address comments

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -1127,6 +1127,12 @@ object SQLConf {
       .booleanConf
       .createWithDefault(true)
 
+  val STREAMING_UI_ENABLED =
+    buildConf("spark.sql.streaming.ui.enabled")
+      .doc("Whether to run the structured streaming UI for the Spark application.")
+      .booleanConf
+      .createWithDefault(true)
+
   val STREAMING_UI_INACTIVE_QUERY_RETENTION =
     buildConf("spark.sql.streaming.ui.numInactiveQueries")
       .doc("The number of inactive queries to retain for structured streaming ui.")
@@ -2255,6 +2261,8 @@ class SQLConf extends Serializable with Logging {
 
   def isUnsupportedOperationCheckEnabled: Boolean = getConf(UNSUPPORTED_OPERATION_CHECK_ENABLED)
 
+  def isStreamingUIEnabled: Boolean = getConf(STREAMING_UI_ENABLED)
+
   def streamingUIInactiveQueryRetention: Int = getConf(STREAMING_UI_INACTIVE_QUERY_RETENTION)
 
   def streamingFileCommitProtocolClass: String = getConf(STREAMING_FILE_COMMIT_PROTOCOL_CLASS)

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/StreamExecution.scala

@@ -307,8 +307,8 @@ abstract class StreamExecution(
       }
 
       // `postEvent` does not throw non fatal exception.
-      val submitTime = triggerClock.getTimeMillis()
-      postEvent(new QueryStartedEvent(id, runId, name, submitTime))
+      val submissionTime = triggerClock.getTimeMillis()
+      postEvent(new QueryStartedEvent(id, runId, name, submissionTime))
 
       // Unblock starting thread
       startLatch.countDown()

sql/core/src/main/scala/org/apache/spark/sql/internal/SharedState.scala

@@ -30,7 +30,6 @@ import org.apache.hadoop.fs.FsUrlStreamHandlerFactory
 
 import org.apache.spark.{SparkConf, SparkContext, SparkException}
 import org.apache.spark.internal.Logging
-import org.apache.spark.internal.config.UI.UI_ENABLED
 import org.apache.spark.sql.SQLContext
 import org.apache.spark.sql.catalyst.catalog._
 import org.apache.spark.sql.execution.CacheManager
@@ -145,14 +144,16 @@ private[sql] class SharedState(
    * A [[StreamingQueryListener]] for structured streaming ui, it contains all streaming query ui
    * data to show.
    */
-  lazy val streamingQueryStatusListener: Option[StreamingQueryStatusListener] =
-    if (conf.get(UI_ENABLED)) {
-      val statusListener = new StreamingQueryStatusListener(SQLConf.get)
+  lazy val streamingQueryStatusListener: Option[StreamingQueryStatusListener] = {
+    val sqlConf = SQLConf.get
+    if (sqlConf.isStreamingUIEnabled) {
+      val statusListener = new StreamingQueryStatusListener(sqlConf)
       sparkContext.ui.foreach(new StreamingQueryTab(statusListener, _))
       Some(statusListener)
     } else {
       None
     }
+  }
 
   /**
    * A catalog that interacts with external systems.

sql/core/src/main/scala/org/apache/spark/sql/streaming/StreamingQueryListener.scala

@@ -82,15 +82,15 @@ object StreamingQueryListener {
    * @param id A unique query id that persists across restarts. See `StreamingQuery.id()`.
    * @param runId A query id that is unique for every start/restart. See `StreamingQuery.runId()`.
    * @param name User-specified name of the query, null if not specified.
-   * @param submitTime The timestamp to start a query.
+   * @param submissionTime The timestamp to start a query.
    * @since 2.1.0
    */
   @Evolving
   class QueryStartedEvent private[sql](
       val id: UUID,
       val runId: UUID,
       val name: String,
-      val submitTime: Long) extends Event
+      val submissionTime: Long) extends Event
 
   /**
    * Event representing any progress updates in a query.

sql/core/src/main/scala/org/apache/spark/sql/streaming/ui/StreamingQueryPage.scala

@@ -29,7 +29,7 @@ import org.apache.spark.sql.catalyst.util.DateTimeUtils.getTimeZone
 import org.apache.spark.sql.streaming.ui.UIUtils._
 import org.apache.spark.ui.{UIUtils => SparkUIUtils, WebUIPage}
 
