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_r328456850
########## 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); + } + + /** + * Return the state pointed by the given pointer. The value will be de-serialized + * with the given serializer. + */ + S helpGetState(long valuePointer, SkipListValueSerializer<S> serializer) { + if (valuePointer == NIL_VALUE_POINTER) { + return null; + } + + 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); + if (valueLen == 0) { + // it is a removed key + return null; + } + + return serializer.deserializeState(bb, + offsetInByteBuffer + SkipListUtils.getValueMetaLen(), valueLen); + } + + /** + * Return the state pointed by the given pointer. The serializer used is the + * {@link #skipListValueSerializer}. Because serializer is not thread safe, so + * this method should only be called in the state map synchronously. + */ + S helpGetState(long valuePointer) { + return helpGetState(valuePointer, skipListValueSerializer); + } + + /** + * Returns the state entry of the node. + */ + private StateEntry<K, N, S> helpGetStateEntry(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); + + K key = skipListKeySerializer.deserializeKey(byteBuffer, keyDataOffset, keyDataLen); + N namespace = skipListKeySerializer.deserializeNamespace(byteBuffer, keyDataOffset, keyDataLen); + long valuePointer = SkipListUtils.getValuePointer(byteBuffer, offsetInByteBuffer); + S state = helpGetState(valuePointer); + + return new StateEntry.SimpleStateEntry<>(key, namespace, state); + } + + // ---------------------------------------------------------------------------------- + + @Override + public Stream<K> getKeys(N namespace) { + updateStat(); + byte[] namespaceBytes = skipListKeySerializer.serializeNamespace(namespace); + ByteBuffer namespaceByteBuffer = ByteBuffer.wrap(namespaceBytes); + Iterator<Long> nodeIter = new NamespaceNodeIterator(namespaceByteBuffer, 0, namespaceBytes.length); + return StreamSupport.stream(Spliterators.spliteratorUnknownSize(nodeIter, 0), false) + .map(this::helpGetKey); + } + + @SuppressWarnings("unchecked") + @Override + public int sizeOfNamespace(Object namespace) { + updateStat(); + byte[] namespaceBytes = skipListKeySerializer.serializeNamespace((N) namespace); + ByteBuffer namespaceByteBuffer = ByteBuffer.wrap(namespaceBytes); + Iterator<Long> nodeIter = new NamespaceNodeIterator(namespaceByteBuffer, 0, namespaceBytes.length); + int size = 0; + while (nodeIter.hasNext()) { + nodeIter.next(); + size++; + } + + return size; + } + + @Nonnull + @Override + public Iterator<StateEntry<K, N, S>> iterator() { + updateStat(); + final Iterator<Long> nodeIter = new NodeIterator(); + return new Iterator<StateEntry<K, N, S>>() { + @Override + public boolean hasNext() { + return nodeIter.hasNext(); + } + + @Override + public StateEntry<K, N, S> next() { + return helpGetStateEntry(nodeIter.next()); + } + }; + } + + @Override + public InternalKvState.StateIncrementalVisitor<K, N, S> getStateIncrementalVisitor(int recommendedMaxNumberOfReturnedRecords) { + return new StateIncrementalVisitor(recommendedMaxNumberOfReturnedRecords); + } + + @Nonnull + @Override + public StateMapSnapshot<K, N, S, ? extends StateMap<K, N, S>> stateSnapshot() { + tryToDeleteNodesPhysically(); + + ResourceGuard.Lease lease; + try { + lease = resourceGuard.acquireResource(); + } catch (Exception e) { + throw new RuntimeException("Acquire resource failed, and can't make snapshot of state map", e); + } + + synchronized (snapshotVersions) { + // increase the map version for copy-on-write and register the snapshot + if (++stateMapVersion < 0) { + // this is just a safety net against overflows, but should never happen in practice (i.e., only after 2^31 snapshots) + throw new IllegalStateException("Version count overflow. Enforcing restart."); + } + + highestRequiredSnapshotVersion = stateMapVersion; Review comment: The current code logic could make sure no parallel invocation of the method, but I agree it's a strong assumption and making `highestRequiredSnapshotVersion` volatile would assure the logic to be correct even under concurrency. Considering taking snapshot is not a frequent operation, making `highestRequiredSnapshotVersion` volatile has low cost but may prevent future issue, so I will apply the change. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
