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From: zsxwing <git@git.apache.org>
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Subject: [GitHub] spark pull request: [SPARK-5124][Core] A standard RPC
 interface an...
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Message-Id: <20150306032511.79EE9E107D@git1-us-west.apache.org>
Date: Fri,  6 Mar 2015 03:25:11 +0000 (UTC)

Github user zsxwing commented on a diff in the pull request:

    https://github.com/apache/spark/pull/4588#discussion_r25923587
  
    --- Diff: core/src/main/scala/org/apache/spark/rpc/akka/AkkaRpcEnv.scala ---
    @@ -0,0 +1,371 @@
    +/*
    + * 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.
    + */
    +
    +package org.apache.spark.rpc.akka
    +
    +import java.net.URI
    +import java.util.concurrent.{ConcurrentHashMap, CountDownLatch}
    +
    +import scala.concurrent.Await
    +import scala.concurrent.duration._
    +import scala.concurrent.Future
    +import scala.language.postfixOps
    +import scala.reflect.ClassTag
    +import scala.util.control.NonFatal
    +
    +import akka.actor.{ActorSystem, ExtendedActorSystem, Actor, ActorRef, Props, Address}
    +import akka.pattern.{ask => akkaAsk}
    +import akka.remote.{AssociatedEvent => AkkaAssociatedEvent}
    +import akka.remote.{DisassociatedEvent => AkkaDisassociatedEvent}
    +import akka.remote.{AssociationErrorEvent, RemotingLifecycleEvent}
    +import org.apache.spark.{SparkException, Logging, SparkConf}
    +import org.apache.spark.rpc._
    +import org.apache.spark.util.{ActorLogReceive, AkkaUtils}
    +
    +/**
    + * A RpcEnv implementation based on Akka.
    + *
    + * TODO Once we remove all usages of Akka in other place, we can move this file to a new project and
    + * remove Akka from the dependencies.
    + *
    + * @param actorSystem
    + * @param conf
    + * @param boundPort
    + */
    +private[spark] class AkkaRpcEnv private (
    +    val actorSystem: ActorSystem, conf: SparkConf, boundPort: Int) extends RpcEnv with Logging {
    +
    +  private val defaultAddress: RpcAddress = {
    +    val address = actorSystem.asInstanceOf[ExtendedActorSystem].provider.getDefaultAddress
    +    // In some test case, ActorSystem doesn't bind to any address.
    +    // So just use some default value since they are only some unit tests
    +    RpcAddress(address.host.getOrElse("localhost"), address.port.getOrElse(boundPort))
    +  }
    +
    +  override val address: RpcAddress = defaultAddress
    +
    +  /**
    +   * A lookup table to search a [[RpcEndpointRef]] for a [[RpcEndpoint]]. We need it to make
    +   * [[RpcEndpoint.self]] work.
    +   */
    +  private val endpointToRef = new ConcurrentHashMap[RpcEndpoint, RpcEndpointRef]()
    +
    +  override val scheduler = new ActionSchedulerImpl(conf)
    +
    +  /**
    +   * Need this map to remove `RpcEndpoint` from `endpointToRef` via a `RpcEndpointRef`
    +   */
    +  private val refToEndpoint = new ConcurrentHashMap[RpcEndpointRef, RpcEndpoint]()
    +
    +  private def registerEndpoint(endpoint: RpcEndpoint, endpointRef: RpcEndpointRef): Unit = {
    +    endpointToRef.put(endpoint, endpointRef)
    +    refToEndpoint.put(endpointRef, endpoint)
    +  }
    +
    +  private def unregisterEndpoint(endpointRef: RpcEndpointRef): Unit = {
    +    val endpoint = refToEndpoint.remove(endpointRef)
    +    if (endpoint != null) {
    +      endpointToRef.remove(endpoint)
    +    }
    +  }
    +
    +  /**
    +   * Retrieve the [[RpcEndpointRef]] of `endpoint`.
    +   */
    +  override def endpointRef(endpoint: RpcEndpoint): RpcEndpointRef = {
    +    val endpointRef = endpointToRef.get(endpoint)
    +    require(endpointRef != null, s"Cannot find RpcEndpointRef of ${endpoint} in ${this}")
    +    endpointRef
    +  }
    +
    +  override def setupEndpoint(name: String, endpoint: RpcEndpoint): RpcEndpointRef = {
    +    setupThreadSafeEndpoint(name, endpoint)
    +  }
    +
    +  override def setupThreadSafeEndpoint(name: String, endpoint: RpcEndpoint): RpcEndpointRef = {
    +    val latch = new CountDownLatch(1)
    +    try {
    +      @volatile var endpointRef: AkkaRpcEndpointRef = null
