1. 简介

这是canal的存储模块com.alibaba.otter.canal.store，能够将binlog解析后的event存储到内存中，由于内存有限，优先使用ITEMSIZE模式进行限制，其次使用MEMSIZE进行限制，MemoryEventStoreWithBuffer作为该模块的核心实现类，基于ReentrantLock提供阻塞的get、put方法。

  • 数据存储在哪里？内存中

  • 存储的对象是什么？EVENT

2. 核心类图

img.png

3. 实体类

public class Event implements Serializable {

    private static final long serialVersionUID = 1333330351758762739L;

    private LogIdentity       logIdentity;                            // 记录数据产生的来源
    private ByteString        rawEntry;

    private long              executeTime;
  	// 打散后的事件类型，主要用于标识事务的开始，变更数据，结束
    private EntryType         entryType;
    private String            journalName;
    private long              position;
    private long              serverId;
    // 事件类型，比如：增删改查
    private EventType         eventType;
    private String            gtid;
    private long              rawLength;
    private int               rowsCount;

    // ==== https://github.com/alibaba/canal/issues/1019
    private CanalEntry.Entry  entry;
}

4. MemoryEventStoreWithBuffer

以下是该类提供的核心方法：

image-20250520224138644

4.1 put(List<Event> data)

  1. 加锁
  2. while 循环检查是否有空位，没有空位，则notFull.await，等待被唤醒，否则，执行doPut
public void put(List<Event> data) throws InterruptedException, CanalStoreException {
    if (data == null || data.isEmpty()) {
        return;
    }

    final ReentrantLock lock = this.lock;
    lock.lockInterruptibly();
    try {
        try {
            while (!checkFreeSlotAt(putSequence.get() + data.size())) { // 检查是否有空位
                notFull.await(); // wait until not full
            }
        } catch (InterruptedException ie) {
            notFull.signal(); // propagate to non-interrupted thread
            throw ie;
        }
        doPut(data);
        if (Thread.interrupted()) {
            throw new InterruptedException();
        }
    } finally {
        lock.unlock();
    }
}

private long getMinimumGetOrAck() {
    long get = getSequence.get();
    long ack = ackSequence.get();
    return ack <= get ? ack : get;
}

private boolean checkFreeSlotAt(final long sequence) {
    final long wrapPoint = sequence - bufferSize;
    final long minPoint = getMinimumGetOrAck();
    if (wrapPoint > minPoint) { // 刚好追上一轮
        return false;
    } else {
        // 在bufferSize模式上，再增加memSize控制
        if (batchMode.isMemSize()) {
            final long memsize = putMemSize.get() - ackMemSize.get();
            if (memsize < bufferSize * bufferMemUnit) {
                return true;
            } else {
                return false;
            }
        } else {
            return true;
        }
    }
}

/**
 * 执行具体的put操作
 */
private void doPut(List<Event> data) {
    long current = putSequence.get();
    long end = current + data.size();

    // 先写数据，再更新对应的cursor,并发度高的情况，putSequence会被get请求可见，拿出了ringbuffer中的老的Entry值
    for (long next = current + 1; next <= end; next++) {
        entries[getIndex(next)] = data.get((int) (next - current - 1));
    }

    putSequence.set(end);

    // 记录一下gets memsize信息，方便快速检索
    if (batchMode.isMemSize()) {
        long size = 0;
        for (Event event : data) {
            size += calculateSize(event);
        }

        putMemSize.getAndAdd(size);
    }
    profiling(data, OP.PUT);
    // tell other threads that store is not empty
    notEmpty.signal();
}

4.2 put(List<Event> data, long timeout, TimeUnit unit)

  1. 加锁
  2. for循环检查是否有空位，如果有，则执行doPut，否则notFull.awaitNanos进行等待
public boolean put(List<Event> data, long timeout, TimeUnit unit) throws InterruptedException, CanalStoreException {
    if (data == null || data.isEmpty()) {
        return true;
    }

    long nanos = unit.toNanos(timeout);
    final ReentrantLock lock = this.lock;
    lock.lockInterruptibly();
    try {
        for (;;) {
            if (checkFreeSlotAt(putSequence.get() + data.size())) {
                doPut(data);
                return true;
            }
            if (nanos <= 0) {
                return false;
            }

            try {
                nanos = notFull.awaitNanos(nanos);
            } catch (InterruptedException ie) {
                notFull.signal(); // propagate to non-interrupted thread
                throw ie;
            }
        }
    } finally {
        lock.unlock();
    }
}

4.3 tryPut(List<Event> data)

