Github user massie commented on a diff in the pull request:
https://github.com/apache/spark/pull/6423#discussion_r32746147
--- Diff:
core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
---
@@ -290,22 +287,15 @@ final class ShuffleBlockFetcherIterator(
sendRequest(fetchRequests.dequeue())
}
- val iteratorTry: Try[Iterator[Any]] = result match {
+ val iteratorTry: Try[InputStream] = result match {
case FailureFetchResult(_, e) =>
Failure(e)
case SuccessFetchResult(blockId, _, buf) =>
// There is a chance that createInputStream can fail (e.g.
fetching a local file that does
// not exist, SPARK-4085). In that case, we should propagate the
right exception so
// the scheduler gets a FetchFailedException.
- Try(buf.createInputStream()).map { is0 =>
- val is = blockManager.wrapForCompression(blockId, is0)
- val iter =
serializerInstance.deserializeStream(is).asKeyValueIterator
- CompletionIterator[Any, Iterator[Any]](iter, {
- // Once the iterator is exhausted, release the buffer and set
currentResult to null
- // so we don't release it again in cleanup.
- currentResult = null
- buf.release()
- })
+ Try(buf.createInputStream()).map { inputStream =>
--- End diff --
We don't need to worry about a memory leak when the task exits with success
or failure since there is a cleanup method registered with the task context,
e.g.
```
// Add a task completion callback (called in both success case and failure
case) to cleanup.
context.addTaskCompletionListener(_ => cleanup())
```
However, you're correct that there would be a memory (and file handle)
leak, if the `InputStream` isn't closed in the `ShuffleReader`. This PR
prevents that since
`serializerInstance.deserializeStream(wrappedStream).asKeyValueIterator`
returns a `NextIterator` which closes the stream when the last record is read.
To be more defensive and potentially simplify the code, it might make sense
to have a call to `ShuffleBlockFetcherIterator.next()` to not just return the
next `InputStream` but also `close()` the last one. This would prevent callers
from having more than one `InputStream` open at a time but I don't think we
want that anyway?
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