presto-main/src/main/java/io/prestosql/operator/exchange/LocalExchangeMemoryManager.java/LocalExchangeMemoryManager/getNotFullFuture
class LocalExchangeMemoryManager:    public synchronized ListenableFuture<?> getNotFullFuture()
    {
        // if we are full and the current not full future is already complete, create a new one
        if (bufferedBytes.get() > maxBufferedBytes && notFullFuture.isDone()) {
            notFullFuture = SettableFuture.create();
        }
        return notFullFuture;
    }