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聊聊maxwell的BinlogConnectorEventListener

来源：SegmentFault 2023-02-24 16:31:57 0浏览收藏

你在学习数据库相关的知识吗？本文《聊聊maxwell的BinlogConnectorEventListener》，主要介绍的内容就涉及到MySQL，如果你想提升自己的开发能力，就不要错过这篇文章，大家要知道编程理论基础和实战操作都是不可或缺的哦！

序

本文主要研究一下maxwell的BinlogConnectorEventListener

BinlogConnectorEventListener

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/replication/BinlogConnectorEventListener.java

class BinlogConnectorEventListener implements BinaryLogClient.EventListener {
    private static final Logger LOGGER = LoggerFactory.getLogger(BinlogConnectorEventListener.class);

    private final BlockingQueue queue;
    private final Timer queueTimer;
    protected final AtomicBoolean mustStop = new AtomicBoolean(false);
    private final BinaryLogClient client;
    private final MaxwellOutputConfig outputConfig;
    private long replicationLag;
    private String gtid;

    public BinlogConnectorEventListener(
        BinaryLogClient client,
        BlockingQueue q,
        Metrics metrics,
        MaxwellOutputConfig outputConfig
    ) {
        this.client = client;
        this.queue = q;
        this.queueTimer =  metrics.getRegistry().timer(metrics.metricName("replication", "queue", "time"));
        this.outputConfig = outputConfig;

        final BinlogConnectorEventListener self = this;
        metrics.register(metrics.metricName("replication", "lag"), (Gauge) () -> self.replicationLag);
    }

    public void stop() {
        mustStop.set(true);
    }

    @Override
    public void onEvent(Event event) {
        long eventSeenAt = 0;
        boolean trackMetrics = false;

        if (event.getHeader().getEventType() == EventType.GTID) {
            gtid = ((GtidEventData)event.getData()).getGtid();
        }

        BinlogConnectorEvent ep = new BinlogConnectorEvent(event, client.getBinlogFilename(), client.getGtidSet(), gtid, outputConfig);

        if (ep.isCommitEvent()) {
            trackMetrics = true;
            eventSeenAt = System.currentTimeMillis();
            replicationLag = eventSeenAt - event.getHeader().getTimestamp();
        }

        while (mustStop.get() != true) {
            try {
                if ( queue.offer(ep, 100, TimeUnit.MILLISECONDS ) ) {
                    break;
                }
            } catch (InterruptedException e) {
                return;
            }
        }

        if (trackMetrics) {
            queueTimer.update(System.currentTimeMillis() - eventSeenAt, TimeUnit.MILLISECONDS);
        }
    }
}

BinlogConnectorEventListener实现了BinaryLogClient.EventListener接口，其onEvent方法创建BinlogConnectorEvent，然后将该event放入queue中

BinlogConnectorEvent

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/replication/BinlogConnectorEvent.java

public class BinlogConnectorEvent {
    public static final String BEGIN = "BEGIN";
    public static final String COMMIT = "COMMIT";
    public static final String SAVEPOINT = "SAVEPOINT";
    private final MaxwellOutputConfig outputConfig;
    private BinlogPosition position;
    private BinlogPosition nextPosition;
    private final Event event;
    private final String gtidSetStr;
    private final String gtid;

    public BinlogConnectorEvent(Event event, String filename, String gtidSetStr, String gtid, MaxwellOutputConfig outputConfig) {
        this.event = event;
        this.gtidSetStr = gtidSetStr;
        this.gtid = gtid;
        EventHeaderV4 hV4 = (EventHeaderV4) event.getHeader();
        this.nextPosition = new BinlogPosition(gtidSetStr, gtid, hV4.getNextPosition(), filename);
        this.position = new BinlogPosition(gtidSetStr, gtid, hV4.getPosition(), filename);
        this.outputConfig = outputConfig;
    }

    public Event getEvent() {
        return event;
    }

    public WriteRowsEventData writeRowsData() {
        return (WriteRowsEventData) event.getData();
    }

    public UpdateRowsEventData updateRowsData() {
        return (UpdateRowsEventData) event.getData();
    }

    public DeleteRowsEventData deleteRowsData() {
        return (DeleteRowsEventData) event.getData();
    }

    public QueryEventData queryData() {
        return (QueryEventData) event.getData();
    }

