向CassandraConnector添加自定义编解码器

Question

是否有方法在CassandraConnector实例化时注册自定义编解码器？

我现在每次打电话给cassandraConnector.withSessionDo时都会注册我的编解码器

val cassandraConnector = CassandraConnector(ssc.sparkContext.getConf)
...
...
.mapPartitions(partition => {
  cassandraConnector.withSessionDo(session => {
    // register custom codecs once for each partition so it isn't loaded as often for each data point
    if (partition.nonEmpty) {
      session.getCluster.getConfiguration.getCodecRegistry
        .register(new TimestampLongCodec)
        .register(new SummaryStatsBlobCodec)
        .register(new JavaHistogramBlobCodec)
    }

这样做有点像反模式。它还会阻塞我们的日志，因为我们有一个火花流服务，每30秒运行一次，它用以下内容填充日志：

16/11/01 14:14:44 WARN CodecRegistry: Ignoring codec SummaryStatsBlobCodec [blob <-> SummaryStats] because it collides with previously registered codec SummaryStatsBlobCodec [blob <-> SummaryStats]
16/11/01 14:14:44 WARN CodecRegistry: Ignoring codec JavaHistogramBlobCodec [blob <-> Histogram] because it collides with previously registered codec JavaHistogramBlobCodec [blob <-> Histogram]
16/11/01 14:14:44 WARN CodecRegistry: Ignoring codec TimestampLongCodec [timestamp <-> java.lang.Long] because it collides with previously registered codec TimestampLongCodec [timestamp <-> java.lang.Long]

编辑：

我试过像这样立即注册：

val cassandraConnector = CassandraConnector(ssc.sparkContext.getConf)
cassandraConnector.withClusterDo(cluster => {
  cluster.getConfiguration.getCodecRegistry
    .register(new TimestampLongCodec)
    .register(new SummaryStatsBlobCodec)
    .register(new JavaHistogramBlobCodec)
})

这个^在本地工作，但是当部署到我们的mesos集群时，它找不到编解码器。我假设这是因为它只在驱动程序中本地注册那些，并且从不将它们添加到executors版本中。

Answer 1

更好的方法是覆盖cassandra连接工厂，如下所示

import com.datastax.driver.core.Cluster
import com.datastax.spark.connector.cql.{CassandraConnectionFactory, CassandraConnectorConf, DefaultConnectionFactory}
object MyConnectionFactory extends CassandraConnectionFactory {
  override def createCluster(conf: CassandraConnectorConf): Cluster = {
    val cluster = DefaultConnectionFactory.createCluster(conf)
    cluster.getConfiguration.getCodecRegistry
      .register(new TimestampLongCodec)
      .register(new SummaryStatsBlobCodec)
      .register(new JavaHistogramBlobCodec)
    cluster
  }
}

并将spark.cassandra.connection.factory参数设置为指向类