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聊聊maxwell的BinlogConnectorDiagnostic

来源：SegmentFault 2023-02-16 15:31:54 0浏览收藏

积累知识，胜过积蓄金银！毕竟在##column_title##开发的过程中，会遇到各种各样的问题，往往都是一些细节知识点还没有掌握好而导致的，因此基础知识点的积累是很重要的。下面本文《聊聊maxwell的BinlogConnectorDiagnostic》，就带大家讲解一下MySQL知识点，若是你对本文感兴趣，或者是想搞懂其中某个知识点，就请你继续往下看吧~

序

本文主要研究一下maxwell的BinlogConnectorDiagnostic

MaxwellDiagnostic

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/monitoring/MaxwellDiagnostic.java

public interface MaxwellDiagnostic {

    String getName();

    boolean isMandatory();

    String getResource();

    CompletableFuture check();

}

MaxwellDiagnostic接口定义了getName、isMandatory、getResource、check方法；check方法返回的是MaxwellDiagnosticResult.Check类型的CompletableFuture

MaxwellDiagnosticResult

maxwell-1.25.1/src/main/java/com/zendesk/maxwell/monitoring/MaxwellDiagnosticResult.java

public class MaxwellDiagnosticResult {

    private final boolean success;
    private final boolean mandatoryFailed;
    private final List checks;

    public MaxwellDiagnosticResult(List checks) {
        success = checks.stream().allMatch(Check::isSuccess);
        mandatoryFailed = checks.stream().anyMatch(check -> !check.success && check.mandatory);
        this.checks = checks;
    }

    public boolean isSuccess() {
        return success;
    }

    public boolean isMandatoryFailed() {
        return mandatoryFailed;
    }

    public List getChecks() {
        return checks;
    }

    public static class Check {
        private final String name;
        private final boolean success;
        private final boolean mandatory;
        private final String resource;
        private final Map info;

        public Check(MaxwellDiagnostic diagnostic, boolean success, Map info) {
            this.name = diagnostic.getName();
            this.success = success;
            this.mandatory = diagnostic.isMandatory();
            this.resource = diagnostic.getResource();
            this.info = info;
        }

        public String getName() {
            return name;
        }

        public boolean isSuccess() {
            return success;
        }

        public boolean isMandatory() {
            return mandatory;
        }

        public String getResource() {
            return resource;
        }

        public Map getInfo() {
            return info;
        }
    }
}

MaxwellDiagnosticResult的构造器接收checks列表；Check定义了name、success、mandatory、resource、info属性

BinlogConnectorDiagnostic

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

public class BinlogConnectorDiagnostic implements MaxwellDiagnostic {

    private final MaxwellContext context;

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

    @Override
    public String getName() {
        return "binlog-connector";
    }

    @Override
    public CompletableFuture check() {
        return getLatency().thenApply(this::normalResult).exceptionally(this::exceptionResult);
    }

    @Override
    public boolean isMandatory() {
        return true;
    }

    @Override
    public String getResource() {
        MaxwellMysqlConfig mysql = context.getConfig().maxwellMysql;
        return mysql.host + ":" + mysql.port;
    }

    public CompletableFuture getLatency() {
        HeartbeatObserver observer = new HeartbeatObserver(context.getHeartbeatNotifier(), Clock.systemUTC());
        try {
            context.heartbeat();
        } catch (Exception e) {
            observer.fail(e);
        }

        return observer.latency;
    }

    private MaxwellDiagnosticResult.Check normalResult(Long latency) {
        Map info = new HashMap();
        info.put("message", "Binlog replication lag is " + latency.toString() + "ms");
        return new MaxwellDiagnosticResult.Check(this, true, info);
    }

    private MaxwellDiagnosticResult.Check exceptionResult(Throwable e) {
        Map info = new HashMap();
        info.put("error", e.getCause().toString());
        return new MaxwellDiagnosticResult.Check(this, false, info);
    }

    //......

}

BinlogConnectorDiagnostic实现了MaxwellDiagnostic接口，它定义了MaxwellContext属性，其getName返回
```
binlog-connector
```
；其isMandatory方法返回true；其getResource方法返回的是mysql的host和port信息；其check方法通过getLatency方法获取latency的CompletableFuture，成功时通过normalResult转换，异常通过exceptionResult转换；getLatency方法创建了HeartbeatObserver并注册到HeartbeatNotifier中，然后执行context.heartbeat()，若出现异常执行observer.fail(e)，最后返回observer.latency

HeartbeatObserver

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

    static class HeartbeatObserver implements Observer {
        final CompletableFuture latency;
        private final HeartbeatNotifier notifier;
        private final Clock clock;

        HeartbeatObserver(HeartbeatNotifier notifier, Clock clock) {
            this.notifier = notifier;
            this.clock = clock;
            this.latency = new CompletableFuture();
            this.latency.whenComplete((value, exception) -> close());
            notifier.addObserver(this);
        }

        @Override
        public void update(Observable o, Object arg) {
            long heartbeatReadTime = clock.millis();
            long latestHeartbeat = (long) arg;
            latency.complete(heartbeatReadTime - latestHeartbeat);
        }

        void fail(Exception e) {
            latency.completeExceptionally(e);
        }

        private void close() {
            notifier.deleteObserver(this);
        }
    }

HeartbeatObserver实现了Observer接口，其构造器将自己注册到HeartbeatNotifier；其update方法更新latestHeartbeat，同时执行latency.complete；其fail方法执行latency.completeExceptionally(e)

HeartbeatNotifier

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

public class HeartbeatNotifier extends Observable {

    protected void heartbeat(long heartbeat) {
        setChanged();
        notifyObservers(heartbeat);
    }

}

HeartbeatNotifier继承了Observable，其heartbeat方法执行setChanged以及notifyObservers

BinlogConnectorReplicator

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

public class BinlogConnectorReplicator extends RunLoopProcess implements Replicator {

    //......

    private RowMap processHeartbeats(RowMap row) {
        String hbClientID = (String) row.getData("client_id");
        if ( !Objects.equals(hbClientID, this.clientID) )
            return row; // plain row -- do not process.

        long lastHeartbeatRead = (Long) row.getData("heartbeat");
        LOGGER.debug("replicator picked up heartbeat: " + lastHeartbeatRead);
        this.lastHeartbeatPosition = row.getPosition().withHeartbeat(lastHeartbeatRead);
        heartbeatNotifier.heartbeat(lastHeartbeatRead);
        return HeartbeatRowMap.valueOf(row.getDatabase(), this.lastHeartbeatPosition, row.getNextPosition().withHeartbeat(lastHeartbeatRead));
    }

    //......

}

BinlogConnectorReplicator的processHeartbeats方法会执行heartbeatNotifier.heartbeat(lastHeartbeatRead)方法

小结

BinlogConnectorDiagnostic实现了MaxwellDiagnostic接口，它定义了MaxwellContext属性，其getName返回

binlog-connector

；其isMandatory方法返回true；其getResource方法返回的是mysql的host和port信息；其check方法通过getLatency方法获取latency的CompletableFuture，成功时通过normalResult转换，异常通过exceptionResult转换；getLatency方法创建了HeartbeatObserver并注册到HeartbeatNotifier中，然后执行context.heartbeat()，若出现异常执行observer.fail(e)，最后返回observer.latency