Blocker Description
Spark UI SQL executions page throws the following error and the page crashes:
HTTP ERROR 500 Problem accessing /SQL/. Reason: Server Error Caused by: java.lang.NullPointerException at scala.collection.immutable.StringOps$.length$extension(StringOps.scala:47) at scala.collection.immutable.StringOps.length(StringOps.scala:47) at scala.collection.IndexedSeqOptimized$class.isEmpty(IndexedSeqOptimized.scala:27) at scala.collection.immutable.StringOps.isEmpty(StringOps.scala:29) at scala.collection.TraversableOnce$class.nonEmpty(TraversableOnce.scala:111) at scala.collection.immutable.StringOps.nonEmpty(StringOps.scala:29) at org.apache.spark.sql.execution.ui.ExecutionTable.descriptionCell(AllExecutionsPage.scala:182) at org.apache.spark.sql.execution.ui.ExecutionTable.row(AllExecutionsPage.scala:155) at org.apache.spark.sql.execution.ui.ExecutionTable$$anonfun$8.apply(AllExecutionsPage.scala:204) at org.apache.spark.sql.execution.ui.ExecutionTable$$anonfun$8.apply(AllExecutionsPage.scala:204) at org.apache.spark.ui.UIUtils$$anonfun$listingTable$2.apply(UIUtils.scala:339) at org.apache.spark.ui.UIUtils$$anonfun$listingTable$2.apply(UIUtils.scala:339) at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234) at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234) at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59) at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48) at scala.collection.TraversableLike$class.map(TraversableLike.scala:234) at scala.collection.AbstractTraversable.map(Traversable.scala:104) at org.apache.spark.ui.UIUtils$.listingTable(UIUtils.scala:339) at org.apache.spark.sql.execution.ui.ExecutionTable.toNodeSeq(AllExecutionsPage.scala:203) at org.apache.spark.sql.execution.ui.AllExecutionsPage.render(AllExecutionsPage.scala:67) at org.apache.spark.ui.WebUI$$anonfun$2.apply(WebUI.scala:82) at org.apache.spark.ui.WebUI$$anonfun$2.apply(WebUI.scala:82) at org.apache.spark.ui.JettyUtils$$anon$3.doGet(JettyUtils.scala:90) at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:848) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:584) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:512) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:213) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134) at org.eclipse.jetty.server.Server.handle(Server.java:534) at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:320) at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:251) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:283) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:108) at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93) at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303) at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148) at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671) at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589) at java.lang.Thread.run(Thread.java:748)
Seems the bug is imported by https://github.com/apache/spark/pull/19681/files#diff-a74d84702d8d47d5269e96740a55a3caR63
