while (now < barrier && result == null) {
            try {
                result = operation.call();
                if (result == null) {
                    LOGGER.trace("Retry attempt {}: no result", attempt);
                    Thread.sleep(sleepMillis);
                }
            } catch (InterruptedException e) {
                throw e;
            } catch (Exception e) {
                LOGGER.trace("Retry attempt {}: operation failure", attempt, e);
                if (e instanceof DoNotRetry) {
                    if (e instanceof RuntimeException) {
                        throw (RuntimeException) e;
                    } else {
                        throw new IllegalStateException(e);
                    }
                }
                if (retryPredicate != null && !retryPredicate.test(e)) {
                    throw new IllegalStateException(e);
                }
            }