recover #2436

core/src/main/scala/org/apache/spark/deploy/master/Master.scala

@@ -732,24 +732,23 @@ private[deploy] class Master(
     }
     // Drivers take strict precedence over executors
     val shuffledAliveWorkers = Random.shuffle(workers.toSeq.filter(_.state == WorkerState.ALIVE))
-    val aliveWorkerNum = shuffledAliveWorkers.size
+    val numWorkersAlive = shuffledAliveWorkers.size
     var curPos = 0
-    for (driver <- waitingDrivers.toList) {
-      // iterate over a copy of waitingDrivers
+    for (driver <- waitingDrivers.toList) { // iterate over a copy of waitingDrivers
       // We assign workers to each waiting driver in a round-robin fashion. For each driver, we
       // start from the last worker that was assigned a driver, and continue onwards until we have
       // explored all alive workers.
-      curPos = (curPos + 1) % aliveWorkerNum
-      val startPos = curPos
       var launched = false
-      while (curPos != startPos && !launched) {
+      var numWorkersVisited = 0
+      while (numWorkersVisited < numWorkersAlive && !launched) {
         val worker = shuffledAliveWorkers(curPos)
+        numWorkersVisited += 1
         if (worker.memoryFree >= driver.desc.mem && worker.coresFree >= driver.desc.cores) {
           launchDriver(worker, driver)
           waitingDrivers -= driver
           launched = true
         }
-        curPos = (curPos + 1) % aliveWorkerNum
+        curPos = (curPos + 1) % numWorkersAlive
       }
     }
     startExecutorsOnWorkers()