package metadata import ( "encoding/json" "fmt" "time" "github.com/Sirupsen/logrus" ) func (m *client) OnChangeWithError(intervalSeconds int, do func(string)) error { return m.onChangeFromVersionWithError("init", intervalSeconds, do) } func (m *client) onChangeFromVersionWithError(version string, intervalSeconds int, do func(string)) error { for { newVersion, err := m.waitVersion(intervalSeconds, version) if err != nil { return err } else if version == newVersion { logrus.Debug("No changes in metadata version") } else { logrus.Debugf("Metadata Version has been changed. Old version: %s. New version: %s.", version, newVersion) version = newVersion do(newVersion) } } return nil } func (m *client) OnChange(intervalSeconds int, do func(string)) { version := "init" updateVersionAndDo := func(v string) { version = v do(version) } interval := time.Duration(intervalSeconds) for { if err := m.onChangeFromVersionWithError(version, intervalSeconds, updateVersionAndDo); err != nil { logrus.Errorf("Error reading metadata version: %v", err) } time.Sleep(interval * time.Second) } } type timeout interface { Timeout() bool } func (m *client) waitVersion(maxWait int, version string) (string, error) { for { resp, err := m.SendRequest(fmt.Sprintf("/version?wait=true&value=%s&maxWait=%d", version, maxWait)) if err != nil { t, ok := err.(timeout) if ok && t.Timeout() { continue } return "", err } err = json.Unmarshal(resp, &version) return version, err } }