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package client
import (
// Waiter is informed of current height, decided whether to quit early
type Waiter func(delta int64) (abort error)
// DefaultWaitStrategy is the standard backoff algorithm,
// but you can plug in another one
func DefaultWaitStrategy(delta int64) (abort error) {
if delta > 10 {
return errors.Errorf("waiting for %d blocks... aborting", delta)
} else if delta > 0 {
// estimate of wait time....
// wait half a second for the next block (in progress)
// plus one second for every full block
delay := time.Duration(delta-1)*time.Second + 500*time.Millisecond
return nil
// Wait for height will poll status at reasonable intervals until
// the block at the given height is available.
// If waiter is nil, we use DefaultWaitStrategy, but you can also
// provide your own implementation
func WaitForHeight(c StatusClient, h int64, waiter Waiter) error {
if waiter == nil {
waiter = DefaultWaitStrategy
delta := int64(1)
for delta > 0 {
s, err := c.Status()
if err != nil {
return err
delta = h - s.SyncInfo.LatestBlockHeight
// wait for the time, or abort early
if err := waiter(delta); err != nil {
return err
return nil
// WaitForOneEvent subscribes to a websocket event for the given
// event time and returns upon receiving it one time, or
// when the timeout duration has expired.
// This handles subscribing and unsubscribing under the hood
func WaitForOneEvent(c EventsClient, evtTyp string, timeout time.Duration) (types.TMEventData, error) {
const subscriber = "helpers"
ctx, cancel := context.WithTimeout(context.Background(), timeout)
defer cancel()
// register for the next event of this type
eventCh, err := c.Subscribe(ctx, subscriber, types.QueryForEvent(evtTyp).String())
if err != nil {
return nil, errors.Wrap(err, "failed to subscribe")
// make sure to unregister after the test is over
defer c.UnsubscribeAll(ctx, subscriber)
select {
case event := <-eventCh:
return event.Data.(types.TMEventData), nil
case <-ctx.Done():
return nil, errors.New("timed out waiting for event")
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