forked from kubernetes/kubernetes
-
-
Notifications
You must be signed in to change notification settings - Fork 0
/
watcher.go
347 lines (316 loc) · 9.56 KB
/
watcher.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
/*
Copyright 2016 The Kubernetes Authors All rights reserved.
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 etcd3
import (
"fmt"
"net/http"
"strings"
"sync"
"k8s.io/kubernetes/pkg/api/unversioned"
"k8s.io/kubernetes/pkg/runtime"
"k8s.io/kubernetes/pkg/storage"
"k8s.io/kubernetes/pkg/watch"
"github.com/coreos/etcd/clientv3"
etcdrpc "github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
"github.com/golang/glog"
"golang.org/x/net/context"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
)
const (
// We have set a buffer in order to reduce times of context switches.
incomingBufSize = 100
outgoingBufSize = 100
)
type watcher struct {
client *clientv3.Client
codec runtime.Codec
versioner storage.Versioner
}
// watchChan implements watch.Interface.
type watchChan struct {
watcher *watcher
key string
initialRev int64
recursive bool
filter storage.FilterFunc
ctx context.Context
cancel context.CancelFunc
incomingEventChan chan *event
resultChan chan watch.Event
errChan chan error
}
func newWatcher(client *clientv3.Client, codec runtime.Codec, versioner storage.Versioner) *watcher {
return &watcher{
client: client,
codec: codec,
versioner: versioner,
}
}
// Watch watches on a key and returns a watch.Interface that transfers relevant notifications.
// If rev is zero, it will return the existing object(s) and then start watching from
// the maximum revision+1 from returned objects.
// If rev is non-zero, it will watch events happened after given revision.
// If recursive is false, it watches on given key.
// If recursive is true, it watches any children and directories under the key, excluding the root key itself.
// filter must be non-nil. Only if filter returns true will the changes be returned.
func (w *watcher) Watch(ctx context.Context, key string, rev int64, recursive bool, filter storage.FilterFunc) (watch.Interface, error) {
if recursive && !strings.HasSuffix(key, "/") {
key += "/"
}
wc := w.createWatchChan(ctx, key, rev, recursive, filter)
go wc.run()
return wc, nil
}
func (w *watcher) createWatchChan(ctx context.Context, key string, rev int64, recursive bool, filter storage.FilterFunc) *watchChan {
wc := &watchChan{
watcher: w,
key: key,
initialRev: rev,
recursive: recursive,
filter: filter,
incomingEventChan: make(chan *event, incomingBufSize),
resultChan: make(chan watch.Event, outgoingBufSize),
errChan: make(chan error, 1),
}
wc.ctx, wc.cancel = context.WithCancel(ctx)
return wc
}
func (wc *watchChan) run() {
go wc.startWatching()
var resultChanWG sync.WaitGroup
resultChanWG.Add(1)
go wc.processEvent(&resultChanWG)
select {
case err := <-wc.errChan:
errResult := parseError(err)
if errResult != nil {
// error result is guaranteed to be received by user before closing ResultChan.
select {
case wc.resultChan <- *errResult:
case <-wc.ctx.Done(): // user has given up all results
}
}
wc.cancel()
case <-wc.ctx.Done():
}
// we need to wait until resultChan wouldn't be sent to anymore
resultChanWG.Wait()
close(wc.resultChan)
}
func (wc *watchChan) Stop() {
wc.cancel()
}
func (wc *watchChan) ResultChan() <-chan watch.Event {
return wc.resultChan
}
// sync tries to retrieve existing data and send them to process.
// The revision to watch will be set to the revision in response.
func (wc *watchChan) sync() error {
opts := []clientv3.OpOption{}
if wc.recursive {
opts = append(opts, clientv3.WithPrefix())
}
getResp, err := wc.watcher.client.Get(wc.ctx, wc.key, opts...)
if err != nil {
return err
}
wc.initialRev = getResp.Header.Revision
for _, kv := range getResp.Kvs {
wc.sendEvent(parseKV(kv))
}
return nil
}
// startWatching does:
// - get current objects if initialRev=0; set initialRev to current rev
// - watch on given key and send events to process.
func (wc *watchChan) startWatching() {
if wc.initialRev == 0 {
if err := wc.sync(); err != nil {
wc.sendError(err)
return
}
}
opts := []clientv3.OpOption{clientv3.WithRev(wc.initialRev + 1)}
if wc.recursive {
opts = append(opts, clientv3.WithPrefix())
}
wch := wc.watcher.client.Watch(wc.ctx, wc.key, opts...)
for wres := range wch {
if wres.Err() != nil {
// If there is an error on server (e.g. compaction), the channel will return it before closed.
wc.sendError(wres.Err())
return
}
for _, e := range wres.Events {
wc.sendEvent(parseEvent(e))
}
}
}
// processEvent processes events from etcd watcher and sends results to resultChan.
func (wc *watchChan) processEvent(wg *sync.WaitGroup) {
defer wg.Done()
for {
select {
case e := <-wc.incomingEventChan:
res := wc.transform(e)
if res == nil {
continue
}
// If user couldn't receive results fast enough, we also block incoming events from watcher.
