spark TransformedDStream 源码
spark TransformedDStream 代码
文件路径：/streaming/src/main/scala/org/apache/spark/streaming/dstream/TransformedDStream.scala
/*
* 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.streaming.dstream
import scala.reflect.ClassTag
import org.apache.spark.SparkException
import org.apache.spark.rdd.RDD
import org.apache.spark.streaming.{Duration, Time}
private[streaming]
class TransformedDStream[U: ClassTag] (
parents: Seq[DStream[_]],
transformFunc: (Seq[RDD[_]], Time) => RDD[U]
) extends DStream[U](parents.head.ssc) {
require(parents.nonEmpty, "List of DStreams to transform is empty")
require(parents.map(_.ssc).distinct.size == 1, "Some of the DStreams have different contexts")
require(parents.map(_.slideDuration).distinct.size == 1,
"Some of the DStreams have different slide durations")
override def dependencies: List[DStream[_]] = parents.toList
override def slideDuration: Duration = parents.head.slideDuration
override def compute(validTime: Time): Option[RDD[U]] = {
val parentRDDs = parents.map { parent => parent.getOrCompute(validTime).getOrElse(
// Guard out against parent DStream that return None instead of Some(rdd) to avoid NPE
throw new SparkException(s"Couldn't generate RDD from parent at time $validTime"))
}
val transformedRDD = transformFunc(parentRDDs, validTime)
if (transformedRDD == null) {
throw new SparkException("Transform function must not return null. " +
"Return SparkContext.emptyRDD() instead to represent no element " +
"as the result of transformation.")
}
Some(transformedRDD)
}
/**
* Wrap a body of code such that the call site and operation scope
* information are passed to the RDDs created in this body properly.
* This has been overridden to make sure that `displayInnerRDDOps` is always `true`, that is,
* the inner scopes and callsites of RDDs generated in `DStream.transform` are always
* displayed in the UI.
*/
override protected[streaming] def createRDDWithLocalProperties[U](
time: Time,
displayInnerRDDOps: Boolean)(body: => U): U = {
super.createRDDWithLocalProperties(time, displayInnerRDDOps = true)(body)
}
}
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