carp84 commented on a change in pull request #9501: [FLINK-12697] [State Backends] Support on-disk state storage for spill-able heap backend URL: https://github.com/apache/flink/pull/9501#discussion_r328464527
########## File path: flink-state-backends/flink-statebackend-heap-spillable/src/main/java/org/apache/flink/runtime/state/heap/CopyOnWriteSkipListStateMap.java ########## @@ -0,0 +1,1527 @@ +/* + * 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.flink.runtime.state.heap; + +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.flink.api.common.typeutils.TypeSerializer; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.core.memory.ByteBufferUtils; +import org.apache.flink.runtime.state.StateEntry; +import org.apache.flink.runtime.state.StateTransformationFunction; +import org.apache.flink.runtime.state.heap.space.Allocator; +import org.apache.flink.runtime.state.heap.space.Chunk; +import org.apache.flink.runtime.state.heap.space.SpaceUtils; +import org.apache.flink.runtime.state.internal.InternalKvState; +import org.apache.flink.util.Preconditions; +import org.apache.flink.util.ResourceGuard; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.Nonnull; + +import java.nio.ByteBuffer; +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.HashSet; +import java.util.Iterator; +import java.util.NoSuchElementException; +import java.util.Set; +import java.util.Spliterators; +import java.util.TreeSet; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ThreadLocalRandom; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.stream.Stream; +import java.util.stream.StreamSupport; + +import static org.apache.flink.runtime.state.heap.SkipListUtils.HEAD_NODE; +import static org.apache.flink.runtime.state.heap.SkipListUtils.NIL_NODE; +import static org.apache.flink.runtime.state.heap.SkipListUtils.NIL_VALUE_POINTER; + +/** + * Implementation of state map which is based on skip list with copy-on-write support. states will + * be serialized to bytes and stored in the space allocated with the given allocator. + * + * @param <K> type of key + * @param <N> type of namespace + * @param <S> type of state + */ +public class CopyOnWriteSkipListStateMap<K, N, S> extends StateMap<K, N, S> implements AutoCloseable { + + private static final Logger LOG = LoggerFactory.getLogger(CopyOnWriteSkipListStateMap.class); + + /** + * Default max number of logically-removed keys to delete one time. + */ + private static final int DEFAULT_MAX_KEYS_TO_DELETE_ONE_TIME = 3; + + /** + * Default ratio of the logically-removed keys to trigger deletion when snapshot. + */ + private static final float DEFAULT_LOGICAL_REMOVED_KEYS_RATIO = 0.2f; + + /** + * The serializer used to serialize the key and namespace to bytes stored in skip list. + */ + private final SkipListKeySerializer<K, N> skipListKeySerializer; + + /** + * The serializer used to serialize the state to bytes stored in skip list. + */ + private final SkipListValueSerializer<S> skipListValueSerializer; + + /** + * Space allocator. + */ + private final Allocator spaceAllocator; + + /** + * The level index header. + */ + private final LevelIndexHeader levelIndexHeader; + + /** + * Seed to generate random index level. + */ + private int randomSeed; + + /** + * The current version of this map. Used for copy-on-write mechanics. + */ + private int stateMapVersion; + + /** + * The highest version of this map that is still required by any unreleased snapshot. + */ + private int highestRequiredSnapshotVersion; + + /** + * Snapshots no more than this version must have been finished, but there may be some + * snapshots more than this version are still running. + */ + private volatile int highestFinishedSnapshotVersion; + + /** + * Maintains an ordered set of version ids that are still used by unreleased snapshots. + */ + private final TreeSet<Integer> snapshotVersions; + + /** + * The size of skip list which includes the logical removed keys. + */ + private int totalSize; + + /** + * Number of requests for this skip list. + */ + private int requestCount; + + /** + * Set of logical removed nodes. + */ + private final Set<Long> logicallyRemovedNodes; + + /** + * Number of keys to remove physically one time. + */ + private int numKeysToDeleteOneTime; + + /** + * Ratio of the logically-removed keys to trigger deletion when snapshot. + */ + private float logicalRemovedKeysRatio; + + /** + * Set of nodes whose values are being pruned by snapshots. + */ + private final Set<Long> pruningValueNodes; + + /** + * Whether this map has been closed. + */ + private final AtomicBoolean closed; + + /** + * Guards for the free