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/*
* 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.api.python
import java.util.{ArrayList => JArrayList}
import scala.collection.JavaConverters._
import scala.collection.mutable
import scala.util.Failure
import scala.util.Try
import net.razorvine.pickle.{Pickler, Unpickler}
import org.apache.spark.SparkException
import org.apache.spark.api.java.JavaRDD
import org.apache.spark.internal.Logging
import org.apache.spark.rdd.RDD
/** Utilities for serialization / deserialization between Python and Java, using Pickle. */
private[spark] object SerDeUtil extends Logging {
class ByteArrayConstructor extends net.razorvine.pickle.objects.ByteArrayConstructor {
override def construct(args: Array[Object]): Object = {
// Deal with an empty byte array pickled by Python 3.
if (args.length == 0) {
Array.emptyByteArray
} else {
super.construct(args)
}
}
}
private var initialized = false
// This should be called before trying to unpickle array.array from Python
// In cluster mode, this should be put in closure
def initialize(): Unit = {
synchronized{
if (!initialized) {
Unpickler.registerConstructor("__builtin__", "bytearray", new ByteArrayConstructor())
Unpickler.registerConstructor("builtins", "bytearray", new ByteArrayConstructor())
Unpickler.registerConstructor("__builtin__", "bytes", new ByteArrayConstructor())
Unpickler.registerConstructor("_codecs", "encode", new ByteArrayConstructor())
initialized = true
}
}
}
initialize()
/**
* Convert an RDD of Java objects to Array (no recursive conversions).
* It is only used by pyspark.sql.
*/
def toJavaArray(jrdd: JavaRDD[Any]): JavaRDD[Array[_]] = {
jrdd.rdd.map {
case objs: JArrayList[_] =>
objs.toArray
case obj if obj.getClass.isArray =>
obj.asInstanceOf[Array[_]].toArray
}.toJavaRDD()
}
/**
* Choose batch size based on size of objects
*/
private[spark] class AutoBatchedPickler(iter: Iterator[Any]) extends Iterator[Array[Byte]] {
private val pickle = new Pickler(/* useMemo = */ true,
/* valueCompare = */ false)
private var batch = 1
private val buffer = new mutable.ArrayBuffer[Any]
override def hasNext: Boolean = iter.hasNext
override def next(): Array[Byte] = {
while (iter.hasNext && buffer.length < batch) {
buffer += iter.next()
}
val bytes = pickle.dumps(buffer.toArray)
val size = bytes.length
// let 1M < size < 10M
if (size < 1024 * 1024) {
batch *= 2
} else if (size > 1024 * 1024 * 10 && batch > 1) {
batch /= 2
}
buffer.clear()
bytes
}
}
/**
* Convert an RDD of Java objects to an RDD of serialized Python objects, that is usable by
* PySpark.
*/
def javaToPython(jRDD: JavaRDD[_]): JavaRDD[Array[Byte]] = {
jRDD.rdd.mapPartitions { iter => new AutoBatchedPickler(iter) }
}
/**
* Convert an RDD of serialized Python objects to RDD of objects, that is usable by PySpark.
*/
def pythonToJava(pyRDD: JavaRDD[Array[Byte]], batched: Boolean): JavaRDD[Any] = {
pyRDD.rdd.mapPartitions { iter =>
initialize()
val unpickle = new Unpickler
iter.flatMap { row =>
val obj = unpickle.loads(row)
if (batched) {
obj match {
case array: Array[Any] => array.toSeq
case _ => obj.asInstanceOf[JArrayList[_]].asScala
}
} else {
Seq(obj)
}
}
}.toJavaRDD()
}
private def checkPickle(t: (Any, Any)): (Boolean, Boolean) = {
val pickle = new Pickler(/* useMemo = */ true,
/* valueCompare = */ false)
val kt = Try {
pickle.dumps(t._1)
}
val vt = Try {
pickle.dumps(t._2)
}
(kt, vt) match {
case (Failure(kf), Failure(vf)) =>
logWarning(s"""
|Failed to pickle Java object as key: ${t._1.getClass.getSimpleName}, falling back
|to 'toString'. Error: ${kf.getMessage}""".stripMargin)
logWarning(s"""
|Failed to pickle Java object as value: ${t._2.getClass.getSimpleName}, falling back
|to 'toString'. Error: ${vf.getMessage}""".stripMargin)
(true, true)
case (Failure(kf), _) =>
logWarning(s"""
|Failed to pickle Java object as key: ${t._1.getClass.getSimpleName}, falling back
|to 'toString'. Error: ${kf.getMessage}""".stripMargin)
(true, false)
case (_, Failure(vf)) =>
logWarning(s"""
|Failed to pickle Java object as value: ${t._2.getClass.getSimpleName}, falling back
|to 'toString'. Error: ${vf.getMessage}""".stripMargin)
(false, true)
case _ =>
(false, false)
}
}
/**
* Convert an RDD of key-value pairs to an RDD of serialized Python objects, that is usable
* by PySpark. By default, if serialization fails, toString is called and the string
* representation is serialized
*/
def pairRDDToPython(rdd: RDD[(Any, Any)], batchSize: Int): RDD[Array[Byte]] = {
val (keyFailed, valueFailed) = rdd.take(1) match {
case Array() => (false, false)
case Array(first) => checkPickle(first)
}
rdd.mapPartitions { iter =>
val cleaned = iter.map { case (k, v) =>
val key = if (keyFailed) k.toString else k
val value = if (valueFailed) v.toString else v
Array[Any](key, value)
}
if (batchSize == 0) {
new AutoBatchedPickler(cleaned)
} else {
val pickle = new Pickler(/* useMemo = */ true,
/* valueCompare = */ false)
cleaned.grouped(batchSize).map(batched => pickle.dumps(batched.asJava))
}
}
}
/**
* Convert an RDD of serialized Python tuple (K, V) to RDD[(K, V)].
*/
def pythonToPairRDD[K, V](pyRDD: RDD[Array[Byte]], batched: Boolean): RDD[(K, V)] = {
def isPair(obj: Any): Boolean = {
Option(obj.getClass.getComponentType).exists(!_.isPrimitive) &&
obj.asInstanceOf[Array[_]].length == 2
}
val rdd = pythonToJava(pyRDD, batched).rdd
rdd.take(1) match {
case Array(obj) if isPair(obj) =>
// we only accept (K, V)
case Array() =>
// we also accept empty collections
case Array(other) => throw new SparkException(
s"RDD element of type ${other.getClass.getName} cannot be used")
}
rdd.map { obj =>
val arr = obj.asInstanceOf[Array[_]]
(arr.head.asInstanceOf[K], arr.last.asInstanceOf[V])
}
}
}