  1. 加锁
  2. 只进行一次检查是否有空位，如果有则执行doPut，否则返回false
public boolean tryPut(List<Event> data) throws CanalStoreException {
    if (data == null || data.isEmpty()) {
        return true;
    }

    final ReentrantLock lock = this.lock;
    lock.lock();
    try {
        if (!checkFreeSlotAt(putSequence.get() + data.size())) {
            return false;
        } else {
            doPut(data);
            return true;
        }
    } finally {
        lock.unlock();
    }
}

4.4 get(Position start, int batchSize)

  1. 加锁
  2. while循环检查是否有足够元素，如果没有则notEmpty.await进行等待，否则执行doGet
public Events<Event> get(Position start, int batchSize) throws InterruptedException, CanalStoreException {
    final ReentrantLock lock = this.lock;
    lock.lockInterruptibly();
    try {
        try {
            while (!checkUnGetSlotAt((LogPosition) start, batchSize))
                notEmpty.await();
        } catch (InterruptedException ie) {
            notEmpty.signal(); // propagate to non-interrupted thread
            throw ie;
        }

        return doGet(start, batchSize);
    } finally {
        lock.unlock();
    }
}

/**
 * 检查是否存在需要get的数据,并且数量>=batchSize
 */
private boolean checkUnGetSlotAt(LogPosition startPosition, int batchSize) {
    if (batchMode.isItemSize()) {
        long current = getSequence.get();
        long maxAbleSequence = putSequence.get();
        long next = current;
        if (startPosition == null || !startPosition.getPostion().isIncluded()) { // 第一次订阅之后，需要包含一下start位置，防止丢失第一条记录
            next = next + 1;// 少一条数据
        }

        if (current < maxAbleSequence && next + batchSize - 1 <= maxAbleSequence) {
            return true;
        } else {
            return false;
        }
    } else {
        // 处理内存大小判断
        long currentSize = getMemSize.get();
        long maxAbleSize = putMemSize.get();

        if (maxAbleSize - currentSize >= batchSize * bufferMemUnit) {
            return true;
        } else {
            return false;
        }
    }
}

private Events<Event> doGet(Position start, int batchSize) throws CanalStoreException {
    LogPosition startPosition = (LogPosition) start;

    long current = getSequence.get();
    long maxAbleSequence = putSequence.get();
    long next = current;
    long end = current;
    // 如果startPosition为null，说明是第一次，默认+1处理
    if (startPosition == null || !startPosition.getPostion().isIncluded()) { // 第一次订阅之后，需要包含一下start位置，防止丢失第一条记录
        next = next + 1;
    }

    if (current >= maxAbleSequence) {
        return new Events<>();
    }

    Events<Event> result = new Events<>();
    List<Event> entrys = result.getEvents();
    long memsize = 0;
    if (batchMode.isItemSize()) {
        end = (next + batchSize - 1) < maxAbleSequence ? (next + batchSize - 1) : maxAbleSequence;
        // 提取数据并返回
        for (; next <= end; next++) {
            Event event = entries[getIndex(next)];
            if (ddlIsolation && isDdl(event.getEventType())) {
                // 如果是ddl隔离，直接返回
                if (entrys.size() == 0) {
                    entrys.add(event);// 如果没有DML事件，加入当前的DDL事件
                    end = next; // 更新end为当前
                } else {
                    // 如果之前已经有DML事件，直接返回了，因为不包含当前next这记录，需要回退一个位置
                    end = next - 1; // next-1一定大于current，不需要判断
                }
                break;
            } else {
                entrys.add(event);
            }
        }
    } else {
        long maxMemSize = batchSize * bufferMemUnit;
        for (; memsize <= maxMemSize && next <= maxAbleSequence; next++) {
            // 永远保证可以取出第一条的记录，避免死锁
            Event event = entries[getIndex(next)];
            if (ddlIsolation && isDdl(event.getEventType())) {
                // 如果是ddl隔离，直接返回
                if (entrys.size() == 0) {
                    entrys.add(event);// 如果没有DML事件，加入当前的DDL事件
                    end = next; // 更新end为当前
                } else {
                    // 如果之前已经有DML事件，直接返回了，因为不包含当前next这记录，需要回退一个位置
                    end = next - 1; // next-1一定大于current，不需要判断
                }
                break;
            } else {
                entrys.add(event);
                memsize += calculateSize(event);
                end = next;// 记录end位点
            }
        }

