#ThingsBoard源码分析3-启动分析2

以下的分析环境基于内存消息队列和默认配置

1. DefaultTransportService

分析初始化方法：

@PostConstruct
public void init() {
    //根据配置判断是否创建限流
    if (rateLimitEnabled) {
        //Just checking the configuration parameters
        new TbRateLimits(perTenantLimitsConf);
        new TbRateLimits(perDevicesLimitsConf);
    }
    this.schedulerExecutor = Executors.newSingleThreadScheduledExecutor(ThingsBoardThreadFactory.forName("transport-scheduler"));
    this.transportCallbackExecutor = Executors.newWorkStealingPool(20);
    this.schedulerExecutor.scheduleAtFixedRate(this::checkInactivityAndReportActivity, new Random().nextInt((int) sessionReportTimeout), sessionReportTimeout, TimeUnit.MILLISECONDS);
  	//transportApiRequestTemplate的创建见下分析①，transportApiRequestTemplate中包含了
    //一个生产者producerTemplate（requestTemplate）     topic:tb_transport.api.responses   ②
    //和一个消费者consumerTemplate （responseTemplate）   topic:tb_transport.api.responses.localHostName ③
    transportApiRequestTemplate = queueProvider.createTransportApiRequestTemplate();
    //此处的producerProvider bean的创建是按照配置文件的值创建的，TbQueueProducerProvider有三个实现类，使用ConditionalOnExpression注解，读取service.type的值（默认monolith）,所以该Bean的实现类是TbCoreQueueProducerProvider，此类的@PostConstruct标记的init()方法初始化的，该类TbCoreQueueProducerProvider初始化了一下变量：
   // 1.toTbCore                    topic:tb_core
   // 2.toTransport                 topic:tb_transport.notifications
   // 3.toRuleEngine                topic:tb_rule_engine
   // 4.toRuleEngineNotifications   topic:tb_rule_engine
   // 5.toTbCoreNotifications       topic:tb_core
    ruleEngineMsgProducer = producerProvider.getRuleEngineMsgProducer();
    tbCoreMsgProducer = producerProvider.getTbCoreMsgProducer();
    transportNotificationsConsumer = queueProvider.createTransportNotificationsConsumer();
    //fullTopic = topic:tb_transport.notifications.localHostName  
    TopicPartitionInfo tpi = partitionService.getNotificationsTopic(ServiceType.TB_TRANSPORT, serviceInfoProvider.getServiceId());
    transportNotificationsConsumer.subscribe(Collections.singleton(tpi));
    //见④分析
    transportApiRequestTemplate.init();
    mainConsumerExecutor.execute(() -> {
        while (!stopped) {
            try {
                ListTbProtoQueueMsgToTransportMsg>> records = transportNotificationsConsumer.poll(notificationsPollDuration);
                if (records.size() == 0) {
                    continue;
                }
                records.forEach(record -> {
                    try {
                        processToTransportMsg(record.getValue());
                    } catch (Throwable e) {
                        log.warn("Failed to process the notification.", e);
                    }
                });
                transportNotificationsConsumer.commit();
            } catch (Exception e) {
                if (!stopped) {
                    log.warn("Failed to obtain messages from queue.", e);
                    try {
                        Thread.sleep(notificationsPollDuration);
                    } catch (InterruptedException e2) {
                        log.trace("Failed to wait until the server has capacity to handle new requests", e2);
                    }
                }
            }
        }
    });
}

① createTransportApiRequestTemplate In InMemoryTbTransportQueueFactory,因为我们没有启用相应的消息队列中间件，我们分析InMemoryTbTransportQueueFactory:

public TbQueueRequestTemplateTbProtoQueueMsgTransportApiRequestMsg>, TbProtoQueueMsgTransportApiResponseMsg>> createTransportApiRequestTemplate() {
    //根据配置文件值queue.transport_api.requests_topic获取到的topic是tb_transport.api.requests创建了生产者
    InMemoryTbQueueProducerTbProtoQueueMsgTransportApiRequestMsg>> producerTemplate =
            new InMemoryTbQueueProducer>(transportApiSettings.getRequestsTopic());
    //根据配置文件值queue.transport_api.responses_topic获取到的topic是tb_transport.api.responses
    //加上serviceId（我们在第二篇分析中提到，本机的HostName作为serviceId，其topic就是tb_transport.api.responses.localHostName
    InMemoryTbQueueConsumerTbProtoQueueMsgTransportApiResponseMsg>> consumerTemplate =
            new InMemoryTbQueueConsumer>(transportApiSettings.getResponsesTopic() + "." + serviceInfoProvider.getServiceId());
    //使用建造者模式返回了TbQueueRequestTemplate实例，其中包含了一个消费者和一个生产者
    DefaultTbQueueRequestTemplate.DefaultTbQueueRequestTemplateBuilder
            TbProtoQueueMsgTransportApiRequestMsg>, TbProtoQueueMsgTransportApiResponseMsg>> templateBuilder = DefaultTbQueueRequestTemplate.builder();

