Permanent)
e = nbselect(w.EventChan)
assert.Equal(t, e.Action, "update", "")
assert.Equal(t, e.Node.Key, "/foo", "")
assert.Equal(t, e.Node.Value, "baz", "")
e = nbselect(w.EventChan)
assert.Nil(t, e, "")
}
// Ensure that the store can recover from a previously saved state.
func TestStoreRecover(t *testing.T) {
s := newStore()

14
store/watcher.go
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@ -18,8 +18,10 @@ package store
type Watcher struct {
EventChan chan *Event
stream bool
recursive bool
sinceIndex uint64
removed bool
remove func()
}
@ -42,13 +44,23 @@ func (w *Watcher) notify(e *Event, originalPath bool, deleted bool) bool {
// For example a watcher is watching at "/foo/bar". And we deletes "/foo". The watcher
// should get notified even if "/foo" is not the path it is watching.
if (w.recursive || originalPath || deleted) && e.Index() >= w.sinceIndex {
w.EventChan <- e
// We cannot block here if the EventChan capacity is full, otherwise
// etcd will hang. EventChan capacity is full when the rate of
// notifications are higher than our send rate.
// If this happens, we close the channel.
select {
case w.EventChan <- e:
default:
// We have missed a notification. Close the channel to indicate this situation.
close(w.EventChan)
}
return true
}
return false
}
// Remove removes the watcher from watcherHub
// The actual remove function is guaranteed to only be executed once
func (w *Watcher) Remove() {
if w.remove != nil {
w.remove()

21
store/watcher_hub.go
View File

@ -38,7 +38,7 @@ func newWatchHub(capacity int) *watcherHub {
// If recursive is true, the first change after index under key will be sent to the event channel of the watcher.
// If recursive is false, the first change after index at key will be sent to the event channel of the watcher.
// If index is zero, watch will start from the current index + 1.
func (wh *watcherHub) watch(key string, recursive bool, index uint64) (*Watcher, *etcdErr.Error) {
func (wh *watcherHub) watch(key string, recursive, stream bool, index uint64) (*Watcher, *etcdErr.Error) {
event, err := wh.EventHistory.scan(key, recursive, index)
if err != nil {
@ -48,6 +48,7 @@ func (wh *watcherHub) watch(key string, recursive bool, index uint64) (*Watcher,
w := &Watcher{
EventChan: make(chan *Event, 1), // use a buffered channel
recursive: recursive,
stream: stream,
sinceIndex: index,
}
@ -73,8 +74,14 @@ func (wh *watcherHub) watch(key string, recursive bool, index uint64) (*Watcher,
}
w.remove = func() {
if w.removed { // avoid remove it twice
return
}
wh.mutex.Lock()
defer wh.mutex.Unlock()
w.removed = true
l.Remove(elem)
atomic.AddInt64(&wh.count, -1)
if l.Len() == 0 {
@ -120,11 +127,13 @@ func (wh *watcherHub) notifyWatchers(e *Event, path string, deleted bool) {
w, _ := curr.Value.(*Watcher)
if w.notify(e, e.Node.Key == path, deleted) {
// if we successfully notify a watcher
// we need to remove the watcher from the list
// and decrease the counter
l.Remove(curr)
atomic.AddInt64(&wh.count, -1)
if !w.stream { // do not remove the stream watcher
// if we successfully notify a watcher
// we need to remove the watcher from the list
// and decrease the counter
l.Remove(curr)
atomic.AddInt64(&wh.count, -1)
}
}
curr = next // update current to the next element in the list

6
store/watcher_test.go
View File

@ -23,7 +23,7 @@ import (
func TestWatcher(t *testing.T) {
s := newStore()
wh := s.WatcherHub
w, err := wh.watch("/foo", true, 1)
w, err := wh.watch("/foo", true, false, 1)
if err != nil {
t.Fatalf("%v", err)
}
@ -46,7 +46,7 @@ func TestWatcher(t *testing.T) {
t.Fatal("recv != send")
}
w, _ = wh.watch("/foo", false, 2)
w, _ = wh.watch("/foo", false, false, 2)
c = w.EventChan
e = newEvent(Create, "/foo/bar", 2, 2)
@ -71,7 +71,7 @@ func TestWatcher(t *testing.T) {
}
// ensure we are doing exact matching rather than prefix matching
w, _ = wh.watch("/fo", true, 1)
w, _ = wh.watch("/fo", true, false, 1)
c = w.EventChan
select {