聊聊maxwell的BootstrapController

序

本文主要研究一下maxwell的BootstrapController

BootstrapController

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/bootstrap/BootstrapController.java

public class BootstrapController extends RunLoopProcess  {
    static final Logger LOGGER = LoggerFactory.getLogger(BootstrapController.class);
    private final long MAX_TX_ELEMENTS = 10000;

    private final ConnectionPool maxwellConnectionPool;
    private final SynchronousBootstrapper bootstrapper;
    private final AbstractProducer producer;
    private final String clientID;
    private final boolean syncMode;
    private Long currentSchemaID;

    public BootstrapController(
        ConnectionPool maxwellConnectionPool,
        AbstractProducer producer,
        SynchronousBootstrapper bootstrapper,
        String clientID,
        boolean syncMode,
        Long currentSchemaID
    ) {
        this.maxwellConnectionPool = maxwellConnectionPool;
        this.producer = producer;
        this.bootstrapper = bootstrapper;
        this.clientID = clientID;
        this.syncMode = syncMode;
        this.currentSchemaID = currentSchemaID;
    }

    // this mutex is used to block rows from being produced while a "synchronous"
    // bootstrap is run
    private Object bootstrapMutex = new Object();

    // this one is used to protect against races in an async producer.
    private Object completionMutex = new Object();
    private BootstrapTask activeTask;
    private RowMapBuffer skippedRows = new RowMapBuffer(MAX_TX_ELEMENTS);

    @Override
    protected void work() throws Exception {
        try {
            doWork();
        } catch ( InterruptedException e ) {
        } catch ( SQLException e ) {
            LOGGER.error("got SQLException trying to bootstrap", e);
        }
    }

    private void doWork() throws Exception {
        List<BootstrapTask> tasks = getIncompleteTasks();
        synchronized(bootstrapMutex) {
            for ( BootstrapTask task : tasks ) {
                LOGGER.debug("starting bootstrap task: {}", task.logString());
                synchronized(completionMutex) {
                    activeTask = task;
                }

                bootstrapper.startBootstrap(task, producer, getCurrentSchemaID());

                synchronized(completionMutex) {
                    pushSkippedRows();
                    activeTask = null;
                }
            }
        }

        Thread.sleep(1000);
    }

    private synchronized Long getCurrentSchemaID() {
        return this.currentSchemaID;
    }

    public synchronized void setCurrentSchemaID(long schemaID) {
        this.currentSchemaID = schemaID;
    }

    private List<BootstrapTask> getIncompleteTasks() throws SQLException {
        ArrayList<BootstrapTask> list = new ArrayList<>();
        try ( Connection cx = maxwellConnectionPool.getConnection() ) {
            PreparedStatement s = cx.prepareStatement("select * from bootstrap where is_complete = 0 and client_id = ? order by id");
            s.setString(1, this.clientID);

            ResultSet rs = s.executeQuery();

            while (rs.next()) {
                list.add(BootstrapTask.valueOf(rs));
            }
        }
        return list;
    }

    public boolean shouldSkip(RowMap row) throws IOException {
        // The main replication thread skips rows of the currently bootstrapped
        // table and the tables that are queued for bootstrap. The bootstrap thread replays them at
        // the end of the bootstrap.

        if ( syncMode )
            synchronized(bootstrapMutex) { return false; }
        else {
            synchronized (completionMutex) {
                if (activeTask == null)
                    return false;

                // async mode with an active task
                if (activeTask.matches(row)) {
                    skippedRows.add(row);
                    return true;
                } else
                    return false;
            }
        }
    }

    private void pushSkippedRows() throws Exception {
        skippedRows.flushToDisk();
        while ( skippedRows.size() > 0 ) {
            RowMap row = skippedRows.removeFirst();
            producer.push(row);
        }
    }

}

• BootstrapController繼承了RunLoopProcess，其work方法執行doWork方法；其doWork方法經過getIncompleteTasks獲取tasks，而後遍歷task挨個執行bootstrapper.startBootstrap(task, producer, getCurrentSchemaID())及pushSkippedRows方法；getIncompleteTasks從數據庫中查詢bootstrap表中is_complete爲0的指定client_id的記錄；pushSkippedRows方法先執行skippedRows.flushToDisk()，而後遍歷移除並執行producer.push(row)

