This repository has been archived by the owner on Nov 8, 2022. It is now read-only.
forked from kubernetes/kubernetes
-
Notifications
You must be signed in to change notification settings - Fork 0
/
detect.go
231 lines (202 loc) · 6.56 KB
/
detect.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package zoo
import (
"fmt"
"math"
"net/url"
"strconv"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/gogo/protobuf/proto"
log "github.com/golang/glog"
"github.com/mesos/mesos-go/detector"
mesos "github.com/mesos/mesos-go/mesosproto"
)
const (
// prefix for nodes listed at the ZK URL path
nodePrefix = "info_"
defaultMinDetectorCyclePeriod = 1 * time.Second
)
// reasonable default for a noop change listener
var ignoreChanged = detector.OnMasterChanged(func(*mesos.MasterInfo) {})
// Detector uses ZooKeeper to detect new leading master.
type MasterDetector struct {
client *Client
leaderNode string
// for one-time zk client initiation
bootstrap sync.Once
// latch: only install, at most, one ignoreChanged listener; see MasterDetector.Detect
ignoreInstalled int32
// detection should not signal master change listeners more frequently than this
minDetectorCyclePeriod time.Duration
}
// Internal constructor function
func NewMasterDetector(zkurls string) (*MasterDetector, error) {
zkHosts, zkPath, err := parseZk(zkurls)
if err != nil {
log.Fatalln("Failed to parse url", err)
return nil, err
}
client, err := newClient(zkHosts, zkPath)
if err != nil {
return nil, err
}
detector := &MasterDetector{
client: client,
minDetectorCyclePeriod: defaultMinDetectorCyclePeriod,
}
log.V(2).Infoln("Created new detector, watching ", zkHosts, zkPath)
return detector, nil
}
func parseZk(zkurls string) ([]string, string, error) {
u, err := url.Parse(zkurls)
if err != nil {
log.V(1).Infof("failed to parse url: %v", err)
return nil, "", err
}
if u.Scheme != "zk" {
return nil, "", fmt.Errorf("invalid url scheme for zk url: '%v'", u.Scheme)
}
return strings.Split(u.Host, ","), u.Path, nil
}
// returns a chan that, when closed, indicates termination of the detector
func (md *MasterDetector) Done() <-chan struct{} {
return md.client.stopped()
}
func (md *MasterDetector) Cancel() {
md.client.stop()
}
//TODO(jdef) execute async because we don't want to stall our client's event loop? if so
//then we also probably want serial event delivery (aka. delivery via a chan) but then we
//have to deal with chan buffer sizes .. ugh. This is probably the least painful for now.
func (md *MasterDetector) childrenChanged(zkc *Client, path string, obs detector.MasterChanged) {
log.V(2).Infof("fetching children at path '%v'", path)
list, err := zkc.list(path)
if err != nil {
log.Warning(err)
return
}
topNode := selectTopNode(list)
if md.leaderNode == topNode {
log.V(2).Infof("ignoring children-changed event, leader has not changed: %v", path)
return
}
log.V(2).Infof("changing leader node from %s -> %s", md.leaderNode, topNode)
md.leaderNode = topNode
var masterInfo *mesos.MasterInfo
if md.leaderNode != "" {
data, err := zkc.data(fmt.Sprintf("%s/%s", path, topNode))
if err != nil {
log.Errorf("unable to retrieve leader data: %v", err.Error())
return
}
masterInfo = new(mesos.MasterInfo)
err = proto.Unmarshal(data, masterInfo)
if err != nil {
log.Errorf("unable to unmarshall MasterInfo data from zookeeper: %v", err)
return
}
}
log.V(2).Infof("detected master info: %+v", masterInfo)
obs.OnMasterChanged(masterInfo)
}
// the first call to Detect will kickstart a connection to zookeeper. a nil change listener may
// be spec'd, result of which is a detector that will still listen for master changes and record
// leaderhip changes internally but no listener would be notified. Detect may be called more than
// once, and each time the spec'd listener will be added to the list of those receiving notifications.
func (md *MasterDetector) Detect(f detector.MasterChanged) (err error) {
// kickstart zk client connectivity
md.bootstrap.Do(func() { go md.client.connect() })
if f == nil {
// only ever install, at most, one ignoreChanged listener. multiple instances of it
// just consume resources and generate misleading log messages.
if !atomic.CompareAndSwapInt32(&md.ignoreInstalled, 0, 1) {
return
}
f = ignoreChanged
}
go md.detect(f)
return nil
}
func (md *MasterDetector) detect(f detector.MasterChanged) {
detectLoop:
for {
started := time.Now()
select {
case <-md.Done():
return
case <-md.client.connections():
// we let the golang runtime manage our listener list for us, in form of goroutines that
// callback to the master change notification listen func's
if watchEnded, err := md.client.watchChildren(currentPath, ChildWatcher(func(zkc *Client, path string) {
md.childrenChanged(zkc, path, f)
})); err == nil {
log.V(2).Infoln("detector listener installed")
select {
case <-watchEnded:
if md.leaderNode != "" {
log.V(1).Infof("child watch ended, signaling master lost")
md.leaderNode = ""
f.OnMasterChanged(nil)
}
case <-md.client.stopped():
return
}
} else {
log.V(1).Infof("child watch ended with error: %v", err)
continue detectLoop
}
}
// rate-limit master changes
if elapsed := time.Now().Sub(started); elapsed > 0 {
log.V(2).Infoln("resting before next detection cycle")
select {
case <-md.Done():
return
case <-time.After(md.minDetectorCyclePeriod - elapsed): // noop
}
}
}
}
func selectTopNode(list []string) (node string) {
var leaderSeq uint64 = math.MaxUint64
for _, v := range list {
if !strings.HasPrefix(v, nodePrefix) {
continue // only care about participants
}
seqStr := strings.TrimPrefix(v, nodePrefix)
seq, err := strconv.ParseUint(seqStr, 10, 64)
if err != nil {
log.Warningf("unexpected zk node format '%s': %v", seqStr, err)
continue
}
if seq < leaderSeq {
leaderSeq = seq
node = v
}
}
if node == "" {
log.V(3).Infoln("No top node found.")
} else {
log.V(3).Infof("Top node selected: '%s'", node)
}
return node
}