聊聊CanalEventDownStreamHandler

public interface CanalEventDownStreamHandler<T> extends CanalLifeCycle {
​
    /**
     * 提交到store之前做一下处理，允许替换Event
     */
    public T before(T events);
​
    /**
     * store处于full后，retry时处理做一下处理
     */
    public T retry(T events);
​
    /**
     * 提交store成功后做一下处理
     */
    public T after(T events);
}

public class AbstractCanalEventDownStreamHandler<T> extends AbstractCanalLifeCycle implements CanalEventDownStreamHandler<T> {
​
    public T before(T events) {
        return events;
    }
​
    public T retry(T events) {
        return events;
    }
​
    public T after(T events) {
        return events;
    }
​
}

public class HeartBeatEntryEventHandler extends AbstractCanalEventDownStreamHandler<List<Event>> {
​
    public List<Event> before(List<Event> events) {
        boolean existHeartBeat = false;
        for (Event event : events) {
            if (event.getEntryType() == EntryType.HEARTBEAT) {
                existHeartBeat = true;
            }
        }
​
        if (!existHeartBeat) {
            return events;
        } else {
            // 目前heartbeat和其他事件是分离的，保险一点还是做一下检查处理
            List<Event> result = new ArrayList<Event>();
            for (Event event : events) {
                if (event.getEntryType() != EntryType.HEARTBEAT) {
                    result.add(event);
                }
            }
​
            return result;
        }
    }
​
}

public class PrometheusCanalEventDownStreamHandler extends AbstractCanalEventDownStreamHandler<List<Event>> {
​
    private final AtomicLong latestExecuteTime  = new AtomicLong(System.currentTimeMillis());
    private final AtomicLong transactionCounter = new AtomicLong(0L);
​
    @Override
    public List<Event> before(List<Event> events) {
        long localExecTime = 0L;
        if (events != null && !events.isEmpty()) {
            for (Event e : events) {
                EntryType type = e.getEntryType();
                if (type == null) continue;
                switch (type) {
                    case TRANSACTIONBEGIN: {
                        long exec = e.getExecuteTime();
                        if (exec > 0) localExecTime = exec;
                        break;
                    }
                    case ROWDATA: {
                        long exec = e.getExecuteTime();
                        if (exec > 0) localExecTime = exec;
                        break;
                    }
                    case TRANSACTIONEND: {
                        long exec = e.getExecuteTime();
                        if (exec > 0) localExecTime = exec;
                        transactionCounter.incrementAndGet();
                        break;
                    }
                    case HEARTBEAT:
                        CanalEntry.EventType eventType = e.getEventType();
                        if (eventType == CanalEntry.EventType.MHEARTBEAT) {
                            localExecTime = System.currentTimeMillis();
                        }
                        break;
                    default:
                        break;
                }
            }
            if (localExecTime > 0) {
                latestExecuteTime.lazySet(localExecTime);
            }
        }
        return events;
    }
​
    @Override
    public void start() {
​
        super.start();
    }
​
    @Override
    public void stop() {
        super.stop();
    }
​
    public AtomicLong getLatestExecuteTime() {
        return latestExecuteTime;
    }
​
    public AtomicLong getTransactionCounter() {
        return transactionCounter;
    }
​
}