    public XidEventData xidData() {
        return (XidEventData) event.getData();
    }

    public TableMapEventData tableMapData() {
        return (TableMapEventData) event.getData();
    }

    public BinlogPosition getPosition() {
        return position;
    }

    public BinlogPosition getNextPosition() {
        return nextPosition;
    }

    public EventType getType() {
        return event.getHeader().getEventType();
    }

    public Long getTableID() {
        EventData data = event.getData();
        switch ( event.getHeader().getEventType() ) {
            case EXT_WRITE_ROWS:
            case WRITE_ROWS:
                return ((WriteRowsEventData) data).getTableId();
            case EXT_UPDATE_ROWS:
            case UPDATE_ROWS:
                return ((UpdateRowsEventData) data).getTableId();
            case EXT_DELETE_ROWS:
            case DELETE_ROWS:
                return ((DeleteRowsEventData) data).getTableId();
            case TABLE_MAP:
                return ((TableMapEventData) data).getTableId();
        }
        return null;
    }

    public boolean isCommitEvent() {
        EventType eventType = getType();
        if (eventType == EventType.XID) {
            return true;
        } else if (eventType == EventType.QUERY) {
            // MyISAM will output a "COMMIT" QUERY_EVENT instead of a XID_EVENT.
            // There's no transaction ID but we can still set "commit: true"
            return COMMIT.equals(queryData().getSql());
        }

        return false;
    }

    private void writeData(Table table, RowMap row, Serializable[] data, BitSet includedColumns) {
        int dataIdx = 0, colIdx = 0;

        for ( ColumnDef cd : table.getColumnList() ) {
            if ( includedColumns.get(colIdx) ) {
                Object json = null;
                if ( data[dataIdx] != null ) {
                    json = cd.asJSON(data[dataIdx], outputConfig);
                }
                row.putData(cd.getName(), json);
                dataIdx++;
            }
            colIdx++;
        }
    }

    private void writeOldData(Table table, RowMap row, Serializable[] oldData, BitSet oldIncludedColumns) {
        int dataIdx = 0, colIdx = 0;

        for ( ColumnDef cd : table.getColumnList() ) {
            if ( oldIncludedColumns.get(colIdx) ) {
                Object json = null;
                if ( oldData[dataIdx] != null ) {
                    json = cd.asJSON(oldData[dataIdx], outputConfig);
                }

                if (!row.hasData(cd.getName())) {
                    /*
                       If we find a column in the BEFORE image that's *not* present in the AFTER image,
                       we're running in binlog_row_image = MINIMAL.  In this case, the BEFORE image acts
                       as a sort of WHERE clause to update rows with the new values (present in the AFTER image),
                       In this case we should put what's in the "before" image into the "data" section, not the "old".
                     */
                    row.putData(cd.getName(), json);
                } else {
                    if (!Objects.equals(row.getData(cd.getName()), json)) {
                        row.putOldData(cd.getName(), json);
                    }
                }
                dataIdx++;
            }
            colIdx++;
        }
    }

    private RowMap buildRowMap(String type, Position position, Position nextPosition, Serializable[] data, Table table, BitSet includedColumns, String rowQuery) {
        RowMap map = new RowMap(
            type,
            table.getDatabase(),
            table.getName(),
            event.getHeader().getTimestamp(),
            table.getPKList(),
            position,
            nextPosition,
            rowQuery
        );

        writeData(table, map, data, includedColumns);
        return map;
    }

    public List jsonMaps(Table table, long lastHeartbeatRead, String rowQuery) {
        ArrayList list = new ArrayList();

        Position position     = Position.valueOf(this.position, lastHeartbeatRead);
        Position nextPosition = Position.valueOf(this.nextPosition, lastHeartbeatRead);

        switch ( getType() ) {
            case WRITE_ROWS:
            case EXT_WRITE_ROWS:
                for ( Serializable[] data : writeRowsData().getRows() ) {
                    list.add(buildRowMap("insert", position, nextPosition, data, table, writeRowsData().getIncludedColumns(), rowQuery));
                }
                break;
            case DELETE_ROWS:
            case EXT_DELETE_ROWS:
                for ( Serializable[] data : deleteRowsData().getRows() ) {
                    list.add(buildRowMap("delete", position, nextPosition, data, table, deleteRowsData().getIncludedColumns(), rowQuery));
                }
                break;
            case UPDATE_ROWS:
            case EXT_UPDATE_ROWS:
                for ( Map.Entry e : updateRowsData().getRows() ) {
                    Serializable[] data = e.getValue();
                    Serializable[] oldData = e.getKey();

