Adding config option for retained stages

core/src/main/scala/spark/ui/jobs/JobProgressUI.scala

@@ -42,7 +42,7 @@ private[spark] class JobProgressUI(val sc: SparkContext) {
 
 private[spark] class JobProgressListener extends SparkListener {
   // How many stages to remember
-  val RETAINED_STAGES = 1000
+  val RETAINED_STAGES = System.getProperty("spark.ui.retained_stages", "1000").toInt
 
   val activeStages = HashSet[Stage]()
   val completedStages = ListBuffer[Stage]()

docs/configuration.md

@@ -135,9 +135,16 @@ Apart from these, the following properties are also available, and may be useful
 </tr>
 <tr>
   <td>spark.ui.port</td>
-  <td>(random)</td>
+  <td>33000</td>
+  <td>
+    Port for your application's dashboard, which shows memory and workload data
+  </td>
+</tr>
+<tr>
+  <td>spark.ui.retained_stages</td>
+  <td>1000</td>
   <td>
-    Port for your application's dashboard, which shows memory usage of each RDD.
+    How many stages the Spark UI remembers before garbage collecting.
   </td>
 </tr>
 <tr>