github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/k8s.io/kubernetes/pkg/watch/filter.go (about) 1 /* 2 Copyright 2014 The Kubernetes Authors All rights reserved. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package watch 18 19 // FilterFunc should take an event, possibly modify it in some way, and return 20 // the modified event. If the event should be ignored, then return keep=false. 21 type FilterFunc func(in Event) (out Event, keep bool) 22 23 // Filter passes all events through f before allowing them to pass on. 24 // Putting a filter on a watch, as an unavoidable side-effect due to the way 25 // go channels work, effectively causes the watch's event channel to have its 26 // queue length increased by one. 27 // 28 // WARNING: filter has a fatal flaw, in that it can't properly update the 29 // Type field (Add/Modified/Deleted) to reflect items beginning to pass the 30 // filter when they previously didn't. 31 // 32 func Filter(w Interface, f FilterFunc) Interface { 33 fw := &filteredWatch{ 34 incoming: w, 35 result: make(chan Event), 36 f: f, 37 } 38 go fw.loop() 39 return fw 40 } 41 42 type filteredWatch struct { 43 incoming Interface 44 result chan Event 45 f FilterFunc 46 } 47 48 // ResultChan returns a channel which will receive filtered events. 49 func (fw *filteredWatch) ResultChan() <-chan Event { 50 return fw.result 51 } 52 53 // Stop stops the upstream watch, which will eventually stop this watch. 54 func (fw *filteredWatch) Stop() { 55 fw.incoming.Stop() 56 } 57 58 // loop waits for new values, filters them, and resends them. 59 func (fw *filteredWatch) loop() { 60 defer close(fw.result) 61 for { 62 event, ok := <-fw.incoming.ResultChan() 63 if !ok { 64 break 65 } 66 filtered, keep := fw.f(event) 67 if keep { 68 fw.result <- filtered 69 } 70 } 71 }