-class StreamingQueryPage(parent: StreamingQueryTab)
+private[ui] class StreamingQueryPage(parent: StreamingQueryTab)
     extends WebUIPage("") with Logging {
   val df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
   df.setTimeZone(getTimeZone("UTC"))
@@ -61,11 +61,11 @@ class StreamingQueryPage(parent: StreamingQueryTab)
     val name = UIUtils.getQueryName(query)
     val status = UIUtils.getQueryStatus(query)
     val duration = if (queryActive) {
-      SparkUIUtils.formatDurationVerbose(System.currentTimeMillis() - query.submitTime)
+      SparkUIUtils.formatDurationVerbose(System.currentTimeMillis() - query.submissionTime)
     } else {
       withNoProgress(query, {
         val endTimeMs = query.lastProgress.timestamp
-        SparkUIUtils.formatDurationVerbose(df.parse(endTimeMs).getTime - query.submitTime)
+        SparkUIUtils.formatDurationVerbose(df.parse(endTimeMs).getTime - query.submissionTime)
       }, "-")
     }
 
@@ -74,7 +74,7 @@ class StreamingQueryPage(parent: StreamingQueryTab)
       <td> {status} </td>
       <td> {query.id} </td>
       <td> <a href={statisticsLink}> {query.runId} </a> </td>
-      <td> {SparkUIUtils.formatDate(query.submitTime)} </td>
+      <td> {SparkUIUtils.formatDate(query.submissionTime)} </td>
       <td> {duration} </td>
       <td> {withNoProgress(query, {
         (query.recentProgress.map(p => withNumberInvalid(p.inputRowsPerSecond)).sum /
@@ -94,8 +94,8 @@ class StreamingQueryPage(parent: StreamingQueryTab)
       .partition(_.isActive)
     val activeQueryTables = if (activeQueries.nonEmpty) {
       val headerRow = Seq(
-        "Query Name", "Status", "Id", "Run ID", "Submit Time", "Duration", "Avg Input /sec",
-        "Avg Process /sec", "Last Batch ID")
+        "Name", "Status", "Id", "Run ID", "Submitted Time", "Duration", "Avg Input /sec",
+        "Avg Process /sec", "Lastest Batch")
 
       Some(SparkUIUtils.listingTable(headerRow, generateDataRow(request, queryActive = true),
         activeQueries, true, None, Seq(null), false))
@@ -105,8 +105,8 @@ class StreamingQueryPage(parent: StreamingQueryTab)
 
     val inactiveQueryTables = if (inactiveQueries.nonEmpty) {
       val headerRow = Seq(
-        "Query Name", "Status", "Id", "Run ID", "Submit Time", "Duration", "Avg Input /sec",
-        "Avg Process /sec", "Last Batch ID", "Error")
+        "Name", "Status", "Id", "Run ID", "Submitted Time", "Duration", "Avg Input /sec",
+        "Avg Process /sec", "Lastest Batch", "Error")
 
       Some(SparkUIUtils.listingTable(headerRow, generateDataRow(request, queryActive = false),
         inactiveQueries, true, None, Seq(null), false))

sql/core/src/main/scala/org/apache/spark/sql/streaming/ui/StreamingQueryStatisticsPage.scala

@@ -30,7 +30,7 @@ import org.apache.spark.sql.catalyst.util.DateTimeUtils.getTimeZone
 import org.apache.spark.sql.streaming.ui.UIUtils._
 import org.apache.spark.ui.{GraphUIData, JsCollector, UIUtils => SparkUIUtils, WebUIPage}
 
-class StreamingQueryStatisticsPage(parent: StreamingQueryTab)
+private[ui] class StreamingQueryStatisticsPage(parent: StreamingQueryTab)
   extends WebUIPage("statistics") with Logging {
   val df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
   df.setTimeZone(getTimeZone("UTC"))
@@ -82,7 +82,7 @@ class StreamingQueryStatisticsPage(parent: StreamingQueryTab)
 
   def generateBasicInfo(query: StreamingQueryUIData): Seq[Node] = {
     val duration = if (query.isActive) {
-      SparkUIUtils.formatDurationVerbose(System.currentTimeMillis() - query.submitTime)
+      SparkUIUtils.formatDurationVerbose(System.currentTimeMillis() - query.submissionTime)
     } else {
       withNoProgress(query, {
         val end = query.lastProgress.timestamp
@@ -100,7 +100,7 @@ class StreamingQueryStatisticsPage(parent: StreamingQueryTab)
       </strong>
       since
       <strong>
-        {SparkUIUtils.formatDate(query.submitTime)}
+        {SparkUIUtils.formatDate(query.submissionTime)}
       </strong>
       (<strong>{numBatches}</strong> completed batches)
     </div>

sql/core/src/main/scala/org/apache/spark/sql/streaming/ui/StreamingQueryStatusListener.scala

