cannal源码赏析 - meta模块

1. CanalMetaManager

/**
 * meta信息管理器
 * 
 * @author jianghang 2012-6-14 下午09:28:48
 * @author zebin.xuzb
 * @version 1.0.0
 */
public interface CanalMetaManager extends CanalLifeCycle {

    /**
     * 增加一个 client订阅 <br/>
     * 如果 client已经存在，则不做任何修改
     */
    void subscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 判断是否订阅
     */
    boolean hasSubscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 取消client订阅
     */
    void unsubscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 获取 cursor 游标
     */
    Position getCursor(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 更新 cursor 游标
     */
    void updateCursor(ClientIdentity clientIdentity, Position position) throws CanalMetaManagerException;

    /**
     * 根据指定的destination列出当前所有的clientIdentity信息
     */
    List<ClientIdentity> listAllSubscribeInfo(String destination) throws CanalMetaManagerException;

    /**
     * 获得该client最新的一个位置
     */
    PositionRange getFirstBatch(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 获得该clientId最新的一个位置
     */
    PositionRange getLastestBatch(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 为 client 产生一个唯一、递增的id
     */
    Long addBatch(ClientIdentity clientIdentity, PositionRange positionRange) throws CanalMetaManagerException;

    /**
     * 指定batchId，插入batch数据
     */
    void addBatch(ClientIdentity clientIdentity, PositionRange positionRange, Long batchId)
                                                                                           throws CanalMetaManagerException;

    /**
     * 根据唯一messageId，查找对应的数据起始信息
     */
    PositionRange getBatch(ClientIdentity clientIdentity, Long batchId) throws CanalMetaManagerException;

    /**
     * 对一个batch的确认
     */
    PositionRange removeBatch(ClientIdentity clientIdentity, Long batchId) throws CanalMetaManagerException;

    /**
     * 查询当前的所有batch信息
     */
    Map<Long, PositionRange> listAllBatchs(ClientIdentity clientIdentity) throws CanalMetaManagerException;

    /**
     * 清除对应的batch信息
     */
    void clearAllBatchs(ClientIdentity clientIdentity) throws CanalMetaManagerException;

}

2. ZooKeeperMetaManager

/**
 * zk 版本的 canal manager， 存储结构：
 *
 * <pre>
 * /otter
 *    canal
 *      destinations
 *        dest1
 *          client1
 *            filter
 *            batch_mark
 *              1
 *              2
 *              3
 * </pre>
 *
 * @author zebin.xuzb @ 2012-6-21
 * @author jianghang
 * @version 1.0.0
 */
public class ZooKeeperMetaManager extends AbstractCanalLifeCycle implements CanalMetaManager {

    private static final String ENCODE = "UTF-8";
    private ZkClientx           zkClientx;

    public void start() {
        super.start();

        Assert.notNull(zkClientx);
    }

    public void stop() {
        zkClientx = null; //关闭时置空
        super.stop();
    }

    public void subscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getClientIdNodePath(clientIdentity.getDestination(),
            clientIdentity.getClientId());

        try {
            zkClientx.createPersistent(path, true);
        } catch (ZkNodeExistsException e) {
            // ignore
        }
        if (clientIdentity.hasFilter()) {
            String filterPath = ZookeeperPathUtils.getFilterPath(clientIdentity.getDestination(),
                clientIdentity.getClientId());

            byte[] bytes = null;
            try {
                bytes = clientIdentity.getFilter().getBytes(ENCODE);
            } catch (UnsupportedEncodingException e) {
                throw new CanalMetaManagerException(e);
            }

            try {
                zkClientx.createPersistent(filterPath, bytes);
            } catch (ZkNodeExistsException e) {
                // ignore
                zkClientx.writeData(filterPath, bytes);
            }
        }
    }

    public boolean hasSubscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getClientIdNodePath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        return zkClientx.exists(path);
    }

    public void unsubscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getClientIdNodePath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        zkClientx.deleteRecursive(path); // 递归删除所有信息
    }

    public List<ClientIdentity> listAllSubscribeInfo(String destination) throws CanalMetaManagerException {
        if (zkClientx == null) { //重新加载时可能为空
            return new ArrayList<>();
        }
        String path = ZookeeperPathUtils.getDestinationPath(destination);
        List<String> childs = null;
        try {
            childs = zkClientx.getChildren(path);
        } catch (ZkNoNodeException e) {
            // ignore
        }

        if (CollectionUtils.isEmpty(childs)) {
            return new ArrayList<>();
        }
        List<Short> clientIds = new ArrayList<>();
        for (String child : childs) {
            if (StringUtils.isNumeric(child)) {
                clientIds.add(ZookeeperPathUtils.getClientId(child));
            }
        }

