Merge pull request #374 from woggling/null-mapout

Generate FetchFailedException even for cached missing map outputs

core/src/main/scala/spark/MapOutputTracker.scala

@@ -139,8 +139,8 @@ private[spark] class MapOutputTracker(actorSystem: ActorSystem, isMaster: Boolea
               case e: InterruptedException =>
             }
           }
-          return mapStatuses.get(shuffleId).map(status =>
-            (status.address, MapOutputTracker.decompressSize(status.compressedSizes(reduceId))))
+          return MapOutputTracker.convertMapStatuses(shuffleId, reduceId,
+                                                     mapStatuses.get(shuffleId))
         } else {
           fetching += shuffleId
         }
@@ -156,21 +156,15 @@ private[spark] class MapOutputTracker(actorSystem: ActorSystem, isMaster: Boolea
         fetchedStatuses = deserializeStatuses(fetchedBytes)
         logInfo("Got the output locations")
         mapStatuses.put(shuffleId, fetchedStatuses)
-        if (fetchedStatuses.contains(null)) {
-          throw new FetchFailedException(null, shuffleId, -1, reduceId,
-            new Exception("Missing an output location for shuffle " + shuffleId))
-        }
       } finally {
         fetching.synchronized {
           fetching -= shuffleId
           fetching.notifyAll()
         }
       }
-      return fetchedStatuses.map(s =>
-        (s.address, MapOutputTracker.decompressSize(s.compressedSizes(reduceId))))
+      return MapOutputTracker.convertMapStatuses(shuffleId, reduceId, fetchedStatuses)
     } else {
-      return statuses.map(s =>
-        (s.address, MapOutputTracker.decompressSize(s.compressedSizes(reduceId))))
+      return MapOutputTracker.convertMapStatuses(shuffleId, reduceId, statuses)
     }
   }
 
@@ -258,6 +252,28 @@ private[spark] class MapOutputTracker(actorSystem: ActorSystem, isMaster: Boolea
 private[spark] object MapOutputTracker {
   private val LOG_BASE = 1.1
 
+  // Convert an array of MapStatuses to locations and sizes for a given reduce ID. If
+  // any of the statuses is null (indicating a missing location due to a failed mapper),
+  // throw a FetchFailedException.
+  def convertMapStatuses(
+        shuffleId: Int,
+        reduceId: Int,
+        statuses: Array[MapStatus]): Array[(BlockManagerId, Long)] = {
+    if (statuses == null) {
+      throw new FetchFailedException(null, shuffleId, -1, reduceId,
+        new Exception("Missing all output locations for shuffle " + shuffleId))
+    }
+    statuses.map {
+      status => 
+        if (status == null) {
+          throw new FetchFailedException(null, shuffleId, -1, reduceId,
+            new Exception("Missing an output location for shuffle " + shuffleId))
+        } else {
+          (status.address, decompressSize(status.compressedSizes(reduceId)))
+        }
+    }
+  }
+
   /**
    * Compress a size in bytes to 8 bits for efficient reporting of map output sizes.
    * We do this by encoding the log base 1.1 of the size as an integer, which can support

core/src/test/scala/spark/MapOutputTrackerSuite.scala

 package spark
 
 import org.scalatest.FunSuite
+import org.scalatest.BeforeAndAfter
 
 import akka.actor._
 import spark.scheduler.MapStatus
 import spark.storage.BlockManagerId
+import spark.util.AkkaUtils
 
-class MapOutputTrackerSuite extends FunSuite {
+class MapOutputTrackerSuite extends FunSuite with BeforeAndAfter {
+  after {
+    System.clearProperty("spark.master.port")
+  }
+ 
   test("compressSize") {
     assert(MapOutputTracker.compressSize(0L) === 0)
     assert(MapOutputTracker.compressSize(1L) === 1)
@@ -71,6 +77,36 @@ class MapOutputTrackerSuite extends FunSuite {
     // The remaining reduce task might try to grab the output dispite the shuffle failure;
     // this should cause it to fail, and the scheduler will ignore the failure due to the
     // stage already being aborted.
-    intercept[Exception] { tracker.getServerStatuses(10, 1) }
+    intercept[FetchFailedException] { tracker.getServerStatuses(10, 1) }
+  }
+
+  test("remote fetch") {
+    System.clearProperty("spark.master.host")
+    val (actorSystem, boundPort) =
+      AkkaUtils.createActorSystem("test", "localhost", 0)
+    System.setProperty("spark.master.port", boundPort.toString)
+    val masterTracker = new MapOutputTracker(actorSystem, true)
+    val slaveTracker = new MapOutputTracker(actorSystem, false)
+    masterTracker.registerShuffle(10, 1)
+    masterTracker.incrementGeneration()
+    slaveTracker.updateGeneration(masterTracker.getGeneration)
+    intercept[FetchFailedException] { slaveTracker.getServerStatuses(10, 0) }
+
+    val compressedSize1000 = MapOutputTracker.compressSize(1000L)
+    val size1000 = MapOutputTracker.decompressSize(compressedSize1000)
+    masterTracker.registerMapOutput(10, 0, new MapStatus(
+      new BlockManagerId("hostA", 1000), Array(compressedSize1000)))
+    masterTracker.incrementGeneration()
+    slaveTracker.updateGeneration(masterTracker.getGeneration)
+    assert(slaveTracker.getServerStatuses(10, 0).toSeq ===
+           Seq((new BlockManagerId("hostA", 1000), size1000)))
+
+    masterTracker.unregisterMapOutput(10, 0, new BlockManagerId("hostA", 1000))
+    masterTracker.incrementGeneration()
+    slaveTracker.updateGeneration(masterTracker.getGeneration)
+    intercept[FetchFailedException] { slaveTracker.getServerStatuses(10, 0) }
+
+    // failure should be cached
+    intercept[FetchFailedException] { slaveTracker.getServerStatuses(10, 0) }
   }
 }