我从Spark（2.0.2）写到Cassandra（3.7）：
someRdd.saveToCassandra("keyspace", "table", writeConf = ifNotExists)
Spark-cassandra-connector（版本2.0.0-M3）一致性配置：
spark.cassandra.output.consistency.level ONE
它在一段时间内工作正常，但现在它开始失败，但有以下异常：
ERROR writer.QueryExecutor: Failed to execute: com.datastax.spark.connector.writer.RichBoundStatement@6ad8868c
com.datastax.driver.core.exceptions.InvalidQueryException: SERIAL is not supported as conditional update commit consistency. Use ANY if you mean "make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads"
at com.datastax.driver.core.Responses$Error.asException(Responses.java:136)
at com.datastax.driver.core.DefaultResultSetFuture.onSet(DefaultResultSetFuture.java:179)
at com.datastax.driver.core.RequestHandler.setFinalResult(RequestHandler.java:173)
at com.datastax.driver.core.RequestHandler.access$2500(RequestHandler.java:43)
at com.datastax.driver.core.RequestHandler$SpeculativeExecution.setFinalResult(RequestHandler.java:788)
at com.datastax.driver.core.RequestHandler$SpeculativeExecution.onSet(RequestHandler.java:607)
at com.datastax.driver.core.Connection$Dispatcher.channelRead0(Connection.java:1012)
at com.datastax.driver.core.Connection$Dispatcher.channelRead0(Connection.java:935)
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:266)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:244)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:846)
at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:831)
at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:346)
at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:254)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:111)
at java.lang.Thread.run(Thread.java:745)
将不胜感激如何解决它。提前谢谢！