spark复习二:Broadcast广播变量和accumulator累加器 技术标签: spark1.shared variable共享变量: scala> val kvphone=sc.parallelize(List((1,"iphone"),(2,"xiaomi"),(3,"oppo"),(4,"huawei"))) kvphone: org.apache.spark.rdd.RDD[(Int, St
public class BroadcastVariable { public static void main(String[] args) { SparkConf conf = new SparkConf() .setAppName("BroadcastVariable") .setMaster("local"); JavaSparkContext sc = new JavaSparkContext(conf); // 在java中,创建共享变量,就是调用SparkContext的broadcast()方法 // 获取的返回...
Spark提供的Broadcast Variable,是只读的。并且在每个节点上只会有一份副本,而不会为每个task都拷贝一份副本。因此其最大作用,就是减少变量到各个节点的网络传输消耗,以及在各个节点上的内存消耗。此外,spark自己内部也使用了高效的广播算法来减少网络消耗。 可以通过调用SparkContext的broadcast()方法,来针对某个变量创...
Variables of broadcast allow the developers of Spark to keep a secured read only cached variable on different nodes. With the needed tasks, only shipping a copy merely. Without having to waste a lot of time and transfer of network input and output, they can be used in giving a node a la...
Accumulator和Broadcast Accumulate packagecom.shujia.spark.coreimportjava.langimportorg.apache.spark.{SparkConf, SparkContext}importorg.apache.spark.rdd.RDDimportorg.apache.spark.util.LongAccumulator object Demo21Accumulator { def main(args: Array[String]): Unit={...
使用BroadcastVariable广播变量,只是将上面的第24行代码改成下一行即可。 scala实现 importorg.apache.spark.{SparkConf,SparkContext}objectBroadcastVariable2{defmain(args:Array[String]):Unit={valconf=newSparkConf().setAppName("BroadcastVariable").setMaster("local")valsc=newSparkContext(conf)valfactor=3val...
就是说,为了能够更加高效的在driver和算子之间共享数据,spark提供了两种有限的共享变量,一者广播变量,一者累加器。 broadcast广播变量 说明 如果我们要在分布式计算里面分发大对象,例如:字典,集合,黑白名单等,这个都会由Driver端进行分发,一般来讲,如果这个变量不是广播变量,那么每个task就会分发一份,这在task数目十分多...
[[org.apache.spark.broadcast.Broadcast]] object for reading it in distributed functions. The variable will be sent to each cluster only once. 函数原型: defbroadcast[T](value:T):Broadcast[T] 广播变量允许程序员将一个只读的变量缓存在每台机器上,而不用在任务之间传递变量。广播变量可被用于有效地给...
("local")valsc =newSparkContext(conf)//1 test for Broadcast//这个变量只能在drive 端修改,不能在executor 端修改 ,从下面的bRDD可以看出 其没有transformation 算子 ,也就是不可以修改//但是可以读取里面的数据值 .value//不产生shuffle 的 优化,但是需要这个RDD 数据量较小//Spark提供的Broadcast Variable...
Broadcast a read-only variable to the cluster, returning a [[org.apache.spark.broadcast.Broadcast]] object for reading it in distributed functions. The variable will be sent to each cluster only once. 函数原型: defbroadcast[T](value:T):Broadcast[T] ...