Docker Swarm Code Analysis Note (4)--swarm join

This is a creation in Article, where the information may have evolved or changed.

Docker SwarmThe join definition of the command:

    {        Name:      "join",        ShortName: "j",        Usage:     "Join a docker cluster",        Flags:     []cli.Flag{flJoinAdvertise, flHeartBeat, flTTL, flJoinRandomDelay, flDiscoveryOpt},        Action:    join,    },

flHeartBeatThe default value is 60s , and the flTTL default value is 180s :

flHeartBeat = cli.StringFlag{    Name:  "heartbeat",    Value: "60s",    Usage: "period between each heartbeat",}flTTL = cli.StringFlag{    Name:  "ttl",    Value: "180s",    Usage: "set the expiration of an ephemeral node",}

joinThe core code of the function:

......for {    log.WithFields(log.Fields{"addr": addr, "discovery": dflag}).Infof("Registering on the discovery service every %s...", hb)    if err := d.Register(addr); err != nil {        log.Error(err)    }    time.Sleep(hb)}......

token.RegisterFunction implementation:

func (s *Discovery) Register(addr string) error {    buf := strings.NewReader(addr)    resp, err := http.Post(fmt.Sprintf("%s/%s/%s?ttl=%d", s.url,        "clusters", s.token, uint64(s.ttl.Seconds())), "application/json", buf)    if err != nil {        return err    }    resp.Body.Close()    return nil}

joinThe command is actually every heartbeat time (for example 60s ), to https://discovery.hub.docker.com/v1/clusters/token/ttl=180 ( ttl take the default value), register the current Docker address ( IP:PORT ).