khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 1 | // Copyright 2016 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 grpcproxy |
| 16 | |
| 17 | import ( |
| 18 | "sync" |
| 19 | ) |
| 20 | |
| 21 | type watchBroadcasts struct { |
| 22 | wp *watchProxy |
| 23 | |
| 24 | // mu protects bcasts and watchers from the coalesce loop. |
| 25 | mu sync.Mutex |
| 26 | bcasts map[*watchBroadcast]struct{} |
| 27 | watchers map[*watcher]*watchBroadcast |
| 28 | |
| 29 | updatec chan *watchBroadcast |
| 30 | donec chan struct{} |
| 31 | } |
| 32 | |
| 33 | // maxCoalesceRecievers prevents a popular watchBroadcast from being coalseced. |
| 34 | const maxCoalesceReceivers = 5 |
| 35 | |
| 36 | func newWatchBroadcasts(wp *watchProxy) *watchBroadcasts { |
| 37 | wbs := &watchBroadcasts{ |
| 38 | wp: wp, |
| 39 | bcasts: make(map[*watchBroadcast]struct{}), |
| 40 | watchers: make(map[*watcher]*watchBroadcast), |
| 41 | updatec: make(chan *watchBroadcast, 1), |
| 42 | donec: make(chan struct{}), |
| 43 | } |
| 44 | go func() { |
| 45 | defer close(wbs.donec) |
| 46 | for wb := range wbs.updatec { |
| 47 | wbs.coalesce(wb) |
| 48 | } |
| 49 | }() |
| 50 | return wbs |
| 51 | } |
| 52 | |
| 53 | func (wbs *watchBroadcasts) coalesce(wb *watchBroadcast) { |
| 54 | if wb.size() >= maxCoalesceReceivers { |
| 55 | return |
| 56 | } |
| 57 | wbs.mu.Lock() |
| 58 | for wbswb := range wbs.bcasts { |
| 59 | if wbswb == wb { |
| 60 | continue |
| 61 | } |
| 62 | wb.mu.Lock() |
| 63 | wbswb.mu.Lock() |
| 64 | // 1. check if wbswb is behind wb so it won't skip any events in wb |
| 65 | // 2. ensure wbswb started; nextrev == 0 may mean wbswb is waiting |
| 66 | // for a current watcher and expects a create event from the server. |
| 67 | if wb.nextrev >= wbswb.nextrev && wbswb.responses > 0 { |
| 68 | for w := range wb.receivers { |
| 69 | wbswb.receivers[w] = struct{}{} |
| 70 | wbs.watchers[w] = wbswb |
| 71 | } |
| 72 | wb.receivers = nil |
| 73 | } |
| 74 | wbswb.mu.Unlock() |
| 75 | wb.mu.Unlock() |
| 76 | if wb.empty() { |
| 77 | delete(wbs.bcasts, wb) |
| 78 | wb.stop() |
| 79 | break |
| 80 | } |
| 81 | } |
| 82 | wbs.mu.Unlock() |
| 83 | } |
| 84 | |
| 85 | func (wbs *watchBroadcasts) add(w *watcher) { |
| 86 | wbs.mu.Lock() |
| 87 | defer wbs.mu.Unlock() |
| 88 | // find fitting bcast |
| 89 | for wb := range wbs.bcasts { |
| 90 | if wb.add(w) { |
| 91 | wbs.watchers[w] = wb |
| 92 | return |
| 93 | } |
| 94 | } |
| 95 | // no fit; create a bcast |
| 96 | wb := newWatchBroadcast(wbs.wp, w, wbs.update) |
| 97 | wbs.watchers[w] = wb |
| 98 | wbs.bcasts[wb] = struct{}{} |
| 99 | } |
| 100 | |
| 101 | // delete removes a watcher and returns the number of remaining watchers. |
| 102 | func (wbs *watchBroadcasts) delete(w *watcher) int { |
| 103 | wbs.mu.Lock() |
| 104 | defer wbs.mu.Unlock() |
| 105 | |
| 106 | wb, ok := wbs.watchers[w] |
| 107 | if !ok { |
| 108 | panic("deleting missing watcher from broadcasts") |
| 109 | } |
| 110 | delete(wbs.watchers, w) |
| 111 | wb.delete(w) |
| 112 | if wb.empty() { |
| 113 | delete(wbs.bcasts, wb) |
| 114 | wb.stop() |
| 115 | } |
| 116 | return len(wbs.bcasts) |
| 117 | } |
| 118 | |
| 119 | func (wbs *watchBroadcasts) stop() { |
| 120 | wbs.mu.Lock() |
| 121 | for wb := range wbs.bcasts { |
| 122 | wb.stop() |
| 123 | } |
| 124 | wbs.bcasts = nil |
| 125 | close(wbs.updatec) |
| 126 | wbs.mu.Unlock() |
| 127 | <-wbs.donec |
| 128 | } |
| 129 | |
| 130 | func (wbs *watchBroadcasts) update(wb *watchBroadcast) { |
| 131 | select { |
| 132 | case wbs.updatec <- wb: |
| 133 | default: |
| 134 | } |
| 135 | } |