    +      val actorRef = actorSystem.actorOf(Props(new Actor with ActorLogReceive with Logging {
    +
    +        // Wait until `endpointRef` is set. TODO better solution?
    +        latch.await()
    +        require(endpointRef != null)
    +        registerEndpoint(endpoint, endpointRef)
    +
    +        override def preStart(): Unit = {
    +          // Listen for remote client network events
    +          context.system.eventStream.subscribe(self, classOf[RemotingLifecycleEvent])
    +          safelyCall(endpoint) {
    +            endpoint.onStart()
    +          }
    +        }
    +
    +        override def receiveWithLogging: Receive = {
    +          case AkkaAssociatedEvent(_, remoteAddress, _) =>
    +            safelyCall(endpoint) {
    +              val event = AssociatedEvent(akkaAddressToRpcAddress(remoteAddress))
    +              val pf = endpoint.receive
    +              if (pf.isDefinedAt(event)) {
    +                pf.apply(event)
    +              }
    +            }
    +
    +          case AkkaDisassociatedEvent(_, remoteAddress, _) =>
    +            safelyCall(endpoint) {
    +              val event = DisassociatedEvent(akkaAddressToRpcAddress(remoteAddress))
    +              val pf = endpoint.receive
    +              if (pf.isDefinedAt(event)) {
    +                pf.apply(event)
    +              }
    +            }
    +
    +          case AssociationErrorEvent(cause, localAddress, remoteAddress, inbound, _) =>
    +            safelyCall(endpoint) {
    +              val event = NetworkErrorEvent(akkaAddressToRpcAddress(remoteAddress), cause)
    +              val pf = endpoint.receive
    +              if (pf.isDefinedAt(event)) {
    +                pf.apply(event)
    +              }
    +            }
    +          case e: RemotingLifecycleEvent =>
    +          // TODO ignore?
    +
    +          case AkkaMessage(message: Any, reply: Boolean)=>
    +            logDebug("Received RPC message: " + AkkaMessage(message, reply))
    +            safelyCall(endpoint) {
    +              val s = sender()
    +              val pf =
    +                if (reply) {
    +                  endpoint.receiveAndReply(new RpcResponse {
    +                    override def fail(e: Throwable): Unit = {
    +                      s ! AkkaFailure(e)
    +                    }
    +
    +                    override def reply(response: Any): Unit = {
    +                      s ! AkkaMessage(response, false)
    +                    }
    +
    +                    override def replyWithSender(response: Any, sender: RpcEndpointRef): Unit = {
    +                      s.!(AkkaMessage(response, true))(
    +                        sender.asInstanceOf[AkkaRpcEndpointRef].actorRef)
    +                    }
    +                  })
    +                } else {
    +                  endpoint.receive
    +                }
    +              try {
    +                if (pf.isDefinedAt(message)) {
    +                  pf.apply(message)
    +                }
    +              } catch {
    +                case NonFatal(e) =>
    +                  if (reply) {
    +                    // If the sender asks a reply, we should send the error back to the sender
    +                    s ! AkkaFailure(e)
    +                  } else {
    +                    throw e
    +                  }
    +              }
    +            }
    +          case message: Any => {
    +            logWarning(s"Unknown message: $message")
    +          }
    +        }
    +
    +        override def postStop(): Unit = {
    +          unregisterEndpoint(endpoint.self)
    +          safelyCall(endpoint) {
    +            endpoint.onStop()
    +          }
    +        }
    +
    +        }), name = name)
    +      endpointRef = new AkkaRpcEndpointRef(defaultAddress, actorRef, conf)
    +      endpointRef
    +    } finally {
    +      latch.countDown()
    +    }
    +  }
    +
    +  /**
    +   * Run `action` safely to avoid to crash the thread. If any non-fatal exception happens, it will
