Github user dafrista commented on a diff in the pull request:
https://github.com/apache/spark/pull/13382#discussion_r65287494
--- Diff:
core/src/main/scala/org/apache/spark/storage/DiskBlockObjectWriter.scala ---
@@ -46,66 +46,82 @@ private[spark] class DiskBlockObjectWriter(
extends OutputStream
with Logging {
+ /**
+ * Guards against close calls, e.g. from a wrapping stream.
+ * Call manualClose to close the stream that was extended by this trait.
+ */
+ private trait ManualCloseOutputStream extends OutputStream {
+ abstract override def close(): Unit = {
+ flush()
+ }
+
+ def manualClose(): Unit = {
+ super.close()
+ }
+ }
+
/** The file channel, used for repositioning / truncating the file. */
private var channel: FileChannel = null
+ private var mcs: ManualCloseOutputStream = null
private var bs: OutputStream = null
private var fos: FileOutputStream = null
private var ts: TimeTrackingOutputStream = null
private var objOut: SerializationStream = null
private var initialized = false
+ private var streamOpen = false
private var hasBeenClosed = false
- private var commitAndCloseHasBeenCalled = false
/**
* Cursors used to represent positions in the file.
*
- * xxxxxxxx|--------|--- |
- * ^ ^ ^
- * | | finalPosition
- * | reportedPosition
- * initialPosition
+ * xxxxxxxx|--------|---|
+ * ^ ^
+ * | committedPosition
+ * reportedPosition
*
- * initialPosition: Offset in the file where we start writing. Immutable.
* reportedPosition: Position at the time of the last update to the
write metrics.
- * finalPosition: Offset where we stopped writing. Set on
closeAndCommit() then never changed.
+ * committedPosition: Offset after last committed write.
* -----: Current writes to the underlying file.
* xxxxx: Existing contents of the file.
*/
- private val initialPosition = file.length()
- private var finalPosition: Long = -1
- private var reportedPosition = initialPosition
+ private var committedPosition = file.length()
+ private var reportedPosition = committedPosition
/**
* Keep track of number of records written and also use this to
periodically
* output bytes written since the latter is expensive to do for each
record.
*/
private var numRecordsWritten = 0
+ private def initialize(): Unit = {
+ fos = new FileOutputStream(file, true)
+ channel = fos.getChannel()
+ ts = new TimeTrackingOutputStream(writeMetrics, fos)
+ class ManualCloseBufferedOutputStream
+ extends BufferedOutputStream(ts, bufferSize) with
ManualCloseOutputStream
+ mcs = new ManualCloseBufferedOutputStream
+ }
+
def open(): DiskBlockObjectWriter = {
if (hasBeenClosed) {
throw new IllegalStateException("Writer already closed. Cannot be
reopened.")
}
- fos = new FileOutputStream(file, true)
- ts = new TimeTrackingOutputStream(writeMetrics, fos)
- channel = fos.getChannel()
- bs = compressStream(new BufferedOutputStream(ts, bufferSize))
+ if (!initialized) {
+ initialize()
+ initialized = true
+ }
+ bs = compressStream(mcs)
objOut = serializerInstance.serializeStream(bs)
- initialized = true
+ streamOpen = true
this
}
override def close() {
if (initialized) {
Utils.tryWithSafeFinally {
- if (syncWrites) {
- // Force outstanding writes to disk and track how long it takes
- objOut.flush()
- val start = System.nanoTime()
- fos.getFD.sync()
- writeMetrics.incWriteTime(System.nanoTime() - start)
- }
+ commit()
--- End diff --
This is interesting. Making `close()` a no-op breaks my understanding of
`OutputStream`, where I expect (a) any buffered data to be written out and (b)
cleaning up resources. But I don't see anywhere that definitely prescribes this
either.
Apart from that, right now having `revertPartialWritesAndClose()` call
`close()` may be causing more confusion -- on this code path, the `commit()`
called on `close()` ends up having no effect because `streamOpen` is set to
false, but it's not so clear. How about introducing a private
`closeResources()` that cleans up only the resources, and have `close()` call
`commit()`, then `closeResources()`; and have `revertPartialWritesAndClose()`
call `closeResources()` instead of `close()`?
If the previous paragraph doesn't make much sense, I can push a commit with
this change.
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