baohe-zhang commented on a change in pull request #28412: URL: https://github.com/apache/spark/pull/28412#discussion_r451892343
########## 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._ + +/** + * An 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 app store is restored. We don't expect write + * operations (except the case for caching) after calling switch to level DB. + */ + +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 val shouldUseInMemoryStore = new AtomicBoolean(true) + + // Flag to indicate whether this hybrid store is closed, use this flag + // to avoid starting background thread after the store is closed + private val closed = new AtomicBoolean(false) + + // 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 = { + getStore().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 IllegalStateException("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 { + closed.set(true) + if (backgroundThread != null && backgroundThread.isAlive()) { + // The background thread is still running, wait for it to finish + backgroundThread.join() + } + } finally { + inMemoryStore.close() + if (levelDB != null) { + levelDB.close() + } + } + } + + override def removeAllByIndexValues[T]( + klass: Class[T], + index: String, + indexValues: Collection[_]): Boolean = { + if (backgroundThread != null) { + throw new IllegalStateException("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, + appId: String, + attemptId: Option[String]): Unit = { + if (closed.get) { + return + } + + backgroundThread = new Thread(() => { + try { + for (klass <- klassMap.keys().asScala) { + val it = inMemoryStore.view(klass).closeableIterator() + while (it.hasNext()) { + levelDB.write(it.next()) + } Review comment: Hi @mridulm, I updated your code and used it on in-memory store - leveldb switching, but only saw little switching time improvement. I am not sure if somewhere wrong. | log size, jobs and tasks per job | 2 jobs, 400 tasks per job | 10 jobs, 400 tasks per job | 50 jobs, 400 tasks per job | 100 jobs, 400 tasks per job | 200 jobs, 400 tasks per job | 500 jobs, 400 tasks per job | 1000 jobs, 400 tasks per job | 5 jobs, 100000 tasks per job | | ------------------------------------------- | ------------------------- | -------------------------- | -------------------------- | --------------------------- | --------------------------- | --------------------------- | ---------------------------- | ---------------------------- | | original switching time | 1s | 2s | 4s | 8s | 16s | 37s | 65s | 90s | | switching time with write(Iterator<T> iter) | 1s | 1s | 4s | 7s | 13s | 34s | 58s | 84s | The code: ``` for (klass <- klassMap.keys().asScala) { val it = inMemoryStore.view(klass).closeableIterator() levelDB.write(it) } ``` ``` public <T> void write(Iterator<T> iter) throws Exception { Preconditions.checkArgument(iter != null, "Non-empty values required."); List<T> values = new ArrayList<>(); iter.forEachRemaining(values::add); // Group by class, in case there are values from different classes in the iterator // Typical usecase is for this to be a single class. for (Map.Entry<? extends Class<?>, ? extends List<?>> entry : values.stream().collect(Collectors.groupingBy(Object::getClass)).entrySet()) { final Iterator<?> valueIter = entry.getValue().iterator(); final Iterator<byte[]> serializedValueIter; { // deserialize outside synchronized block List<byte[]> list = new ArrayList<>(entry.getValue().size()); for (Object value : entry.getValue()) { list.add(serializer.serialize(value)); } serializedValueIter = list.iterator(); } final Class<?> valueClass = entry.getKey(); final LevelDBTypeInfo ti = getTypeInfo(valueClass); // Batching updates per type synchronized (ti) { final LevelDBTypeInfo.Index naturalIndex = ti.naturalIndex(); final Collection<LevelDBTypeInfo.Index> indices = ti.indices(); try (WriteBatch batch = db().createWriteBatch()) { while (valueIter.hasNext()) { final Object value = valueIter.next(); assert serializedValueIter.hasNext(); final byte[] serializedObject = serializedValueIter.next(); Object existing; try { existing = get(naturalIndex.entityKey(null, value), valueClass); } catch (NoSuchElementException e) { existing = null; } PrefixCache cache = new PrefixCache(value); byte[] naturalKey = naturalIndex.toKey(naturalIndex.getValue(value)); for (LevelDBTypeInfo.Index idx : indices) { byte[] prefix = cache.getPrefix(idx); idx.add(batch, value, existing, serializedObject, naturalKey, prefix); } } assert !serializedValueIter.hasNext(); db().write(batch); } } } } ``` I think using multiple threads to write data to leveldb might shorten the switching time but it would introduce more overhead to SHS. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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