func (p *MQTTPublisher) discoverBrokerEndpoint() error {
endpoint, err := catalog.DiscoverCatalogEndpoint(service.DNSSDServiceType)
if err != nil {
return err
}
rcc := service.NewRemoteCatalogClient(endpoint)
res, _, err := rcc.FindServices("meta.serviceType", "equals", DNSSDServiceTypeMQTT, 1, 50)
if err != nil {
return err
}
supportsPub := false
for _, s := range res {
for _, proto := range s.Protocols {
for _, m := range proto.Methods {
if m == "PUB" {
supportsPub = true
break
}
}
if !supportsPub {
continue
}
logger.Println(proto.Endpoint["url"])
if ProtocolType(proto.Type) == ProtocolTypeMQTT {
p.config.URL = proto.Endpoint["url"].(string)
break
}
}
}
err = p.config.Validate()
if err != nil {
return err
}
return nil
}
// Registers service in the remote catalog
// endpoint: catalog endpoint. If empty - will be discovered using DNS-SD
// s: service registration
// sigCh: channel for shutdown signalisation from upstream
func RegisterServiceWithKeepalive(endpoint string, discover bool, s Service, sigCh <-chan bool, wg *sync.WaitGroup) {
defer wg.Done()
var err error
if discover {
endpoint, err = utils.DiscoverCatalogEndpoint(DNSSDServiceType)
if err != nil {
logger.Printf("RegisterServiceWithKeepalive() ERROR: Failed to discover the endpoint: %v", err.Error())
return
}
}
// Configure client
client := NewRemoteCatalogClient(endpoint)
// Will not keepalive registration with a negative TTL
if s.Ttl <= 0 {
logger.Println("RegisterServiceWithKeepalive() WARNING: Registration has ttl <= 0. Will not start the keepalive routine")
RegisterService(client, &s)
return
}
logger.Printf("RegisterServiceWithKeepalive() Will register and update registration periodically: %v/%v", endpoint, s.Id)
// Configure & start the keepalive routine
ksigCh := make(chan bool)
kerrCh := make(chan error)
go keepAlive(client, &s, ksigCh, kerrCh)
for {
select {
// catch an error from the keepAlive routine
case e := <-kerrCh:
logger.Println("RegisterServiceWithKeepalive() ERROR:", e)
// Re-discover the endpoint if needed and start over
if discover {
endpoint, err = utils.DiscoverCatalogEndpoint(DNSSDServiceType)
if err != nil {
logger.Println("RegisterServiceWithKeepalive() ERROR:", err.Error())
return
}
}
logger.Println("RegisterServiceWithKeepalive() Will use the new endpoint: ", endpoint)
client := NewRemoteCatalogClient(endpoint)
go keepAlive(client, &s, ksigCh, kerrCh)
// catch a shutdown signal from the upstream
case <-sigCh:
logger.Printf("RegisterServiceWithKeepalive() Removing the registration %v/%v...", endpoint, s.Id)
// signal shutdown to the keepAlive routine & close channels
select {
case ksigCh <- true:
// delete entry in the remote catalog
client.Delete(s.Id)
case <-time.After(1 * time.Second):
logger.Printf("RegisterDeviceWithKeepalive(): timeout removing registration %v/%v: catalog unreachable", endpoint, s.Id)
}
close(ksigCh)
close(kerrCh)
return
}
}
}