moquette改造笔记(二)：优化BrokerInterceptor notifyTopicPu

摘要：优化逻辑优化方向向启动方法一样，每次调用的方法都是在线程池中新建一个任务具体代码解释新建一个用来实现调用方法。改造笔记三优化中的线程池

下面部分是io.moquette.spi.impl.BrokerInterceptor.java部分源码

@Override
    public void notifyClientConnected(final MqttConnectMessage msg) {
        for (final InterceptHandler handler : this.handlers.get(InterceptConnectMessage.class)) {
            LOG.debug("Sending MQTT CONNECT message to interceptor. CId={}, interceptorId={}",
                    msg.payload().clientIdentifier(), handler.getID());
            executor.execute(() -> handler.onConnect(new InterceptConnectMessage(msg)));
        }
    }

    @Override
    public void notifyClientDisconnected(final String clientID, final String username) {
        for (final InterceptHandler handler : this.handlers.get(InterceptDisconnectMessage.class)) {
            LOG.debug("Notifying MQTT client disconnection to interceptor. CId={}, username={}, interceptorId={}",
                clientID, username, handler.getID());
            executor.execute(() -> handler.onDisconnect(new InterceptDisconnectMessage(clientID, username)));
        }
    }

    @Override
    public void notifyClientConnectionLost(final String clientID, final String username) {
        for (final InterceptHandler handler : this.handlers.get(InterceptConnectionLostMessage.class)) {
            LOG.debug("Notifying unexpected MQTT client disconnection to interceptor CId={}, username={}, " +
                "interceptorId={}", clientID, username, handler.getID());
            executor.execute(() -> handler.onConnectionLost(new InterceptConnectionLostMessage(clientID, username)));
        }
    }

    @Override
    public void notifyTopicPublished(final MqttPublishMessage msg, final String clientID, final String username) {
        msg.retain();

        executor.execute(() -> {
                try {
                    int messageId = msg.variableHeader().messageId();
                    String topic = msg.variableHeader().topicName();
                    for (InterceptHandler handler : handlers.get(InterceptPublishMessage.class)) {
                        LOG.debug("Notifying MQTT PUBLISH message to interceptor. CId={}, messageId={}, topic={}, "
                                + "interceptorId={}", clientID, messageId, topic, handler.getID());
                        handler.onPublish(new InterceptPublishMessage(msg, clientID, username));
                    }
                } finally {
                    ReferenceCountUtil.release(msg);
                }
        });
    }

    @Override
    public void notifyTopicSubscribed(final Subscription sub, final String username) {
        for (final InterceptHandler handler : this.handlers.get(InterceptSubscribeMessage.class)) {
            LOG.debug("Notifying MQTT SUBSCRIBE message to interceptor. CId={}, topicFilter={}, interceptorId={}",
                sub.getClientId(), sub.getTopicFilter(), handler.getID());
            executor.execute(() -> handler.onSubscribe(new InterceptSubscribeMessage(sub, username)));
        }
    }

可以发现在除了notifyTopicPublished()，其它方法中，在for循环中每次for循环，对于InterceptHandler的调用都是在线程池中每次都是新执行一个任务，但是在notifyTopicPublished()方法中是在一个线程中for循环依次调用，这样处理首先没有用到线程池的多线程，其次是一旦某个InterceptHandler的notifyTopicPublished方法是阻塞的，那么后面的InterceptHandler的notifyTopicPublished()都会被阻塞。

优化方向：向启动方法一样，每次调用InterceptHandler的notifyTopicPublished方法都是在线程池中新建一个任务

具体代码：

public class PublishTask implements Runnable {
        final MqttPublishMessage msg;
        final InterceptHandler interceptHandler;
        final String clientId;
        final String username;

        PublishTask(MqttPublishMessage msg, InterceptHandler interceptHandler, String clientId, String username) {
            this.msg = msg;
            this.interceptHandler = interceptHandler;
            this.clientId = clientId;
            this.username = username;
        }

        @Override
        public void run() {
            try {
                interceptHandler.onPublish(new InterceptPublishMessage(msg, clientId, username));
            } finally {
                ReferenceCountUtil.release(msg);
            }
        }

        @Override
        public String toString() {
            return "PublishTask{" +
                    "msg=" + msg +
                    ", interceptHandler=" + interceptHandler +
                    ", clientId="" + clientId + """ +
                    ", username="" + username + """ +
                    "}";
        }

        public InterceptHandler getInterceptHandler() {
            return interceptHandler;
        }
    }


    @Override
    public void notifyTopicPublished(final MqttPublishMessage msg, final String clientID, final String username) {

        msg.retain();

        try {
            for (InterceptHandler handler : handlers.get(InterceptPublishMessage.class)) {
                executor.execute(new PublishTask(msg.retainedDuplicate(), handler, clientID, username));
            }
        } finally {
            ReferenceCountUtil.release(msg);
        }


//        executor.execute(() -> {
//                try {
//                    int messageId = msg.variableHeader().messageId();
//                    String topic = msg.variableHeader().topicName();
//                    for (InterceptHandler handler : handlers.get(InterceptPublishMessage.class)) {
//                        LOG.debug("Notifying MQTT PUBLISH message to interceptor. CId={}, messageId={}, topic={}, "
//                                + "interceptorId={}", clientID, messageId, topic, handler.getID());
//                        handler.onPublish(new InterceptPublishMessage(msg, clientID, username));
//                    }
//                } finally {
//                    ReferenceCountUtil.release(msg);
//                }
//        });
    }

解释：
（1）新建一个PublishTask用来实现调用handler.onPublish()方法。其中要注意
new PublishTask(msg.retainedDuplicate(), handler, clientID, username)中的msg.retainedDuplicate()
还要主要在两个finally中ReferenceCountUtil.release(msg);

（2）PublishTask的toString()和getInterceptHandler()可以先不用管，会在其它地方用到，下一篇文章会讲到。
moquette改造笔记(三)：优化BrokerInterceptor 中的线程池