[Spark-3490] Disable SparkUI for tests

We currently open many ephemeral ports during the tests, and as a result we occasionally can't bind to new ones. This has caused the `DriverSuite` and the `SparkSubmitSuite` to fail intermittently.

By disabling the `SparkUI` when it's not needed, we already cut down on the number of ports opened significantly, on the order of the number of `SparkContexts` ever created. We must keep it enabled for a few tests for the UI itself, however.

Author: Andrew Or <andrewor14@gmail.com>

Closes #2363 from andrewor14/disable-ui-for-tests and squashes the following commits:

332a7d5 [Andrew Or] No need to set spark.ui.port to 0 anymore
30c93a2 [Andrew Or] Simplify streaming UISuite
a431b84 [Andrew Or] Fix streaming test failures
8f5ae53 [Andrew Or] Fix no new line at the end
29c9b5b [Andrew Or] Disable SparkUI for tests

5 files changed, 47 insertions, 21 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index c6c5b8f22b..218b353dd9 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -220,8 +220,14 @@ class SparkContext(config: SparkConf) extends Logging {
     new MetadataCleaner(MetadataCleanerType.SPARK_CONTEXT, this.cleanup, conf)
 
   // Initialize the Spark UI, registering all associated listeners
-  private[spark] val ui = new SparkUI(this)
-  ui.bind()
+  private[spark] val ui: Option[SparkUI] =
+    if (conf.getBoolean("spark.ui.enabled", true)) {
+      Some(new SparkUI(this))
+    } else {
+      // For tests, do not enable the UI
+      None
+    }
+  ui.foreach(_.bind())
 
   /** A default Hadoop Configuration for the Hadoop code (e.g. file systems) that we reuse. */
   val hadoopConfiguration = SparkHadoopUtil.get.newConfiguration(conf)
@@ -990,7 +996,7 @@ class SparkContext(config: SparkConf) extends Logging {
   /** Shut down the SparkContext. */
   def stop() {
     postApplicationEnd()
-    ui.stop()
+    ui.foreach(_.stop())
     // Do this only if not stopped already - best case effort.
     // prevent NPE if stopped more than once.
     val dagSchedulerCopy = dagScheduler
diff --git a/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedSchedulerBackend.scala b/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedSchedulerBackend.scala
index 5b5257269d..9a0cb1c6c6 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedSchedulerBackend.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedSchedulerBackend.scala
@@ -292,7 +292,7 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, actorSystem: A
       logInfo(s"Add WebUI Filter. $filterName, $filterParams, $proxyBase")
       conf.set("spark.ui.filters", filterName)
       conf.set(s"spark.$filterName.params", filterParams)
-      JettyUtils.addFilters(scheduler.sc.ui.getHandlers, conf)
+      scheduler.sc.ui.foreach { ui => JettyUtils.addFilters(ui.getHandlers, conf) }
     }
   }
 }
diff --git a/core/src/main/scala/org/apache/spark/scheduler/cluster/SimrSchedulerBackend.scala b/core/src/main/scala/org/apache/spark/scheduler/cluster/SimrSchedulerBackend.scala
index 513d74a08a..ee10aa061f 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/cluster/SimrSchedulerBackend.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/cluster/SimrSchedulerBackend.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.scheduler.cluster
 
-import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.fs.{Path, FileSystem}
 
 import org.apache.spark.{Logging, SparkContext, SparkEnv}
@@ -47,16 +46,17 @@ private[spark] class SimrSchedulerBackend(
 
     val conf = SparkHadoopUtil.get.newConfiguration(sc.conf)
     val fs = FileSystem.get(conf)
+    val appUIAddress = sc.ui.map(_.appUIAddress).getOrElse("")
 
     logInfo("Writing to HDFS file: "  + driverFilePath)
     logInfo("Writing Akka address: "  + driverUrl)
-    logInfo("Writing Spark UI Address: " + sc.ui.appUIAddress)
+    logInfo("Writing Spark UI Address: " + appUIAddress)
 
     // Create temporary file to prevent race condition where executors get empty driverUrl file
     val temp = fs.create(tmpPath, true)
     temp.writeUTF(driverUrl)
     temp.writeInt(maxCores)
-    temp.writeUTF(sc.ui.appUIAddress)
+    temp.writeUTF(appUIAddress)
     temp.close()
 
