Colin Woodbury created SPARK-21022:
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Summary: foreach swallows exceptions
Key: SPARK-21022
URL: https://issues.apache.org/jira/browse/SPARK-21022
Project: Spark
Issue Type: Bug
Components: Spark Core
Affects Versions: 2.1.1
Reporter: Colin Woodbury
Priority: Minor
A `RDD.foreach` or `RDD.foreachPartition` call will swallow Exceptions thrown
inside its closure, but not if the exception was thrown earlier in the call
chain. An example:
{code:none}
package examples
import org.apache.spark._
object Shpark {
def main(args: Array[String]) {
implicit val sc: SparkContext = new SparkContext(
new SparkConf().setMaster("local[*]").setAppName("blahfoobar")
)
/* DOESN'T THROW
sc.parallelize(0 until 10000000)
.foreachPartition { _.map { i =>
println("BEFORE THROW")
throw new Exception("Testing exception handling")
println(i)
}}
*/
/* DOESN'T THROW, nor does anything print.
* Commenting out the exception runs the prints.
* (i.e. `foreach` is sufficient to "run" an RDD)
sc.parallelize(0 until 100000)
.foreach({ i =>
println("BEFORE THROW")
throw new Exception("Testing exception handling")
println(i)
})
*/
/* Throws! */
sc.parallelize(0 until 100000)
.map({ i =>
println("BEFORE THROW")
throw new Exception("Testing exception handling")
i
})
.foreach(i => println(i))
println("JOB DONE!")
System.in.read
sc.stop()
}
}
{code}
When exceptions are swallowed, the jobs don't seem to fail, and the driver
exits normally. When one _is_ thrown, as in the last example, the exception
successfully rises up to the driver and can be caught with `catch`.
The expected behaviour is for exceptions in `foreach` to throw and crash the
driver, as they would with `map`.
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