SPARK-2792. Fix reading too much or too little data from each stream …

…in ExternalMap / Sorter

All these changes are from mridulm's work in #1609, but extracted here to fix this specific issue and make it easier to merge not 1.1. This particular set of changes is to make sure that we read exactly the right range of bytes from each spill file in EAOM: some serializers can write bytes after the last object (e.g. the TC_RESET flag in Java serialization) and that would confuse the previous code into reading it as part of the next batch. There are also improvements to cleanup to make sure files are closed.

In addition to bringing in the changes to ExternalAppendOnlyMap, I also copied them to the corresponding code in ExternalSorter and updated its test suite to test for the same issues.

Author: Matei Zaharia <matei@databricks.com>

Closes #1722 from mateiz/spark-2792 and squashes the following commits:

5d4bfb5 [Matei Zaharia] Make objectStreamReset counter count the last object written too
18fe865 [Matei Zaharia] Update docs on objectStreamReset
576ee83 [Matei Zaharia] Allow objectStreamReset to be 0
0374217 [Matei Zaharia] Remove super paranoid code to close file handles
bda37bb [Matei Zaharia] Implement Mridul's ExternalAppendOnlyMap fixes in ExternalSorter too
0d6dad7 [Matei Zaharia] Added Mridul's test changes for ExternalAppendOnlyMap
9a78e4b [Matei Zaharia] Add @mridulm's fixes to ExternalAppendOnlyMap for batch sizes

core/src/main/scala/org/apache/spark/serializer/JavaSerializer.scala

@@ -35,16 +35,15 @@ private[spark] class JavaSerializationStream(out: OutputStream, counterReset: In
   /**
    * Calling reset to avoid memory leak:
    * http://stackoverflow.com/questions/1281549/memory-leak-traps-in-the-java-standard-api
-   * But only call it every 10,000th time to avoid bloated serialization streams (when
+   * But only call it every 100th time to avoid bloated serialization streams (when
    * the stream 'resets' object class descriptions have to be re-written)
    */
   def writeObject[T: ClassTag](t: T): SerializationStream = {
     objOut.writeObject(t)
+    counter += 1
     if (counterReset > 0 && counter >= counterReset) {
       objOut.reset()
       counter = 0
-    } else {
-      counter += 1
     }
     this
   }

core/src/main/scala/org/apache/spark/util/collection/ExternalAppendOnlyMap.scala

@@ -17,7 +17,7 @@
 
 package org.apache.spark.util.collection
 
-import java.io.{InputStream, BufferedInputStream, FileInputStream, File, Serializable, EOFException}
+import java.io._
 import java.util.Comparator
 
 import scala.collection.BufferedIterator
@@ -28,7 +28,7 @@ import com.google.common.io.ByteStreams
 
 import org.apache.spark.{Logging, SparkEnv}
 import org.apache.spark.annotation.DeveloperApi
-import org.apache.spark.serializer.Serializer
+import org.apache.spark.serializer.{DeserializationStream, Serializer}
 import org.apache.spark.storage.{BlockId, BlockManager}
 import org.apache.spark.util.collection.ExternalAppendOnlyMap.HashComparator
 
@@ -199,13 +199,16 @@ class ExternalAppendOnlyMap[K, V, C](
 
     // Flush the disk writer's contents to disk, and update relevant variables
     def flush() = {
-      writer.commitAndClose()
-      val bytesWritten = writer.bytesWritten
+      val w = writer
+      writer = null
+      w.commitAndClose()
+      val bytesWritten = w.bytesWritten
       batchSizes.append(bytesWritten)
       _diskBytesSpilled += bytesWritten
       objectsWritten = 0
     }
 
+    var success = false
     try {
       val it = currentMap.destructiveSortedIterator(keyComparator)
       while (it.hasNext) {
@@ -215,16 +218,28 @@ class ExternalAppendOnlyMap[K, V, C](
 
         if (objectsWritten == serializerBatchSize) {
           flush()
-          writer.close()
           writer = blockManager.getDiskWriter(blockId, file, serializer, fileBufferSize)
         }
       }
       if (objectsWritten > 0) {
         flush()
+      } else if (writer != null) {
+        val w = writer
+        writer = null
+        w.revertPartialWritesAndClose()
       }
+      success = true
     } finally {
-      // Partial failures cannot be tolerated; do not revert partial writes
-      writer.close()
+      if (!success) {
+        // This code path only happens if an exception was thrown above before we set success;
+        // close our stuff and let the exception be thrown further
+        if (writer != null) {
+          writer.revertPartialWritesAndClose()
+        }
+        if (file.exists()) {
+          file.delete()
+        }
+      }
     }
 
     currentMap = new SizeTrackingAppendOnlyMap[K, C]
@@ -389,27 +404,51 @@ class ExternalAppendOnlyMap[K, V, C](
    * An iterator that returns (K, C) pairs in sorted order from an on-disk map
    */
   private class DiskMapIterator(file: File, blockId: BlockId, batchSizes: ArrayBuffer[Long])
-    extends Iterator[(K, C)] {
-    private val fileStream = new FileInputStream(file)
-    private val bufferedStream = new BufferedInputStream(fileStream, fileBufferSize)
+    extends Iterator[(K, C)]
+  {
+    private val batchOffsets = batchSizes.scanLeft(0L)(_ + _)  // Size will be batchSize.length + 1
+    assert(file.length() == batchOffsets(batchOffsets.length - 1))
+
+    private var batchIndex = 0  // Which batch we're in
+    private var fileStream: FileInputStream = null
 
