go.etcd.io/etcd@v3.3.27+incompatible/clientv3/namespace/watch.go (about) 1 // Copyright 2017 The etcd Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package namespace 16 17 import ( 18 "context" 19 "sync" 20 21 "github.com/coreos/etcd/clientv3" 22 ) 23 24 type watcherPrefix struct { 25 clientv3.Watcher 26 pfx string 27 28 wg sync.WaitGroup 29 stopc chan struct{} 30 stopOnce sync.Once 31 } 32 33 // NewWatcher wraps a Watcher instance so that all Watch requests 34 // are prefixed with a given string and all Watch responses have 35 // the prefix removed. 36 func NewWatcher(w clientv3.Watcher, prefix string) clientv3.Watcher { 37 return &watcherPrefix{Watcher: w, pfx: prefix, stopc: make(chan struct{})} 38 } 39 40 func (w *watcherPrefix) Watch(ctx context.Context, key string, opts ...clientv3.OpOption) clientv3.WatchChan { 41 // since OpOption is opaque, determine range for prefixing through an OpGet 42 op := clientv3.OpGet(key, opts...) 43 end := op.RangeBytes() 44 pfxBegin, pfxEnd := prefixInterval(w.pfx, []byte(key), end) 45 if pfxEnd != nil { 46 opts = append(opts, clientv3.WithRange(string(pfxEnd))) 47 } 48 49 wch := w.Watcher.Watch(ctx, string(pfxBegin), opts...) 50 51 // translate watch events from prefixed to unprefixed 52 pfxWch := make(chan clientv3.WatchResponse) 53 w.wg.Add(1) 54 go func() { 55 defer func() { 56 close(pfxWch) 57 w.wg.Done() 58 }() 59 for wr := range wch { 60 for i := range wr.Events { 61 wr.Events[i].Kv.Key = wr.Events[i].Kv.Key[len(w.pfx):] 62 if wr.Events[i].PrevKv != nil { 63 wr.Events[i].PrevKv.Key = wr.Events[i].Kv.Key 64 } 65 } 66 select { 67 case pfxWch <- wr: 68 case <-ctx.Done(): 69 return 70 case <-w.stopc: 71 return 72 } 73 } 74 }() 75 return pfxWch 76 } 77 78 func (w *watcherPrefix) Close() error { 79 err := w.Watcher.Close() 80 w.stopOnce.Do(func() { close(w.stopc) }) 81 w.wg.Wait() 82 return err 83 }