kafka SnapshotRegistry 源码

kafka SnapshotRegistry 代码

文件路径：/metadata/src/main/java/org/apache/kafka/timeline/SnapshotRegistry.java

/*
 * 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.kafka.timeline;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.stream.Collectors;

import org.apache.kafka.common.utils.LogContext;
import org.slf4j.Logger;


/**
 * A registry containing snapshots of timeline data structures.
 * We generally expect a small number of snapshots-- perhaps 1 or 2 at a time.
 * Therefore, we use ArrayLists here rather than a data structure with higher overhead.
 */
public class SnapshotRegistry {
    public final static long LATEST_EPOCH = Long.MAX_VALUE;

    /**
     * Iterate through the list of snapshots in order of creation, such that older
     * snapshots come first.
     */
    class SnapshotIterator implements Iterator<Snapshot> {
        Snapshot cur;
        Snapshot result = null;

        SnapshotIterator(Snapshot start) {
            cur = start;
        }

        @Override
        public boolean hasNext() {
            return cur != head;
        }

        @Override
        public Snapshot next() {
            result = cur;
            cur = cur.next();
            return result;
        }

        @Override
        public void remove() {
            if (result == null) {
                throw new IllegalStateException();
            }
            deleteSnapshot(result);
            result = null;
        }
    }

    /**
     * Iterate through the list of snapshots in reverse order of creation, such that
     * the newest snapshot is first.
     */
    class ReverseSnapshotIterator implements Iterator<Snapshot> {
        Snapshot cur;

        ReverseSnapshotIterator() {
            cur = head.prev();
        }

        @Override
        public boolean hasNext() {
            return cur != head;
        }

        @Override
        public Snapshot next() {
            Snapshot result = cur;
            cur = cur.prev();
            return result;
        }
    }

    private final Logger log;

    /**
     * A map from snapshot epochs to snapshot data structures.
     */
    private final HashMap<Long, Snapshot> snapshots = new HashMap<>();

    /**
     * The head of a list of snapshots, sorted by epoch.
     */
    private final Snapshot head = new Snapshot(Long.MIN_VALUE);

    /**
     * Collection of all Revertable registered with this registry
     */
    private final List<Revertable> revertables = new ArrayList<>();

    public SnapshotRegistry(LogContext logContext) {
        this.log = logContext.logger(SnapshotRegistry.class);
    }

    /**
     * Returns a snapshot iterator that iterates from the snapshots with the
     * lowest epoch to those with the highest.
     */
    public Iterator<Snapshot> iterator() {
        return new SnapshotIterator(head.next());
    }

    /**
     * Returns a snapshot iterator that iterates from the snapshots with the
     * lowest epoch to those with the highest, starting at the snapshot with the
     * given epoch.
     */
    public Iterator<Snapshot> iterator(long epoch) {
        return iterator(getSnapshot(epoch));
    }

    /**
     * Returns a snapshot iterator that iterates from the snapshots with the
     * lowest epoch to those with the highest, starting at the given snapshot.
     */
    public Iterator<Snapshot> iterator(Snapshot snapshot) {
        return new SnapshotIterator(snapshot);
    }

    /**
     * Returns a reverse snapshot iterator that iterates from the snapshots with the
     * highest epoch to those with the lowest.
     */
    public Iterator<Snapshot> reverseIterator() {
        return new ReverseSnapshotIterator();
    }

    /**
     * Returns a sorted list of snapshot epochs.
     */
    public List<Long> epochsList() {
        List<Long> result = new ArrayList<>();
        for (Iterator<Snapshot> iterator = iterator(); iterator.hasNext(); ) {
            result.add(iterator.next().epoch());
        }
        return result;
    }

    public boolean hasSnapshot(long epoch) {
        return snapshots.containsKey(epoch);
    }

