Explain the concept of Spark’s lineage graph in fault tolerance.

Spark’s lineage graph is a directed acyclic graph (DAG) that represents the dependencies between RDDs and the transformations applied to them. In fault tolerance, the lineage graph plays a crucial role in recovery and recomputation. When a partition of an RDD is lost due to a node failure, Spark can use the lineage graph to identify the transformations that led to the lost partition and recompute it from the available data. By tracing back the lineage, Spark ensures fault tolerance and recovers lost data without needing to rerun the entire computation.