akka-cluster对每个节点的每种状态变化都会在系统消息队列里发布相关的事件。通过订阅有关节点状态变化的消息就可以获取每个节点的状态。这部分已经在之前关于akka-cluster的讨论里介绍过了。由于akka-typed里采用了新的消息交流协议，而系统消息的发布和订阅也算是消息交换，也受交流协议约束。所以想通过重写以前示范的ClusterMemberStatus来了解一下akka-typed环境下节点状态变化消息监听的一些机制。
我们需要一个actor来订阅系统发布的节点状态变化消息。这里涉及到系统、actor两端的信息交流。假设向系统订阅是一种消息的发送，那么得到的节点状态变化消息就是系统的response了。先看看actor里的消息定义：
object MonitorActor {
sealed trait ClusterEvent
private case class MemberStatus(event: MemberEvent) extends ClusterEvent
private case class ReachStatus(event: ReachabilityEvent) extends ClusterEvent
def apply(): Behavior[ClusterEvent] = Behaviors.setup[ClusterEvent] { ctx =>
val memberEventAdapter: ActorRef[MemberEvent] = ctx.messageAdapter(MemberStatus)
val reachEventAdapter: ActorRef[ReachabilityEvent] = ctx.messageAdapter(ReachStatus)
Cluster(ctx.system).subscriptions ! Subscribe(memberEventAdapter,classOf[MemberEvent])
Cluster(ctx.system).subscriptions ! Subscribe(reachEventAdapter,classOf[ReachabilityEvent])
...
}
首先，response 分为 MemberEvent, ReachabilityEvent两种。MonitorActor处理的消息类型是ClusterEvent。为了处理系统返回的response类型，即MemberEvent,ReachabilityEvent，必须提供这两种类型到ClusterEvent的转换。通过ctx.messageAdapter登记MemberEvent -> MemberStatus, ReachabilityEvent -> ReachStatus两种类型转换机制使MonitorActor可以接收到MemberStatus, ReachStatus两种消息：
object MonitorActor {
sealed trait ClusterEvent
private case class MemberStatus(event: MemberEvent) extends ClusterEvent
private case class ReachStatus(event: ReachabilityEvent) extends ClusterEvent
def apply(): Behavior[ClusterEvent] = Behaviors.setup[ClusterEvent] { ctx =>
val memberEventAdapter: ActorRef[MemberEvent] = ctx.messageAdapter(MemberStatus)
val reachEventAdapter: ActorRef[ReachabilityEvent] = ctx.messageAdapter(ReachStatus)
Cluster(ctx.system).subscriptions ! Subscribe(memberEventAdapter,classOf[MemberEvent])
Cluster(ctx.system).subscriptions ! Subscribe(reachEventAdapter,classOf[ReachabilityEvent])
Behaviors.receiveMessage { event =>
event match {
case MemberStatus(status) =>
status match {
case MemberJoined(member) =>
ctx.log.info("**************** Member joined: [{}] ***************", member.address)
case MemberJoined(member) =>
ctx.log.info("**************** Member joined: [{}] ***************", member.address)
case MemberUp(member) =>
ctx.log.info("**************** Member is Up: [{}] ***************", member.address)
case MemberRemoved(member, previousStatus) =>
ctx.log.info("**************** Member is Removed: [{}] after {} ***************",
member.address, previousStatus)
case MemberLeft(member) =>
ctx.log.info("**************** Member left: [{}] ***************", member.address)
case MemberExited(member) =>
ctx.log.info("**************** Member exited: [{}] ***************", member.address)
case _: MemberEvent => // ignore
}
case ReachStatus(status) =>
status match {
case UnreachableMember(member) =>
ctx.log.info("**************** Member detected as unreachable: [{}] ***************", member)
case ReachableMember(member) =>
ctx.log.info("**************** Member back to reachable: [{}] ***************", member)
}
}
Behaviors.same
}
}
}
还需要一个actor, 什么都不干。存粹构建一个MonitorActor：
object RootActor {
def apply(): Behavior[Nothing] = Behaviors.setup[Nothing] {ctx =>
ctx.spawn(MonitorActor(),"listner")
Behaviors.empty
}
}
好了，看看main是怎么实现的吧：
object ClusterMemberStatus {
import com.typesafe.config.ConfigFactory
def main(args: Array[String]): Unit = {
val ports =
if (args.isEmpty)
Seq(25251, 25252, 0)
else
args.toSeq.map(_.toInt)
ports.foreach { port =>
startup(port)
}
}
def startup(port: Int): Unit = {
val config = ConfigFactory.parseString(s"""
akka.remote.artery.canonical.port=$port
""").withFallback(ConfigFactory.load("cluster.conf"))
ActorSystem[Nothing](RootActor(),"ClusterSystem",config)
}
}
下面是测试结果显示：