of space when state map is closed. This is mainly + * used to synchronize with snapshots. + */ + private final ResourceGuard resourceGuard; + + public CopyOnWriteSkipListStateMap( + @Nonnull TypeSerializer<K> keySerializer, + @Nonnull TypeSerializer<N> namespaceSerializer, + @Nonnull TypeSerializer<S> stateSerializer, + @Nonnull Allocator spaceAllocator) { + this(keySerializer, namespaceSerializer, stateSerializer, spaceAllocator, + DEFAULT_MAX_KEYS_TO_DELETE_ONE_TIME, DEFAULT_LOGICAL_REMOVED_KEYS_RATIO); + } + + public CopyOnWriteSkipListStateMap( + @Nonnull TypeSerializer<K> keySerializer, + @Nonnull TypeSerializer<N> namespaceSerializer, + @Nonnull TypeSerializer<S> stateSerializer, + @Nonnull Allocator spaceAllocator, + int numKeysToDeleteOneTime, + float logicalRemovedKeysRatio) { + this.skipListKeySerializer = new SkipListKeySerializer<>(keySerializer, namespaceSerializer); + this.skipListValueSerializer = new SkipListValueSerializer<>(stateSerializer); + this.spaceAllocator = spaceAllocator; + Preconditions.checkArgument(numKeysToDeleteOneTime >= 0, + "numKeysToDeleteOneTime should be non-negative, but is " + numKeysToDeleteOneTime); + this.numKeysToDeleteOneTime = numKeysToDeleteOneTime; + Preconditions.checkArgument(logicalRemovedKeysRatio >= 0 && logicalRemovedKeysRatio <= 1, + "logicalRemovedKeysRatio should be in [0, 1], but is " + logicalRemovedKeysRatio); + this.logicalRemovedKeysRatio = logicalRemovedKeysRatio; + + this.levelIndexHeader = new OnHeapLevelIndexHeader(); + this.randomSeed = ThreadLocalRandom.current().nextInt() | 0x0100; + + this.stateMapVersion = 0; + this.highestRequiredSnapshotVersion = 0; + this.highestFinishedSnapshotVersion = 0; + this.snapshotVersions = new TreeSet<>(); + + this.totalSize = 0; + this.requestCount = 0; + + this.logicallyRemovedNodes = new HashSet<>(); + this.pruningValueNodes = ConcurrentHashMap.newKeySet(); + + this.closed = new AtomicBoolean(false); + this.resourceGuard = new ResourceGuard(); + } + + @Override + public int size() { + return totalSize - logicallyRemovedNodes.size(); + } + + /** + * Returns total size of this map, including logically removed state. + */ + public int totalSize() { + return totalSize; + } + + public int getRequestCount() { + return requestCount; + } + + @Override + public S get(K key, N namespace) { + updateStat(); + + long node = getNodeInternal(key, namespace); + + if (node == NIL_NODE) { + return null; + } + + return helpGetNodeState(node); + } + + @Override + public boolean containsKey(K key, N namespace) { + updateStat(); + + long node = getNodeInternal(key, namespace); + + return node != NIL_NODE; + } + + @Override + public void put(K key, N namespace, S state) { + updateStat(); + ByteBuffer keyByteBuffer = getKeyByteBuffer(key, namespace); + int keyLen = keyByteBuffer.limit(); + byte[] value = skipListValueSerializer.serialize(state); + + putNode(keyByteBuffer, 0, keyLen, value, false); + } + + @Override + public S putAndGetOld(K key, N namespace, S state) { + updateStat(); + ByteBuffer keyByteBuffer = getKeyByteBuffer(key, namespace); + int keyLen = keyByteBuffer.limit(); + byte[] value = skipListValueSerializer.serialize(state); + + return putNode(keyByteBuffer, 0, keyLen, value, true); + } + + @Override + public void remove(K key, N namespace) { + updateStat(); + ByteBuffer keyByteBuffer = getKeyByteBuffer(key, namespace); + int keyLen = keyByteBuffer.limit(); + + removeNode(keyByteBuffer, 0, keyLen, false); + } + + @Override + public S removeAndGetOld(K key, N namespace) { + updateStat(); + ByteBuffer keyByteBuffer = getKeyByteBuffer(key, namespace); + int keyLen = keyByteBuffer.limit(); + + return removeNode(keyByteBuffer, 0, keyLen, true); + } + + @Override + public <T> void transform( + K key, + N namespace, + T value, + StateTransformationFunction<S, T> transformation) throws Exception { + updateStat(); + ByteBuffer keyByteBuffer = getKeyByteBuffer(key, namespace); + int keyLen = keyByteBuffer.limit(); + + long node = getNode(keyByteBuffer, 0, keyLen); + S oldState = node == NIL_NODE ? null : helpGetNodeState(node); + S newState = transformation.apply(oldState, value); + byte[] stateBytes = skipListValueSerializer.serialize(newState); + putNode(keyByteBuffer, 0, keyLen, stateBytes, false); + } + + // Detail implementation methods --------------------------------------------------------------- + + /** + * Find the node containing the given key. + * + * @param keyByteBuffer byte buffer storing the key. + * @param keyOffset offset of the key. + * @param keyLen length of the key. + * @return id of the node. NIL_NODE will be returned if key