SynchronousBootstrapper

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/bootstrap/SynchronousBootstrapper.java

public class SynchronousBootstrapper {
    static final Logger LOGGER = LoggerFactory.getLogger(SynchronousBootstrapper.class);
    private static final long INSERTED_ROWS_UPDATE_PERIOD_MILLIS = 250;
    private final MaxwellContext context;

    private long lastInsertedRowsUpdateTimeMillis = 0;

    public SynchronousBootstrapper(MaxwellContext context) {
        this.context = context;
    }


    public void startBootstrap(BootstrapTask task, AbstractProducer producer, Long currentSchemaID) throws Exception {
        performBootstrap(task, producer, currentSchemaID);
        completeBootstrap(task, producer);
    }

    private Schema captureSchemaForBootstrap(BootstrapTask task) throws SQLException {
        try ( Connection cx = getConnection(task.database) ) {
            CaseSensitivity s = MaxwellMysqlStatus.captureCaseSensitivity(cx);
            SchemaCapturer c = new SchemaCapturer(cx, s, task.database, task.table);
            return c.capture();
        }
    }

    public void performBootstrap(BootstrapTask task, AbstractProducer producer, Long currentSchemaID) throws Exception {
        LOGGER.debug("bootstrapping requested for " + task.logString());

        Schema schema = captureSchemaForBootstrap(task);
        Database database = findDatabase(schema, task.database);
        Table table = findTable(task.table, database);

        producer.push(bootstrapStartRowMap(task, table));
        LOGGER.info(String.format("bootstrapping started for %s.%s", task.database, task.table));

        try ( Connection streamingConnection = getStreamingConnection(task.database)) {
            setBootstrapRowToStarted(task.id);
            ResultSet resultSet = getAllRows(task.database, task.table, table, task.whereClause, streamingConnection);
            int insertedRows = 0;
            lastInsertedRowsUpdateTimeMillis = 0; // ensure updateInsertedRowsColumn is called at least once
            while ( resultSet.next() ) {
                RowMap row = bootstrapEventRowMap("bootstrap-insert", table.database, table.name, table.getPKList(), task.comment);
                setRowValues(row, resultSet, table);
                row.setSchemaId(currentSchemaID);

                Scripting scripting = context.getConfig().scripting;
                if ( scripting != null )
                    scripting.invoke(row);

                if ( LOGGER.isDebugEnabled() )
                    LOGGER.debug("bootstrapping row : " + row.toJSON());

                producer.push(row);
                Thread.sleep(1);
                ++insertedRows;

                updateInsertedRowsColumn(insertedRows, task.id);
            }
            setBootstrapRowToCompleted(insertedRows, task.id);
        } catch ( NoSuchElementException e ) {
            LOGGER.info("bootstrapping aborted for " + task.logString());
        }
    }

    public void completeBootstrap(BootstrapTask task, AbstractProducer producer) throws Exception {
        producer.push(bootstrapEventRowMap("bootstrap-complete", task.database, task.table, new ArrayList<>(), task.comment));
        LOGGER.info("bootstrapping ended for " + task.logString());
    }

    //......

}

• SynchronousBootstrapper的startBootstrap方法執行performBootstrap及completeBootstrap方法；其中performBootstrap方法執行producer.push(bootstrapStartRowMap(task, table))，以後根據task指定的數據庫、表及條件查詢記錄，而後遍歷結果集producer.push(row)；completeBootstrap方法執行producer.push(bootstrapEventRowMap("bootstrap-complete", task.database, task.table, new ArrayList<>(), task.comment))

小結

BootstrapController繼承了RunLoopProcess，其work方法執行doWork方法；其doWork方法經過getIncompleteTasks獲取tasks，而後遍歷task挨個執行bootstrapper.startBootstrap(task, producer, getCurrentSchemaID())及pushSkippedRows方法；getIncompleteTasks從數據庫中查詢bootstrap表中is_complete爲0的指定client_id的記錄；pushSkippedRows方法先執行skippedRows.flushToDisk()，而後遍歷移除並執行producer.push(row)

doc

• BootstrapController