[SPARK-21563][CORE] Fix race condition when serializing TaskDescriptions and adding jars

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -1490,6 +1490,8 @@ class SparkContext(config: SparkConf) extends Logging {
   /**
    * Add a file to be downloaded with this Spark job on every node.
    *
+   * If a file is added during execution, it will not be available until the next TaskSet starts.
+   *
    * @param path can be either a local file, a file in HDFS (or other Hadoop-supported
    * filesystems), or an HTTP, HTTPS or FTP URI. To access the file in Spark jobs,
    * use `SparkFiles.get(fileName)` to find its download location.
@@ -1506,6 +1508,8 @@ class SparkContext(config: SparkConf) extends Logging {
   /**
    * Add a file to be downloaded with this Spark job on every node.
    *
+   * If a file is added during execution, it will not be available until the next TaskSet starts.
+   *
    * @param path can be either a local file, a file in HDFS (or other Hadoop-supported
    * filesystems), or an HTTP, HTTPS or FTP URI. To access the file in Spark jobs,
    * use `SparkFiles.get(fileName)` to find its download location.
@@ -1792,6 +1796,9 @@ class SparkContext(config: SparkConf) extends Logging {
 
   /**
    * Adds a JAR dependency for all tasks to be executed on this `SparkContext` in the future.
+   *
+   * If a jar is added during execution, it will not be available until the next TaskSet starts.
+   *
    * @param path can be either a local file, a file in HDFS (or other Hadoop-supported filesystems),
    * an HTTP, HTTPS or FTP URI, or local:/path for a file on every worker node.
    */

core/src/main/scala/org/apache/spark/scheduler/TaskSetManager.scala

@@ -56,6 +56,10 @@ private[spark] class TaskSetManager(
 
   private val conf = sched.sc.conf
 
+  // SPARK-21563 make a copy of the jars/files so they are consistent across the TaskSet
+  private val addedJars = HashMap[String, Long](sched.sc.addedJars.toSeq: _*)
+  private val addedFiles = HashMap[String, Long](sched.sc.addedFiles.toSeq: _*)
+
   // Quantile of tasks at which to start speculation
   val SPECULATION_QUANTILE = conf.getDouble("spark.speculation.quantile", 0.75)
   val SPECULATION_MULTIPLIER = conf.getDouble("spark.speculation.multiplier", 1.5)
@@ -502,8 +506,8 @@ private[spark] class TaskSetManager(
           execId,
           taskName,
           index,
-          sched.sc.addedFiles,
-          sched.sc.addedJars,
+          addedFiles,
+          addedJars,
           task.localProperties,
           serializedTask)
       }

core/src/test/scala/org/apache/spark/scheduler/TaskSetManagerSuite.scala

@@ -32,7 +32,7 @@ import org.apache.spark.internal.config
 import org.apache.spark.internal.Logging
 import org.apache.spark.serializer.SerializerInstance
 import org.apache.spark.storage.BlockManagerId
-import org.apache.spark.util.{AccumulatorV2, ManualClock}
+import org.apache.spark.util.{AccumulatorV2, ManualClock, Utils}
 
 class FakeDAGScheduler(sc: SparkContext, taskScheduler: FakeTaskScheduler)
   extends DAGScheduler(sc) {
@@ -1214,6 +1214,38 @@ class TaskSetManagerSuite extends SparkFunSuite with LocalSparkContext with Logg
     verify(taskSetManagerSpy, times(1)).addPendingTask(anyInt())
   }
 
+  test("SPARK-21563 context's added jars shouldn't change mid-TaskSet") {
+    sc = new SparkContext("local", "test")
+    val addedJarsPreTaskSet = Map[String, Long](sc.addedJars.toSeq: _*)
+    assert(addedJarsPreTaskSet.size === 0)
+
+    sched = new FakeTaskScheduler(sc, ("exec1", "host1"))
+    val taskSet1 = FakeTask.createTaskSet(3)
+    val manager1 = new TaskSetManager(sched, taskSet1, MAX_TASK_FAILURES, clock = new ManualClock)
+
+    // all tasks from the first taskset have the same jars
+    val taskOption1 = manager1.resourceOffer("exec1", "host1", NO_PREF)
+    assert(taskOption1.get.addedJars === addedJarsPreTaskSet)
+    val taskOption2 = manager1.resourceOffer("exec1", "host1", NO_PREF)
+    assert(taskOption2.get.addedJars === addedJarsPreTaskSet)
+
+    // even with a jar added mid-TaskSet
+    val jarPath = Thread.currentThread().getContextClassLoader.getResource("TestUDTF.jar")
+    sc.addJar(jarPath.toString)
+    val addedJarsMidTaskSet = Map[String, Long](sc.addedJars.toSeq: _*)
+    assert(addedJarsPreTaskSet !== addedJarsMidTaskSet)
+    val taskOption3 = manager1.resourceOffer("exec1", "host1", NO_PREF)
+    // which should have the old version of the jars list
+    assert(taskOption3.get.addedJars === addedJarsPreTaskSet)
+
+    // and then the jar does appear in the next TaskSet
+    val taskSet2 = FakeTask.createTaskSet(1)
+    val manager2 = new TaskSetManager(sched, taskSet2, MAX_TASK_FAILURES, clock = new ManualClock)
+
+    val taskOption4 = manager2.resourceOffer("exec1", "host1", NO_PREF)
+    assert(taskOption4.get.addedJars === addedJarsMidTaskSet)
+  }
+
   private def createTaskResult(
       id: Int,
       accumUpdates: Seq[AccumulatorV2[_, _]] = Seq.empty): DirectTaskResult[Int] = {