| /* |
| * 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.jackrabbit.oak.segment; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| import static com.google.common.collect.Sets.newHashSet; |
| |
| import java.security.SecureRandom; |
| import java.util.Set; |
| import java.util.UUID; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| import org.jetbrains.annotations.NotNull; |
| |
| /** |
| * Tracker of references to segment identifiers and segment instances |
| * that are currently kept in memory and factory for creating {@link SegmentId} |
| * instances. |
| */ |
| public class SegmentTracker implements SegmentIdProvider { |
| private static final long MSB_MASK = ~(0xfL << 12); |
| |
| private static final long VERSION = (0x4L << 12); |
| |
| private static final long LSB_MASK = ~(0xfL << 60); |
| |
| private static final long DATA = 0xAL << 60; |
| |
| private static final long BULK = 0xBL << 60; |
| |
| /** |
| * The random number source for generating new segment identifiers. |
| */ |
| @NotNull |
| private final SecureRandom random = new SecureRandom(); |
| |
| /** |
| * Hash table of weak references to segment identifiers that are |
| * currently being accessed. The size of the table is always a power |
| * of two, which optimizes the {@code refresh()} operation. The table is |
| * indexed by the random identifier bits, which guarantees uniform |
| * distribution of entries. Each table entry is either {@code null} |
| * (when there are no matching identifiers) or a list of weak references |
| * to the matching identifiers. |
| */ |
| @NotNull |
| private final SegmentIdTable[] tables = new SegmentIdTable[32]; |
| |
| /** |
| * Number of segment tracked since this tracker was instantiated |
| */ |
| @NotNull |
| private final AtomicInteger segmentCounter = new AtomicInteger(); |
| |
| @NotNull |
| private final SegmentIdFactory segmentIdFactory; |
| |
| public SegmentTracker(@NotNull SegmentIdFactory segmentIdFactory) { |
| this.segmentIdFactory = checkNotNull(segmentIdFactory); |
| for (int i = 0; i < tables.length; i++) { |
| tables[i] = new SegmentIdTable(); |
| } |
| } |
| |
| @Override |
| public int getSegmentIdCount() { |
| return segmentCounter.get(); |
| } |
| |
| /** |
| * Returns all segment identifiers that are currently referenced in memory. |
| * |
| * @return referenced segment identifiers |
| */ |
| public synchronized Set<SegmentId> getReferencedSegmentIds() { |
| Set<SegmentId> ids = newHashSet(); |
| for (SegmentIdTable table : tables) { |
| table.collectReferencedIds(ids); |
| } |
| return ids; |
| } |
| |
| /** |
| * Get an existing {@code SegmentId} with the given {@code msb} and {@code |
| * lsb} or create a new one if no such id exists with this tracker. |
| * |
| * @param msb most significant bits of the segment id |
| * @param lsb least significant bits of the segment id |
| * @return the segment id |
| */ |
| @Override |
| @NotNull |
| public SegmentId newSegmentId(long msb, long lsb) { |
| int index = ((int) msb) & (tables.length - 1); |
| return tables[index].newSegmentId(msb, lsb, segmentIdFactory); |
| } |
| |
| /** |
| * Create and track a new segment id for data segments. |
| * |
| * @return the segment id |
| */ |
| @Override |
| @NotNull |
| public SegmentId newDataSegmentId() { |
| return newSegmentId(DATA); |
| } |
| |
| /** |
| * Create and track a new segment id for bulk segments. |
| * |
| * @return the segment id |
| */ |
| @Override |
| @NotNull |
| public SegmentId newBulkSegmentId() { |
| return newSegmentId(BULK); |
| } |
| |
| @NotNull |
| private SegmentId newSegmentId(long type) { |
| segmentCounter.incrementAndGet(); |
| long msb = (random.nextLong() & MSB_MASK) | VERSION; |
| long lsb = (random.nextLong() & LSB_MASK) | type; |
| return newSegmentId(msb, lsb); |
| } |
| |
| public synchronized void clearSegmentIdTables(@NotNull Set<UUID> reclaimed, @NotNull String gcInfo) { |
| for (SegmentIdTable table : tables) { |
| table.clearSegmentIdTables(reclaimed, gcInfo); |
| } |
| } |
| |
| } |