Github user uncleGen commented on a diff in the pull request: https://github.com/apache/spark/pull/16827#discussion_r99739390 --- Diff: core/src/main/scala/org/apache/spark/SparkConf.scala --- @@ -779,6 +781,31 @@ private[spark] object SparkConf extends Logging { } /** + * check if the given config key-value is valid. + */ + private def checkValidSetting(key: String, value: String, conf: SparkConf): Unit = { + key match { + case "spark.master" => + // First, there is no need to set 'spark.master' multi-times with different values. + // Second, It is possible for users to set the different 'spark.master' in code with + // `spark-submit` command, and will confuse users. + // So, we should do once check if the 'spark.master' already exists in settings and if + // the previous value is the same with current value. Throw a IllegalArgumentException when + // previous value is different with current value. + val previousOne = try { + Some(conf.get(key)) + } catch { + case e: NoSuchElementException => + None + } + if (previousOne.isDefined && !previousOne.get.equals(value)) { + throw new IllegalArgumentException(s"'spark.master' should not be set with different " + + s"value, previous value is ${previousOne.get} and current value is $value") + } --- End diff -- here, we choose to throw IllegalArgumentException to fail job. Besides, we can also choose to log a warning in a gentle way.
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