Explanation

Executors stop upon application completion by default.

Correct. Executors only persist during the lifetime of an application.

A notable exception to that is when Dynamic Resource Allocation is enabled (which it is not by default). With Dynamic Resource Allocation enabled, executors are terminated when they are idle,

independent of whether the application has been completed or not.

An executor can serve multiple applications.

Wrong. An executor is always specific to the application. It is terminated when the application completes (exception see above).

Each node hosts a single executor.

No. Each node can host one or more executors.

Executors store data in memory only.

No. Executors can store data in memory or on disk.

Executors are launched by the driver.

Incorrect. Executors are launched by the cluster manager on behalf of the driver.

More info: Job Scheduling - Spark 3.1.2 Documentation, How Applications are Executed on a Spark Cluster | Anatomy of a Spark Application | InformIT, and Spark Jargon for Starters. This blog is to

clear some of the… | by Mageswaran D | Medium