[GitHub] [spark] LantaoJin commented on a change in pull request #23951: [SPARK-27038][CORE][YARN] Re-implement RackResolver to reduce resolving time

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LantaoJin commented on a change in pull request #23951: [SPARK-27038][CORE][YARN] Re-implement RackResolver to reduce resolving time
URL: https://github.com/apache/spark/pull/23951#discussion_r263340561
 
 

 ##########
 File path: core/src/test/scala/org/apache/spark/scheduler/TaskSetManagerSuite.scala
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 @@ -1602,4 +1617,28 @@ class TaskSetManagerSuite extends SparkFunSuite with LocalSparkContext with Logg
     verify(sched.dagScheduler).taskEnded(manager.tasks(3), Success, result.value(),
       result.accumUpdates, info3)
   }
+
+  test("SPARK-27038: Verify the rack resolving time and result when initialing TaskSetManager") {
+    sc = new SparkContext("local", "test")
+    for (i <- 1 to 100) {
+      FakeRackUtil.assignHostToRack("host" + i, "rack" + i)
+    }
+    sched = new FakeTaskScheduler(sc,
+      ("execA", "host1"), ("execB", "host2"), ("execC", "host3"))
+    sched.slowRackResolve = true
+    val locations = new ArrayBuffer[Seq[TaskLocation]]()
+    for (i <- 1 to 100) {
+      locations += Seq(TaskLocation("host" + i))
+    }
+    val taskSet = FakeTask.createTaskSet(100, locations: _*)
+    val clock = new ManualClock
+    val manager = new TaskSetManager(sched, taskSet, MAX_TASK_FAILURES, clock = clock)
+    var total = 0
+    for (i <- 1 to 100) {
+      total += manager.getPendingTasksForRack("rack" + i).length
+    }
+    assert(total === 100) // verify the total number always equals 100 with/without SPARK-27038
+    // verify elapsed time should be less than 1s, without SPARK-27038, it should be larger 10s
+    assert(manager.addTaskElapsedTime < 1)
 
 Review comment:
   Thanks @squito , I changed it with a simulation function of `runResolveCommand()` in `org.apache.hadoop.net.ScriptBasedMapping`. I think it could equal to time reducing.

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