[SPARK-12819] Deprecate TaskContext.isRunningLocally()

We've already removed local execution but didn't deprecate `TaskContext.isRunningLocally()`; we should deprecate it for 2.0.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #10751 from JoshRosen/remove-local-exec-from-taskcontext.

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

@@ -68,11 +68,6 @@ private[spark] class CacheManager(blockManager: BlockManager) extends Logging {
           logInfo(s"Partition $key not found, computing it")
           val computedValues = rdd.computeOrReadCheckpoint(partition, context)
 
-          // If the task is running locally, do not persist the result
-          if (context.isRunningLocally) {
-            return computedValues
-          }
-
           // Otherwise, cache the values and keep track of any updates in block statuses
           val updatedBlocks = new ArrayBuffer[(BlockId, BlockStatus)]
           val cachedValues = putInBlockManager(key, computedValues, storageLevel, updatedBlocks)

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

@@ -97,8 +97,9 @@ abstract class TaskContext extends Serializable {
 
   /**
    * Returns true if the task is running locally in the driver program.
-   * @return
+   * @return false
    */
+  @deprecated("Local execution was removed, so this always returns false", "2.0.0")
   def isRunningLocally(): Boolean
 
   /**

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

@@ -33,7 +33,6 @@ private[spark] class TaskContextImpl(
     override val taskMemoryManager: TaskMemoryManager,
     @transient private val metricsSystem: MetricsSystem,
     internalAccumulators: Seq[Accumulator[Long]],
-    val runningLocally: Boolean = false,
     val taskMetrics: TaskMetrics = TaskMetrics.empty)
   extends TaskContext
   with Logging {
@@ -85,7 +84,7 @@ private[spark] class TaskContextImpl(
 
   override def isCompleted(): Boolean = completed
 
-  override def isRunningLocally(): Boolean = runningLocally
+  override def isRunningLocally(): Boolean = false
 
   override def isInterrupted(): Boolean = interrupted
 

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

@@ -74,8 +74,7 @@ private[spark] abstract class Task[T](
       attemptNumber,
       taskMemoryManager,
       metricsSystem,
-      internalAccumulators,
-      runningLocally = false)
+      internalAccumulators)
     TaskContext.setTaskContext(context)
     context.taskMetrics.setHostname(Utils.localHostName())
     context.taskMetrics.setAccumulatorsUpdater(context.collectInternalAccumulators)

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

@@ -82,15 +82,6 @@ class CacheManagerSuite extends SparkFunSuite with LocalSparkContext with Before
     assert(value.toList === List(5, 6, 7))
   }
 
-  test("get uncached local rdd") {
-    // Local computation should not persist the resulting value, so don't expect a put().
-    when(blockManager.get(RDDBlockId(0, 0))).thenReturn(None)
-
-    val context = new TaskContextImpl(0, 0, 0, 0, null, null, Seq.empty, runningLocally = true)
-    val value = cacheManager.getOrCompute(rdd, split, context, StorageLevel.MEMORY_ONLY)
-    assert(value.toList === List(1, 2, 3, 4))
-  }
-
   test("verify task metrics updated correctly") {
     cacheManager = sc.env.cacheManager
     val context = TaskContext.empty()