At its core, queueStream() is just a queue of RDDs that we have after the Spark streaming (pre-2.0) turns into RDD:
- Documentation for structured streaming (Spark 2.0+): https://spark.apache.org/docs/2.1.0/structured-streaming-programming-guide.html
- Documentation for streaming (pre-Spark 2.0): https://spark.apache.org/docs/latest/streaming-programming-guide.html