does no exist. + */ + @VisibleForTesting + long getNode(ByteBuffer keyByteBuffer, int keyOffset, int keyLen) { + int deleteCount = 0; + long prevNode = findPredecessor(keyByteBuffer, keyOffset, 1); + long currentNode = helpGetNextNode(prevNode, 0); + long nextNode; + + int c; + while (currentNode != NIL_NODE) { + nextNode = helpGetNextNode(currentNode, 0); + + boolean isRemoved = isNodeRemoved(currentNode); + if (isRemoved) { + // remove the node physically when there is no snapshot running + if (highestRequiredSnapshotVersion == 0 && deleteCount < numKeysToDeleteOneTime) { + doPhysicalRemove(currentNode, prevNode, nextNode); + logicallyRemovedNodes.remove(currentNode); + totalSize--; + deleteCount++; + } else { + prevNode = currentNode; + } + currentNode = nextNode; + continue; + } + + c = compareByteBufferAndNode(keyByteBuffer, keyOffset, keyLen, currentNode); + + // find the key + if (c == 0) { + return currentNode; + } + + // the key is less than the current node, and nodes after current + // node can not be equal to the key. + if (c < 0) { + break; + } + + prevNode = currentNode; + currentNode = helpGetNextNode(currentNode, 0); + } + + return NIL_NODE; + } + + /** + * Put the key into the skip list. If the key does not exist before, a new node + * will be created. If the key exists before, the old state will be returned. + * + * @param keyByteBuffer byte buffer storing the key. + * @param keyOffset offset of the key. + * @param keyLen length of the key. + * @param value the value. + * @param returnOldState whether to return old state. + * @return the old state. Null will be returned if key does not exist or returnOldState is false. + */ + @VisibleForTesting + S putNode(ByteBuffer keyByteBuffer, int keyOffset, int keyLen, byte[] value, boolean returnOldState) { + int deleteCount = 0; + long prevNode = findPredecessor(keyByteBuffer, keyOffset, 1); + long currentNode = helpGetNextNode(prevNode, 0); + long nextNode; + + int c; + for ( ; ; ) { + if (currentNode != NIL_NODE) { + nextNode = helpGetNextNode(currentNode, 0); + + boolean isRemoved = isNodeRemoved(currentNode); + + // note that the key may be put again before the node is physically removed, + // so the node still need to compare with the key although they can not be + // physically removed here + if (isRemoved && highestRequiredSnapshotVersion == 0 && deleteCount < numKeysToDeleteOneTime) { + doPhysicalRemove(currentNode, prevNode, nextNode); + logicallyRemovedNodes.remove(currentNode); + totalSize--; + deleteCount++; + currentNode = nextNode; + continue; + } + + c = compareByteBufferAndNode(keyByteBuffer, keyOffset, keyLen, currentNode); + + if (c > 0) { + prevNode = currentNode; + currentNode = nextNode; + continue; + } + + if (c == 0) { + int version = SkipListUtils.helpGetNodeLatestVersion(currentNode, spaceAllocator); + boolean needCopyOnWrite = version < highestRequiredSnapshotVersion; + long oldValuePointer; + + if (needCopyOnWrite) { + oldValuePointer = updateValueWithCopyOnWrite(currentNode, value); + } else { + oldValuePointer = updateValueWithReplace(currentNode, value); + } + + byte oldStatus = helpSetNodeStatus(currentNode, SkipListUtils.NodeStatus.PUT.getValue()); + if (oldStatus == SkipListUtils.NodeStatus.REMOVE.getValue()) { + logicallyRemovedNodes.remove(currentNode); + } + + S oldState = null; + if (returnOldState) { + oldState = helpGetState(oldValuePointer); + } + + // for the replace, old value space need to free + if (!needCopyOnWrite) { + spaceAllocator.free(oldValuePointer); + } + + return oldState; + } + } + + // if current node is NIL_NODE or larger than the key, a new node will be inserted + break; + } + + int level = getRandomIndexLevel(); + levelIndexHeader.updateLevel(level); + + int totalMetaKeyLen = SkipListUtils.getKeyMetaLen(level) + keyLen; + long node = this.spaceAllocator.allocate(totalMetaKeyLen); + + int totalValueLen = SkipListUtils.getValueMetaLen() + value.length; + long valuePointer = spaceAllocator.allocate(totalValueLen); + + doWriteKey(node, level, keyByteBuffer, keyOffset, keyLen, valuePointer, currentNode); + doWriteValue(valuePointer, value, stateMapVersion, node, NIL_VALUE_POINTER); + + helpSetNextNode(prevNode, node, 0); + + if (level > 0) { + SkipListUtils.buildLevelIndex(node, level, keyByteBuffer, keyOffset, levelIndexHeader, spaceAllocator); + } + + totalSize++; + + return null; + } + + /** + * Remove the key from the skip list. The key can be removed logically or physically. + * Logical remove means put a null value whose size is 0. If the key exists before, + * the old value state will be returned. + * + * @param