// Because storing events in local will cause more memory usage.
// The worst case would be closing the fast watcher.
select {
case wc.resultChan <- *res:
case <-wc.ctx.Done():
return
}
case <-wc.ctx.Done():
return
}
}
}
// transform transforms an event into a result for user if not filtered.
// TODO (Optimization):
// - Save remote round-trip.
// Currently, DELETE and PUT event don't contain the previous value.
// We need to do another Get() in order to get previous object and have logic upon it.
// We could potentially do some optimizations:
// - For PUT, we can save current and previous objects into the value.
// - For DELETE, See https://github.com/coreos/etcd/issues/4620
func (wc *watchChan) transform(e *event) (res *watch.Event) {
curObj, oldObj, err := prepareObjs(wc.ctx, e, wc.watcher.client, wc.watcher.codec, wc.watcher.versioner)
if err != nil {
wc.sendError(err)
return nil
}
switch {
case e.isDeleted:
if !wc.filter(oldObj) {
return nil
}
res = &watch.Event{
Type: watch.Deleted,
Object: oldObj,
}
case e.isCreated:
if !wc.filter(curObj) {
return nil
}
res = &watch.Event{
Type: watch.Added,
Object: curObj,
}
default:
curObjPasses := wc.filter(curObj)
oldObjPasses := wc.filter(oldObj)
switch {
case curObjPasses && oldObjPasses:
res = &watch.Event{
Type: watch.Modified,
Object: curObj,
}
case curObjPasses && !oldObjPasses:
res = &watch.Event{
Type: watch.Added,
Object: curObj,
}
case !curObjPasses && oldObjPasses:
res = &watch.Event{
Type: watch.Deleted,
Object: oldObj,
}
}
}
return res
}
func parseError(err error) *watch.Event {
var status *unversioned.Status
switch {
case err == etcdrpc.ErrCompacted:
status = &unversioned.Status{
Status: unversioned.StatusFailure,
Message: err.Error(),
Code: http.StatusGone,
Reason: unversioned.StatusReasonExpired,
}
default:
status = &unversioned.Status{
Status: unversioned.StatusFailure,
Message: err.Error(),
Code: http.StatusInternalServerError,
Reason: unversioned.StatusReasonInternalError,
}
}
return &watch.Event{
Type: watch.Error,
Object: status,
}
}
func (wc *watchChan) sendError(err error) {
// Context.canceled is an expected behavior.
// We should just stop all goroutines in watchChan without returning error.
// TODO: etcd client should return context.Canceled instead of grpc specific error.
if grpc.Code(err) == codes.Canceled || err == context.Canceled {
return
}
select {
case wc.errChan <- err:
case <-wc.ctx.Done():
}
}
func (wc *watchChan) sendEvent(e *event) {
if len(wc.incomingEventChan) == incomingBufSize {
glog.V(2).Infof("Fast watcher, slow processing. Number of buffered events: %d."+
"Probably caused by slow decoding, user not receiving fast, or other processing logic",
incomingBufSize)
}
select {
case wc.incomingEventChan <- e:
case <-wc.ctx.Done():
}
}
func prepareObjs(ctx context.Context, e *event, client *clientv3.Client, codec runtime.Codec, versioner storage.Versioner) (curObj runtime.Object, oldObj runtime.Object, err error) {
if !e.isDeleted {
curObj, err = decodeObj(codec, versioner, e.value, e.rev)
if err != nil {
return nil, nil, err
}
}
if e.isDeleted || !e.isCreated {
getResp, err := client.Get(ctx, e.key, clientv3.WithRev(e.rev-1))
if err != nil {
return nil, nil, err
}
// Note that this sends the *old* object with the etcd revision for the time at
// which it gets deleted.
// We assume old object is returned only in Deleted event. Users (e.g. cacher) need
// to have larger than previous rev to tell the ordering.
oldObj, err = decodeObj(codec, versioner, getResp.Kvs[0].Value, e.rev)
if err != nil {
return nil, nil, err
}
}
return curObj, oldObj, nil
}
func decodeObj(codec runtime.Codec, versioner storage.Versioner, data []byte, rev int64) (runtime.Object, error) {
obj, err := runtime.Decode(codec, []byte(data))
if err != nil {
return nil, err
}
// ensure resource version is set on the object we load from etcd
if err := versioner.UpdateObject(obj, uint64(rev)); err != nil {
return nil, fmt.Errorf("failure to version api object (%d) %#v: %v", rev, obj, err)
}
return obj, nil
}