org.apache.spark.util.ListenerBus.scala Maven / Gradle / Ivy
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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.util
import java.util.concurrent.CopyOnWriteArrayList
import scala.collection.JavaConverters._
import scala.reflect.ClassTag
import scala.util.control.NonFatal
import com.codahale.metrics.Timer
import org.apache.spark.internal.Logging
/**
* An event bus which posts events to its listeners.
*/
private[spark] trait ListenerBus[L <: AnyRef, E] extends Logging {
private[this] val listenersPlusTimers = new CopyOnWriteArrayList[(L, Option[Timer])]
// Marked `private[spark]` for access in tests.
private[spark] def listeners = listenersPlusTimers.asScala.map(_._1).asJava
/**
* Returns a CodaHale metrics Timer for measuring the listener's event processing time.
* This method is intended to be overridden by subclasses.
*/
protected def getTimer(listener: L): Option[Timer] = None
/**
* Add a listener to listen events. This method is thread-safe and can be called in any thread.
*/
final def addListener(listener: L): Unit = {
listenersPlusTimers.add((listener, getTimer(listener)))
}
/**
* Remove a listener and it won't receive any events. This method is thread-safe and can be called
* in any thread.
*/
final def removeListener(listener: L): Unit = {
listenersPlusTimers.asScala.find(_._1 eq listener).foreach { listenerAndTimer =>
listenersPlusTimers.remove(listenerAndTimer)
}
}
/**
* This can be overridden by subclasses if there is any extra cleanup to do when removing a
* listener. In particular AsyncEventQueues can clean up queues in the LiveListenerBus.
*/
def removeListenerOnError(listener: L): Unit = {
removeListener(listener)
}
/**
* Post the event to all registered listeners. The `postToAll` caller should guarantee calling
* `postToAll` in the same thread for all events.
*/
def postToAll(event: E): Unit = {
// JavaConverters can create a JIterableWrapper if we use asScala.
// However, this method will be called frequently. To avoid the wrapper cost, here we use
// Java Iterator directly.
val iter = listenersPlusTimers.iterator
while (iter.hasNext) {
val listenerAndMaybeTimer = iter.next()
val listener = listenerAndMaybeTimer._1
val maybeTimer = listenerAndMaybeTimer._2
val maybeTimerContext = if (maybeTimer.isDefined) {
maybeTimer.get.time()
} else {
null
}
try {
doPostEvent(listener, event)
if (Thread.interrupted()) {
// We want to throw the InterruptedException right away so we can associate the interrupt
// with this listener, as opposed to waiting for a queue.take() etc. to detect it.
throw new InterruptedException()
}
} catch {
case ie: InterruptedException =>
logError(s"Interrupted while posting to ${Utils.getFormattedClassName(listener)}. " +
s"Removing that listener.", ie)
removeListenerOnError(listener)
case NonFatal(e) if !isIgnorableException(e) =>
logError(s"Listener ${Utils.getFormattedClassName(listener)} threw an exception", e)
} finally {
if (maybeTimerContext != null) {
maybeTimerContext.stop()
}
}
}
}
/**
* Post an event to the specified listener. `onPostEvent` is guaranteed to be called in the same
* thread for all listeners.
*/
protected def doPostEvent(listener: L, event: E): Unit
/** Allows bus implementations to prevent error logging for certain exceptions. */
protected def isIgnorableException(e: Throwable): Boolean = false
private[spark] def findListenersByClass[T <: L : ClassTag](): Seq[T] = {
val c = implicitly[ClassTag[T]].runtimeClass
listeners.asScala.filter(_.getClass == c).map(_.asInstanceOf[T]).toSeq
}
}