22:14:52.755 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:25251] *************** 22:14:52.810 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:51081] - Received InitJoinAck message from [Actor[akka://ClusterSystem@127.0.0.1:25251/system/cluster/core/daemon#313431252]] to [akka://ClusterSystem@127.0.0.1:51081] 22:14:52.825 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25251] - Node [akka://ClusterSystem@127.0.0.1:51081] is JOINING, roles [dc-default] 22:14:52.825 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member joined: [akka://ClusterSystem@127.0.0.1:51081] *************** 22:14:52.829 [ClusterSystem-akka.actor.internal-dispatcher-7] DEBUG akka.cluster.typed.internal.receptionist.ClusterReceptionist - ClusterReceptionist [akka://ClusterSystem@127.0.0.1:25251] - Node added [UniqueAddress(akka://ClusterSystem@127.0.0.1:51081,567025403336682144)] 22:14:52.858 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:51081] - Welcome from [akka://ClusterSystem@127.0.0.1:25251] 22:14:52.858 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:25251] *************** 22:14:52.858 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member joined: [akka://ClusterSystem@127.0.0.1:51081] *************** 22:14:52.858 [ClusterSystem-akka.actor.internal-dispatcher-13] DEBUG akka.cluster.typed.internal.receptionist.ClusterReceptionist - ClusterReceptionist [akka://ClusterSystem@127.0.0.1:51081] - Node added [UniqueAddress(akka://ClusterSystem@127.0.0.1:25251,6076326462170320177)] 22:14:53.044 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25251] - Leader is moving node [akka://ClusterSystem@127.0.0.1:51081] to [Up] 22:14:53.044 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:51081] *************** 22:14:53.679 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:51081] *************** 22:14:57.707 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25251] - Received InitJoin message from [Actor[akka://ClusterSystem@127.0.0.1:25252/system/cluster/core/daemon/joinSeedNodeProcess-1#1472023843]] to [akka://ClusterSystem@127.0.0.1:25251] 22:14:57.707 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25251] - Sending InitJoinAck message from node [akka://ClusterSystem@127.0.0.1:25251] to [Actor[akka://ClusterSystem@127.0.0.1:25252/system/cluster/core/daemon/joinSeedNodeProcess-1#1472023843]] (version [2.6.5]) 22:14:57.732 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25252] - Received InitJoinAck message from [Actor[akka://ClusterSystem@127.0.0.1:25251/system/cluster/core/daemon#313431252]] to [akka://ClusterSystem@127.0.0.1:25252] 22:14:57.734 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25251] - Node [akka://ClusterSystem@127.0.0.1:25252] is JOINING, roles [dc-default] 22:14:57.735 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member joined: [akka://ClusterSystem@127.0.0.1:25252] *************** 22:14:57.735 [ClusterSystem-akka.actor.internal-dispatcher-26] DEBUG akka.cluster.typed.internal.receptionist.ClusterReceptionist - ClusterReceptionist [akka://ClusterSystem@127.0.0.1:25251] - Node added [UniqueAddress(akka://ClusterSystem@127.0.0.1:25252,-6913064885699273532)] 22:14:57.737 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25252] - Welcome from [akka://ClusterSystem@127.0.0.1:25251] 22:14:57.737 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:25251] *************** 22:14:57.738 [ClusterSystem-akka.actor.internal-dispatcher-30] DEBUG akka.cluster.typed.internal.receptionist.ClusterReceptionist - ClusterReceptionist [akka://ClusterSystem@127.0.0.1:25252] - Node added [UniqueAddress(akka://ClusterSystem@127.0.0.1:25251,6076326462170320177)] 22:14:57.738 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member joined: [akka://ClusterSystem@127.0.0.1:25252] *************** 22:14:57.738 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:51081] *************** 22:14:57.738 [ClusterSystem-akka.actor.internal-dispatcher-30] DEBUG akka.cluster.typed.internal.receptionist.ClusterReceptionist - ClusterReceptionist [akka://ClusterSystem@127.0.0.1:25252] - Node added [UniqueAddress(akka://ClusterSystem@127.0.0.1:51081,567025403336682144)] 22:14:57.740 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member joined: [akka://ClusterSystem@127.0.0.1:25252] *************** 22:14:57.740 [ClusterSystem-akka.actor.internal-dispatcher-16] DEBUG akka.cluster.typed.internal.receptionist.ClusterReceptionist - ClusterReceptionist [akka://ClusterSystem@127.0.0.1:51081] - Node added [UniqueAddress(akka://ClusterSystem@127.0.0.1:25252,-6913064885699273532)] 22:14:58.134 [ClusterSystem-akka.actor.default-dispatcher-3] INFO akka.cluster.Cluster - Cluster Node [akka://ClusterSystem@127.0.0.1:25251] - Leader is moving node [akka://ClusterSystem@127.0.0.1:25252] to [Up] 22:14:58.134 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:25252] *************** 22:14:58.755 [ClusterSystem-akka.actor.default-dispatcher-3] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:25252] *************** 22:14:59.146 [ClusterSystem-akka.actor.default-dispatcher-14] INFO com.learn.akka.MonitorActor$ - **************** Member is Up: [akka://ClusterSystem@127.0.0.1:25252] ***************
