package gopherdiscovery
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import (
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"errors"
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"log"
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"strings"
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"nanomsg.org/go-mangos"
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"nanomsg.org/go-mangos/protocol/respondent"
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"nanomsg.org/go-mangos/protocol/sub"
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"golang.org/x/net/context"
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"nanomsg.org/go-mangos/transport/ipc"
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"nanomsg.org/go-mangos/transport/tcp"
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)
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type DiscoveryClient struct {
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// url for the survey heartbeat
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// for example tcp://127.0.0.1:40007
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urlServer string
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// url for the Pub/Sub
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// in this url you are going to get the changes on the set of nodes
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// for example tcp://127.0.0.1:50007
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urlPubSub string
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// Service that needs to be discovered, for example for a web server could be
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// http://192.168.1.1:8080
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service string
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ctx context.Context
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cancel context.CancelFunc
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sock mangos.Socket
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subscriber *Subscriber
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}
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type Subscriber struct {
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// url for the Pub/Sub
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url string
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ctx context.Context
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sock mangos.Socket
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changes chan []string
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}
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func Client(urlServer string, service string) (*DiscoveryClient, error) {
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return ClientWithSub(urlServer, "", service)
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}
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func ClientWithSub(urlServer string, urlPubSub string, service string) (*DiscoveryClient, error) {
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var sock mangos.Socket
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var err error
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var subscriber *Subscriber
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ctx, cancel := context.WithCancel(context.Background())
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if urlPubSub != "" {
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subCtx, _ := context.WithCancel(ctx)
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subscriber, err = NewSubscriber(subCtx, urlPubSub)
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if err != nil {
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return nil, err
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}
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}
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sock, err = respondent.NewSocket()
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if err != nil {
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return nil, err
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}
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sock.AddTransport(ipc.NewTransport())
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sock.AddTransport(tcp.NewTransport())
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err = sock.Dial(urlServer)
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if err != nil {
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return nil, err
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}
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client := &DiscoveryClient{
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urlServer: urlServer,
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urlPubSub: urlPubSub,
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service: service,
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ctx: ctx,
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cancel: cancel,
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sock: sock,
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subscriber: subscriber,
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}
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go client.run()
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return client, nil
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}
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func (d *DiscoveryClient) Peers() (chan []string, error) {
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if d.subscriber == nil {
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return nil, errors.New("No subscribe url is provided to discover the Peers")
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}
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return d.subscriber.Changes(), nil
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}
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func (d *DiscoveryClient) Cancel() {
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d.cancel()
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}
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func (d *DiscoveryClient) run() {
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var err error
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for {
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_, err = d.sock.Recv()
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if err != nil {
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log.Println("DiscoveryClient: Cannot receive the SURVEY", err.Error())
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} else {
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select {
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case <-d.ctx.Done():
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return
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default:
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err = d.sock.Send([]byte(d.service))
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if err != nil {
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log.Println("DiscoveryClient: Cannot send the SURVEY response", err.Error())
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}
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}
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}
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}
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}
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func NewSubscriber(ctx context.Context, url string) (*Subscriber, error) {
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var sock mangos.Socket
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var err error
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sock, err = sub.NewSocket()
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if err != nil {
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return nil, err
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}
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sock.AddTransport(ipc.NewTransport())
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sock.AddTransport(tcp.NewTransport())
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err = sock.Dial(url)
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if err != nil {
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return nil, err
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}
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// subscribes to everything
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err = sock.SetOption(mangos.OptionSubscribe, []byte(""))
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if err != nil {
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return nil, err
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}
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subscriber := &Subscriber{
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url: url,
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ctx: ctx,
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sock: sock,
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changes: make(chan []string, 8),
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}
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go subscriber.run()
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return subscriber, nil
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}
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func (s *Subscriber) Changes() chan []string {
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return s.changes
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}
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func (s *Subscriber) run() {
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var msg []byte
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var err error
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for {
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select {
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case <-s.ctx.Done():
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close(s.changes)
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return
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default:
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msg, err = s.sock.Recv()
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if err != nil {
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log.Println("DiscoveryClient: Cannot SUBSCRIBE to the changes", err.Error())
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}
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// non-blocking send to the channel, discards changes if the channel is not ready
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select {
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case s.changes <- strings.Split(string(msg), "|"):
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default:
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}
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}
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}
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}
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