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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.
*/
// scalastyle:off println
package org.apache.spark.examples
import java.util.Random
import org.apache.spark.{SparkConf, SparkContext}
/**
* Usage: SimpleSkewedGroupByTest [numMappers] [numKVPairs] [valSize] [numReducers] [ratio]
*/
object SimpleSkewedGroupByTest {
def main(args: Array[String]) {
val sparkConf = new SparkConf().setAppName("SimpleSkewedGroupByTest")
var numMappers = if (args.length > 0) args(0).toInt else 2
var numKVPairs = if (args.length > 1) args(1).toInt else 1000
var valSize = if (args.length > 2) args(2).toInt else 1000
var numReducers = if (args.length > 3) args(3).toInt else numMappers
var ratio = if (args.length > 4) args(4).toInt else 5.0
val sc = new SparkContext(sparkConf)
val pairs1 = sc.parallelize(0 until numMappers, numMappers).flatMap { p =>
val ranGen = new Random
var result = new Array[(Int, Array[Byte])](numKVPairs)
for (i <- 0 until numKVPairs) {
val byteArr = new Array[Byte](valSize)
ranGen.nextBytes(byteArr)
val offset = ranGen.nextInt(1000) * numReducers
if (ranGen.nextDouble < ratio / (numReducers + ratio - 1)) {
// give ratio times higher chance of generating key 0 (for reducer 0)
result(i) = (offset, byteArr)
} else {
// generate a key for one of the other reducers
val key = 1 + ranGen.nextInt(numReducers-1) + offset
result(i) = (key, byteArr)
}
}
result
}.cache
// Enforce that everything has been calculated and in cache
pairs1.count
println("RESULT: " + pairs1.groupByKey(numReducers).count)
// Print how many keys each reducer got (for debugging)
// println("RESULT: " + pairs1.groupByKey(numReducers)
// .map{case (k,v) => (k, v.size)}
// .collectAsMap)
sc.stop()
}
}
// scalastyle:on println
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