Kundan Kumarr explains how the two execution modes differ with Apache Spark:
Whenever we submit a Spark application to the cluster, the Driver or the Spark App Master should get started. And the Driver will be starting N number of workers. Spark driver will be managing spark context object to share the data and coordinates with the workers and cluster manager across the cluster. Cluster Manager can be Spark Standalone or Hadoop YARN or Mesos. Workers will be assigned a task and it will consolidate and collect the result back to the driver. A spark application gets executed within the cluster in two different modes – one is cluster mode and the second is client mode.
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