Scala and Spark for Big Data Analytics

Fault tolerance semantics

Delivering end-to-end exactly once semantics was one of the key goals behind the design of Structured streaming, which implements the Structured streaming sources, the output sinks, and the execution engine to reliably track the exact progress of the processing so that it can handle any kind of failure by restarting and/or reprocessing. Every streaming source is assumed to have offsets (similar to Kafka offsets) to track the read position in the stream. The engine uses checkpointing and write ahead logs to record the offset range of the data being processed in each trigger. The streaming sinks are designed to be idempotent for handling reprocessing. Together, using replayable sources and idempotent sinks, Structured ...