        Collections.sort(clientIds); // 进行一个排序
        List<ClientIdentity> clientIdentities = Lists.newArrayList();
        for (Short clientId : clientIds) {
            path = ZookeeperPathUtils.getFilterPath(destination, clientId);
            byte[] bytes = zkClientx.readData(path, true);
            String filter = null;
            if (bytes != null) {
                try {
                    filter = new String(bytes, ENCODE);
                } catch (UnsupportedEncodingException e) {
                    throw new CanalMetaManagerException(e);
                }
            }
            clientIdentities.add(new ClientIdentity(destination, clientId, filter));
        }

        return clientIdentities;
    }

    public Position getCursor(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getCursorPath(clientIdentity.getDestination(), clientIdentity.getClientId());

        byte[] data = zkClientx.readData(path, true);
        if (data == null || data.length == 0) {
            return null;
        }

        return JsonUtils.unmarshalFromByte(data, Position.class);
    }

    public void updateCursor(ClientIdentity clientIdentity, Position position) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getCursorPath(clientIdentity.getDestination(), clientIdentity.getClientId());
        byte[] data = JsonUtils.marshalToByte(position, JSONWriter.Feature.WriteClassName);
        try {
            zkClientx.writeData(path, data);
        } catch (ZkNoNodeException e) {
            zkClientx.createPersistent(path, data, true);// 第一次节点不存在，则尝试重建
        }
    }

    public Long addBatch(ClientIdentity clientIdentity, PositionRange positionRange) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getBatchMarkPath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        byte[] data = JsonUtils.marshalToByte(positionRange, JSONWriter.Feature.WriteClassName);
        String batchPath = zkClientx
            .createPersistentSequential(path + ZookeeperPathUtils.ZOOKEEPER_SEPARATOR, data, true);
        String batchIdString = StringUtils.substringAfterLast(batchPath, ZookeeperPathUtils.ZOOKEEPER_SEPARATOR);
        return ZookeeperPathUtils.getBatchMarkId(batchIdString);
    }

    public void addBatch(ClientIdentity clientIdentity, PositionRange positionRange,
                         Long batchId) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils
            .getBatchMarkWithIdPath(clientIdentity.getDestination(), clientIdentity.getClientId(), batchId);
        byte[] data = JsonUtils.marshalToByte(positionRange, JSONWriter.Feature.WriteClassName);
        zkClientx.createPersistent(path, data, true);
    }

    public PositionRange removeBatch(ClientIdentity clientIdentity, Long batchId) throws CanalMetaManagerException {
        String batchsPath = ZookeeperPathUtils.getBatchMarkPath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        List<String> nodes = zkClientx.getChildren(batchsPath);
        if (CollectionUtils.isEmpty(nodes)) {
            // 没有batch记录
            return null;
        }

        // 找到最小的Id
        ArrayList<Long> batchIds = new ArrayList<>(nodes.size());
        for (String batchIdString : nodes) {
            batchIds.add(Long.valueOf(batchIdString));
        }
        Long minBatchId = Collections.min(batchIds);
        if (!minBatchId.equals(batchId)) {
            // 检查一下提交的ack/rollback，必须按batchId分出去的顺序提交，否则容易出现丢数据
            throw new CanalMetaManagerException(String.format("batchId:%d is not the firstly:%d", batchId, minBatchId));
        }

        if (!batchIds.contains(batchId)) {
            // 不存在对应的batchId
            return null;
        }
        PositionRange positionRange = getBatch(clientIdentity, batchId);
        if (positionRange != null) {
            String path = ZookeeperPathUtils
                .getBatchMarkWithIdPath(clientIdentity.getDestination(), clientIdentity.getClientId(), batchId);
            zkClientx.delete(path);
        }

        return positionRange;
    }

    public PositionRange getBatch(ClientIdentity clientIdentity, Long batchId) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils
            .getBatchMarkWithIdPath(clientIdentity.getDestination(), clientIdentity.getClientId(), batchId);
        byte[] data = zkClientx.readData(path, true);
        if (data == null) {
            return null;
        }