    }

    PositionRange<LogPosition> range = new PositionRange<>();
    result.setPositionRange(range);

    range.setStart(CanalEventUtils.createPosition(entrys.get(0)));
    range.setEnd(CanalEventUtils.createPosition(entrys.get(result.getEvents().size() - 1)));
    range.setEndSeq(end);
    // 记录一下是否存在可以被ack的点

    for (int i = entrys.size() - 1; i >= 0; i--) {
        Event event = entrys.get(i);
        // GTID模式,ack的位点必须是事务结尾,因为下一次订阅的时候mysql会发送这个gtid之后的next,如果在事务头就记录了会丢这最后一个事务
        if ((CanalEntry.EntryType.TRANSACTIONBEGIN == event.getEntryType() && StringUtils.isEmpty(event.getGtid()))
            || CanalEntry.EntryType.TRANSACTIONEND == event.getEntryType() || isDdl(event.getEventType())) {
            // 将事务头/尾设置可被为ack的点
            range.setAck(CanalEventUtils.createPosition(event));
            break;
        }
    }

    if (getSequence.compareAndSet(current, end)) {
        getMemSize.addAndGet(memsize);
        notFull.signal();
        profiling(result.getEvents(), OP.GET);
        return result;
    } else {
        return new Events<>();
    }
}

4.5 get(Position start, int batchSize, long timeout, TimeUnit unit)

public Events<Event> get(Position start, int batchSize, long timeout, TimeUnit unit) throws InterruptedException,
                                                                                    CanalStoreException {
    long nanos = unit.toNanos(timeout);
    final ReentrantLock lock = this.lock;
    lock.lockInterruptibly();
    try {
        for (;;) {
            if (checkUnGetSlotAt((LogPosition) start, batchSize)) {
                return doGet(start, batchSize);
            }

            if (nanos <= 0) {
                // 如果时间到了，有多少取多少
                return doGet(start, batchSize);
            }

            try {
                nanos = notEmpty.awaitNanos(nanos);
            } catch (InterruptedException ie) {
                notEmpty.signal(); // propagate to non-interrupted thread
                throw ie;
            }

        }
    } finally {
        lock.unlock();
    }
}

4.6 tryGet(Position start, int batchSize)

public Events<Event> tryGet(Position start, int batchSize) throws CanalStoreException {
    final ReentrantLock lock = this.lock;
    lock.lock();
    try {
        return doGet(start, batchSize);
    } finally {
        lock.unlock();
    }
}

5. Test

5.1 MemoryEventStoreBase

public class MemoryEventStoreBase {

    private static final String MYSQL_ADDRESS = "127.0.0.1";

    protected void sleep(Long time) {
        try {
            Thread.sleep(time);
        } catch (InterruptedException e) {
            Assert.fail();
        }
    }

    protected Event buildEvent(String binlogFile, long offset, long timestamp) {
        Header.Builder headerBuilder = Header.newBuilder();
        headerBuilder.setLogfileName(binlogFile);
        headerBuilder.setLogfileOffset(offset);
        headerBuilder.setExecuteTime(timestamp);
        headerBuilder.setEventLength(1024);
        Entry.Builder entryBuilder = Entry.newBuilder();
        entryBuilder.setHeader(headerBuilder.build());
        Entry entry = entryBuilder.build();

        return new Event(new LogIdentity(new InetSocketAddress(MYSQL_ADDRESS, 3306), 1234L), entry);
    }

    protected Event buildEvent(String binlogFile, long offset, long timestamp, long eventLenght) {
        Header.Builder headerBuilder = Header.newBuilder();
        headerBuilder.setLogfileName(binlogFile);
        headerBuilder.setLogfileOffset(offset);
        headerBuilder.setExecuteTime(timestamp);
        headerBuilder.setEventLength(eventLenght);
        Entry.Builder entryBuilder = Entry.newBuilder();
        entryBuilder.setHeader(headerBuilder.build());
        Entry entry = entryBuilder.build();

        return new Event(new LogIdentity(new InetSocketAddress(MYSQL_ADDRESS, 3306), 1234L), entry);
    }
}

5.2 MemoryEventStoreMemBatchTest

  1. testOnePut
  2. testOnePutExceedLimit
  3. testFullPut
  4. testOnePutOneGet
  5. testFullPutBatchGet
  6. testBlockPutOneGet
  7. testRollback
  8. testAck
public class MemoryEventStoreMemBatchTest extends MemoryEventStoreBase {

