presto-main/src/main/java/io/prestosql/server/remotetask/HttpRemoteTask.java/HttpRemoteTask/updateSplitQueueSpace
class HttpRemoteTask:    private synchronized void updateSplitQueueSpace()
    {
        if (!whenSplitQueueHasSpaceThreshold.isPresent()) {
            return;
        }
        splitQueueHasSpace = getQueuedPartitionedSplitCount() < whenSplitQueueHasSpaceThreshold.getAsInt();
        if (splitQueueHasSpace) {
            whenSplitQueueHasSpace.complete(null, executor);
        }
    }