keyByteBuffer byte buffer storing the key. + * @param keyOffset offset of the key. + * @param keyLen length of the key. + * @param returnOldState whether to return old state. + * @return the old state. Null will be returned if key does not exist or returnOldState is false. + */ + private S removeNode(ByteBuffer keyByteBuffer, int keyOffset, int keyLen, boolean returnOldState) { + int deleteCount = 0; + long prevNode = findPredecessor(keyByteBuffer, keyOffset, 1); + long currentNode = helpGetNextNode(prevNode, 0); + long nextNode; + + int c; + while (currentNode != NIL_NODE) { + nextNode = helpGetNextNode(currentNode, 0); + + boolean isRemoved = isNodeRemoved(currentNode); + if (isRemoved && highestRequiredSnapshotVersion == 0 && deleteCount < numKeysToDeleteOneTime) { + doPhysicalRemove(currentNode, prevNode, nextNode); + logicallyRemovedNodes.remove(currentNode); + currentNode = nextNode; + totalSize--; + deleteCount++; + continue; + } + + c = compareByteBufferAndNode(keyByteBuffer, keyOffset, keyLen, currentNode); + + if (c < 0) { + break; + } + + if (c > 0) { + prevNode = currentNode; + currentNode = nextNode; + continue; + } + + // if the node has been logically removed, and can not be physically + // removed here, just return null + if (isRemoved && highestRequiredSnapshotVersion != 0) { + return null; + } + + long oldValuePointer; + boolean oldValueNeedFree; + + if (highestRequiredSnapshotVersion == 0) { + // do physically remove only when there is no snapshot running + oldValuePointer = doPhysicalRemoveAndGetValue(currentNode, prevNode, nextNode); + // the node has been logically removed, and remove it from the set + if (isRemoved) { + logicallyRemovedNodes.remove(currentNode); + } + oldValueNeedFree = true; + totalSize--; + } else { + int version = SkipListUtils.helpGetNodeLatestVersion(currentNode, spaceAllocator); + if (version < highestRequiredSnapshotVersion) { + // the newest-version value may be used by snapshots, and update it with copy-on-write + oldValuePointer = updateValueWithCopyOnWrite(currentNode, null); + oldValueNeedFree = false; + } else { + // replace the newest-version value. + oldValuePointer = updateValueWithReplace(currentNode, null); + oldValueNeedFree = true; + } + + helpSetNodeStatus(currentNode, SkipListUtils.NodeStatus.REMOVE.getValue()); + logicallyRemovedNodes.add(currentNode); + } + + S oldState = null; + if (returnOldState) { + oldState = helpGetState(oldValuePointer); + } + + if (oldValueNeedFree) { + spaceAllocator.free(oldValuePointer); + } + + return oldState; + } + + return null; + } + + /** + * Find the predecessor node for the given key at the given level. + * The key is in the byte buffer positioning at the given offset. + * + * @param keyByteBuffer byte buffer which contains the key. + * @param keyOffset offset of the key in the byte buffer. + * @param level the level. + * @return node id before the key at the given level. + */ + private long findPredecessor(ByteBuffer keyByteBuffer, int keyOffset, int level) { + return SkipListUtils.findPredecessor(keyByteBuffer, keyOffset, level, levelIndexHeader, spaceAllocator); + } + + /** + * Compare the first skip list key in the given byte buffer with the second skip list key in the given node. + * + * @param keyByteBuffer byte buffer storing the first key. + * @param keyOffset offset of the first key in byte buffer. + * @param keyLen length of the first key. + * @param targetNode the node storing the second key. + * @return Returns a negative integer, zero, or a positive integer as the first key is less than, + * equal to, or greater than the second. + */ + private int compareByteBufferAndNode(ByteBuffer keyByteBuffer, int keyOffset, int keyLen, long targetNode) { + return SkipListUtils.compareByteBufferAndNode(keyByteBuffer, keyOffset, targetNode, spaceAllocator); + } + + /** + * Compare the first namespace in the given byte buffer with the second namespace in the given node. + * + * @param namespaceByteBuffer byte buffer storing the first namespace. + * @param namespaceOffset offset of the first namespace in byte buffer. + * @param namespaceLen length of the first namespace. + * @param targetNode the node storing the second namespace. + * @return Returns a negative integer, zero, or a positive integer as the first key is less than, + * equal to, or greater than the second. + */ + private int compareNamespaceAndNode(ByteBuffer namespaceByteBuffer, int namespaceOffset, int namespaceLen, long targetNode) { + Chunk chunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(targetNode)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(targetNode); + ByteBuffer