     // An intermediate stream that reads from exactly one batch
     // This guards against pre-fetching and other arbitrary behavior of higher level streams
-    private var batchStream = nextBatchStream()
-    private var compressedStream = blockManager.wrapForCompression(blockId, batchStream)
-    private var deserializeStream = ser.deserializeStream(compressedStream)
+    private var deserializeStream = nextBatchStream()
     private var nextItem: (K, C) = null
     private var objectsRead = 0
 
     /**
      * Construct a stream that reads only from the next batch.
      */
-    private def nextBatchStream(): InputStream = {
-      if (batchSizes.length > 0) {
-        ByteStreams.limit(bufferedStream, batchSizes.remove(0))
+    private def nextBatchStream(): DeserializationStream = {
+      // Note that batchOffsets.length = numBatches + 1 since we did a scan above; check whether
+      // we're still in a valid batch.
+      if (batchIndex < batchOffsets.length - 1) {
+        if (deserializeStream != null) {
+          deserializeStream.close()
+          fileStream.close()
+          deserializeStream = null
+          fileStream = null
+        }
+
+        val start = batchOffsets(batchIndex)
+        fileStream = new FileInputStream(file)
+        fileStream.getChannel.position(start)
+        batchIndex += 1
+
+        val end = batchOffsets(batchIndex)
+
+        assert(end >= start, "start = " + start + ", end = " + end +
+          ", batchOffsets = " + batchOffsets.mkString("[", ", ", "]"))
+
+        val bufferedStream = new BufferedInputStream(ByteStreams.limit(fileStream, end - start))
+        val compressedStream = blockManager.wrapForCompression(blockId, bufferedStream)
+        ser.deserializeStream(compressedStream)
       } else {
         // No more batches left
-        bufferedStream
+        cleanup()
+        null
       }
     }
 
@@ -424,10 +463,8 @@ class ExternalAppendOnlyMap[K, V, C](
         val item = deserializeStream.readObject().asInstanceOf[(K, C)]
         objectsRead += 1
         if (objectsRead == serializerBatchSize) {
-          batchStream = nextBatchStream()
-          compressedStream = blockManager.wrapForCompression(blockId, batchStream)
-          deserializeStream = ser.deserializeStream(compressedStream)
           objectsRead = 0
+          deserializeStream = nextBatchStream()
         }
         item
       } catch {
@@ -439,6 +476,9 @@ class ExternalAppendOnlyMap[K, V, C](
 
     override def hasNext: Boolean = {
       if (nextItem == null) {
+        if (deserializeStream == null) {
+          return false
+        }
         nextItem = readNextItem()
       }
       nextItem != null
@@ -455,7 +495,11 @@ class ExternalAppendOnlyMap[K, V, C](
 
     // TODO: Ensure this gets called even if the iterator isn't drained.
     private def cleanup() {
-      deserializeStream.close()
+      batchIndex = batchOffsets.length  // Prevent reading any other batch
+      val ds = deserializeStream
+      deserializeStream = null
+      fileStream = null
+      ds.close()
       file.delete()
     }
   }

core/src/main/scala/org/apache/spark/util/collection/ExternalSorter.scala

@@ -26,7 +26,7 @@ import scala.collection.mutable
 import com.google.common.io.ByteStreams
 
 import org.apache.spark.{Aggregator, SparkEnv, Logging, Partitioner}
-import org.apache.spark.serializer.Serializer
+import org.apache.spark.serializer.{DeserializationStream, Serializer}
 import org.apache.spark.storage.BlockId
 
 /**
@@ -273,13 +273,16 @@ private[spark] class ExternalSorter[K, V, C](
     // Flush the disk writer's contents to disk, and update relevant variables.
     // The writer is closed at the end of this process, and cannot be reused.
     def flush() = {
-      writer.commitAndClose()
-      val bytesWritten = writer.bytesWritten
+      val w = writer
+      writer = null
+      w.commitAndClose()
+      val bytesWritten = w.bytesWritten
       batchSizes.append(bytesWritten)
       _diskBytesSpilled += bytesWritten
       objectsWritten = 0
     }
 
