/usr/share/gocode/src/github.com/mesos/mesos-go/detector/standalone.go is in golang-github-mesos-mesos-go-dev 0.0.2+dfsg-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 | package detector
import (
"encoding/binary"
"encoding/json"
"fmt"
"io/ioutil"
"net"
"net/http"
"strconv"
"sync"
"time"
log "github.com/golang/glog"
mesos "github.com/mesos/mesos-go/mesosproto"
"github.com/mesos/mesos-go/upid"
"golang.org/x/net/context"
)
const (
defaultMesosHttpClientTimeout = 10 * time.Second //TODO(jdef) configurable via fiag?
defaultMesosLeaderSyncInterval = 30 * time.Second //TODO(jdef) configurable via fiag?
defaultMesosMasterPort = 5050
)
// enables easier unit testing
type fetcherFunc func(ctx context.Context, address string) (*upid.UPID, error)
type Standalone struct {
ch chan *mesos.MasterInfo
client *http.Client
tr *http.Transport
pollOnce sync.Once
initial *mesos.MasterInfo
done chan struct{}
cancelOnce sync.Once
leaderSyncInterval time.Duration
httpClientTimeout time.Duration
assumedMasterPort int
poller func(pf fetcherFunc)
fetchPid fetcherFunc
}
// Create a new stand alone master detector.
func NewStandalone(mi *mesos.MasterInfo) *Standalone {
log.V(2).Infof("creating new standalone detector for %+v", mi)
stand := &Standalone{
ch: make(chan *mesos.MasterInfo),
tr: &http.Transport{},
initial: mi,
done: make(chan struct{}),
leaderSyncInterval: defaultMesosLeaderSyncInterval,
httpClientTimeout: defaultMesosHttpClientTimeout,
assumedMasterPort: defaultMesosMasterPort,
}
stand.poller = stand._poller
stand.fetchPid = stand._fetchPid
return stand
}
func (s *Standalone) String() string {
return fmt.Sprintf("{initial: %+v}", s.initial)
}
// Detecting the new master.
func (s *Standalone) Detect(o MasterChanged) error {
log.V(2).Info("Detect()")
s.pollOnce.Do(func() {
log.V(1).Info("spinning up asyc master detector poller")
// delayed initialization allows unit tests to modify timeouts before detection starts
s.client = &http.Client{
Transport: s.tr,
Timeout: s.httpClientTimeout,
}
go s.poller(s.fetchPid)
})
if o != nil {
log.V(1).Info("spawning asyc master detector listener")
go func() {
log.V(2).Infof("waiting for polled to send updates")
pollWaiter:
for {
select {
case mi, ok := <-s.ch:
if !ok {
break pollWaiter
}
log.V(1).Infof("detected master change: %+v", mi)
o.OnMasterChanged(mi)
case <-s.done:
return
}
}
o.OnMasterChanged(nil)
}()
} else {
log.Warningf("detect called with a nil master change listener")
}
return nil
}
func (s *Standalone) Done() <-chan struct{} {
return s.done
}
func (s *Standalone) Cancel() {
s.cancelOnce.Do(func() { close(s.done) })
}
// poll for changes to master leadership via current leader's /state.json endpoint.
// we poll the `initial` leader, aborting if none was specified.
//
// TODO(jdef) follow the leader: change who we poll based on the prior leader
// TODO(jdef) somehow determine all masters in cluster from the state.json?
//
func (s *Standalone) _poller(pf fetcherFunc) {
defer func() {
defer s.Cancel()
log.Warning("shutting down standalone master detection")
}()
if s.initial == nil {
log.Errorf("aborting master poller since initial master info is nil")
return
}
addr := s.initial.GetHostname()
if len(addr) == 0 {
if s.initial.GetIp() == 0 {
log.Warningf("aborted mater poller since initial master info has no host")
return
}
ip := make([]byte, 4)
binary.BigEndian.PutUint32(ip, s.initial.GetIp())
addr = net.IP(ip).To4().String()
}
port := uint32(s.assumedMasterPort)
if s.initial.Port != nil && *s.initial.Port != 0 {
port = *s.initial.Port
}
addr = net.JoinHostPort(addr, strconv.Itoa(int(port)))
log.V(1).Infof("polling for master leadership at '%v'", addr)
var lastpid *upid.UPID
for {
startedAt := time.Now()
ctx, cancel := context.WithTimeout(context.Background(), s.leaderSyncInterval)
if pid, err := pf(ctx, addr); err == nil {
if !pid.Equal(lastpid) {
log.V(2).Infof("detected leadership change from '%v' to '%v'", lastpid, pid)
lastpid = pid
elapsed := time.Now().Sub(startedAt)
mi := CreateMasterInfo(pid)
select {
case s.ch <- mi: // noop
case <-time.After(s.leaderSyncInterval - elapsed):
// no one heard the master change, oh well - poll again
goto continuePolling
case <-s.done:
cancel()
return
}
} else {
log.V(2).Infof("no change to master leadership: '%v'", lastpid)
}
} else if err == context.DeadlineExceeded {
if lastpid != nil {
lastpid = nil
select {
case s.ch <- nil: // lost master
case <-s.done: // no need to cancel ctx
return
}
}
goto continuePolling
} else {
select {
case <-s.done:
cancel()
return
default:
if err != context.Canceled {
log.Error(err)
}
}
}
if remaining := s.leaderSyncInterval - time.Now().Sub(startedAt); remaining > 0 {
log.V(3).Infof("master leader poller sleeping for %v", remaining)
time.Sleep(remaining)
}
continuePolling:
cancel()
}
}
// assumes that address is in host:port format
func (s *Standalone) _fetchPid(ctx context.Context, address string) (*upid.UPID, error) {
//TODO(jdef) need SSL support
uri := fmt.Sprintf("http://%s/state.json", address)
req, err := http.NewRequest("GET", uri, nil)
if err != nil {
return nil, err
}
var pid *upid.UPID
err = s.httpDo(ctx, req, func(res *http.Response, err error) error {
if err != nil {
return err
}
defer res.Body.Close()
if res.StatusCode != 200 {
return fmt.Errorf("HTTP request failed with code %d: %v", res.StatusCode, res.Status)
}
blob, err1 := ioutil.ReadAll(res.Body)
if err1 != nil {
return err1
}
log.V(3).Infof("Got mesos state, content length %v", len(blob))
type State struct {
Leader string `json:"leader"` // ex: master(1)@10.22.211.18:5050
}
state := &State{}
err = json.Unmarshal(blob, state)
if err != nil {
return err
}
pid, err = upid.Parse(state.Leader)
return err
})
return pid, err
}
type responseHandler func(*http.Response, error) error
// hacked from https://blog.golang.org/context
func (s *Standalone) httpDo(ctx context.Context, req *http.Request, f responseHandler) error {
// Run the HTTP request in a goroutine and pass the response to f.
ch := make(chan error, 1)
go func() { ch <- f(s.client.Do(req)) }()
select {
case <-ctx.Done():
s.tr.CancelRequest(req)
<-ch // Wait for f to return.
return ctx.Err()
case err := <-ch:
return err
}
}
|