targetKeyByteBuffer = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + + int level = SkipListUtils.getLevel(targetKeyByteBuffer, offsetInByteBuffer); + int targetKeyOffset = offsetInByteBuffer + SkipListUtils.getKeyDataOffset(level); + + return SkipListKeyComparator.compareNamespaceAndNode(namespaceByteBuffer, namespaceOffset, namespaceLen, + targetKeyByteBuffer, targetKeyOffset); + } + + /** + * Update the value of the node with copy-on-write mode. The old value will + * be linked after the new value, and can be still accessed. + * + * @param node the node to update. + * @param value the value. + * @return the old value pointer. + */ + private long updateValueWithCopyOnWrite(long node, byte[] value) { + // a null value indicates this is a removed node + int valueSize = value == null ? 0 : value.length; + int totalValueLen = SkipListUtils.getValueMetaLen() + valueSize; + long valuePointer = spaceAllocator.allocate(totalValueLen); + + Chunk nodeChunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInNodeChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer nodeByteBuffer = nodeChunk.getByteBuffer(offsetInNodeChunk); + int offsetInNodeByteBuffer = nodeChunk.getOffsetInByteBuffer(offsetInNodeChunk); + long oldValuePointer = SkipListUtils.getValuePointer(nodeByteBuffer, offsetInNodeByteBuffer); + + doWriteValue(valuePointer, value, stateMapVersion, node, oldValuePointer); + + // update value pointer in node after the new value has points the older value so that + // old value can be accessed concurrently + SkipListUtils.putValuePointer(nodeByteBuffer, offsetInNodeByteBuffer, valuePointer); + + return oldValuePointer; + } + + /** + * Update the value of the node with replace mode. The old value will be unlinked and replaced + * by the new value, and can not be accessed later. Note that the space of the old value + * is not freed here, and the caller of this method should be responsible for the space management. + * + * @param node the node whose value will be replaced. + * @param value the value. + * @return the old value pointer. + */ + private long updateValueWithReplace(long node, byte[] value) { + // a null value indicates this is a removed node + int valueSize = value == null ? 0 : value.length; + int totalValueLen = SkipListUtils.getValueMetaLen() + valueSize; + long valuePointer = spaceAllocator.allocate(totalValueLen); + + Chunk nodeChunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInNodeChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer nodeByteBuffer = nodeChunk.getByteBuffer(offsetInNodeChunk); + int offsetInNodeByteBuffer = nodeChunk.getOffsetInByteBuffer(offsetInNodeChunk); + + long oldValuePointer = SkipListUtils.getValuePointer(nodeByteBuffer, offsetInNodeByteBuffer); + long nextValuePointer = SkipListUtils.helpGetNextValuePointer(oldValuePointer, spaceAllocator); + + doWriteValue(valuePointer, value, stateMapVersion, node, nextValuePointer); + + // update value pointer in node after the new value has points the older value so that + // old value can be accessed concurrently + SkipListUtils.putValuePointer(nodeByteBuffer, offsetInNodeByteBuffer, valuePointer); + + return oldValuePointer; + } + + /** + * Removes the node physically, and free all space used by the key and value. + * + * @param node node to remove. + * @param prevNode previous node at the level 0. + * @param nextNode next node at the level 0. + */ + private void doPhysicalRemove(long node, long prevNode, long nextNode) { + // set next node of prevNode at level 0 to nextNode + helpSetNextNode(prevNode, nextNode, 0); + + // remove the level index for the node + SkipListUtils.removeLevelIndex(node, spaceAllocator, levelIndexHeader); + + // free space used by key and value + long valuePointer = SkipListUtils.helpGetValuePointer(node, spaceAllocator); + this.spaceAllocator.free(node); + SkipListUtils.removeAllValues(valuePointer, spaceAllocator); + } + + /** + * Removes the node physically, and return the newest-version value pointer. + * Space used by key and value will be freed here, but the space of newest-version + * value will not be freed, and the caller should be responsible for the free + * of space. + * + * @param node node to remove. + * @param prevNode previous node at the level 0. + * @param nextNode next node at the level 0. + * @return newest-version value pointer. + */ + private long doPhysicalRemoveAndGetValue(long node, long prevNode, long nextNode) { + // set next node of prevNode at level 0 to nextNode + helpSetNextNode(prevNode, nextNode, 0); + + // remove the level index for the node + SkipListUtils.removeLevelIndex(node, spaceAllocator, levelIndexHeader); + + // free space used by key and value + long valuePointer = SkipListUtils.helpGetValuePointer(node, spaceAllocator); + long nextValuePointer = SkipListUtils.helpGetNextValuePointer(valuePointer, spaceAllocator); + this.spaceAllocator.free(node); + SkipListUtils.removeAllValues(nextValuePointer, spaceAllocator); + + return valuePointer; + } + + /** + * Return a random level for new node. + */ + private int getRandomIndexLevel() { + int x = randomSeed; + x ^= x << 13; + x ^= x >>> 17; + x ^= x << 5; + randomSeed = x; + // test highest and lowest bits + if ((x & 0x8001) != 0) { + return 0; + } + int level = 1; + int curMax = levelIndexHeader.getLevel(); + x >>>= 1; + while ((x & 1) != 0) { + ++level; + x >>>= 1; + // the level only be increased by step + if (level > curMax) { + break; + } + } + return level; + } + + /** + * Write the meta and data for the key to the given node. + * + * @param node the node for the key to write. + * @param level level of this node. + * @param keyByteBuffer byte buffer storing the key. + * @param keyOffset offset of key in byte buffer. + * @param keyLen length of the key. + * @param valuePointer pointer to value. + * @param nextNode next node on level 0. + */ + private void doWriteKey( + long node, + int level, + ByteBuffer keyByteBuffer, + int keyOffset, + int keyLen, + long valuePointer, + long nextNode) { + Chunk chunk = this.spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer bb = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + + SkipListUtils.putLevelAndNodeStatus(bb, offsetInByteBuffer, level, SkipListUtils.NodeStatus.PUT.getValue()); + SkipListUtils.putKeyLen(bb, offsetInByteBuffer, keyLen); + SkipListUtils.putValuePointer(bb, offsetInByteBuffer, valuePointer); + SkipListUtils.putNextKeyPointer(bb, offsetInByteBuffer, nextNode); + SkipListUtils.putKeyData(bb, offsetInByteBuffer, keyByteBuffer, keyOffset, keyLen, level); + } + + /** + * Write the meta and data for the value to the space where the value pointer points. + * + * @param valuePointer pointer to the space where the meta and data is written. + * @param value data of the value. + * @param version version of this value. + * @param keyPointer pointer to the key. + * @param nextValuePointer pointer to the next value. + */ + private void doWriteValue( + long valuePointer, + byte[] value, + int version, + long keyPointer, + long nextValuePointer) { + Chunk chunk = this.spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(valuePointer)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(valuePointer); + ByteBuffer bb = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + + SkipListUtils.putValueVersion(bb, offsetInByteBuffer, version); + SkipListUtils.putKeyPointer(bb, offsetInByteBuffer, keyPointer); + SkipListUtils.putNextValuePointer(bb, offsetInByteBuffer, nextValuePointer); + SkipListUtils.putValueLen(bb, offsetInByteBuffer, value == null ? 0 : value.length); + if (value != null) { + SkipListUtils.putValueData(bb, offsetInByteBuffer, value); + } + } + + /** + * Find the first node with the given namespace at level 0. + * + * @param namespaceByteBuffer byte buffer storing the namespace. + * @param namespaceOffset offset of the namespace. + * @param namespaceLen length of the namespace. + * @return the first node with the given namespace. + * NIL_NODE will be returned if not exist. + */ + private long getFirstNodeWithNamespace(ByteBuffer namespaceByteBuffer, int namespaceOffset, int namespaceLen) { + int currentLevel = levelIndexHeader.getLevel(); + long prevNode = HEAD_NODE; + long currentNode = helpGetNextNode(prevNode, currentLevel); + + int c; + // find the predecessor node at level 0. + for ( ; ; ) { + if (currentNode != NIL_NODE) { + c = compareNamespaceAndNode(namespaceByteBuffer, namespaceOffset, namespaceLen, currentNode); + if (c > 0) { + prevNode = currentNode; + currentNode = helpGetNextNode(prevNode, currentLevel); + continue; + } + } + + currentLevel--; + if (currentLevel < 0) { + break; + } + currentNode = helpGetNextNode(prevNode, currentLevel); + } + + // find the first node that has not been logically removed + while (currentNode != NIL_NODE) { + if (isNodeRemoved(currentNode)) { + currentNode = helpGetNextNode(currentNode, 0); + continue; + } + + c = compareNamespaceAndNode(namespaceByteBuffer, namespaceOffset, namespaceLen, currentNode); + if (c == 0) { + return currentNode; + } + + if (c < 0) { + break; + } + } + + return NIL_NODE; + } + + /** + * Try to delete some nodes that has been logically removed. + */ + private void