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[SPARK-24107][CORE] ChunkedByteBuffer.writeFully method has not reset the limit value #21175

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[SPARK-24107][CORE] ChunkedByteBuffer.writeFully method has not reset the limit value #21175

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fae1814
restore bytes limit value
Apr 26, 2018
623f26d
add ChunkedByteBufferSuite unit test
Apr 27, 2018
5ba6867
Merge branch 'master' into bugfix-ChunkedByteBuffer
Apr 27, 2018
c585131
ChunkedByteBufferSuite improve unit test
Apr 27, 2018
a2a82f1
change assert size
Apr 27, 2018
217ec9d
add SPARK-24107:
Apr 27, 2018
2bc19a3
change ByteArrayWritableChannel's size
Apr 27, 2018
c9a6816
add configure bufferWriteChunkSize
Apr 27, 2018
fa99a19
sc.conf.set spark.buffer.write.chunkSize
Apr 27, 2018
fb527c8
add try finally
Apr 27, 2018
e78ef39
fixed the style
May 2, 2018
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13 changes: 9 additions & 4 deletions core/src/main/scala/org/apache/spark/util/io/ChunkedByteBuffer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -63,10 +63,15 @@ private[spark] class ChunkedByteBuffer(var chunks: Array[ByteBuffer]) {
*/
def writeFully(channel: WritableByteChannel): Unit = {
for (bytes <- getChunks()) {
while (bytes.remaining() > 0) {
val ioSize = Math.min(bytes.remaining(), bufferWriteChunkSize)
bytes.limit(bytes.position() + ioSize)
channel.write(bytes)
val curChunkLimit = bytes.limit()
while (bytes.hasRemaining) {
try {
val ioSize = Math.min(bytes.remaining(), bufferWriteChunkSize)
bytes.limit(bytes.position() + ioSize)
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The rationale for the limit() isn't super-clear, but that was a problem in the original PR which introduced the bug (#18730). I'm commenting here only for cross-reference reference for folks who come across this patch in the future. I believe that the original motivation was http://www.evanjones.ca/java-bytebuffer-leak.html

channel.write(bytes)
} finally {
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I don't think we need the try and finally here because getChunks() returns duplicated ByteBuffers which have their own position and limit.

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I think the problem is, bytes.limit(bytes.position() + ioSize) will change the result of bytes.hasRemaining, so we have to restore the limit in each loop.

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I get your point. if there is an exception, there is no next loop and we don't need to restore the limit. so try finally is not needed

bytes.limit(curChunkLimit)
}
}
}
}
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17 changes: 15 additions & 2 deletions core/src/test/scala/org/apache/spark/io/ChunkedByteBufferSuite.scala
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Expand Up @@ -21,11 +21,12 @@ import java.nio.ByteBuffer

import com.google.common.io.ByteStreams
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add an empty line behind 22 to separate spark and third-party group.


import org.apache.spark.SparkFunSuite
import org.apache.spark.{SharedSparkContext, SparkFunSuite}
import org.apache.spark.internal.config
import org.apache.spark.network.util.ByteArrayWritableChannel
import org.apache.spark.util.io.ChunkedByteBuffer

class ChunkedByteBufferSuite extends SparkFunSuite {
class ChunkedByteBufferSuite extends SparkFunSuite with SharedSparkContext {

test("no chunks") {
val emptyChunkedByteBuffer = new ChunkedByteBuffer(Array.empty[ByteBuffer])
Expand Down Expand Up @@ -56,6 +57,18 @@ class ChunkedByteBufferSuite extends SparkFunSuite {
assert(chunkedByteBuffer.getChunks().head.position() === 0)
}

test("SPARK-24107: writeFully() write buffer which is larger than bufferWriteChunkSize") {
try {
sc.conf.set(config.BUFFER_WRITE_CHUNK_SIZE, 32L * 1024L * 1024L)
val chunkedByteBuffer = new ChunkedByteBuffer(Array(ByteBuffer.allocate(40 * 1024 * 1024)))
val byteArrayWritableChannel = new ByteArrayWritableChannel(chunkedByteBuffer.size.toInt)
chunkedByteBuffer.writeFully(byteArrayWritableChannel)
assert(byteArrayWritableChannel.length() === chunkedByteBuffer.size)
} finally {
sc.conf.remove(config.BUFFER_WRITE_CHUNK_SIZE)
}
}

test("toArray()") {
val empty = ByteBuffer.wrap(Array.empty[Byte])
val bytes = ByteBuffer.wrap(Array.tabulate(8)(_.toByte))
Expand Down