package watch import ( "fmt" "log" "os" "reflect" "time" consulapi "github.com/hashicorp/consul/api" ) const ( // retryInterval is the base retry value retryInterval = 5 * time.Second // maximum back off time, this is to prevent // exponential runaway maxBackoffTime = 180 * time.Second ) // Run is used to run a watch plan func (p *Plan) Run(address string) error { // Setup the client p.address = address conf := consulapi.DefaultConfig() conf.Address = address conf.Datacenter = p.Datacenter conf.Token = p.Token client, err := consulapi.NewClient(conf) if err != nil { return fmt.Errorf("Failed to connect to agent: %v", err) } p.client = client // Create the logger output := p.LogOutput if output == nil { output = os.Stderr } logger := log.New(output, "", log.LstdFlags) // Loop until we are canceled failures := 0 OUTER: for !p.shouldStop() { // Invoke the handler index, result, err := p.Watcher(p) // Check if we should terminate since the function // could have blocked for a while if p.shouldStop() { break } // Handle an error in the watch function if err != nil { // Perform an exponential backoff failures++ retry := retryInterval * time.Duration(failures*failures) if retry > maxBackoffTime { retry = maxBackoffTime } logger.Printf("consul.watch: Watch (type: %s) errored: %v, retry in %v", p.Type, err, retry) select { case <-time.After(retry): continue OUTER case <-p.stopCh: return nil } } // Clear the failures failures = 0 // If the index is unchanged do nothing if index == p.lastIndex { continue } // Update the index, look for change oldIndex := p.lastIndex p.lastIndex = index if oldIndex != 0 && reflect.DeepEqual(p.lastResult, result) { continue } // Handle the updated result p.lastResult = result if p.Handler != nil { p.Handler(index, result) } } return nil } // Stop is used to stop running the watch plan func (p *Plan) Stop() { p.stopLock.Lock() defer p.stopLock.Unlock() if p.stop { return } p.stop = true close(p.stopCh) } func (p *Plan) shouldStop() bool { select { case <-p.stopCh: return true default: return false } }