tryToDeleteNodesPhysically() { + if (highestRequiredSnapshotVersion != 0) { + return; + } + + int threshold = (int) (totalSize * logicalRemovedKeysRatio); + int size = logicallyRemovedNodes.size(); + if (size > threshold) { + deleteLogicallyRemovedNodes(size - threshold); + } + } + + private void deleteLogicallyRemovedNodes(int maxNodes) { + int count = 0; + Iterator<Long> nodeIterator = logicallyRemovedNodes.iterator(); + while (count < maxNodes && nodeIterator.hasNext()) { + deleteNode(nodeIterator.next()); + nodeIterator.remove(); + totalSize--; + count++; + } + } + + private void deleteNode(long node) { + long prevNode = SkipListUtils.findPredecessor(node, 1, levelIndexHeader, spaceAllocator); + long currentNode = helpGetNextNode(prevNode, 0); + while (currentNode != node) { + prevNode = currentNode; + currentNode = helpGetNextNode(prevNode, 0); + } + + long nextNode = helpGetNextNode(currentNode, 0); + doPhysicalRemove(currentNode, prevNode, nextNode); + } + + /** + * Release all resource used by the map. + */ + private void releaseAllResource() { + long node = levelIndexHeader.getNextNode(0); + while (node != NIL_NODE) { + long nextNode = helpGetNextNode(node, 0); + long valuePointer = SkipListUtils.helpGetValuePointer(node, spaceAllocator); + spaceAllocator.free(node); + SkipListUtils.removeAllValues(valuePointer, spaceAllocator); + node = nextNode; + } + totalSize = 0; + logicallyRemovedNodes.clear(); + } + + /** + * Returns the value pointer used by the snapshot of the given version. + * + * @param snapshotVersion version of snapshot. + * @return the value pointer used by the given snapshot. NIL_VALUE_POINTER + * will be returned if there is no value for this snapshot. + */ + long getValueForSnapshot(long node, int snapshotVersion) { + long snapshotValuePointer = NIL_VALUE_POINTER; + long valuePointer = SkipListUtils.helpGetValuePointer(node, spaceAllocator); + + while (valuePointer != NIL_VALUE_POINTER) { + int version = SkipListUtils.helpGetValueVersion(valuePointer, spaceAllocator); + + // the first value whose version is less than snapshotVersion + if (version < snapshotVersion) { + snapshotValuePointer = valuePointer; + break; + } + + valuePointer = SkipListUtils.helpGetNextValuePointer(valuePointer, spaceAllocator); + } + + return snapshotValuePointer; + } + + /** + * Returns the value pointer used by the snapshot of the given version, + * and useless version values will be pruned. + * + * @param snapshotVersion version of snapshot. + * @return the value pointer used by the given snapshot. NIL_VALUE_POINTER + * will be returned if there is no value for this snapshot. + */ + long getAndPruneValueForSnapshot(long node, int snapshotVersion) { + // whether the node is being pruned by some snapshot + boolean isPruning = pruningValueNodes.add(node); + try { + long snapshotValuePointer = NIL_VALUE_POINTER; + long valuePointer = SkipListUtils.helpGetValuePointer(node, spaceAllocator); + while (valuePointer != NIL_VALUE_POINTER) { + int version = SkipListUtils.helpGetValueVersion(valuePointer, spaceAllocator); + + // find the first value whose version is less than snapshotVersion + if (version < snapshotVersion && snapshotValuePointer == NIL_VALUE_POINTER) { + snapshotValuePointer = valuePointer; + if (!isPruning) { + break; + } + } + + // if the version of the value is no more than highestFinishedSnapshotVersion, + // snapshots that is running and to be run will not use the values who are + // older than this version, so these values can be safely removed. + if (highestFinishedSnapshotVersion >= version) { + long nextValuePointer = SkipListUtils.helpGetNextValuePointer(valuePointer, spaceAllocator); + if (nextValuePointer != NIL_VALUE_POINTER) { + SkipListUtils.helpSetNextValuePointer(valuePointer, NIL_VALUE_POINTER, spaceAllocator); + SkipListUtils.removeAllValues(nextValuePointer, spaceAllocator); + } + break; + } + + valuePointer = SkipListUtils.helpGetNextValuePointer(valuePointer, spaceAllocator); + } + + return snapshotValuePointer; + } finally { + // only remove the node from the set when this snapshot has pruned values + if (isPruning) { + pruningValueNodes.remove(node); + } + } + } + + /** + * Update some statistics. + */ + private void updateStat() { + requestCount++; + } + + /** + * Find the node containing the given key. + * + * @param key the key. + * @param namespace the namespace. + * @return id of the node. NIL_NODE will be returned if key does no exist. + */ + private long getNodeInternal(K key, N namespace) { + ByteBuffer keyByteBuffer = getKeyByteBuffer(key, namespace); + int keyLen = keyByteBuffer.limit(); + + return