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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 scala.collection.JavaConverters._
import scala.util.{Failure, Success, Try}
import org.apache.hadoop.conf.Configuration
import org.apache.hadoop.io._
import org.apache.spark.SparkException
import org.apache.spark.broadcast.Broadcast
import org.apache.spark.internal.Logging
import org.apache.spark.rdd.RDD
import org.apache.spark.util.{SerializableConfiguration, Utils}
/**
* A trait for use with reading custom classes in PySpark. Implement this trait and add custom
* transformation code by overriding the convert method.
*/
trait Converter[T, + U] extends Serializable {
def convert(obj: T): U
}
private[python] object Converter extends Logging {
def getInstance(converterClass: Option[String],
defaultConverter: Converter[Any, Any]): Converter[Any, Any] = {
converterClass.map { cc =>
Try {
val c = Utils.classForName(cc).newInstance().asInstanceOf[Converter[Any, Any]]
logInfo(s"Loaded converter: $cc")
c
} match {
case Success(c) => c
case Failure(err) =>
logError(s"Failed to load converter: $cc")
throw err
}
}.getOrElse { defaultConverter }
}
}
/**
* A converter that handles conversion of common [[org.apache.hadoop.io.Writable]] objects.
* Other objects are passed through without conversion.
*/
private[python] class WritableToJavaConverter(
conf: Broadcast[SerializableConfiguration]) extends Converter[Any, Any] {
/**
* Converts a [[org.apache.hadoop.io.Writable]] to the underlying primitive, String or
* object representation
*/
private def convertWritable(writable: Writable): Any = {
writable match {
case iw: IntWritable => iw.get()
case dw: DoubleWritable => dw.get()
case lw: LongWritable => lw.get()
case fw: FloatWritable => fw.get()
case t: Text => t.toString
case bw: BooleanWritable => bw.get()
case byw: BytesWritable =>
val bytes = new Array[Byte](byw.getLength)
System.arraycopy(byw.getBytes(), 0, bytes, 0, byw.getLength)
bytes
case n: NullWritable => null
case aw: ArrayWritable =>
// Due to erasure, all arrays appear as Object[] and they get pickled to Python tuples.
// Since we can't determine element types for empty arrays, we will not attempt to
// convert to primitive arrays (which get pickled to Python arrays). Users may want
// write custom converters for arrays if they know the element types a priori.
aw.get().map(convertWritable(_))
case mw: MapWritable =>
val map = new java.util.HashMap[Any, Any]()
mw.asScala.foreach { case (k, v) => map.put(convertWritable(k), convertWritable(v)) }
map
case w: Writable => WritableUtils.clone(w, conf.value.value)
case other => other
}
}
override def convert(obj: Any): Any = {
obj match {
case writable: Writable =>
convertWritable(writable)
case _ =>
obj
}
}
}
/**
* A converter that converts common types to [[org.apache.hadoop.io.Writable]]. Note that array
* types are not supported since the user needs to subclass [[org.apache.hadoop.io.ArrayWritable]]
* to set the type properly. See [[org.apache.spark.api.python.DoubleArrayWritable]] and
* [[org.apache.spark.api.python.DoubleArrayToWritableConverter]] for an example. They are used in
* PySpark RDD `saveAsNewAPIHadoopFile` doctest.
*/
private[python] class JavaToWritableConverter extends Converter[Any, Writable] {
/**
* Converts common data types to [[org.apache.hadoop.io.Writable]]. Note that array types are not
* supported out-of-the-box.
*/
private def convertToWritable(obj: Any): Writable = {
obj match {
case i: java.lang.Integer => new IntWritable(i)
case d: java.lang.Double => new DoubleWritable(d)
case l: java.lang.Long => new LongWritable(l)
case f: java.lang.Float => new FloatWritable(f)
case s: java.lang.String => new Text(s)
case b: java.lang.Boolean => new BooleanWritable(b)
case aob: Array[Byte] => new BytesWritable(aob)
case null => NullWritable.get()
case map: java.util.Map[_, _] =>
val mapWritable = new MapWritable()
map.asScala.foreach { case (k, v) =>
mapWritable.put(convertToWritable(k), convertToWritable(v))
}
mapWritable
case array: Array[Any] => {
val arrayWriteable = new ArrayWritable(classOf[Writable])
arrayWriteable.set(array.map(convertToWritable(_)))
arrayWriteable
}
case other => throw new SparkException(
s"Data of type ${other.getClass.getName} cannot be used")
}
}
override def convert(obj: Any): Writable = obj match {
case writable: Writable => writable
case other => convertToWritable(other)
}
}
/** Utilities for working with Python objects <-> Hadoop-related objects */
private[python] object PythonHadoopUtil {
/**
* Convert a [[java.util.Map]] of properties to a [[org.apache.hadoop.conf.Configuration]]
*/
def mapToConf(map: java.util.Map[String, String]): Configuration = {
val conf = new Configuration()
map.asScala.foreach { case (k, v) => conf.set(k, v) }
conf
}
/**
* Merges two configurations, returns a copy of left with keys from right overwriting
* any matching keys in left
*/
def mergeConfs(left: Configuration, right: Configuration): Configuration = {
val copy = new Configuration(left)
right.asScala.foreach(entry => copy.set(entry.getKey, entry.getValue))
copy
}
/**
* Converts an RDD of key-value pairs, where key and/or value could be instances of
* [[org.apache.hadoop.io.Writable]], into an RDD of base types, or vice versa.
*/
def convertRDD[K, V](rdd: RDD[(K, V)],
keyConverter: Converter[Any, Any],
valueConverter: Converter[Any, Any]): RDD[(Any, Any)] = {
rdd.map { case (k, v) => (keyConverter.convert(k), valueConverter.convert(v)) }
}
}
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