[SPARK-9824] [CORE] Fix the issue that InternalAccumulator leaks WeakReference

`InternalAccumulator.create` doesn't call `registerAccumulatorForCleanup` to register itself with ContextCleaner, so `WeakReference`s for these accumulators in `Accumulators.originals` won't be removed.

This PR added `registerAccumulatorForCleanup` for internal accumulators to avoid the memory leak.

Author: zsxwing <zsxwing@gmail.com>

Closes #8108 from zsxwing/internal-accumulators-leak.

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

@@ -382,14 +382,18 @@ private[spark] object InternalAccumulator {
    * add to the same set of accumulators. We do this to report the distribution of accumulator
    * values across all tasks within each stage.
    */
-  def create(): Seq[Accumulator[Long]] = {
-    Seq(
-      // Execution memory refers to the memory used by internal data structures created
-      // during shuffles, aggregations and joins. The value of this accumulator should be
-      // approximately the sum of the peak sizes across all such data structures created
-      // in this task. For SQL jobs, this only tracks all unsafe operators and ExternalSort.
-      new Accumulator(
-        0L, AccumulatorParam.LongAccumulatorParam, Some(PEAK_EXECUTION_MEMORY), internal = true)
-    ) ++ maybeTestAccumulator.toSeq
+  def create(sc: SparkContext): Seq[Accumulator[Long]] = {
+    val internalAccumulators = Seq(
+        // Execution memory refers to the memory used by internal data structures created
+        // during shuffles, aggregations and joins. The value of this accumulator should be
+        // approximately the sum of the peak sizes across all such data structures created
+        // in this task. For SQL jobs, this only tracks all unsafe operators and ExternalSort.
+        new Accumulator(
+          0L, AccumulatorParam.LongAccumulatorParam, Some(PEAK_EXECUTION_MEMORY), internal = true)
+      ) ++ maybeTestAccumulator.toSeq
+    internalAccumulators.foreach { accumulator =>
+      sc.cleaner.foreach(_.registerAccumulatorForCleanup(accumulator))
+    }
+    internalAccumulators
   }
 }

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

@@ -81,7 +81,7 @@ private[spark] abstract class Stage(
    * accumulators here again will override partial values from the finished tasks.
    */
   def resetInternalAccumulators(): Unit = {
-    _internalAccumulators = InternalAccumulator.create()
+    _internalAccumulators = InternalAccumulator.create(rdd.sparkContext)
   }
 
   /**

core/src/test/scala/org/apache/spark/AccumulatorSuite.scala

@@ -160,7 +160,8 @@ class AccumulatorSuite extends SparkFunSuite with Matchers with LocalSparkContex
   }
 
   test("internal accumulators in TaskContext") {
-    val accums = InternalAccumulator.create()
+    sc = new SparkContext("local", "test")
+    val accums = InternalAccumulator.create(sc)
     val taskContext = new TaskContextImpl(0, 0, 0, 0, null, null, accums)
     val internalMetricsToAccums = taskContext.internalMetricsToAccumulators
     val collectedInternalAccums = taskContext.collectInternalAccumulators()