        PositionRange positionRange = JsonUtils.unmarshalFromByte(data, PositionRange.class);
        return positionRange;
    }

    public void clearAllBatchs(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        String path = ZookeeperPathUtils.getBatchMarkPath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        List<String> batchChilds = zkClientx.getChildren(path);

        for (String batchChild : batchChilds) {
            String batchPath = path + ZookeeperPathUtils.ZOOKEEPER_SEPARATOR + batchChild;
            zkClientx.delete(batchPath);
        }
    }

    public PositionRange getLastestBatch(ClientIdentity clientIdentity) {
        String path = ZookeeperPathUtils.getBatchMarkPath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        List<String> nodes = null;
        try {
            nodes = zkClientx.getChildren(path);
        } catch (ZkNoNodeException e) {
            // ignore
        }

        if (CollectionUtils.isEmpty(nodes)) {
            return null;
        }
        // 找到最大的Id
        ArrayList<Long> batchIds = new ArrayList<>(nodes.size());
        for (String batchIdString : nodes) {
            batchIds.add(Long.valueOf(batchIdString));
        }
        Long maxBatchId = Collections.max(batchIds);
        PositionRange result = getBatch(clientIdentity, maxBatchId);
        if (result == null) { // 出现为null，说明zk节点有变化，重新获取
            return getLastestBatch(clientIdentity);
        } else {
            return result;
        }
    }

    public PositionRange getFirstBatch(ClientIdentity clientIdentity) {
        String path = ZookeeperPathUtils.getBatchMarkPath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        List<String> nodes = null;
        try {
            nodes = zkClientx.getChildren(path);
        } catch (ZkNoNodeException e) {
            // ignore
        }

        if (CollectionUtils.isEmpty(nodes)) {
            return null;
        }
        // 找到最小的Id
        ArrayList<Long> batchIds = new ArrayList<>(nodes.size());
        for (String batchIdString : nodes) {
            batchIds.add(Long.valueOf(batchIdString));
        }
        Long minBatchId = Collections.min(batchIds);
        PositionRange result = getBatch(clientIdentity, minBatchId);
        if (result == null) { // 出现为null，说明zk节点有变化，重新获取
            return getFirstBatch(clientIdentity);
        } else {
            return result;
        }
    }

    public Map<Long, PositionRange> listAllBatchs(ClientIdentity clientIdentity) {
        String path = ZookeeperPathUtils.getBatchMarkPath(clientIdentity.getDestination(),
            clientIdentity.getClientId());
        List<String> nodes = null;
        try {
            nodes = zkClientx.getChildren(path);
        } catch (ZkNoNodeException e) {
            // ignore
        }

        if (CollectionUtils.isEmpty(nodes)) {
            return Maps.newHashMap();
        }
        // 找到最大的Id
        ArrayList<Long> batchIds = new ArrayList<>(nodes.size());
        for (String batchIdString : nodes) {
            batchIds.add(Long.valueOf(batchIdString));
        }

        Collections.sort(batchIds); // 从小到大排序
        Map<Long, PositionRange> positionRanges = Maps.newLinkedHashMap();
        for (Long batchId : batchIds) {
            PositionRange result = getBatch(clientIdentity, batchId);
            if (result == null) {// 出现为null，说明zk节点有变化，重新获取
                return listAllBatchs(clientIdentity);
            } else {
                positionRanges.put(batchId, result);
            }
        }

        return positionRanges;
    }

    // =========== setter ==========

    public void setZkClientx(ZkClientx zkClientx) {
        this.zkClientx = zkClientx;
    }

}

3. MemoryMetaManager

/**
 * 内存版实现
 * 
 * @author zebin.xuzb @ 2012-7-2
 * @version 1.0.0
 */
public class MemoryMetaManager extends AbstractCanalLifeCycle implements CanalMetaManager {

    protected Map<String, List<ClientIdentity>>              destinations;
    protected Map<ClientIdentity, MemoryClientIdentityBatch> batches;
    protected Map<ClientIdentity, Position>                  cursors;

    public void start() {
        super.start();

        batches = MigrateMap.makeComputingMap(MemoryClientIdentityBatch::create);

        cursors = new MapMaker().makeMap();

        destinations = MigrateMap.makeComputingMap(destination -> new ArrayList<>());
    }

    public void stop() {
        super.stop();

        destinations.clear();
        cursors.clear();
        for (MemoryClientIdentityBatch batch : batches.values()) {
            batch.clearPositionRanges();
        }
    }

    public synchronized void subscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        List<ClientIdentity> clientIdentitys = destinations.get(clientIdentity.getDestination());

        if (clientIdentitys.contains(clientIdentity)) {
            clientIdentitys.remove(clientIdentity);
        }

        clientIdentitys.add(clientIdentity);
    }

    public synchronized boolean hasSubscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        List<ClientIdentity> clientIdentitys = destinations.get(clientIdentity.getDestination());
        return clientIdentitys != null && clientIdentitys.contains(clientIdentity);
    }

    public synchronized void unsubscribe(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        List<ClientIdentity> clientIdentitys = destinations.get(clientIdentity.getDestination());
        if (clientIdentitys != null && clientIdentitys.contains(clientIdentity)) {
            clientIdentitys.remove(clientIdentity);
        }
    }

