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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.*/packageorg.apache.spark.utilimportjava.util.concurrent.atomic.AtomicBooleanimportjava.util.concurrent.{BlockingQueue, LinkedBlockingDeque}
importscala.util.control.NonFatalimportorg.apache.spark.Logging/** * An event loop to receive events from the caller and process all events in the event thread. It * will start an exclusive event thread to process all events. * * Note: The event queue will grow indefinitely. So subclasses should make sure `onReceive` can * handle events in time to avoid the potential OOM.*/private[spark] abstractclassEventLoop[E](name: String) extendsLogging {
privatevaleventQueue:BlockingQueue[E] =newLinkedBlockingDeque[E]()
privatevalstopped=newAtomicBoolean(false)
privatevaleventThread=newThread(name) {
setDaemon(true)
overridedefrun():Unit= {
try {
while (!stopped.get) {
valevent= eventQueue.take()
try {
onReceive(event)
} catch {
caseNonFatal(e) => {
try {
onError(e)
} catch {
caseNonFatal(e) => logError("Unexpected error in "+ name, e)
}
}
}
}
} catch {
caseie: InterruptedException=>// exit even if eventQueue is not emptycaseNonFatal(e) => logError("Unexpected error in "+ name, e)
}
}
}
defstart():Unit= {
if (stopped.get) {
thrownewIllegalStateException(name +" has already been stopped")
}
// Call onStart before starting the event thread to make sure it happens before onReceive
onStart()
eventThread.start()
}
defstop():Unit= {
if (stopped.compareAndSet(false, true)) {
eventThread.interrupt()
varonStopCalled=falsetry {
eventThread.join()
// Call onStop after the event thread exits to make sure onReceive happens before onStop
onStopCalled =true
onStop()
} catch {
caseie: InterruptedException=>Thread.currentThread().interrupt()
if (!onStopCalled) {
// ie is thrown from `eventThread.join()`. Otherwise, we should not call `onStop` since// it's already called.
onStop()
}
}
} else {
// Keep quiet to allow calling `stop` multiple times.
}
}
/** * Put the event into the event queue. The event thread will process it later.*/defpost(event: E):Unit= {
eventQueue.put(event)
}
/** * Return if the event thread has already been started but not yet stopped.*/defisActive:Boolean= eventThread.isAlive
/** * Invoked when `start()` is called but before the event thread starts.*/protecteddefonStart():Unit= {}
/** * Invoked when `stop()` is called and the event thread exits.*/protecteddefonStop():Unit= {}
/** * Invoked in the event thread when polling events from the event queue. * * Note: Should avoid calling blocking actions in `onReceive`, or the event thread will be blocked * and cannot process events in time. If you want to call some blocking actions, run them in * another thread.*/protecteddefonReceive(event: E):Unit/** * Invoked if `onReceive` throws any non fatal error. Any non fatal error thrown from `onError` * will be ignored.*/protecteddefonError(e: Throwable):Unit
}