baohe-zhang commented on a change in pull request #28412: URL: https://github.com/apache/spark/pull/28412#discussion_r437578109
########## File path: core/src/main/scala/org/apache/spark/deploy/history/HybridStore.scala ########## @@ -0,0 +1,185 @@ +/* + * 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.deploy.history + +import java.io.IOException +import java.util.Collection +import java.util.concurrent.ConcurrentHashMap +import java.util.concurrent.atomic.AtomicBoolean + +import scala.collection.JavaConverters._ + +import org.apache.spark.util.kvstore._ + +/** + * A implementation of KVStore that accelerates event logs loading. + * + * When rebuilding the application state from event logs, HybridStore will + * write data to InMemoryStore at first and use a background thread to dump + * data to LevelDB once the writing to InMemoryStore is completed. + */ + +private[history] class HybridStore extends KVStore { + + private val inMemoryStore = new InMemoryStore() + + private var levelDB: LevelDB = null + + // Flag to indicate whether we should use inMemoryStore or levelDB + private[history] val shouldUseInMemoryStore = new AtomicBoolean(true) + + // A background thread that dumps data from inMemoryStore to levelDB + private var backgroundThread: Thread = null + + // A hash map that stores all classes that had been writen to inMemoryStore + private val klassMap = new ConcurrentHashMap[Class[_], Boolean] + + override def getMetadata[T](klass: Class[T]): T = { + getStore().getMetadata(klass) + } + + override def setMetadata(value: Object): Unit = { + getStore().setMetadata(value) + } + + override def read[T](klass: Class[T], naturalKey: Object): T = { + getStore().read(klass, naturalKey) + } + + override def write(value: Object): Unit = { + val store = getStore() + store.write(value) + + if (backgroundThread == null) { + // New classes won't be dumped once the background thread is started + klassMap.putIfAbsent(value.getClass(), true) + } + } + + override def delete(klass: Class[_], naturalKey: Object): Unit = { + if (backgroundThread != null) { + throw new RuntimeException("delete() shouldn't be called after " + + "the hybrid store begins switching to levelDB") + } + + getStore().delete(klass, naturalKey) + } + + override def view[T](klass: Class[T]): KVStoreView[T] = { + getStore().view(klass) + } + + override def count(klass: Class[_]): Long = { + getStore().count(klass) + } + + override def count(klass: Class[_], index: String, indexedValue: Object): Long = { + getStore().count(klass, index, indexedValue) + } + + override def close(): Unit = { + try { + if (backgroundThread != null && backgroundThread.isAlive()) { + // The background thread is still running, wait for it to finish + backgroundThread.join() + } + if (levelDB != null) { + levelDB.close() + } + } catch { + case ioe: IOException => throw ioe + } finally { + inMemoryStore.close() + } + } + + override def removeAllByIndexValues[T]( + klass: Class[T], + index: String, + indexValues: Collection[_]): Boolean = { + if (backgroundThread != null) { + throw new RuntimeException("removeAllByIndexValues() shouldn't be called after " + + "the hybrid store begins switching to levelDB") + } + + getStore().removeAllByIndexValues(klass, index, indexValues) + } + + def setLevelDB(levelDB: LevelDB): Unit = { + this.levelDB = levelDB + } + + /** + * This method is called when the writing is done for inMemoryStore. A + * background thread will be created and be started to dump data in inMemoryStore + * to levelDB. Once the dumping is completed, the underlying kvstore will be + * switched to levelDB. + */ + def switchToLevelDB(listener: HybridStore.SwitchToLevelDBListener): Unit = { + backgroundThread = new Thread(() => { + var exception: Option[Exception] = None + + try { + for (klass <- klassMap.keys().asScala) { + val it = inMemoryStore.view(klass).closeableIterator() + while (it.hasNext()) { + levelDB.write(it.next()) + } + } + } catch { + case e: Exception => + exception = Some(e) + } + + exception match { + case Some(e) => + listener.onSwitchToLevelDBFail(e) + case None => + listener.onSwitchToLevelDBSuccess() + shouldUseInMemoryStore.set(false) + inMemoryStore.close() + } + }) + backgroundThread.setDaemon(true) + backgroundThread.setName("hybridstore-switch-to-leveldb") + backgroundThread.start() + } + + /** + * This method return the store that we should use. + */ + private def getStore(): KVStore = { + if (shouldUseInMemoryStore.get) { + inMemoryStore + } else { + levelDB + } + } + Review comment: removed empty line. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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