    @Test
    public void testOnePut() {
      	// 默认是初始化16K
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();
        // 尝试阻塞
        try {
            eventStore.put(buildEvent("1", 1L, 1L, 1024));
        } catch (Exception e) {
            Assert.fail(e.getMessage());
        }
        // 尝试阻塞+超时
        boolean result = false;
        try {
            result = eventStore.put(buildEvent("1", 1L, 1L), 1000L, TimeUnit.MILLISECONDS);
            Assert.assertTrue(result);
        } catch (Exception e) {
            Assert.fail(e.getMessage());
        }
        // 尝试
        result = eventStore.tryPut(buildEvent("1", 1L, 1L));
        Assert.assertTrue(result);

        eventStore.stop();
    }

    @Test
    public void testOnePutExceedLimit() {
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBufferSize(1);
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();
        // 尝试阻塞
        try {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L, 1025));// 只有一条记录，第一条超过也允许放入
            Assert.assertTrue(result);
        } catch (Exception e) {
            Assert.fail(e.getMessage());
        }

        eventStore.stop();
    }

    @Test
    public void testFullPut() {
        int bufferSize = 16;
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBufferSize(bufferSize);
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();

        for (int i = 0; i < bufferSize; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + i));
            Assert.assertTrue(result);
        }

        boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + bufferSize));
        Assert.assertFalse(result);

        try {
            result = eventStore.put(buildEvent("1", 1L, 1L + bufferSize), 1000L, TimeUnit.MILLISECONDS);
        } catch (CanalStoreException | InterruptedException e) {
            Assert.fail(e.getMessage());
        }

        Assert.assertFalse(result);

        eventStore.stop();
    }

    @Test
    public void testOnePutOneGet() {
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();

        boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L));
        Assert.assertTrue(result);

        Position position = eventStore.getFirstPosition();
        Events<Event> entrys = eventStore.tryGet(position, 1);
        Assert.assertTrue(entrys.getEvents().size() == 1);
        Assert.assertEquals(position, entrys.getPositionRange().getStart());
        Assert.assertEquals(position, entrys.getPositionRange().getEnd());

        eventStore.stop();
    }

    @Test
    public void testFullPutBatchGet() {
        int bufferSize = 16;
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBufferSize(bufferSize);
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();

        for (int i = 0; i < bufferSize; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + i));
            sleep(100L);
            Assert.assertTrue(result);
        }

        Position first = eventStore.getFirstPosition();
        Position lastest = eventStore.getLatestPosition();
        Assert.assertEquals(first, CanalEventUtils.createPosition(buildEvent("1", 1L, 1L)));
        Assert.assertEquals(lastest, CanalEventUtils.createPosition(buildEvent("1", 1L, 1L + bufferSize - 1)));

        System.out.println("start get");
        Events<Event> entrys1 = eventStore.tryGet(first, bufferSize);
        System.out.println("first get size : " + entrys1.getEvents().size());

        Assert.assertTrue(entrys1.getEvents().size() == bufferSize);
        Assert.assertEquals(first, entrys1.getPositionRange().getStart());
        Assert.assertEquals(lastest, entrys1.getPositionRange().getEnd());

        Assert.assertEquals(first, CanalEventUtils.createPosition(entrys1.getEvents().get(0)));
        Assert.assertEquals(lastest, CanalEventUtils.createPosition(entrys1.getEvents().get(bufferSize - 1)));
        eventStore.stop();
    }

    @Ignore
    @Test
    public void testBlockPutOneGet() {
        final MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBufferSize(16);
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();

        final int batchSize = 10;
        for (int i = 0; i < batchSize; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L));
            Assert.assertTrue(result);
        }

        final Position position = eventStore.getFirstPosition();
        try {
            Events<Event> entrys = eventStore.get(position, batchSize);
            Assert.assertTrue(entrys.getEvents().size() == batchSize);
            Assert.assertEquals(position, entrys.getPositionRange().getStart());
            Assert.assertEquals(position, entrys.getPositionRange().getEnd());
        } catch (CanalStoreException | InterruptedException e) {
        }

        ExecutorService executor = Executors.newFixedThreadPool(1);
        executor.submit(() -> {
            boolean result = false;
            try {
                eventStore.get(position, batchSize);
            } catch (CanalStoreException e) {
            } catch (InterruptedException e) {
                System.out.println("interrupt occured.");
                result = true;
            }
            Assert.assertTrue(result);
        });

        try {
            Thread.sleep(1000L);
        } catch (InterruptedException e) {
            Assert.fail(e.getMessage());
        }
        executor.shutdownNow();

        try {
            Thread.sleep(1000L);
        } catch (InterruptedException e) {
            Assert.fail(e.getMessage());
        }
        eventStore.stop();
    }

    @Test
    public void testRollback() {
        int bufferSize = 16;
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBufferSize(bufferSize);
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();

        for (int i = 0; i < bufferSize / 2; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + i));
            sleep(100L);
            Assert.assertTrue(result);
        }

        sleep(50L);
        Position first = eventStore.getFirstPosition();
        Position lastest = eventStore.getLatestPosition();
        Assert.assertEquals(first, CanalEventUtils.createPosition(buildEvent("1", 1L, 1L)));
        Assert.assertEquals(lastest, CanalEventUtils.createPosition(buildEvent("1", 1L, 1L + bufferSize / 2 - 1)));

