ConditionalExecution<?> operation;
                while ((operation = waitForNextOperation()) != null) {
                    runBatch(operation);
                }
            } finally {
                shutDown();
            }
        }

        private ConditionalExecution<?> waitForNextOperation() {
            lock.lock();
            try {

                T operation;
                while ((operation = waitForNextOperation()) != null) {
                    runBatch(operation);
                }
            } catch (Throwable t) {
                addFailure(t);
            } finally {
                shutDown();
            }
        }

        @Nullable
        private T waitForNextOperation() {
            lock.lock();
            try {