getNode(keyByteBuffer, 0, keyLen); + } + + /** + * Get the {@link ByteBuffer} wrapping up the serialized key bytes. + * + * @param key the key. + * @param namespace the namespace. + * @return the {@link ByteBuffer} wrapping up the serialized key bytes. + */ + private ByteBuffer getKeyByteBuffer(K key, N namespace) { + byte[] keyBytes = skipListKeySerializer.serialize(key, namespace); + return ByteBuffer.wrap(keyBytes); + } + + // Help methods --------------------------------------------------------------- + + /** + * Whether the node has been logically removed. + */ + private boolean isNodeRemoved(long node) { + return SkipListUtils.isNodeRemoved(node, spaceAllocator); + } + + /** + * Set the next node of the given node at the given level. + */ + private void helpSetNextNode(long node, long nextNode, int level) { + SkipListUtils.helpSetNextNode(node, nextNode, level, levelIndexHeader, spaceAllocator); + } + + /** + * Return the next of the given node at the given level. + */ + long helpGetNextNode(long node, int level) { + return SkipListUtils.helpGetNextNode(node, level, this.levelIndexHeader, this.spaceAllocator); + } + + /** + * Returns the length of the value. + */ + int helpGetValueLen(long valuePointer) { + return SkipListUtils.helpGetValueLen(valuePointer, spaceAllocator); + } + + /** + * Set node status to the given new status, and return old status. + */ + private byte helpSetNodeStatus(long node, byte newStatus) { + Chunk chunk = this.spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer bb = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + byte oldStatus = SkipListUtils.getNodeStatus(bb, offsetInByteBuffer); + if (oldStatus != newStatus) { + int level = SkipListUtils.getLevel(bb, offsetInByteBuffer); + SkipListUtils.putLevelAndNodeStatus(bb, offsetInByteBuffer, level, newStatus); + } + + return oldStatus; + } + + /** + * Return the state of the node. null will be returned if the node is removed. + */ + @VisibleForTesting + S helpGetNodeState(long node) { + Chunk chunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer byteBuffer = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + long valuePointer = SkipListUtils.getValuePointer(byteBuffer, offsetInByteBuffer); + + return helpGetState(valuePointer); + } + + /** + * Returns the byte arrays of serialized key and namespace. + * + * @param node the node. + * @return a tuple of byte arrays of serialized key and namespace + */ + Tuple2<byte[], byte[]> helpGetBytesForKeyAndNamespace(long node) { + Chunk chunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer byteBuffer = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + + int level = SkipListUtils.getLevel(byteBuffer, offsetInByteBuffer); + int keyDataOffset = offsetInByteBuffer + SkipListUtils.getKeyDataOffset(level); + + return skipListKeySerializer.getSerializedKeyAndNamespace(byteBuffer, keyDataOffset); + } + + /** + * Returns the byte array of serialized state. + * + * @param valuePointer pointer to value. + * @return byte array of serialized value. + */ + byte[] helpGetBytesForState(long valuePointer) { + Chunk chunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(valuePointer)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(valuePointer); + ByteBuffer bb = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + + int valueLen = SkipListUtils.getValueLen(bb, offsetInByteBuffer); + byte[] valueBytes = new byte[valueLen]; + ByteBufferUtils.copyFromBufferToArray(bb, offsetInByteBuffer + SkipListUtils.getValueMetaLen(), valueBytes, + 0, valueLen); + + return valueBytes; + } + + /** + * Returns the key of the node. + */ + private K helpGetKey(long node) { + Chunk chunk = spaceAllocator.getChunkById(SpaceUtils.getChunkIdByAddress(node)); + int offsetInChunk = SpaceUtils.getChunkOffsetByAddress(node); + ByteBuffer byteBuffer = chunk.getByteBuffer(offsetInChunk); + int offsetInByteBuffer = chunk.getOffsetInByteBuffer(offsetInChunk); + + int level = SkipListUtils.getLevel(byteBuffer, offsetInByteBuffer); + int keyDataLen = SkipListUtils.getKeyLen(byteBuffer, offsetInByteBuffer); + int keyDataOffset = offsetInByteBuffer + SkipListUtils.getKeyDataOffset(level); + + return skipListKeySerializer.deserializeKey(byteBuffer, keyDataOffset, keyDataLen); + } Review comment: We could use the same (reuse) `ByteBuffer`, `keyDataOffset` and `keyDataLen` when `deserializeKey` and `deserializeNamespace`, which won't be possible if we nested the calculation of offset and length into `SkipListKeySerializer` methods. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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