    public synchronized List<ClientIdentity> listAllSubscribeInfo(String destination) throws CanalMetaManagerException {
        // fixed issue #657, fixed ConcurrentModificationException
        return Lists.newArrayList(destinations.get(destination));
    }

    public Position getCursor(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        return cursors.get(clientIdentity);
    }

    public void updateCursor(ClientIdentity clientIdentity, Position position) throws CanalMetaManagerException {
        cursors.put(clientIdentity, position);
    }

    public Long addBatch(ClientIdentity clientIdentity, PositionRange positionRange) throws CanalMetaManagerException {
        return batches.get(clientIdentity).addPositionRange(positionRange);
    }

    public void addBatch(ClientIdentity clientIdentity, PositionRange positionRange, Long batchId)
                                                                                                  throws CanalMetaManagerException {
        batches.get(clientIdentity).addPositionRange(positionRange, batchId);// 添加记录到指定batchId
    }

    public PositionRange removeBatch(ClientIdentity clientIdentity, Long batchId) throws CanalMetaManagerException {
        return batches.get(clientIdentity).removePositionRange(batchId);
    }

    public PositionRange getBatch(ClientIdentity clientIdentity, Long batchId) throws CanalMetaManagerException {
        return batches.get(clientIdentity).getPositionRange(batchId);
    }

    public PositionRange getLastestBatch(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        return batches.get(clientIdentity).getLastestPositionRange();
    }

    public PositionRange getFirstBatch(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        return batches.get(clientIdentity).getFirstPositionRange();
    }

    public Map<Long, PositionRange> listAllBatchs(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        return batches.get(clientIdentity).listAllPositionRange();
    }

    public void clearAllBatchs(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        batches.get(clientIdentity).clearPositionRanges();
    }

    // ============================

    public static class MemoryClientIdentityBatch {

        private ClientIdentity           clientIdentity;
        private Map<Long, PositionRange> batches          = new MapMaker().makeMap();
        private AtomicLong               atomicMaxBatchId = new AtomicLong(1);

        public static MemoryClientIdentityBatch create(ClientIdentity clientIdentity) {
            return new MemoryClientIdentityBatch(clientIdentity);
        }

        public MemoryClientIdentityBatch(){

        }

        protected MemoryClientIdentityBatch(ClientIdentity clientIdentity){
            this.clientIdentity = clientIdentity;
        }

        public synchronized void addPositionRange(PositionRange positionRange, Long batchId) {
            updateMaxId(batchId);
            batches.put(batchId, positionRange);
        }

        public synchronized Long addPositionRange(PositionRange positionRange) {
            Long batchId = atomicMaxBatchId.getAndIncrement();
            batches.put(batchId, positionRange);
            return batchId;
        }

        public synchronized PositionRange removePositionRange(Long batchId) {
            if (batches.containsKey(batchId)) {
                Long minBatchId = Collections.min(batches.keySet());
                if (!minBatchId.equals(batchId)) {
                    // 检查一下提交的ack/rollback，必须按batchId分出去的顺序提交，否则容易出现丢数据
                    throw new CanalMetaManagerException(String.format("batchId:%d is not the firstly:%d",
                        batchId,
                        minBatchId));
                }
                return batches.remove(batchId);
            } else {
                return null;
            }
        }

        public synchronized PositionRange getPositionRange(Long batchId) {
            return batches.get(batchId);
        }

        public synchronized PositionRange getLastestPositionRange() {
            if (batches.size() == 0) {
                return null;
            } else {
                Long batchId = Collections.max(batches.keySet());
                return batches.get(batchId);
            }
        }

        public synchronized PositionRange getFirstPositionRange() {
            if (batches.size() == 0) {
                return null;
            } else {
                Long batchId = Collections.min(batches.keySet());
                return batches.get(batchId);
            }
        }

        public synchronized Map<Long, PositionRange> listAllPositionRange() {
            Set<Long> batchIdSets = batches.keySet();
            List<Long> batchIds = new ArrayList<>(batchIdSets);
            Collections.sort(new ArrayList<>(batchIds));

            return Maps.newHashMap(batches);
        }

        public synchronized void clearPositionRanges() {
            batches.clear();
        }

        private synchronized void updateMaxId(Long batchId) {
            if (atomicMaxBatchId.get() < batchId + 1) {
                atomicMaxBatchId.set(batchId + 1);
            }
        }

        // ============ setter & getter =========

        public ClientIdentity getClientIdentity() {
            return clientIdentity;
        }

        public void setClientIdentity(ClientIdentity clientIdentity) {
            this.clientIdentity = clientIdentity;
        }

