khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 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 grpcproxy |
| 16 | |
| 17 | import ( |
| 18 | "context" |
| 19 | "math" |
| 20 | "sync" |
| 21 | |
| 22 | "github.com/coreos/etcd/clientv3" |
| 23 | "github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes" |
| 24 | |
| 25 | "golang.org/x/time/rate" |
| 26 | "google.golang.org/grpc" |
| 27 | ) |
| 28 | |
| 29 | const ( |
| 30 | lostLeaderKey = "__lostleader" // watched to detect leader loss |
| 31 | retryPerSecond = 10 |
| 32 | ) |
| 33 | |
| 34 | type leader struct { |
| 35 | ctx context.Context |
| 36 | w clientv3.Watcher |
| 37 | // mu protects leaderc updates. |
| 38 | mu sync.RWMutex |
| 39 | leaderc chan struct{} |
| 40 | disconnc chan struct{} |
| 41 | donec chan struct{} |
| 42 | } |
| 43 | |
| 44 | func newLeader(ctx context.Context, w clientv3.Watcher) *leader { |
| 45 | l := &leader{ |
| 46 | ctx: clientv3.WithRequireLeader(ctx), |
| 47 | w: w, |
| 48 | leaderc: make(chan struct{}), |
| 49 | disconnc: make(chan struct{}), |
| 50 | donec: make(chan struct{}), |
| 51 | } |
| 52 | // begin assuming leader is lost |
| 53 | close(l.leaderc) |
| 54 | go l.recvLoop() |
| 55 | return l |
| 56 | } |
| 57 | |
| 58 | func (l *leader) recvLoop() { |
| 59 | defer close(l.donec) |
| 60 | |
| 61 | limiter := rate.NewLimiter(rate.Limit(retryPerSecond), retryPerSecond) |
| 62 | rev := int64(math.MaxInt64 - 2) |
| 63 | for limiter.Wait(l.ctx) == nil { |
| 64 | wch := l.w.Watch(l.ctx, lostLeaderKey, clientv3.WithRev(rev), clientv3.WithCreatedNotify()) |
| 65 | cresp, ok := <-wch |
| 66 | if !ok { |
| 67 | l.loseLeader() |
| 68 | continue |
| 69 | } |
| 70 | if cresp.Err() != nil { |
| 71 | l.loseLeader() |
| 72 | if rpctypes.ErrorDesc(cresp.Err()) == grpc.ErrClientConnClosing.Error() { |
| 73 | close(l.disconnc) |
| 74 | return |
| 75 | } |
| 76 | continue |
| 77 | } |
| 78 | l.gotLeader() |
| 79 | <-wch |
| 80 | l.loseLeader() |
| 81 | } |
| 82 | } |
| 83 | |
| 84 | func (l *leader) loseLeader() { |
| 85 | l.mu.RLock() |
| 86 | defer l.mu.RUnlock() |
| 87 | select { |
| 88 | case <-l.leaderc: |
| 89 | default: |
| 90 | close(l.leaderc) |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | // gotLeader will force update the leadership status to having a leader. |
| 95 | func (l *leader) gotLeader() { |
| 96 | l.mu.Lock() |
| 97 | defer l.mu.Unlock() |
| 98 | select { |
| 99 | case <-l.leaderc: |
| 100 | l.leaderc = make(chan struct{}) |
| 101 | default: |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | func (l *leader) disconnectNotify() <-chan struct{} { return l.disconnc } |
| 106 | |
| 107 | func (l *leader) stopNotify() <-chan struct{} { return l.donec } |
| 108 | |
| 109 | // lostNotify returns a channel that is closed if there has been |
| 110 | // a leader loss not yet followed by a leader reacquire. |
| 111 | func (l *leader) lostNotify() <-chan struct{} { |
| 112 | l.mu.RLock() |
| 113 | defer l.mu.RUnlock() |
| 114 | return l.leaderc |
| 115 | } |