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moby--moby/daemon/discovery.go

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package daemon
import (
"errors"
"fmt"
"reflect"
"strconv"
"time"
log "github.com/Sirupsen/logrus"
"github.com/docker/docker/pkg/discovery"
// Register the libkv backends for discovery.
_ "github.com/docker/docker/pkg/discovery/kv"
)
const (
// defaultDiscoveryHeartbeat is the default value for discovery heartbeat interval.
defaultDiscoveryHeartbeat = 20 * time.Second
// defaultDiscoveryTTLFactor is the default TTL factor for discovery
defaultDiscoveryTTLFactor = 3
)
var errDiscoveryDisabled = errors.New("discovery is disabled")
type discoveryReloader interface {
discovery.Watcher
Stop()
Reload(backend, address string, clusterOpts map[string]string) error
}
type daemonDiscoveryReloader struct {
backend discovery.Backend
ticker *time.Ticker
term chan bool
}
func (d *daemonDiscoveryReloader) Watch(stopCh <-chan struct{}) (<-chan discovery.Entries, <-chan error) {
return d.backend.Watch(stopCh)
}
func discoveryOpts(clusterOpts map[string]string) (time.Duration, time.Duration, error) {
var (
heartbeat = defaultDiscoveryHeartbeat
ttl = defaultDiscoveryTTLFactor * defaultDiscoveryHeartbeat
)
if hb, ok := clusterOpts["discovery.heartbeat"]; ok {
h, err := strconv.Atoi(hb)
if err != nil {
return time.Duration(0), time.Duration(0), err
}
heartbeat = time.Duration(h) * time.Second
ttl = defaultDiscoveryTTLFactor * heartbeat
}
if tstr, ok := clusterOpts["discovery.ttl"]; ok {
t, err := strconv.Atoi(tstr)
if err != nil {
return time.Duration(0), time.Duration(0), err
}
ttl = time.Duration(t) * time.Second
if _, ok := clusterOpts["discovery.heartbeat"]; !ok {
h := int(t / defaultDiscoveryTTLFactor)
heartbeat = time.Duration(h) * time.Second
}
if ttl <= heartbeat {
return time.Duration(0), time.Duration(0),
fmt.Errorf("discovery.ttl timer must be greater than discovery.heartbeat")
}
}
return heartbeat, ttl, nil
}
// initDiscovery initialized the nodes discovery subsystem by connecting to the specified backend
// and start a registration loop to advertise the current node under the specified address.
func initDiscovery(backendAddress, advertiseAddress string, clusterOpts map[string]string) (discoveryReloader, error) {
heartbeat, backend, err := parseDiscoveryOptions(backendAddress, clusterOpts)
if err != nil {
return nil, err
}
reloader := &daemonDiscoveryReloader{
backend: backend,
ticker: time.NewTicker(heartbeat),
term: make(chan bool),
}
// We call Register() on the discovery backend in a loop for the whole lifetime of the daemon,
// but we never actually Watch() for nodes appearing and disappearing for the moment.
reloader.advertise(advertiseAddress)
return reloader, nil
}
func (d *daemonDiscoveryReloader) advertise(address string) {
d.registerAddr(address)
go d.advertiseHeartbeat(address)
}
func (d *daemonDiscoveryReloader) registerAddr(addr string) {
if err := d.backend.Register(addr); err != nil {
log.Warnf("Registering as %q in discovery failed: %v", addr, err)
}
}
// advertiseHeartbeat registers the current node against the discovery backend using the specified
// address. The function never returns, as registration against the backend comes with a TTL and
// requires regular heartbeats.
func (d *daemonDiscoveryReloader) advertiseHeartbeat(address string) {
for {
select {
case <-d.ticker.C:
d.registerAddr(address)
case <-d.term:
return
}
}
}
// Reload makes the watcher to stop advertising and reconfigures it to advertise in a new address.
func (d *daemonDiscoveryReloader) Reload(backendAddress, advertiseAddress string, clusterOpts map[string]string) error {
d.Stop()
heartbeat, backend, err := parseDiscoveryOptions(backendAddress, clusterOpts)
if err != nil {
return err
}
d.backend = backend
d.ticker = time.NewTicker(heartbeat)
d.advertise(advertiseAddress)
return nil
}
// Stop terminates the discovery advertising.
func (d *daemonDiscoveryReloader) Stop() {
d.ticker.Stop()
d.term <- true
}
func parseDiscoveryOptions(backendAddress string, clusterOpts map[string]string) (time.Duration, discovery.Backend, error) {
heartbeat, ttl, err := discoveryOpts(clusterOpts)
if err != nil {
return 0, nil, err
}
backend, err := discovery.New(backendAddress, heartbeat, ttl, clusterOpts)
if err != nil {
return 0, nil, err
}
return heartbeat, backend, nil
}
// modifiedDiscoverySettings returns whether the discovery configuration has been modified or not.
func modifiedDiscoverySettings(config *Config, backendType, advertise string, clusterOpts map[string]string) bool {
if config.ClusterStore != backendType || config.ClusterAdvertise != advertise {
return true
}
if (config.ClusterOpts == nil && clusterOpts == nil) ||
(config.ClusterOpts == nil && len(clusterOpts) == 0) ||
(len(config.ClusterOpts) == 0 && clusterOpts == nil) {
return false
}
return !reflect.DeepEqual(config.ClusterOpts, clusterOpts)
}