Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/11498#discussion_r54933191
--- Diff:
core/src/main/scala/org/apache/spark/storage/disk/DiskBlockObjectWriter.scala
---
@@ -0,0 +1,125 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.storage.disk
+
+import java.io.{File, OutputStream}
+
+import org.apache.spark.Logging
+import org.apache.spark.serializer.{SerializationStream,
SerializerInstance}
+import org.apache.spark.storage.BlockId
+import org.apache.spark.util.Utils
+
+/**
+ * A class for writing JVM objects directly to a file on disk. This class
allows data to be appended
+ * to an existing block and can guarantee atomicity in the case of faults
as it allows the caller to
+ * revert partial writes.
+ *
+ * This class does not support concurrent writes. Also, once the writer
has been opened it cannot be
+ * reopened again.
+ */
+private[spark] class DiskBlockObjectWriter(
+ diskBlockWriter: DiskBlockWriter,
+ serializerInstance: SerializerInstance,
+ val blockId: BlockId = null)
+ extends Logging {
+
+ private var bs: OutputStream = null
+ private var objOut: SerializationStream = null
+ private var initialized = false
+ private var hasBeenClosed = false
+ private var commitAndCloseHasBeenCalled = false
+
+ def file: File = diskBlockWriter.file
+
+ def open(): DiskBlockObjectWriter = {
+ if (hasBeenClosed) {
+ throw new IllegalStateException("Writer already closed. Cannot be
reopened.")
+ }
+ bs = diskBlockWriter.open()
+ objOut = serializerInstance.serializeStream(bs)
+ initialized = true
+ this
+ }
+
+ def close() {
+ if (initialized) {
+ Utils.tryWithSafeFinally {
+ if (diskBlockWriter.syncWrites) {
+ objOut.flush()
+ }
+ } {
+ objOut.close()
+ }
+ bs = null
+ objOut = null
+ initialized = false
+ hasBeenClosed = true
+ }
+ }
+
+ /**
+ * Flush the partial writes and commit them as a single atomic block.
+ */
+ def commitAndClose(): Unit = {
+ if (initialized) {
+ objOut.flush()
+ }
+ diskBlockWriter.commitAndClose()
+ commitAndCloseHasBeenCalled = true
+ }
+
+
+ /**
+ * Reverts writes that haven't been flushed yet. Callers should invoke
this function
+ * when there are runtime exceptions. This method will not throw, though
it may be
+ * unsuccessful in truncating written data.
+ *
+ * @return the file that this DiskBlockObjectWriter wrote to.
+ */
+ def revertPartialWritesAndClose(): File = {
+ if (initialized) {
+ objOut.flush()
+ }
+ diskBlockWriter.revertPartialWritesAndClose()
--- End diff --
I'm not 100% confident that the wrapping / delegation is handled properly
in all of these close methods, so I'm going to take a self-review pass to try
to figure that out.
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