    }

}

4. PeriodMixedMetaManager

/**
 * 基于定时刷新的策略的mixed实现
 * 
 * <pre>
 * 几个优化：
 * 1. 去除batch数据刷新到zk中，切换时batch数据可忽略，重新从头开始获取
 * 2. cursor的更新，启用定时刷新，合并多次请求。如果最近没有变化则不更新
 * </pre>
 * 
 * @author jianghang 2012-9-11 下午02:41:15
 * @version 1.0.0
 */
public class PeriodMixedMetaManager extends MemoryMetaManager implements CanalMetaManager {

    private static final Logger      logger     = LoggerFactory.getLogger(PeriodMixedMetaManager.class);
    private ScheduledExecutorService executor;
    private ZooKeeperMetaManager     zooKeeperMetaManager;
    @SuppressWarnings("serial")
    private final Position           nullCursor = new Position() {
                                                };
    private long                     period     = 1000;                                                 // 单位ms
    private Set<ClientIdentity>      updateCursorTasks;

    public void start() {
        super.start();
        Assert.notNull(zooKeeperMetaManager);
        if (!zooKeeperMetaManager.isStart()) {
            zooKeeperMetaManager.start();
        }

        executor = Executors.newScheduledThreadPool(1);
        destinations = MigrateMap.makeComputingMap(destination -> zooKeeperMetaManager.listAllSubscribeInfo(destination));

        cursors = MigrateMap.makeComputingMap(clientIdentity -> {
            Position position = zooKeeperMetaManager.getCursor(clientIdentity);
            if (position == null) {
                return nullCursor; // 返回一个空对象标识，避免出现异常
            } else {
                return position;
            }
        });

        batches = MigrateMap.makeComputingMap(clientIdentity -> {
            // 读取一下zookeeper信息，初始化一次
            MemoryClientIdentityBatch batches = MemoryClientIdentityBatch.create(clientIdentity);
            Map<Long, PositionRange> positionRanges = zooKeeperMetaManager.listAllBatchs(clientIdentity);
            for (Map.Entry<Long, PositionRange> entry : positionRanges.entrySet()) {
                batches.addPositionRange(entry.getValue(), entry.getKey()); // 添加记录到指定batchId
            }
            return batches;
        });

        updateCursorTasks = Collections.synchronizedSet(new HashSet<>());

        // 启动定时工作任务
        executor.scheduleAtFixedRate(() -> {
            List<ClientIdentity> tasks = new ArrayList<>(updateCursorTasks);
            for (ClientIdentity clientIdentity : tasks) {
                try {
                    updateCursorTasks.remove(clientIdentity);

                    // 定时将内存中的最新值刷到zookeeper中，多次变更只刷一次
                    zooKeeperMetaManager.updateCursor(clientIdentity, getCursor(clientIdentity));
                } catch (Throwable e) {
                    // ignore
                    logger.error("period update" + clientIdentity.toString() + " curosr failed!", e);
                }
            }
        }, period, period, TimeUnit.MILLISECONDS);
    }

    public void stop() {
        super.stop();

        if (zooKeeperMetaManager.isStart()) {
            zooKeeperMetaManager.stop();
        }

        executor.shutdownNow();
        destinations.clear();
        batches.clear();
    }

    public void subscribe(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.subscribe(clientIdentity);

        // 订阅信息频率发生比较低，不需要做定时merge处理
        executor.submit(() -> zooKeeperMetaManager.subscribe(clientIdentity));
    }

    public void unsubscribe(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.unsubscribe(clientIdentity);

        // 订阅信息频率发生比较低，不需要做定时merge处理
        executor.submit(() -> zooKeeperMetaManager.unsubscribe(clientIdentity));
    }

    public void updateCursor(ClientIdentity clientIdentity, Position position) throws CanalMetaManagerException {
        super.updateCursor(clientIdentity, position);
        updateCursorTasks.add(clientIdentity);// 添加到任务队列中进行触发
    }

    public Position getCursor(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        Position position = super.getCursor(clientIdentity);
        if (position == nullCursor) {
            return null;
        } else {
            return position;
        }
    }

