spark WindowedDStream 源码
spark WindowedDStream 代码
文件路径：/streaming/src/main/scala/org/apache/spark/streaming/dstream/WindowedDStream.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.rdd.RDD
import org.apache.spark.storage.StorageLevel
import org.apache.spark.streaming._
import org.apache.spark.streaming.Duration
private[streaming]
class WindowedDStream[T: ClassTag](
parent: DStream[T],
_windowDuration: Duration,
_slideDuration: Duration)
extends DStream[T](parent.ssc) {
if (!_windowDuration.isMultipleOf(parent.slideDuration)) {
throw new Exception("The window duration of windowed DStream (" + _windowDuration + ") " +
"must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
}
if (!_slideDuration.isMultipleOf(parent.slideDuration)) {
throw new Exception("The slide duration of windowed DStream (" + _slideDuration + ") " +
"must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
}
// Persist parent level by default, as those RDDs are going to be obviously reused.
parent.persist(StorageLevel.MEMORY_ONLY_SER)
def windowDuration: Duration = _windowDuration
override def dependencies: List[DStream[T]] = List(parent)
override def slideDuration: Duration = _slideDuration
override def parentRememberDuration: Duration = rememberDuration + windowDuration
override def persist(level: StorageLevel): DStream[T] = {
// Do not let this windowed DStream be persisted as windowed (union-ed) RDDs share underlying
// RDDs and persisting the windowed RDDs would store numerous copies of the underlying data.
// Instead control the persistence of the parent DStream.
parent.persist(level)
this
}
override def compute(validTime: Time): Option[RDD[T]] = {
val currentWindow = new Interval(validTime - windowDuration + parent.slideDuration, validTime)
val rddsInWindow = parent.slice(currentWindow)
Some(ssc.sc.union(rddsInWindow))
}
}
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