akka 叢集 Sharding分片

分片上下級結構

叢集(多臺節點機) —> 每臺節點機(1個片區) —> 每個片區(多個分片) —> 每個分片(多個實體)

實體： 分片管理的 Actor
Shards ：分片是統一管理的一組實體
ShardRegion ： 片區，部署在每個叢集節點上，對分片進行管理
ShardCoordinator : cluster-singleton 叢集單例, 決定分片屬於哪個片區

工作原理

ShardRegion 在節點上啟動

帶實體ID的訊息--> 片區ShardRegion ,請求分片位置-->ShardCoordinator-->決定哪個ShardRegion將擁有Shard-->

ShardRegion 確認請求並建立 Shard supervisor 做為子actor -->shard actor 建立 entity -->ShardRegion和Shard 定位entity

分割槽的分片規則

所有片區組成分散式分片管理層，帶實體ID的訊息直接發給本機片區，分片管理層路由訊息， ShardRegion建立需要提供基於ShardRegion.MessageExtractor的實現 ，必須提供從訊息抽取分片和實體ID的函式

示例實現

package shard

import akka.actor.AbstractActor
import akka.actor.ActorRef
import akka.actor.ActorSystem
import akka.actor.Props
import akka.cluster.sharding.ClusterSharding
import akka.cluster.sharding.ClusterShardingSettings
import akka.cluster.sharding.ShardCoordinator
import akka.cluster.sharding.ShardRegion
import akka.japi.Option
import akka.japi.pf.ReceiveBuilder
import com.typesafe.config.ConfigFactory
import org.slf4j.LoggerFactory
import java.io.Serializable
import java.time.Clock.system
import java.time.Clock.system
import java.util.*
import java.time.Clock.system


/**
 * Created by: tankx
 * Date: 2019/7/16
 * Description: 叢集分片示例
 */


//分佈到叢集環境中
class DogActor : AbstractActor() {

    var log = LoggerFactory.getLogger(DogActor::class.java)

    override fun createReceive(): Receive {
        return ReceiveBuilder.create().matchAny(this::receive).build()
    }

    fun receive(obj: Any) {

        log.info("收到訊息: $obj")
        if (obj is DogMsg) {
            log.info("${obj.id} ${obj.msg}")
        }

    }

}

//定義訊息（必須帶有實體ID進行分片）
data class DogMsg(var id: Int, var msg: String) : Serializable

//分片規則
class ShardExtractor : ShardRegion.MessageExtractor {
    //提取實體ID，實體對應的actor
    override fun entityId(message: Any?): String {
        if (message is DogMsg) {
            return message.id.toString()
        } else {
            throw RuntimeException("無法識別訊息型別 $message")
        }
    }

    //根據實體ID，計算出對應分片ID
    override fun shardId(message: Any?): String {
        //var numberOfShards: Int = 10 //簡單的分割槽數取模 return message.id%numberOfShards
        if (message is DogMsg) {
            //return (message.id % 10).toString()
            return message.id.toString()
        } else {
            throw RuntimeException("無法識別訊息型別 $message")
        }
    }

    //對訊息可進行拆封操作
    override fun entityMessage(message: Any): Any {
        return message
    }

}
//分割槽停止時會派發的訊息型別
object handOffStopMessage

fun createActorSystem(port: Int): ActorSystem {
    val config = ConfigFactory.parseString(
        "akka.remote.artery.canonical.port=$port"
    ).withFallback(
        ConfigFactory.load()
    )

    var actorSystem = ActorSystem.create("custerA", config);

    return actorSystem

}

fun startShardRegion(port: Int) {


    var actorSystem = createActorSystem(port)

    val settings = ClusterShardingSettings.create(actorSystem)//.withRole("ClusterShardRole")

    val shardReg = ClusterSharding.get(actorSystem).start(
        "dogShard",
        Props.create(DogActor::class.java),
        settings,
        ShardExtractor(),
        ShardCoordinator.LeastShardAllocationStrategy(10, 1),
        handOffStopMessage
    )

    for (i in 1..10) {

        shardReg.tell(DogMsg(i, " wang"), ActorRef.noSender())

        Thread.sleep(3000)
    }

}


fun shardRegProxy() {

    var actorSystem = createActorSystem(2663)

    //startProxy 代理模式,即它不會承載任何實體本身，但知道如何將訊息委託到正確的位置
    ClusterSharding.get(actorSystem)
        .startProxy("dogShard", Optional.empty(), ShardExtractor())
        .let { println("  shard proxy $it started.") }

    Thread.sleep(3000)

    var shardReg = ClusterSharding.get(actorSystem).shardRegion("dogShard")


    for (i in 1..100) {

        shardReg.tell(DogMsg(i, "C wang"), ActorRef.noSender())

        Thread.sleep(1500)
    }
}

再分別啟動入口

fun main() {
    startShardRegion(2661)
}

fun main() {
    startShardRegion(2662)
}

fun main() {

    shardRegProxy()

}

配置檔案：

akka {
  actor {
    provider = "cluster"
  }

  # For the sample, just bind to loopback and do not allow access from the network
  # the port is overridden by the logic in main class
  remote.artery {
    enabled = on
    transport = tcp
    canonical.port = 0
    canonical.hostname = 127.0.0.1
  }

  cluster {
    seed-nodes = [
      "akka://[email protected]:2661",
      "akka://[email protected]:2662"]

    # auto downing is NOT safe for production deployments.
    # you may want to use it during development, read more about it in the docs.
    auto-down-unreachable-after = 10s
  }
}

注意

以上示例需在同屬一個叢集，訊息才能正常中轉，所以一定要保障 ActorSystem.create(name,config) name 為一致！（調了半天訊息一直沒有傳送成功，原來是這裡的問題，KAO!）

同一個叢集同一個ActorSystem name!

不然會報異常：

No coordinator found to register. Probably, no seed-nodes configured and manual cluster join not performed

&n