A Discretized Stream (DStream), the basic abstraction in Spark Streaming, is a continuous sequence of RDDsrepresenting a continuous stream of data. DStreams can either be created from live data (such as, data from HDFS, Kafka or Flume) or it can be generated by transformationexisting DStreams using operations such as map, window and reduceByKeyAndWindow.
Internally, there are few basic properties by which DStreams is characterized:
1. DStream depends on the list of other DStreams.
2. A time interval at which the DStream generates an RDD
3. A function that is used to generate an RDD after each time interval