[SPARK-11066] Update DAGScheduler's "misbehaved ResultHandler"

Restrict tasks (of job) to only 1 to ensure that the causing Exception asserted for job failure is the deliberately thrown DAGSchedulerSuiteDummyException intended, not an UnsupportedOperationException from any second/subsequent tasks that can propagate from a race condition during code execution.

Author: shellberg <sah@zepler.org>

Closes #9076 from shellberg/shellberg-DAGSchedulerSuite-misbehavedResultHandlerTest-patch-1.

1 files changed, 11 insertions, 2 deletions

diff --git a/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala
index 697c195e4a..5b01ddb298 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala
@@ -1375,18 +1375,27 @@ class DAGSchedulerSuite
     assert(sc.parallelize(1 to 10, 2).count() === 10)
   }
 
+  /**
+   * The job will be failed on first task throwing a DAGSchedulerSuiteDummyException.
+   *  Any subsequent task WILL throw a legitimate java.lang.UnsupportedOperationException.
+   *  If multiple tasks, there exists a race condition between the SparkDriverExecutionExceptions
+   *  and their differing causes as to which will represent result for job...
+   */
   test("misbehaved resultHandler should not crash DAGScheduler and SparkContext") {
     val e = intercept[SparkDriverExecutionException] {
+      // Number of parallelized partitions implies number of tasks of job
       val rdd = sc.parallelize(1 to 10, 2)
       sc.runJob[Int, Int](
         rdd,
         (context: TaskContext, iter: Iterator[Int]) => iter.size,
-        Seq(0, 1),
+        // For a robust test assertion, limit number of job tasks to 1; that is,
+        // if multiple RDD partitions, use id of any one partition, say, first partition id=0
+        Seq(0),
         (part: Int, result: Int) => throw new DAGSchedulerSuiteDummyException)
     }
     assert(e.getCause.isInstanceOf[DAGSchedulerSuiteDummyException])
 
-    // Make sure we can still run commands
+    // Make sure we can still run commands on our SparkContext
     assert(sc.parallelize(1 to 10, 2).count() === 10)
   }