    // =============== setter / getter ================

    public void setZooKeeperMetaManager(ZooKeeperMetaManager zooKeeperMetaManager) {
        this.zooKeeperMetaManager = zooKeeperMetaManager;
    }

    public void setPeriod(long period) {
        this.period = period;
    }

}

5. FileMixedMetaManager

/**
 * 基于文件刷新的metaManager实现
 * 
 * <pre>
 * 策略：
 * 1. 先写内存，然后定时刷新数据到File
 * 2. 数据采取overwrite模式(只保留最后一次)，通过logger实施append模式(记录历史版本)
 * </pre>
 * 
 * @author jianghang 2013-4-15 下午05:55:57
 * @version 1.0.4
 */
public class FileMixedMetaManager extends MemoryMetaManager implements CanalMetaManager {

    private static final Logger      logger       = LoggerFactory.getLogger(FileMixedMetaManager.class);
    private static final Charset     charset      = StandardCharsets.UTF_8;
    private File                     dataDir;
    private String                   dataFileName = "meta.dat";
    private Map<String, File>        dataFileCaches;
    private ScheduledExecutorService executor;
    @SuppressWarnings("serial")
    private final Position           nullCursor   = new Position() {
                                                  };
    private long                     period       = 1000;                                               // 单位ms
    private Set<ClientIdentity>      updateCursorTasks;

    public void start() {
        super.start();
        Assert.notNull(dataDir);
        if (!dataDir.exists()) {
            try {
                FileUtils.forceMkdir(dataDir);
            } catch (IOException e) {
                throw new CanalMetaManagerException(e);
            }
        }

        if (!dataDir.canRead() || !dataDir.canWrite()) {
            throw new CanalMetaManagerException("dir[" + dataDir.getPath() + "] can not read/write");
        }

        dataFileCaches = MigrateMap.makeComputingMap(this::getDataFile);

        executor = Executors.newScheduledThreadPool(1);
        destinations = MigrateMap.makeComputingMap(this::loadClientIdentity);

        cursors = MigrateMap.makeComputingMap(clientIdentity -> {
            Position position = loadCursor(clientIdentity.getDestination(), clientIdentity);
            if (position == null) {
                return nullCursor; // 返回一个空对象标识，避免出现异常
            } else {
                return position;
            }
        });

        updateCursorTasks = Collections.synchronizedSet(new HashSet<>());

        // 启动定时工作任务
        executor.scheduleAtFixedRate(() -> {
            List<ClientIdentity> tasks = new ArrayList<>(updateCursorTasks);
            for (ClientIdentity clientIdentity : tasks) {
                MDC.put("destination", String.valueOf(clientIdentity.getDestination()));
                try {
                    updateCursorTasks.remove(clientIdentity);

                    // 定时将内存中的最新值刷到file中，多次变更只刷一次
                    if (logger.isInfoEnabled()) {
                        LogPosition cursor = (LogPosition) getCursor(clientIdentity);
                        logger.info("clientId:{} cursor:[{},{},{},{},{}] address[{}]", clientIdentity.getClientId(), cursor.getPostion().getJournalName(),
                                cursor.getPostion().getPosition(), cursor.getPostion().getTimestamp(),
                                cursor.getPostion().getServerId(), cursor.getPostion().getGtid(),
                                cursor.getIdentity().getSourceAddress().toString());
                    }
                    flushDataToFile(clientIdentity.getDestination());
                } catch (Throwable e) {
                    // ignore
                    logger.error("period update" + clientIdentity.toString() + " curosr failed!", e);
                }
            }
        },
            period,
            period,
            TimeUnit.MILLISECONDS);
    }

    public void stop() {
        flushDataToFile();// 刷新数据

        super.stop();
        executor.shutdownNow();
        destinations.clear();
        batches.clear();
    }

    public void subscribe(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.subscribe(clientIdentity);

        // 订阅信息频率发生比较低，不需要做定时merge处理
        executor.submit(() -> flushDataToFile(clientIdentity.getDestination()));
    }

    public void unsubscribe(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.unsubscribe(clientIdentity);

        // 订阅信息频率发生比较低，不需要做定时merge处理
        executor.submit(() -> flushDataToFile(clientIdentity.getDestination()));
    }

    public void updateCursor(ClientIdentity clientIdentity, Position position) throws CanalMetaManagerException {
        updateCursorTasks.add(clientIdentity);// 添加到任务队列中进行触发
        super.updateCursor(clientIdentity, position);
    }

    public Position getCursor(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        Position position = super.getCursor(clientIdentity);
        if (position == nullCursor) {
            return null;
        } else {
            return position;
        }
    }

    // ============================ helper method ======================

    private File getDataFile(String destination) {
        File destinationMetaDir = new File(dataDir, destination);
        if (!destinationMetaDir.exists()) {
            try {
                FileUtils.forceMkdir(destinationMetaDir);
            } catch (IOException e) {
                throw new CanalMetaManagerException(e);
            }
        }

        return new File(destinationMetaDir, dataFileName);
    }

    private FileMetaInstanceData loadDataFromFile(File dataFile) {
        try {
            if (!dataFile.exists()) {
                return null;
            }