    /**
     * Gets the snapshot for a specific epoch.
     */
    public Snapshot getSnapshot(long epoch) {
        Snapshot snapshot = snapshots.get(epoch);
        if (snapshot == null) {
            throw new RuntimeException("No in-memory snapshot for epoch " + epoch + ". Snapshot " +
                "epochs are: " + epochsList().stream().map(e -> e.toString()).
                    collect(Collectors.joining(", ")));
        }
        return snapshot;
    }

    /**
     * Creates a new snapshot at the given epoch.
     *
     * If {@code epoch} already exists and it is the last snapshot then just return that snapshot.
     *
     * @param epoch             The epoch to create the snapshot at.  The current epoch
     *                          will be advanced to one past this epoch.
     */
    public Snapshot getOrCreateSnapshot(long epoch) {
        Snapshot last = head.prev();
        if (last.epoch() > epoch) {
            throw new RuntimeException("Can't create a new in-memory snapshot at epoch " + epoch +
                " because there is already a snapshot with epoch " + last.epoch());
        } else if (last.epoch() == epoch) {
            return last;
        }
        Snapshot snapshot = new Snapshot(epoch);
        last.appendNext(snapshot);
        snapshots.put(epoch, snapshot);
        log.debug("Creating in-memory snapshot {}", epoch);
        return snapshot;
    }

    /**
     * Reverts the state of all data structures to the state at the given epoch.
     *
     * @param targetEpoch       The epoch of the snapshot to revert to.
     */
    public void revertToSnapshot(long targetEpoch) {
        Snapshot target = getSnapshot(targetEpoch);
        Iterator<Snapshot> iterator = iterator(target);
        iterator.next();
        while (iterator.hasNext()) {
            Snapshot snapshot = iterator.next();
            log.debug("Deleting in-memory snapshot {} because we are reverting to {}",
                snapshot.epoch(), targetEpoch);
            iterator.remove();
        }
        target.handleRevert();
    }

    /**
     * Deletes the snapshot with the given epoch.
     *
     * @param targetEpoch       The epoch of the snapshot to delete.
     */
    public void deleteSnapshot(long targetEpoch) {
        deleteSnapshot(getSnapshot(targetEpoch));
    }

    /**
     * Deletes the given snapshot.
     *
     * @param snapshot          The snapshot to delete.
     */
    public void deleteSnapshot(Snapshot snapshot) {
        Snapshot prev = snapshot.prev();
        if (prev != head) {
            prev.mergeFrom(snapshot);
        } else {
            snapshot.erase();
        }
        log.debug("Deleting in-memory snapshot {}", snapshot.epoch());
        snapshots.remove(snapshot.epoch(), snapshot);
    }

    /**
     * Deletes all the snapshots up to the given epoch
     *
     * @param targetEpoch       The epoch to delete up to.
     */
    public void deleteSnapshotsUpTo(long targetEpoch) {
        for (Iterator<Snapshot> iterator = iterator(); iterator.hasNext(); ) {
            Snapshot snapshot = iterator.next();
            if (snapshot.epoch() >= targetEpoch) {
                return;
            }
            iterator.remove();
        }
    }

    /**
     * Return the latest epoch.
     */
    public long latestEpoch() {
        return head.prev().epoch();
    }

    /**
     * Associate with this registry.
     */
    public void register(Revertable revertable) {
        revertables.add(revertable);
    }

    /**
     * Delete all snapshots and resets all of the Revertable object registered.
     */
    public void reset() {
        deleteSnapshotsUpTo(LATEST_EPOCH);

        for (Revertable revertable : revertables) {
            revertable.reset();
        }
    }
}

相关信息

kafka 源码目录

相关文章

kafka BaseHashTable 源码

kafka Delta 源码

kafka Revertable 源码

kafka Snapshot 源码

kafka SnapshottableHashTable 源码

kafka TimelineHashMap 源码

kafka TimelineHashSet 源码

kafka TimelineInteger 源码

kafka TimelineLong 源码

kafka TimelineObject 源码