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/*
* 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
import scala.concurrent.Future
import scala.reflect.ClassTag
import org.apache.spark.util.RpcUtils
import org.apache.spark.{SparkException, Logging, SparkConf}
/**
* A reference for a remote [[RpcEndpoint]]. [[RpcEndpointRef]] is thread-safe.
*/
private[spark] abstract class RpcEndpointRef(@transient conf: SparkConf)
extends Serializable with Logging {
private[this] val maxRetries = RpcUtils.numRetries(conf)
private[this] val retryWaitMs = RpcUtils.retryWaitMs(conf)
private[this] val defaultAskTimeout = RpcUtils.askRpcTimeout(conf)
/**
* return the address for the [[RpcEndpointRef]]
*/
def address: RpcAddress
def name: String
/**
* Sends a one-way asynchronous message. Fire-and-forget semantics.
*/
def send(message: Any): Unit
/**
* Send a message to the corresponding [[RpcEndpoint.receiveAndReply)]] and return a [[Future]] to
* receive the reply within the specified timeout.
*
* This method only sends the message once and never retries.
*/
def ask[T: ClassTag](message: Any, timeout: RpcTimeout): Future[T]
/**
* Send a message to the corresponding [[RpcEndpoint.receiveAndReply)]] and return a [[Future]] to
* receive the reply within a default timeout.
*
* This method only sends the message once and never retries.
*/
def ask[T: ClassTag](message: Any): Future[T] = ask(message, defaultAskTimeout)
/**
* Send a message to the corresponding [[RpcEndpoint]] and get its result within a default
* timeout, or throw a SparkException if this fails even after the default number of retries.
* The default `timeout` will be used in every trial of calling `sendWithReply`. Because this
* method retries, the message handling in the receiver side should be idempotent.
*
* Note: this is a blocking action which may cost a lot of time, so don't call it in an message
* loop of [[RpcEndpoint]].
*
* @param message the message to send
* @tparam T type of the reply message
* @return the reply message from the corresponding [[RpcEndpoint]]
*/
def askWithRetry[T: ClassTag](message: Any): T = askWithRetry(message, defaultAskTimeout)
/**
* Send a message to the corresponding [[RpcEndpoint.receive]] and get its result within a
* specified timeout, throw a SparkException if this fails even after the specified number of
* retries. `timeout` will be used in every trial of calling `sendWithReply`. Because this method
* retries, the message handling in the receiver side should be idempotent.
*
* Note: this is a blocking action which may cost a lot of time, so don't call it in an message
* loop of [[RpcEndpoint]].
*
* @param message the message to send
* @param timeout the timeout duration
* @tparam T type of the reply message
* @return the reply message from the corresponding [[RpcEndpoint]]
*/
def askWithRetry[T: ClassTag](message: Any, timeout: RpcTimeout): T = {
// TODO: Consider removing multiple attempts
var attempts = 0
var lastException: Exception = null
while (attempts < maxRetries) {
attempts += 1
try {
val future = ask[T](message, timeout)
val result = timeout.awaitResult(future)
if (result == null) {
throw new SparkException("RpcEndpoint returned null")
}
return result
} catch {
case ie: InterruptedException => throw ie
case e: Exception =>
lastException = e
logWarning(s"Error sending message [message = $message] in $attempts attempts", e)
}
if (attempts < maxRetries) {
Thread.sleep(retryWaitMs)
}
}
throw new SparkException(
s"Error sending message [message = $message]", lastException)
}
}
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