下面是本次示范的全部源代码：
build.sbt
name := "learn-akka-typed" version := "0.1" scalaVersion := "2.13.1" scalacOptions in Compile ++= Seq("-deprecation", "-feature", "-unchecked", "-Xlog-reflective-calls", "-Xlint") javacOptions in Compile ++= Seq("-Xlint:unchecked", "-Xlint:deprecation") val AkkaVersion = "2.6.5" val AkkaPersistenceCassandraVersion = "1.0.0" libraryDependencies ++= Seq( "com.typesafe.akka" %% "akka-cluster-sharding-typed" % AkkaVersion, "com.typesafe.akka" %% "akka-persistence-typed" % AkkaVersion, "com.typesafe.akka" %% "akka-persistence-query" % AkkaVersion, "com.typesafe.akka" %% "akka-serialization-jackson" % AkkaVersion, "com.typesafe.akka" %% "akka-persistence-cassandra" % AkkaPersistenceCassandraVersion, "com.typesafe.akka" %% "akka-slf4j" % AkkaVersion, "ch.qos.logback" % "logback-classic" % "1.2.3" )
cluster.conf
akka { actor { provider = cluster serialization-bindings { "com.learn.akka.CborSerializable" = jackson-cbor } } remote { artery { canonical.hostname = "127.0.0.1" canonical.port = 0 } } cluster { seed-nodes = [ "akka://ClusterSystem@127.0.0.1:25251", "akka://ClusterSystem@127.0.0.1:25252"] } }
ClusterMemberStatus.scala
package com.learn.akka import akka.actor.typed._ import akka.actor.typed.scaladsl.Behaviors import akka.cluster.ClusterEvent._ import akka.cluster.typed.Subscribe import akka.cluster.typed.Cluster import akka.actor.typed.ActorSystem object MonitorActor { sealed trait ClusterEvent private case class MemberStatus(event: MemberEvent) extends ClusterEvent private case class ReachStatus(event: ReachabilityEvent) extends ClusterEvent def apply(): Behavior[ClusterEvent] = Behaviors.setup[ClusterEvent] { ctx => val memberEventAdapter: ActorRef[MemberEvent] = ctx.messageAdapter(MemberStatus) val reachEventAdapter: ActorRef[ReachabilityEvent] = ctx.messageAdapter(ReachStatus) Cluster(ctx.system).subscriptions ! Subscribe(memberEventAdapter,classOf[MemberEvent]) Cluster(ctx.system).subscriptions ! Subscribe(reachEventAdapter,classOf[ReachabilityEvent]) Behaviors.receiveMessage { event => event match { case MemberStatus(status) => status match { case MemberJoined(member) => ctx.log.info("**************** Member joined: [{}] ***************", member.address) case MemberJoined(member) => ctx.log.info("**************** Member joined: [{}] ***************", member.address) case MemberUp(member) => ctx.log.info("**************** Member is Up: [{}] ***************", member.address) case MemberRemoved(member, previousStatus) => ctx.log.info("**************** Member is Removed: [{}] after {} ***************", member.address, previousStatus) case MemberLeft(member) => ctx.log.info("**************** Member left: [{}] ***************", member.address) case MemberExited(member) => ctx.log.info("**************** Member exited: [{}] ***************", member.address) case _: MemberEvent => // ignore } case ReachStatus(status) => status match { case UnreachableMember(member) => ctx.log.info("**************** Member detected as unreachable: [{}] ***************", member) case ReachableMember(member) => ctx.log.info("**************** Member back to reachable: [{}] ***************", member) } } Behaviors.same } } } object RootActor { def apply(): Behavior[Nothing] = Behaviors.setup[Nothing] {ctx => ctx.spawn(MonitorActor(),"listner") Behaviors.empty } } object ClusterMemberStatus { import com.typesafe.config.ConfigFactory def main(args: Array[String]): Unit = { val ports = if (args.isEmpty) Seq(25251, 25252, 0) else args.toSeq.map(_.toInt) ports.foreach { port => startup(port) } } def startup(port: Int): Unit = { val config = ConfigFactory.parseString(s""" akka.remote.artery.canonical.port=$port """).withFallback(ConfigFactory.load("cluster.conf")) ActorSystem[Nothing](RootActor(),"ClusterSystem",config) } }