     // "Atomic" rename
diff --git a/core/src/main/scala/org/apache/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala b/core/src/main/scala/org/apache/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
index 06872ace2e..2f45d192e1 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
@@ -67,8 +67,10 @@ private[spark] class SparkDeploySchedulerBackend(
     val javaOpts = sparkJavaOpts ++ extraJavaOpts
     val command = Command("org.apache.spark.executor.CoarseGrainedExecutorBackend",
       args, sc.executorEnvs, classPathEntries, libraryPathEntries, javaOpts)
+    val appUIAddress = sc.ui.map(_.appUIAddress).getOrElse("")
+    val eventLogDir = sc.eventLogger.map(_.logDir)
     val appDesc = new ApplicationDescription(sc.appName, maxCores, sc.executorMemory, command,
-      sc.ui.appUIAddress, sc.eventLogger.map(_.logDir))
+      appUIAddress, eventLogDir)
 
     client = new AppClient(sc.env.actorSystem, masters, appDesc, this, conf)
     client.start()
diff --git a/core/src/test/scala/org/apache/spark/ui/UISuite.scala b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
index 038746d2ed..2f56642956 100644
--- a/core/src/test/scala/org/apache/spark/ui/UISuite.scala
+++ b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
@@ -36,11 +36,25 @@ import scala.xml.Node
 
 class UISuite extends FunSuite {
 
+  /**
+   * Create a test SparkContext with the SparkUI enabled.
+   * It is safe to `get` the SparkUI directly from the SparkContext returned here.
+   */
+  private def newSparkContext(): SparkContext = {
+    val conf = new SparkConf()
+      .setMaster("local")
+      .setAppName("test")
+      .set("spark.ui.enabled", "true")
+    val sc = new SparkContext(conf)
+    assert(sc.ui.isDefined)
+    sc
+  }
+
   ignore("basic ui visibility") {
-    withSpark(new SparkContext("local", "test")) { sc =>
+    withSpark(newSparkContext()) { sc =>
       // test if the ui is visible, and all the expected tabs are visible
       eventually(timeout(10 seconds), interval(50 milliseconds)) {
-        val html = Source.fromURL(sc.ui.appUIAddress).mkString
+        val html = Source.fromURL(sc.ui.get.appUIAddress).mkString
         assert(!html.contains("random data that should not be present"))
         assert(html.toLowerCase.contains("stages"))
         assert(html.toLowerCase.contains("storage"))
@@ -51,7 +65,7 @@ class UISuite extends FunSuite {
   }
 
   ignore("visibility at localhost:4040") {
-    withSpark(new SparkContext("local", "test")) { sc =>
+    withSpark(newSparkContext()) { sc =>
       // test if visible from http://localhost:4040
       eventually(timeout(10 seconds), interval(50 milliseconds)) {
         val html = Source.fromURL("http://localhost:4040").mkString
@@ -61,8 +75,8 @@ class UISuite extends FunSuite {
   }
 
   ignore("attaching a new tab") {
-    withSpark(new SparkContext("local", "test")) { sc =>
-      val sparkUI = sc.ui
+    withSpark(newSparkContext()) { sc =>
+      val sparkUI = sc.ui.get
 
       val newTab = new WebUITab(sparkUI, "foo") {
         attachPage(new WebUIPage("") {
@@ -73,7 +87,7 @@ class UISuite extends FunSuite {
       }
       sparkUI.attachTab(newTab)
       eventually(timeout(10 seconds), interval(50 milliseconds)) {
-        val html = Source.fromURL(sc.ui.appUIAddress).mkString
+        val html = Source.fromURL(sparkUI.appUIAddress).mkString
         assert(!html.contains("random data that should not be present"))
 
         // check whether new page exists
@@ -87,7 +101,7 @@ class UISuite extends FunSuite {
       }
 
       eventually(timeout(10 seconds), interval(50 milliseconds)) {
-        val html = Source.fromURL(sc.ui.appUIAddress.stripSuffix("/") + "/foo").mkString
+        val html = Source.fromURL(sparkUI.appUIAddress.stripSuffix("/") + "/foo").mkString
         // check whether new page exists
         assert(html.contains("magic"))
       }
@@ -129,16 +143,20 @@ class UISuite extends FunSuite {
   }
 
   test("verify appUIAddress contains the scheme") {
-    withSpark(new SparkContext("local", "test")) { sc =>
-      val uiAddress = sc.ui.appUIAddress
-      assert(uiAddress.equals("http://" + sc.ui.appUIHostPort))
+    withSpark(newSparkContext()) { sc =>
+      val ui = sc.ui.get
+      val uiAddress = ui.appUIAddress
+      val uiHostPort = ui.appUIHostPort
+      assert(uiAddress.equals("http://" + uiHostPort))
     }
   }
 
   test("verify appUIAddress contains the port") {
-    withSpark(new SparkContext("local", "test")) { sc =>
-      val splitUIAddress = sc.ui.appUIAddress.split(':')
-      assert(splitUIAddress(2).toInt == sc.ui.boundPort)
+    withSpark(newSparkContext()) { sc =>
+      val ui = sc.ui.get
+      val splitUIAddress = ui.appUIAddress.split(':')
+      val boundPort = ui.boundPort
+      assert(splitUIAddress(2).toInt == boundPort)
     }
   }
 }