How is it created

While creating SparkSession, SparkContext will also be created in getOrCreate. TODO - Add more info.

Things in SparkContext

As a function entry for Spark programming, SparkContext wraps lots of key components, including:

• LiveListenerBus: Message center for SparkListenerEvent, like StageSubmitted, StageCompleted, etc. Listeners will receive events and update their status, like UI update.
• SparkEnv: provides serializer, MapOutputTracker to track the output from map, ShuffleManager, BroadcastManager, MemoryManager.
• HeartbeatReceiver - TODO
• SchedulerBackend
• TaskScheduler
• DAGScheduler
• ExecutorAllocationManager - TODO