tendermint/rpc/client/helpers.go

package client

import (
	"time"

	"github.com/pkg/errors"
)

// Waiter is informed of current height, decided whether to quit early
type Waiter func(delta int) (abort error)

// DefaultWaitStrategy is the standard backoff algorithm,
// but you can plug in another one
func DefaultWaitStrategy(delta int) (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
		time.Sleep(delay)
	}
	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 int, waiter Waiter) error {
	if waiter == nil {
		waiter = DefaultWaitStrategy
	}
	delta := 1
	for delta > 0 {
		s, err := c.Status()
		if err != nil {
			return err
		}
		delta = h - s.LatestBlockHeight
		// wait for the time, or abort early
		if err := waiter(delta); err != nil {
			return err
		}
	}
	return nil
}