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[SPARK-24809] [SQL] Serializing LongToUnsafeRowMap in executor may result in data error #21772

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[SPARK-24809] [SQL] Serializing LongToUnsafeRowMap in executor may result in data error #21772

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[SPARK-24809] [SQL] Serializing LongHashedRelation in executor may re…
liutang123 Jul 15, 2018
f67ff4d
[SPARK-24809][SQL] updte code style, add UT.
liutang123 Jul 19, 2018
06a9547
do not change existing code
liutang123 Jul 24, 2018
c9ebfd0
optimize code style.
liutang123 Jul 24, 2018
6246dfa
small update.
liutang123 Jul 29, 2018
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13 changes: 8 additions & 5 deletions sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -726,9 +726,10 @@ private[execution] final class LongToUnsafeRowMap(val mm: TaskMemoryManager, cap

writeLong(array.length)
writeLongArray(writeBuffer, array, array.length)
val used = ((cursor - Platform.LONG_ARRAY_OFFSET) / 8).toInt
writeLong(used)
writeLongArray(writeBuffer, page, used)

val usedWordsNumber = ((cursor - Platform.LONG_ARRAY_OFFSET) / 8).toInt
writeLong(usedWordsNumber)
writeLongArray(writeBuffer, page, usedWordsNumber)

@viirya viirya Jul 23, 2018

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If no good reason, shall we revert this change? Looks like you only rename it?

}

override def writeExternal(output: ObjectOutput): Unit = {
Expand Down Expand Up @@ -770,8 +771,10 @@ private[execution] final class LongToUnsafeRowMap(val mm: TaskMemoryManager, cap
val length = readLong().toInt
mask = length - 2
array = readLongArray(readBuffer, length)
val pageLength = readLong().toInt
page = readLongArray(readBuffer, pageLength)
val usedWordsNumber = readLong().toInt
// Set cursor because cursor is used in write function.

@viirya viirya Jul 24, 2018

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maybe: Restore cursor variable to make this map able to be serialized again on executors?

cursor = usedWordsNumber * 8 + Platform.LONG_ARRAY_OFFSET
page = readLongArray(readBuffer, usedWordsNumber)

@viirya viirya Jul 23, 2018

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ditto. Can you just update cursor and revert other unrelated change?

}

override def readExternal(in: ObjectInput): Unit = {
Expand Down
33 changes: 33 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/execution/joins/HashedRelationSuite.scala
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Expand Up @@ -278,6 +278,39 @@ class HashedRelationSuite extends SparkFunSuite with SharedSQLContext {
map.free()
}

test("SPARK-24809: Serializing LongHashedRelation in executor may result in data error") {

@viirya viirya Jul 23, 2018

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Is it possible to have an end-to-end test for this?

@liutang123 liutang123 Jul 24, 2018

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I think this UT can cover the case I had met.
End-to-end test is too hard to structure because this case just occurs when executor's memory is not enough to hold the block and the broadcast cache is removed by the garbage collector.

val unsafeProj = UnsafeProjection.create(Array[DataType](LongType))
val originalMap = new LongToUnsafeRowMap(mm, 1)

val key1 = 1L
val value1 = new Random().nextLong()

val key2 = 2L
val value2 = new Random().nextLong()

@viirya viirya Jul 24, 2018

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Is it necessary to use Random here? Can we use two arbitrary long values?


originalMap.append(key1, unsafeProj(InternalRow(value1)))
originalMap.append(key2, unsafeProj(InternalRow(value2)))
originalMap.optimize()

val resultRow = new UnsafeRow(1)
assert(originalMap.getValue(key1, resultRow).getLong(0) === value1)
assert(originalMap.getValue(key2, resultRow).getLong(0) === value2)

@viirya viirya Jul 24, 2018

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We don't need to test LongToUnsafeRowMap's normal feature here. We just need to verify the map after two ser/de can work normally.


val ser = new KryoSerializer(

@cloud-fan cloud-fan Jul 28, 2018

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we can write sparkContext.env.serializer.newInstance()

(new SparkConf).set("spark.kryo.referenceTracking", "false")).newInstance()

val mapSerializedInDriver = ser.deserialize[LongToUnsafeRowMap](ser.serialize(originalMap))

@viirya viirya Jul 24, 2018

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nit:

// Simulate serialize/deserialize twice on driver and executor
val firstTimeSerialized = ...
val secondTimeSerialized = ...

val mapSerializedInExecutor =
ser.deserialize[LongToUnsafeRowMap](ser.serialize(mapSerializedInDriver))

assert(mapSerializedInExecutor.getValue(key1, resultRow).getLong(0) === value1)
assert(mapSerializedInExecutor.getValue(key2, resultRow).getLong(0) === value2)

originalMap.free()
mapSerializedInDriver.free()
mapSerializedInExecutor.free()
}

test("Spark-14521") {
val ser = new KryoSerializer(
(new SparkConf).set("spark.kryo.referenceTracking", "false")).newInstance()
Expand Down