        System.out.println("start get");
        Events<Event> entrys1 = eventStore.tryGet(first, bufferSize);
        System.out.println("first get size : " + entrys1.getEvents().size());

        eventStore.rollback();

        entrys1 = eventStore.tryGet(first, bufferSize);
        System.out.println("after rollback get size : " + entrys1.getEvents().size());
        Assert.assertTrue(entrys1.getEvents().size() == bufferSize / 2);

        // 继续造数据
        for (int i = bufferSize / 2; i < bufferSize; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + i));
            sleep(100L);
            Assert.assertTrue(result);
        }

        Events<Event> entrys2 = eventStore.tryGet(entrys1.getPositionRange().getEnd(), bufferSize);
        System.out.println("second get size : " + entrys2.getEvents().size());

        eventStore.rollback();

        entrys2 = eventStore.tryGet(entrys1.getPositionRange().getEnd(), bufferSize);
        System.out.println("after rollback get size : " + entrys2.getEvents().size());
        Assert.assertTrue(entrys2.getEvents().size() == bufferSize);

        first = eventStore.getFirstPosition();
        lastest = eventStore.getLatestPosition();
        List<Event> entrys = new ArrayList<>(entrys2.getEvents());
        Assert.assertTrue(entrys.size() == bufferSize);
        Assert.assertEquals(first, entrys2.getPositionRange().getStart());
        Assert.assertEquals(lastest, entrys2.getPositionRange().getEnd());

        Assert.assertEquals(first, CanalEventUtils.createPosition(entrys.get(0)));
        Assert.assertEquals(lastest, CanalEventUtils.createPosition(entrys.get(bufferSize - 1)));
        eventStore.stop();
    }

    @Test
    public void testAck() {
        int bufferSize = 16;
        MemoryEventStoreWithBuffer eventStore = new MemoryEventStoreWithBuffer();
        eventStore.setBufferSize(bufferSize);
        eventStore.setBatchMode(BatchMode.MEMSIZE);
        eventStore.start();

        for (int i = 0; i < bufferSize / 2; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + i));
            sleep(100L);
            Assert.assertTrue(result);
        }

        sleep(50L);
        Position first = eventStore.getFirstPosition();
        Position lastest = eventStore.getLatestPosition();
        Assert.assertEquals(first, CanalEventUtils.createPosition(buildEvent("1", 1L, 1L)));
        Assert.assertEquals(lastest, CanalEventUtils.createPosition(buildEvent("1", 1L, 1L + bufferSize / 2 - 1)));

        System.out.println("start get");
        Events<Event> entrys1 = eventStore.tryGet(first, bufferSize);
        System.out.println("first get size : " + entrys1.getEvents().size());

        eventStore.cleanUntil(entrys1.getPositionRange().getEnd());
        sleep(50L);

        // 继续造数据
        for (int i = bufferSize / 2; i < bufferSize; i++) {
            boolean result = eventStore.tryPut(buildEvent("1", 1L, 1L + i));
            sleep(100L);
            Assert.assertTrue(result);
        }

        Events<Event> entrys2 = eventStore.tryGet(entrys1.getPositionRange().getEnd(), bufferSize);
        System.out.println("second get size : " + entrys2.getEvents().size());

        eventStore.rollback();

        entrys2 = eventStore.tryGet(entrys1.getPositionRange().getEnd(), bufferSize);
        System.out.println("after rollback get size : " + entrys2.getEvents().size());

        first = eventStore.getFirstPosition();
        lastest = eventStore.getLatestPosition();
        List<Event> entrys = new ArrayList<>(entrys2.getEvents());
        // Assert.assertEquals(first, entrys2.getPositionRange().getStart());
        Assert.assertEquals(lastest, entrys2.getPositionRange().getEnd());

        // Assert.assertEquals(first,
        // CanalEventUtils.createPosition(entrys.get(0)));
        Assert.assertEquals(lastest, CanalEventUtils.createPosition(entrys.get(entrys.size() - 1)));

        // 全部ack掉
        eventStore.cleanUntil(entrys2.getPositionRange().getEnd());

        // 最后就拿不到数据
        Events<Event> entrys3 = eventStore.tryGet(entrys1.getPositionRange().getEnd(), bufferSize);
        System.out.println("third get size : " + entrys3.getEvents().size());
        Assert.assertEquals(0, entrys3.getEvents().size());

        eventStore.stop();
    }
}

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