Add watcher type and the ability to remove watcher

[tevino]

camlistore.org/pkg/throttle is broken, switched to go4.org/net/throttle

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1. GetW ExistsW and ChildrenW return a *Watcher at the position of <-chan Event
2. The watcher could be removed(thus stopped) by Conn.RemoveWatcher(watcher)
3. The chan within a manually removed watcher will receive a special
   Event with ErrWatcherRemoved
4. WatchType and WatchPathType are exported

[cerisier]

Does this have any chance to be merged ? Is there something we can do to help get it merged ?

[tevino]

I'm not sure if @samuel is still maintaining this repo.
You can just use the fork (as I did) for now. @cerisier

[pantianying]

Does this have any chance to be merged ? Is there something we can do to help get it merged ?

I used this library in my project, which caused a memory leak. The pprof file shows that addwatcher () takes up too much memory, so I want to use removeaddwatcher (). Have you actually used the PR code? My project is https://github.com/apache/dubbo-go，Looking forward to communicating with you

[wanyvic]

I found the same problem from my source code

//conn.go line 950
c.watchersLock.Lock() 
defer c.watchersLock.Unlock() 
ch := make(chan Event, 1)    //canot remove. caused memory leak
wpt := watchPathType{path, watchType} 
c.watchers[wpt] = append(c.watchers[wpt], ch) 

@samuel