[SPARK-13413] Remove SparkContext.metricsSystem

## What changes were proposed in this pull request?

This patch removes SparkContext.metricsSystem. SparkContext.metricsSystem returns MetricsSystem, which is a private class. I think it was added by accident.

In addition, I also removed an unused private[spark] method schedulerBackend setter.

## How was the this patch tested?

N/A.

Author: Reynold Xin <rxin@databricks.com>

This patch had conflicts when merged, resolved by
Committer: Josh Rosen <joshrosen@databricks.com>

Closes #11282 from rxin/SPARK-13413.

2 files changed, 7 insertions, 8 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index c001df31aa..cd7eed382e 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -297,9 +297,6 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
   val sparkUser = Utils.getCurrentUserName()
 
   private[spark] def schedulerBackend: SchedulerBackend = _schedulerBackend
-  private[spark] def schedulerBackend_=(sb: SchedulerBackend): Unit = {
-    _schedulerBackend = sb
-  }
 
   private[spark] def taskScheduler: TaskScheduler = _taskScheduler
   private[spark] def taskScheduler_=(ts: TaskScheduler): Unit = {
@@ -322,8 +319,6 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
   def applicationId: String = _applicationId
   def applicationAttemptId: Option[String] = _applicationAttemptId
 
-  def metricsSystem: MetricsSystem = if (_env != null) _env.metricsSystem else null
-
   private[spark] def eventLogger: Option[EventLoggingListener] = _eventLogger
 
   private[spark] def executorAllocationManager: Option[ExecutorAllocationManager] =
@@ -514,9 +509,9 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
 
     // The metrics system for Driver need to be set spark.app.id to app ID.
     // So it should start after we get app ID from the task scheduler and set spark.app.id.
-    metricsSystem.start()
+    _env.metricsSystem.start()
     // Attach the driver metrics servlet handler to the web ui after the metrics system is started.
-    metricsSystem.getServletHandlers.foreach(handler => ui.foreach(_.attachHandler(handler)))
+    _env.metricsSystem.getServletHandlers.foreach(handler => ui.foreach(_.attachHandler(handler)))
 
     _eventLogger =
       if (isEventLogEnabled) {
diff --git a/project/MimaExcludes.scala b/project/MimaExcludes.scala
index 97a1e8b433..746223f39e 100644
--- a/project/MimaExcludes.scala
+++ b/project/MimaExcludes.scala
@@ -261,9 +261,13 @@ object MimaExcludes {
         ProblemFilters.exclude[MissingMethodProblem]("org.apache.spark.graphx.Graph.mapReduceTriplets"),
         ProblemFilters.exclude[MissingMethodProblem]("org.apache.spark.graphx.Graph.mapReduceTriplets$default$3"),
         ProblemFilters.exclude[MissingMethodProblem]("org.apache.spark.graphx.impl.GraphImpl.mapReduceTriplets")
-      ) ++Seq(
+      ) ++ Seq(
           // SPARK-13426 Remove the support of SIMR
           ProblemFilters.exclude[MissingMethodProblem]("org.apache.spark.SparkMasterRegex.SIMR_REGEX")
+      ) ++ Seq(
+        // SPARK-13413 Remove SparkContext.metricsSystem/schedulerBackend_ setter
+        ProblemFilters.exclude[MissingMethodProblem]("org.apache.spark.SparkContext.metricsSystem"),
+        ProblemFilters.exclude[MissingMethodProblem]("org.apache.spark.SparkContext.schedulerBackend_=")
       )
     case v if v.startsWith("1.6") =>
       Seq(