    +   * call `endpoint.onError`. If `endpoint.onError` throws any non-fatal exception, just log it.
    +   */
    +  private def safelyCall(endpoint: RpcEndpoint)(action: => Unit): Unit = {
    +    try {
    +      action
    +    } catch {
    +      case NonFatal(e) => {
    +        try {
    +          endpoint.onError(e)
    +        } catch {
    +          case NonFatal(e) => logError(s"Ignore error: ${e.getMessage}", e)
    +        }
    +      }
    +    }
    +  }
    +
    +  private def akkaAddressToRpcAddress(address: Address): RpcAddress = {
    +    RpcAddress(address.host.getOrElse(defaultAddress.host),
    +      address.port.getOrElse(defaultAddress.port))
    +  }
    +
    +  override def setupDriverEndpointRef(name: String): RpcEndpointRef = {
    +    new AkkaRpcEndpointRef(defaultAddress, AkkaUtils.makeDriverRef(name, conf, actorSystem), conf)
    +  }
    +
    +  override def setupEndpointRefByUrl(url: String): RpcEndpointRef = {
    +    val timeout = Duration.create(conf.getLong("spark.akka.lookupTimeout", 30), "seconds")
    +    val ref = Await.result(actorSystem.actorSelection(url).resolveOne(timeout), timeout)
    +    // TODO defaultAddress is wrong
    +    new AkkaRpcEndpointRef(defaultAddress, ref, conf)
    +  }
    +
    +  override def setupEndpointRef(
    +      systemName: String, address: RpcAddress, endpointName: String): RpcEndpointRef = {
    +    setupEndpointRefByUrl(uriOf(systemName, address, endpointName))
    +  }
    +
    +  override def uriOf(systemName: String, address: RpcAddress, endpointName: String): String = {
    +    AkkaUtils.address(
    +      AkkaUtils.protocol(actorSystem), systemName, address.host, address.port, endpointName)
    +  }
    +
    +
    +  override def shutdown(): Unit = {
    +    actorSystem.shutdown()
    +  }
    +
    +  override def stop(endpoint: RpcEndpointRef): Unit = {
    +    require(endpoint.isInstanceOf[AkkaRpcEndpointRef])
    +    actorSystem.stop(endpoint.asInstanceOf[AkkaRpcEndpointRef].actorRef)
    +  }
    +
    +  override def awaitTermination(): Unit = {
    +    actorSystem.awaitTermination()
    +  }
    +
    +  override def toString = s"${getClass.getSimpleName}($actorSystem)"
    +}
    +
    +private[spark] object AkkaRpcEnv {
    +
    +  def apply(config: RpcEnvConfig): RpcEnv = {
    +    val (actorSystem, boundPort) = AkkaUtils.createActorSystem(
    +        config.name, config.host, config.port, config.conf, config.securityManager)
    +    new AkkaRpcEnv(actorSystem, config.conf, boundPort)
    +  }
    +
    +}
    +
    +private[akka] class AkkaRpcEndpointRef(
    +    @transient defaultAddress: RpcAddress,
    +    val actorRef: ActorRef,
    +    @transient conf: SparkConf) extends RpcEndpointRef with Serializable with Logging {
    +  // `defaultAddress` and `conf` won't be used after initialization. So it's safe to be transient.
    +
    +  private[this] val maxRetries = conf.getInt("spark.akka.num.retries", 3)
    +  private[this] val retryWaitMs = conf.getLong("spark.akka.retry.wait", 3000)
    +  private[this] val defaultTimeout = conf.getLong("spark.akka.lookupTimeout", 30) seconds
    +
    +  override val address: RpcAddress = {
    +    val akkaAddress = actorRef.path.address
    +    RpcAddress(akkaAddress.host.getOrElse(defaultAddress.host),
    +      akkaAddress.port.getOrElse(defaultAddress.port))
    +  }
    +
    +  override val name: String = actorRef.path.name
    +
    +  override def askWithReply[T: ClassTag](message: Any): T = askWithReply(message, defaultTimeout)
    +
    +  override def askWithReply[T: ClassTag](message: Any, timeout: FiniteDuration): T = {
    --- End diff --
    
    Just found a disadvantage of the util class idea. Every RpcEndpoint using askWithReply has to create the following fields:
    ```Scala
      private[this] val maxRetries = conf.getInt("spark.akka.num.retries", 3)
      private[this] val retryWaitMs = conf.getLong("spark.akka.retry.wait", 3000)
      private[this] val defaultTimeout = conf.getLong("spark.akka.lookupTimeout", 30) seconds
    ```
    Maintaining such codes in many places looks not a good idea.


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