大資料教程分享Actor學習筆記

　　好程式設計師 大資料 培訓 分享Actor學習筆記，在scala中她能實現很強大的功能,他是基於併發機制的一個事件模型

　　 我們現在學的scala2.10.x版本就是之前的Actor

　　 同步 :在主程式上排隊執行的任務,只有前一個任務執行完畢後,才能執行下一個任務

　　 非同步 :指不進入主程式,而進入"任務對列"的任務,只有等主程式任務執行完畢,"任務對列"開始請求主程式,請求任務執行,該任務會進入主程式

java

共享變數 -- 加鎖

會出現鎖死問題

scala

Actor不共享資料

沒有鎖的概念

Actor通訊之間需要message(通訊)

Aactor執行順序

1.首先呼叫start()方法啟動Actor

2.呼叫start()方法後act()方法會被執行

3.Actor之間進行傳送訊息

Actor傳送訊息的三種方式

! -> 傳送非同步訊息,沒有返回值

!? -> 傳送同步訊息,有返回值,會有執行緒等待

!! -> 傳送非同步訊息,有返回值,返回值型別Future[Any](用來獲取非同步操作結果)

Actor並行執行

//注意,這兩個actor會並行執行,當其中一個for迴圈結束後,actor結束

object ActorDemo01 {

def main(args: Array[String]): Unit = {

MyActor1.start()

MyActor2.start()

}

}

object MyActor1 extends Actor{

override def act(): Unit = {

for (i <- 1 to 10){

println(s"actor => $i")

Thread.sleep(2000)

}

}

object MyActor2 extends Actor{

override def act(): Unit = {

for (i <- 1 to 5){

println(s"actor2 => $i")

Thread.sleep(2000)

}

}

}

}

用Actor不斷接受訊息

執行第一種方式,非同步

object ActorDemo02 {

def main(args: Array[String]): Unit = {

val actor: MyActor = new MyActor

actor.start()

//並行執行

actor ! "start" // !->非同步

actor ! "stop"

println("傳送完成")

}

}

class MyActor extends Actor{

override def act(): Unit = {

while (true){ //死迴圈

receive { //接收

case "start" => {

println("starting")

Thread.sleep(1000)

println("started")

}

case "stop" => {

println("stopping")

Thread.sleep(1000)

println("stopped")

}

}

}

}

}

第二種方式: 利用react來代替receive,也就是說react執行緒可複用,比receive更高效

object ActorDemo03 {

def main(args: Array[String]): Unit = {

val actor: MyActor3 = new MyActor3

actor.start()

actor ! "start"

actor ! "stop"

println("成功了")

}

}

class MyActor3 extends Actor{

override def act(): Unit = {

loop {

react{

case "start" =>{

println("starting")

Thread.sleep(1000)

println("sarted")

}

case "stop" =>{

println("stoppting")

Thread.sleep(1000)

println("stopped")

}

}

}

}

}

結合樣例類練習Actor傳送訊息

//建立樣例類

case class AsyncMsg(id: Int, msg: String)

case class SyncMsg(id: Int, msg: String)

case class ReplyMsg(id: Int, msg: String)

object ActorDemo01 extends Actor {

override def act(): Unit = {

while (true) {

receive {

case "start" => println("starting...")

case AsyncMsg(id, msg) =>

{

println(s"id:$id,msg:$msg")

sender ! ReplyMsg(1,"sucess") //接收到訊息後返回響應訊息

}

case SyncMsg(id,msg) => {

println(s"id:$id,msg:$msg")

sender ! ReplyMsg(2,"sucess")

}

}

}

}

}

object ActorTest{

def main(args: Array[String]): Unit = {

val actor: Actor = ActorDemo01.start()

// //非同步傳送訊息,沒有返回值

// actor ! AsyncMsg(3,"heihei")

// println("非同步訊息傳送完成,沒有返回值")

// //同步傳送訊息,有返回值

// val text: Any = actor !? SyncMsg(4,"OK")

// println(text)

// println("同步訊息傳送成功")

//非同步傳送訊息,有返回值,返回型別為Future[Any]

val reply: Future[Any] = actor !! SyncMsg(5,"OK is 不存在的")

Thread.sleep(2000)

if (reply.isSet){

val applyMsg: Any = reply.apply()

println(applyMsg)

}else{

println("Nothing")

}

}

}

Actor並行化的wordcount

class Task extends Actor {

override def act(): Unit = {

loop {

react {

case SubmitTask(fileName) => {

val contents = Source.fromFile(new File(fileName)).mkString

val arr = contents.split("\r\n")

val result = arr.flatMap(_.split(" ")).map((_, 1)).groupBy(_._1).mapValues(_.length)

//val result = arr.flatMap(_.split(" ")).map((_, 1)).groupBy(_._1).mapValues(_.foldLeft(0)(_ + _._2))

sender ! ResultTask(result)

}

case StopTask => {

exit()

}

}

}

}

}

object WorkCount {

def main(args: Array[String]) {

val files = Array("c://words.txt", "c://words.log")

val replaySet = new mutable.HashSet[Future[Any]]

val resultList = new mutable.ListBuffer[ResultTask]

for(f <- files) {

val t = new Task

val replay = t.start() !! SubmitTask(f)

replaySet += replay

}

while(replaySet.size > 0){

val toCumpute = replaySet.filter(_.isSet)

for(r <- toCumpute){

val result = r.apply()

resultList += result.asInstanceOf[ResultTask]

replaySet.remove(r)

}

Thread.sleep(100)

}

val finalResult = resultList.map(_.result).flatten.groupBy(_._1).mapValues(x => x.foldLeft(0)(_ + _._2))

println(finalResult)

}

}

case class SubmitTask(fileName: String)

case object StopTask

case class ResultTask(result: Map[String, Int])