            String json = FileUtils.readFileToString(dataFile, charset);
            return JsonUtils.unmarshalFromString(json, FileMetaInstanceData.class);
        } catch (IOException e) {
            throw new CanalMetaManagerException(e);
        }
    }

    private void flushDataToFile() {
        for (String destination : destinations.keySet()) {
            flushDataToFile(destination);
        }
    }

    private void flushDataToFile(String destination) {
        flushDataToFile(destination, dataFileCaches.get(destination));
    }

    private void flushDataToFile(String destination, File dataFile) {
        FileMetaInstanceData data = new FileMetaInstanceData();
        if (destinations.containsKey(destination)) {
            synchronized (destination.intern()) { // 基于destination控制一下并发更新
                data.setDestination(destination);

                List<FileMetaClientIdentityData> clientDatas = new ArrayList<>();
                List<ClientIdentity> clientIdentitys = destinations.get(destination);
                for (ClientIdentity clientIdentity : clientIdentitys) {
                    FileMetaClientIdentityData clientData = new FileMetaClientIdentityData();
                    clientData.setClientIdentity(clientIdentity);
                    Position position = cursors.get(clientIdentity);
                    if (position != null && position != nullCursor) {
                        clientData.setCursor((LogPosition) position);
                    }

                    clientDatas.add(clientData);
                }

                data.setClientDatas(clientDatas);
            }
            //fixed issue https://github.com/alibaba/canal/issues/4312
            //客户端数据为空时不覆盖文件内容 （适合单客户端）
            if(data.getClientDatas().isEmpty()){
                return;
            }
            String json = JsonUtils.marshalToString(data);
            try {
                FileUtils.writeStringToFile(dataFile, json);
            } catch (IOException e) {
                throw new CanalMetaManagerException(e);
            }
        }
    }

    private List<ClientIdentity> loadClientIdentity(String destination) {
        List<ClientIdentity> result = Lists.newArrayList();

        FileMetaInstanceData data = loadDataFromFile(dataFileCaches.get(destination));
        if (data == null) {
            return result;
        }

        List<FileMetaClientIdentityData> clientDatas = data.getClientDatas();
        if (clientDatas == null) {
            return result;
        }

        for (FileMetaClientIdentityData clientData : clientDatas) {
            if (clientData.getClientIdentity().getDestination().equals(destination)) {
                result.add(clientData.getClientIdentity());
            }
        }

        return result;
    }

    private Position loadCursor(String destination, ClientIdentity clientIdentity) {
        FileMetaInstanceData data = loadDataFromFile(dataFileCaches.get(destination));
        if (data == null) {
            return null;
        }

        List<FileMetaClientIdentityData> clientDatas = data.getClientDatas();
        if (clientDatas == null) {
            return null;
        }

        for (FileMetaClientIdentityData clientData : clientDatas) {
            if (clientData.getClientIdentity() != null && clientData.getClientIdentity().equals(clientIdentity)) {
                return clientData.getCursor();
            }
        }

        return null;
    }

    /**
     * 描述一个clientIdentity对应的数据对象
     * 
     * @author jianghang 2013-4-15 下午06:19:40
     * @version 1.0.4
     */
    public static class FileMetaClientIdentityData {

        private ClientIdentity clientIdentity;
        private LogPosition    cursor;

        public FileMetaClientIdentityData(){

        }

        public FileMetaClientIdentityData(ClientIdentity clientIdentity, MemoryClientIdentityBatch batch,
                                          LogPosition cursor){
            this.clientIdentity = clientIdentity;
            this.cursor = cursor;
        }

        public ClientIdentity getClientIdentity() {
            return clientIdentity;
        }

        public void setClientIdentity(ClientIdentity clientIdentity) {
            this.clientIdentity = clientIdentity;
        }

        public Position getCursor() {
            return cursor;
        }

        public void setCursor(LogPosition cursor) {
            this.cursor = cursor;
        }

    }

    /**
     * 描述整个canal instance对应数据对象
     * 
     * @author jianghang 2013-4-15 下午06:20:22
     * @version 1.0.4
     */
    public static class FileMetaInstanceData {

        private String                           destination;
        private List<FileMetaClientIdentityData> clientDatas;

        public FileMetaInstanceData(){

        }

        public FileMetaInstanceData(String destination, List<FileMetaClientIdentityData> clientDatas){
            this.destination = destination;
            this.clientDatas = clientDatas;
        }

        public String getDestination() {
            return destination;
        }

        public void setDestination(String destination) {
            this.destination = destination;
        }

        public List<FileMetaClientIdentityData> getClientDatas() {
            return clientDatas;
        }

        public void setClientDatas(List<FileMetaClientIdentityData> clientDatas) {
            this.clientDatas = clientDatas;
        }

