lib/Dropbox/RequestUtil.php
static function runWithRetry($maxRetries, $action)
    {
        Checker::argNat("maxRetries", $maxRetries);

        $retryDelay = 1;
        $numRetries = 0;
        while (true) {
            try {
                return $action();
            }
            // These exception types are the ones we think are possibly transient errors.
            catch (Exception_NetworkIO $ex) {
                $savedEx = $ex;
            }
            catch (Exception_ServerError $ex) {
                $savedEx = $ex;
            }
            catch (Exception_RetryLater $ex) {
                $savedEx = $ex;
            }

            // We maxed out our retries.  Propagate the last exception we got.
            if ($numRetries >= $maxRetries) throw $savedEx;

            $numRetries++;
            sleep($retryDelay);
            $retryDelay *= 2;  // Exponential back-off.
        }
        throw new \RuntimeException("unreachable");
    }
static function runWithRetry($maxRetries, $action)
    {
        Checker::argNat("maxRetries", $maxRetries);

        $retryDelay = 1;
        $numRetries = 0;
        while (true) {
            try {
                return $action();
            }
            // These exception types are the ones we think are possibly transient errors.
            catch (Exception_NetworkIO $ex) {
                $savedEx = $ex;
            }
            catch (Exception_ServerError $ex) {
                $savedEx = $ex;
            }
            catch (Exception_RetryLater $ex) {
                $savedEx = $ex;
            }

            // We maxed out our retries.  Propagate the last exception we got.
            if ($numRetries >= $maxRetries) throw $savedEx;

            $numRetries++;
            sleep($retryDelay);
            $retryDelay *= 2;  // Exponential back-off.
        }
        throw new \RuntimeException("unreachable");
    }
@param int $maxRetries
The number of times to retry it the action if it fails with one of the transient
API errors.  A value of 1 means we'll try the action once and if it fails, we
will retry once.

@param callable $action
The the action you want to retry.

@return mixed
Whatever is returned by the $action callable.