title: Reset the value to the configuration "spark.executor.instances"
body: <p>We have a YARN cluster and we use Spark 2.3.2 version. I wanted to use Spark's dynamic resource allocation while submitting the spark applications but in the spark-defaults.conf file the value of the property <code>spark.executor.instances</code> is set to 16. From my understanding, I should not set <code>spark.executor.instances</code> if we wanted to use dynamic resource allocation. Otherwise, even if the dynamic resource allocation is enabled, it is getting overridden by the property <code>spark.executor.instances</code>.</p>
  <p>I can't edit the spark-defaults.conf, so I wanted to reset the value assigned to <code>spark.executor.instances</code> through the <code>--conf</code> argument to spark-submit. I tried setting it to blank or 0 but in both of the cases, the job failed with <code>spark.executor.instances</code> should be a positive number.</p>
  <p>Given this situation, how can I successfully use Spark's dynamic resource allocation?.</p>
  <p>One more observation is, I do not see that the dynamic resource allocation enabled in the spark-defaults.conf file. Isn't it a default property since Spark 2.0?.</p>