+    var success = false
     try {
       val it = collection.destructiveSortedIterator(partitionKeyComparator)
       while (it.hasNext) {
@@ -299,13 +302,23 @@ private[spark] class ExternalSorter[K, V, C](
       }
       if (objectsWritten > 0) {
         flush()
+      } else if (writer != null) {
+        val w = writer
+        writer = null
+        w.revertPartialWritesAndClose()
+      }
+      success = true
+    } finally {
+      if (!success) {
+        // This code path only happens if an exception was thrown above before we set success;
+        // close our stuff and let the exception be thrown further
+        if (writer != null) {
+          writer.revertPartialWritesAndClose()
+        }
+        if (file.exists()) {
+          file.delete()
+        }
       }
-      writer.close()
-    } catch {
-      case e: Exception =>
-        writer.close()
-        file.delete()
-        throw e
     }
 
     if (usingMap) {
@@ -472,36 +485,58 @@ private[spark] class ExternalSorter[K, V, C](
    * partitions to be requested in order.
    */
   private[this] class SpillReader(spill: SpilledFile) {
-    val fileStream = new FileInputStream(spill.file)
-    val bufferedStream = new BufferedInputStream(fileStream, fileBufferSize)
+    // Serializer batch offsets; size will be batchSize.length + 1
+    val batchOffsets = spill.serializerBatchSizes.scanLeft(0L)(_ + _)
 
     // Track which partition and which batch stream we're in. These will be the indices of
     // the next element we will read. We'll also store the last partition read so that
     // readNextPartition() can figure out what partition that was from.
     var partitionId = 0
     var indexInPartition = 0L
-    var batchStreamsRead = 0
+    var batchId = 0
     var indexInBatch = 0
     var lastPartitionId = 0
 
     skipToNextPartition()
 
-    // An intermediate stream that reads from exactly one batch
+
+    // Intermediate file and deserializer streams that read from exactly one batch
     // This guards against pre-fetching and other arbitrary behavior of higher level streams
-    var batchStream = nextBatchStream()
-    var compressedStream = blockManager.wrapForCompression(spill.blockId, batchStream)
-    var deserStream = serInstance.deserializeStream(compressedStream)
+    var fileStream: FileInputStream = null
+    var deserializeStream = nextBatchStream()  // Also sets fileStream
+
     var nextItem: (K, C) = null
     var finished = false
 
     /** Construct a stream that only reads from the next batch */
-    def nextBatchStream(): InputStream = {
-      if (batchStreamsRead < spill.serializerBatchSizes.length) {
-        batchStreamsRead += 1
-        ByteStreams.limit(bufferedStream, spill.serializerBatchSizes(batchStreamsRead - 1))
+    def nextBatchStream(): DeserializationStream = {
+      // Note that batchOffsets.length = numBatches + 1 since we did a scan above; check whether
+      // we're still in a valid batch.
+      if (batchId < batchOffsets.length - 1) {
+        if (deserializeStream != null) {
+          deserializeStream.close()
+          fileStream.close()
+          deserializeStream = null
+          fileStream = null
+        }
+
+        val start = batchOffsets(batchId)
+        fileStream = new FileInputStream(spill.file)
+        fileStream.getChannel.position(start)
+        batchId += 1
+
+        val end = batchOffsets(batchId)
+
+        assert(end >= start, "start = " + start + ", end = " + end +
+          ", batchOffsets = " + batchOffsets.mkString("[", ", ", "]"))
+
+        val bufferedStream = new BufferedInputStream(ByteStreams.limit(fileStream, end - start))
+        val compressedStream = blockManager.wrapForCompression(spill.blockId, bufferedStream)
+        serInstance.deserializeStream(compressedStream)
       } else {
-        // No more batches left; give an empty stream
-        bufferedStream
+        // No more batches left
+        cleanup()
+        null
       }
     }
 
@@ -525,27 +560,27 @@ private[spark] class ExternalSorter[K, V, C](
      * If no more pairs are left, return null.
      */
     private def readNextItem(): (K, C) = {
-      if (finished) {
+      if (finished || deserializeStream == null) {
         return null
       }
-      val k = deserStream.readObject().asInstanceOf[K]
-      val c = deserStream.readObject().asInstanceOf[C]
+      val k = deserializeStream.readObject().asInstanceOf[K]
+      val c = deserializeStream.readObject().asInstanceOf[C]
       lastPartitionId = partitionId
       // Start reading the next batch if we're done with this one
       indexInBatch += 1
       if (indexInBatch == serializerBatchSize) {
-        batchStream = nextBatchStream()
-        compressedStream = blockManager.wrapForCompression(spill.blockId, batchStream)
-        deserStream = serInstance.deserializeStream(compressedStream)
         indexInBatch = 0
+        deserializeStream = nextBatchStream()
       }
       // Update the partition location of the element we're reading
       indexInPartition += 1
       skipToNextPartition()
       // If we've finished reading the last partition, remember that we're done
       if (partitionId == numPartitions) {
         finished = true
-        deserStream.close()
+        if (deserializeStream != null) {
+          deserializeStream.close()
+        }
       }
       (k, c)
     }
@@ -578,6 +613,17 @@ private[spark] class ExternalSorter[K, V, C](
         item
       }
     }
+
+    // Clean up our open streams and put us in a state where we can't read any more data
+    def cleanup() {
+      batchId = batchOffsets.length  // Prevent reading any other batch
+      val ds = deserializeStream
+      deserializeStream = null
+      fileStream = null
+      ds.close()
+      // NOTE: We don't do file.delete() here because that is done in ExternalSorter.stop().
+      // This should also be fixed in ExternalAppendOnlyMap.
+    }
   }
 
   /**