    templateBuilder.queueAdmin(new TbQueueAdmin() {
        @Override
        public void createTopicIfNotExists(String topic) {}

        @Override
        public void destroy() {}
    });

    templateBuilder.requestTemplate(producerTemplate);
    templateBuilder.responseTemplate(consumerTemplate);
    templateBuilder.maxPendingRequests(transportApiSettings.getMaxPendingRequests());
    templateBuilder.maxRequestTimeout(transportApiSettings.getMaxRequestsTimeout());
    templateBuilder.pollInterval(transportApiSettings.getResponsePollInterval());
    return templateBuilder.build();
}

④init() in DefaultTbQueueRequestTemplate:

public void init() {
    queueAdmin.createTopicIfNotExists(responseTemplate.getTopic());
    //按照是使用的中间件，实现不同的初始化方法，Inmemory该方法体为空
    this.requestTemplate.init();
    tickTs = System.currentTimeMillis();
    //见③，订阅主题为 tb_transport.api.responses.localHostName
    responseTemplate.subscribe();
    executor.submit(() -> {
        long nextCleanupMs = 0L;
        while (!stopped) {
            try {
                //从消息队列里面获取消息
                ListResponse> responses = responseTemplate.poll(pollInterval);
                ...........

2.TbCoreTransportApiService

• 
  

  PostConstruct注解方法：

  
  
  
  

@PostConstruct
public void init() {
this.transportCallbackExecutor = Executors.newWorkStealingPool(maxCallbackThreads);
//topic是配置文件queue.transport_api.responses_topic的值默认为：tb_transport.api.responses ⑤
TbQueueProducer producer = tbCoreQueueFactory.createTransportApiResponseProducer();
//topic是配置文件queue.transport_api.requests_topic的值，默认为：tb_transport.api.requests ⑥
TbQueueConsumer consumer = tbCoreQueueFactory.createTransportApiRequestConsumer();

DefaultTbQueueResponseTemplate.DefaultTbQueueResponseTemplateBuilder
        , TbProtoQueueMsg> builder = DefaultTbQueueResponseTemplate.builder();
builder.requestTemplate(consumer);
builder.responseTemplate(producer);
builder.maxPendingRequests(maxPendingRequests);
builder.requestTimeout(requestTimeout);
builder.pollInterval(responsePollDuration);
builder.executor(transportCallbackExecutor);
builder.handler(transportApiService);
transportApiTemplate = builder.build();

- `@EventListener(ApplicationReadyEvent.class)`注解方法，调用了`transportApiTemplate.init(transportApiService);``transportApiTemplate`即上一步创建的`DefaultTbQueueResponseTemplate`对象`init()`方法为：

```java
@Override
public void init(TbQueueHandler handler) {
   //按照是使用的中间件，实现不同的初始化方法，Inmemory该方法体为空
    this.responseTemplate.init();
    //见⑥，订阅主题为tb_transport.api.requests
    requestTemplate.subscribe();
    loopExecutor.submit(() -> {
        while (!stopped) {
            try {
                while (pendingRequestCount.get() >= maxPendingRequests) {
                    try {
                        Thread.sleep(pollInterval);
                    } catch (InterruptedException e) {
                        log.trace("Failed to wait until the server has capacity to handle new requests", e);
                    }
                }
                List requests = requestTemplate.poll(pollInterval);
                ...........

总结

DefaultTransportService和TbCoreTransportApiService方法的启动并不是很复杂，我们需要将主要的关注点放在两个Bean初始化消费者和生产者的topic上面，thingsboard将使用中间件将消息解耦，如果按照传统的调试方法很容易找不到消息的流向，此时我们将topic作为关键的切入点，方便后面整个数据流的分析。

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