    }

    public void setDataDir(String dataDir) {
        this.dataDir = new File(dataDir);
    }

    public void setDataDirByFile(File dataDir) {
        this.dataDir = dataDir;
    }

    public void setPeriod(long period) {
        this.period = period;
    }

}

6. MixedMetaManager

/**
 * 组合memory + zookeeper的使用模式
 *
 * @author jianghang 2012-7-11 下午03:58:00
 * @version 1.0.0
 */

public class MixedMetaManager extends MemoryMetaManager implements CanalMetaManager {

    private ExecutorService      executor;
    private ZooKeeperMetaManager zooKeeperMetaManager;
    @SuppressWarnings("serial")
    private final Position       nullCursor = new Position() {
                                            };

    public void start() {
        super.start();
        Assert.notNull(zooKeeperMetaManager);
        if (!zooKeeperMetaManager.isStart()) {
            zooKeeperMetaManager.start();
        }

        executor = Executors.newFixedThreadPool(1);
        destinations = MigrateMap.makeComputingMap(destination -> zooKeeperMetaManager.listAllSubscribeInfo(destination));

        cursors = MigrateMap.makeComputingMap(clientIdentity -> {
            Position position = zooKeeperMetaManager.getCursor(clientIdentity);
            if (position == null) {
                return nullCursor; // 返回一个空对象标识，避免出现异常
            } else {
                return position;
            }
        });

        batches = MigrateMap.makeComputingMap(clientIdentity -> {
            // 读取一下zookeeper信息，初始化一次
            MemoryClientIdentityBatch batches = MemoryClientIdentityBatch.create(clientIdentity);
            Map<Long, PositionRange> positionRanges = zooKeeperMetaManager.listAllBatchs(clientIdentity);
            for (Map.Entry<Long, PositionRange> entry : positionRanges.entrySet()) {
                batches.addPositionRange(entry.getValue(), entry.getKey()); // 添加记录到指定batchId
            }
            return batches;
        });
    }

    public void stop() {
        super.stop();

        if (zooKeeperMetaManager.isStart()) {
            zooKeeperMetaManager.stop();
        }

        executor.shutdownNow();
        destinations.clear();
        batches.clear();
    }

    public void subscribe(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.subscribe(clientIdentity);

        executor.submit(() -> zooKeeperMetaManager.subscribe(clientIdentity));
    }

    public void unsubscribe(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.unsubscribe(clientIdentity);

        executor.submit(() -> zooKeeperMetaManager.unsubscribe(clientIdentity));
    }

    public void updateCursor(final ClientIdentity clientIdentity, final Position position)
                                                                                          throws CanalMetaManagerException {
        super.updateCursor(clientIdentity, position);

        // 异步刷新
        executor.submit(() -> zooKeeperMetaManager.updateCursor(clientIdentity, position));
    }

    @Override
    public Position getCursor(ClientIdentity clientIdentity) throws CanalMetaManagerException {
        Position position = super.getCursor(clientIdentity);
        if (position == nullCursor) {
            return null;
        } else {
            return position;
        }
    }

    public Long addBatch(final ClientIdentity clientIdentity, final PositionRange positionRange)
                                                                                                throws CanalMetaManagerException {
        final Long batchId = super.addBatch(clientIdentity, positionRange);
        // 异步刷新
        executor.submit(() -> zooKeeperMetaManager.addBatch(clientIdentity, positionRange, batchId));
        return batchId;
    }

    public void addBatch(final ClientIdentity clientIdentity, final PositionRange positionRange, final Long batchId)
                                                                                                                    throws CanalMetaManagerException {
        super.addBatch(clientIdentity, positionRange, batchId);
        // 异步刷新
        executor.submit(() -> zooKeeperMetaManager.addBatch(clientIdentity, positionRange, batchId));
    }

    public PositionRange removeBatch(final ClientIdentity clientIdentity, final Long batchId)
                                                                                             throws CanalMetaManagerException {
        PositionRange positionRange = super.removeBatch(clientIdentity, batchId);
        // 异步刷新
        executor.submit(() -> {
            zooKeeperMetaManager.removeBatch(clientIdentity, batchId);
        });

        return positionRange;
    }

    public void clearAllBatchs(final ClientIdentity clientIdentity) throws CanalMetaManagerException {
        super.clearAllBatchs(clientIdentity);

        // 异步刷新
        executor.submit(() -> zooKeeperMetaManager.clearAllBatchs(clientIdentity));
    }

    // =============== setter / getter ================
    public void setZooKeeperMetaManager(ZooKeeperMetaManager zooKeeperMetaManager) {
        this.zooKeeperMetaManager = zooKeeperMetaManager;
    }
}