[SPARK-2635] Fix race condition at SchedulerBackend.isReady in standalone mode

In SPARK-1946(PR #900), configuration <code>spark.scheduler.minRegisteredExecutorsRatio</code> was introduced. However, in standalone mode, there is a race condition where isReady() can return true because totalExpectedExecutors has not been correctly set.

Because expected executors is uncertain in standalone mode, the PR try to use CPU cores(<code>--total-executor-cores</code>) as expected resources to judge whether SchedulerBackend is ready.

Author: li-zhihui <zhihui.li@intel.com>
Author: Li Zhihui <zhihui.li@intel.com>

Closes #1525 from li-zhihui/fixre4s and squashes the following commits:

e9a630b [Li Zhihui] Rename variable totalExecutors and clean codes
abf4860 [Li Zhihui] Push down variable totalExpectedResources to children classes
ca54bd9 [li-zhihui] Format log with String interpolation
88c7dc6 [li-zhihui] Few codes and docs refactor
41cf47e [li-zhihui] Fix race condition at SchedulerBackend.isReady in standalone mode

2 files changed, 19 insertions, 17 deletions

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 9f085eef46..33500d967e 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
@@ -47,19 +47,19 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, actorSystem: A
 {
   // Use an atomic variable to track total number of cores in the cluster for simplicity and speed
   var totalCoreCount = new AtomicInteger(0)
-  var totalExpectedExecutors = new AtomicInteger(0)
+  var totalRegisteredExecutors = new AtomicInteger(0)
   val conf = scheduler.sc.conf
   private val timeout = AkkaUtils.askTimeout(conf)
   private val akkaFrameSize = AkkaUtils.maxFrameSizeBytes(conf)
-  // Submit tasks only after (registered executors / total expected executors) 
+  // Submit tasks only after (registered resources / total expected resources) 
   // is equal to at least this value, that is double between 0 and 1.
-  var minRegisteredRatio = conf.getDouble("spark.scheduler.minRegisteredExecutorsRatio", 0)
-  if (minRegisteredRatio > 1) minRegisteredRatio = 1
-  // Whatever minRegisteredExecutorsRatio is arrived, submit tasks after the time(milliseconds).
+  var minRegisteredRatio =
+    math.min(1, conf.getDouble("spark.scheduler.minRegisteredResourcesRatio", 0))
+  // Submit tasks after maxRegisteredWaitingTime milliseconds
+  // if minRegisteredRatio has not yet been reached  
   val maxRegisteredWaitingTime =
-    conf.getInt("spark.scheduler.maxRegisteredExecutorsWaitingTime", 30000)
+    conf.getInt("spark.scheduler.maxRegisteredResourcesWaitingTime", 30000)
   val createTime = System.currentTimeMillis()
-  var ready = if (minRegisteredRatio <= 0) true else false
 
   class DriverActor(sparkProperties: Seq[(String, String)]) extends Actor {
     private val executorActor = new HashMap[String, ActorRef]
@@ -94,12 +94,7 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, actorSystem: A
           executorAddress(executorId) = sender.path.address
           addressToExecutorId(sender.path.address) = executorId
           totalCoreCount.addAndGet(cores)
-          if (executorActor.size >= totalExpectedExecutors.get() * minRegisteredRatio && !ready) {
-            ready = true
-            logInfo("SchedulerBackend is ready for scheduling beginning, registered executors: " +
-              executorActor.size + ", total expected executors: " + totalExpectedExecutors.get() +
-              ", minRegisteredExecutorsRatio: " + minRegisteredRatio)
-          }
+          totalRegisteredExecutors.addAndGet(1)
           makeOffers()
         }
 
@@ -268,14 +263,17 @@ class CoarseGrainedSchedulerBackend(scheduler: TaskSchedulerImpl, actorSystem: A
     }
   }
 
+  def sufficientResourcesRegistered(): Boolean = true
+
   override def isReady(): Boolean = {
-    if (ready) {
+    if (sufficientResourcesRegistered) {
+      logInfo("SchedulerBackend is ready for scheduling beginning after " +
+        s"reached minRegisteredResourcesRatio: $minRegisteredRatio")
       return true
     }
     if ((System.currentTimeMillis() - createTime) >= maxRegisteredWaitingTime) {
-      ready = true
       logInfo("SchedulerBackend is ready for scheduling beginning after waiting " +
-        "maxRegisteredExecutorsWaitingTime: " + maxRegisteredWaitingTime)
+        s"maxRegisteredResourcesWaitingTime: $maxRegisteredWaitingTime(ms)")
       return true
     }
     false
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 a28446f6c8..589dba2e40 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
@@ -36,6 +36,7 @@ private[spark] class SparkDeploySchedulerBackend(
   var shutdownCallback : (SparkDeploySchedulerBackend) => Unit = _
 
   val maxCores = conf.getOption("spark.cores.max").map(_.toInt)
+  val totalExpectedCores = maxCores.getOrElse(0)
 
   override def start() {
     super.start()
@@ -97,7 +98,6 @@ private[spark] class SparkDeploySchedulerBackend(
 
   override def executorAdded(fullId: String, workerId: String, hostPort: String, cores: Int,
     memory: Int) {
-    totalExpectedExecutors.addAndGet(1)
     logInfo("Granted executor ID %s on hostPort %s with %d cores, %s RAM".format(
       fullId, hostPort, cores, Utils.megabytesToString(memory)))
   }
@@ -110,4 +110,8 @@ private[spark] class SparkDeploySchedulerBackend(
     logInfo("Executor %s removed: %s".format(fullId, message))
     removeExecutor(fullId.split("/")(1), reason.toString)
   }
+
+  override def sufficientResourcesRegistered(): Boolean = {
+    totalCoreCount.get() >= totalExpectedCores * minRegisteredRatio
+  }
 }