                    RowMap r = buildRowMap("update", position, nextPosition, data, table, updateRowsData().getIncludedColumns(), rowQuery);
                    writeOldData(table, r, oldData, updateRowsData().getIncludedColumnsBeforeUpdate());
                    list.add(r);
                }
                break;
        }

        return list;
    }
}

BinlogConnectorEvent提供了jsonMaps方法，该方法根据event.getHeader().getEventType()类型来做不同处理，主要通过buildRowMap、writeOldData这几个方法来实现；buildRowMap方法返回RowMap类型，writeOldData方法主要判断是否putOldData

BinlogConnectorReplicator

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/replication/BinlogConnectorReplicator.java

public class BinlogConnectorReplicator extends RunLoopProcess implements Replicator {

    //......

    public RowMap getRow() throws Exception {
        BinlogConnectorEvent event;

        if ( stopOnEOF && hitEOF )
            return null;

        if ( !replicatorStarted )
            throw new ReplicatorNotReadyException("replicator not started!");

        while (true) {
            if (rowBuffer != null && !rowBuffer.isEmpty()) {
                RowMap row = rowBuffer.removeFirst();

                if ( row != null && isMaxwellRow(row) && row.getTable().equals("heartbeats") )
                    return processHeartbeats(row);
                else
                    return row;
            }

            event = pollEvent();

            if (event == null) {
                if ( stopOnEOF ) {
                    if ( client.isConnected() )
                        continue;
                    else
                        return null;
                } else {
                    try {
                        ensureReplicatorThread();
                    } catch ( ClientReconnectedException e ) {}
                    return null;
                }
            }

            switch (event.getType()) {
                case WRITE_ROWS:
                case EXT_WRITE_ROWS:
                case UPDATE_ROWS:
                case EXT_UPDATE_ROWS:
                case DELETE_ROWS:
                case EXT_DELETE_ROWS:
                    LOGGER.warn("Started replication stream inside a transaction.  This shouldn't normally happen.");
                    LOGGER.warn("Assuming new transaction at unexpected event:" + event);

                    queue.offerFirst(event);
                    rowBuffer = getTransactionRows(event);
                    break;
                case TABLE_MAP:
                    TableMapEventData data = event.tableMapData();
                    tableCache.processEvent(getSchema(), this.filter, data.getTableId(), data.getDatabase(), data.getTable());
                    break;
                case QUERY:
                    QueryEventData qe = event.queryData();
                    String sql = qe.getSql();
                    if (BinlogConnectorEvent.BEGIN.equals(sql)) {
                        try {
                            rowBuffer = getTransactionRows(event);
                        } catch ( ClientReconnectedException e ) {
                            // rowBuffer should already be empty by the time we get to this switch
                            // statement, but we null it for clarity
                            rowBuffer = null;
                            break;
                        }
                        rowBuffer.setServerId(event.getEvent().getHeader().getServerId());
                        rowBuffer.setThreadId(qe.getThreadId());
                        rowBuffer.setSchemaId(getSchemaId());
                    } else {
                        processQueryEvent(event);
                    }
                    break;
                case ROTATE:
                    tableCache.clear();
                    if ( stopOnEOF && event.getPosition().getOffset() > 0 ) {
                        this.binlogEventListener.mustStop.set(true);
                        this.client.disconnect();
                        this.hitEOF = true;
                        return null;
                    }
                    break;
                default:
                    break;
            }

        }
    }

    protected BinlogConnectorEvent pollEvent() throws InterruptedException {
        return queue.poll(100, TimeUnit.MILLISECONDS);
    }

    //......

}

BinlogConnectorReplicator提供了getRow方法，它先从rowBuffer取row，取不到则通过pollEvent方法从queue中取event，之后根据不同的event.getType()来做不同处理，有的会通过getTransactionRows(event)来给rowBuffer赋值

小结

BinlogConnectorEventListener实现了BinaryLogClient.EventListener接口，其onEvent方法创建BinlogConnectorEvent，然后将该event放入queue中；BinlogConnectorReplicator提供了getRow方法，它会通过pollEvent从queue中拉取BinlogConnectorEvent，解析为RowMap