@@ -33,7 +33,7 @@ import org.apache.spark.sql.streaming.{StreamingQueryListener, StreamingQueryPro
  * UI data for both active and inactive query.
  * TODO: Add support for history server.
  */
-class StreamingQueryStatusListener(sqlConf: SQLConf) extends StreamingQueryListener {
+private[sql] class StreamingQueryStatusListener(sqlConf: SQLConf) extends StreamingQueryListener {
 
   private val timestampFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'") // ISO8601
   timestampFormat.setTimeZone(DateTimeUtils.getTimeZone("UTC"))
@@ -50,7 +50,7 @@ class StreamingQueryStatusListener(sqlConf: SQLConf) extends StreamingQueryListe
 
   override def onQueryStarted(event: StreamingQueryListener.QueryStartedEvent): Unit = {
     activeQueryStatus.putIfAbsent(event.runId,
-      new StreamingQueryUIData(event.name, event.id, event.runId, event.submitTime))
+      new StreamingQueryUIData(event.name, event.id, event.runId, event.submissionTime))
   }
 
   override def onQueryProgress(event: StreamingQueryListener.QueryProgressEvent): Unit = {
@@ -62,20 +62,19 @@ class StreamingQueryStatusListener(sqlConf: SQLConf) extends StreamingQueryListe
     queryStatus.updateProcess(event.progress, streamingProgressRetention)
   }
 
-  override def onQueryTerminated(event: StreamingQueryListener.QueryTerminatedEvent): Unit = {
+  override def onQueryTerminated(
+      event: StreamingQueryListener.QueryTerminatedEvent): Unit = synchronized {
     val queryStatus = activeQueryStatus.remove(event.runId)
     if (queryStatus != null) {
       queryStatus.queryTerminated(event)
-      inactiveQueryStatus.synchronized {
-        inactiveQueryStatus += queryStatus
-        while (inactiveQueryStatus.length >= inactiveQueryStatusRetention) {
-          inactiveQueryStatus.dequeue()
-        }
+      inactiveQueryStatus += queryStatus
+      while (inactiveQueryStatus.length >= inactiveQueryStatusRetention) {
+        inactiveQueryStatus.dequeue()
       }
     }
   }
 
-  def allQueryStatus: Seq[StreamingQueryUIData] = inactiveQueryStatus.synchronized {
+  def allQueryStatus: Seq[StreamingQueryUIData] = synchronized {
     activeQueryStatus.values().asScala.toSeq ++ inactiveQueryStatus
   }
 }
@@ -88,7 +87,7 @@ private[ui] class StreamingQueryUIData(
     val name: String,
     val id: UUID,
     val runId: UUID,
-    val submitTime: Long) {
+    val submissionTime: Long) {
 
   /** Holds the most recent query progress updates. */
   private val progressBuffer = new mutable.Queue[StreamingQueryProgress]()

sql/core/src/main/scala/org/apache/spark/sql/streaming/ui/StreamingQueryTab.scala

@@ -19,8 +19,9 @@ package org.apache.spark.sql.streaming.ui
 import org.apache.spark.internal.Logging
 import org.apache.spark.ui.{SparkUI, SparkUITab}
 
-class StreamingQueryTab(val statusListener: StreamingQueryStatusListener, sparkUI: SparkUI)
-  extends SparkUITab(sparkUI, "StreamingQuery") with Logging {
+private[sql] class StreamingQueryTab(
+    val statusListener: StreamingQueryStatusListener,
+    sparkUI: SparkUI) extends SparkUITab(sparkUI, "StreamingQuery") with Logging {
 
   override val name = "Structured Streaming"
 

sql/core/src/test/scala/org/apache/spark/sql/streaming/ui/StreamingQueryPageSuite.scala

@@ -97,7 +97,7 @@ class StreamingQueryPageSuite extends SharedSparkSession with BeforeAndAfter {
     when(streamQuery.name).thenReturn("query")
     when(streamQuery.id).thenReturn(id)
     when(streamQuery.runId).thenReturn(id)
-    when(streamQuery.submitTime).thenReturn(1L)
+    when(streamQuery.submissionTime).thenReturn(1L)
     when(streamQuery.lastProgress).thenReturn(progress)
     when(streamQuery.recentProgress).thenReturn(Array(progress))
     when(streamQuery.exception).thenReturn(None)