SPARK-3028. sparkEventToJson should support SparkListenerExecutorMetrics...

...Update

Author: Sandy Ryza <sandy@cloudera.com>

Closes #1961 from sryza/sandy-spark-3028 and squashes the following commits:

dccdff5 [Sandy Ryza] Fix compile error
f883ded [Sandy Ryza] SPARK-3028. sparkEventToJson should support SparkListenerExecutorMetricsUpdate

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

@@ -127,6 +127,8 @@ private[spark] class EventLoggingListener(
     logEvent(event, flushLogger = true)
   override def onApplicationEnd(event: SparkListenerApplicationEnd) =
     logEvent(event, flushLogger = true)
+  // No-op because logging every update would be overkill
+  override def onExecutorMetricsUpdate(event: SparkListenerExecutorMetricsUpdate) { }
 
   /**
    * Stop logging events.

core/src/main/scala/org/apache/spark/util/JsonProtocol.scala

@@ -72,8 +72,9 @@ private[spark] object JsonProtocol {
       case applicationEnd: SparkListenerApplicationEnd =>
         applicationEndToJson(applicationEnd)
 
-      // Not used, but keeps compiler happy
+      // These aren't used, but keeps compiler happy
       case SparkListenerShutdown => JNothing
+      case SparkListenerExecutorMetricsUpdate(_, _) => JNothing
     }
   }