實現功能
- 讀取用戶throttling配置，對broker的連接、消息進行限制，以保證broker在最健康、最效率的時間去serve
類圖
這里寫圖片描述
- 它的流量限制是使用GlobalTrafficShapingHandler去完成的，由GlobalTrafficShapingHandlerProvider來提供。
public class GlobalTrafficShapingHandlerProvider
implements Provider<GlobalTrafficShapingHandler> {
private static final Logger LOGGER = LoggerFactory.getLogger(GlobalTrafficShapingHandlerProvider.class);
private final ShutdownRegistry shutdownRegistry;
private final ThrottlingConfigurationService throttlingConfigurationService;
@Inject
GlobalTrafficShapingHandlerProvider(ShutdownRegistry shutdownRegistry,
ThrottlingConfigurationService throttlingConfigurationService) {
this.shutdownRegistry = shutdownRegistry;
this.throttlingConfigurationService = throttlingConfigurationService;
}
@Override
public GlobalTrafficShapingHandler get() {
ThreadFactory threadFactory = new ThreadFactoryBuilder().setNameFormat("global-traffic-shaping-executor-%d").build();
ScheduledExecutorService globalTrafficShapingExecutorService = Executors.newSingleThreadScheduledExecutor(threadFactory);
GlobalTrafficShapingExecutorShutdown shutdown = new GlobalTrafficShapingExecutorShutdown(globalTrafficShapingExecutorService);
this.shutdownRegistry.register(shutdown);
long incomingLimit = this.throttlingConfigurationService.incomingLimit();
LOGGER.debug("Throttling incoming traffic to {} B/s", incomingLimit);
long outgoingLimit = this.throttlingConfigurationService.outgoingLimit();
LOGGER.debug("Throttling outgoing traffic to {} B/s", outgoingLimit);
GlobalTrafficShapingHandler handler = new GlobalTrafficShapingHandler(globalTrafficShapingExecutorService, outgoingLimit, incomingLimit, 1000L);
ValueChangedCallback changedCallback = createValueChangedCallback(handler);
this.throttlingConfigurationService.incomingLimitChanged(changedCallback);
this.throttlingConfigurationService.outgoingLimitChanged(changedCallback);
return handler;
}
@NotNull
private ValueChangedCallback<Long> createValueChangedCallback(GlobalTrafficShapingHandler handler) {
return new ThrottlingTrafficLimitValueChangedCallback(handler, this.throttlingConfigurationService);
}
private static class ThrottlingTrafficLimitValueChangedCallback
implements ValueChangedCallback<Long> {
private final GlobalTrafficShapingHandler globalTrafficShapingHandler;
private final ThrottlingConfigurationService throttlingConfigurationService;
public ThrottlingTrafficLimitValueChangedCallback(GlobalTrafficShapingHandler globalTrafficShapingHandler,
ThrottlingConfigurationService throttlingConfigurationService) {
this.globalTrafficShapingHandler = globalTrafficShapingHandler;
this.throttlingConfigurationService = throttlingConfigurationService;
}
@Override
public void valueChanged(Long newValue) {
this.globalTrafficShapingHandler.configure(
this.throttlingConfigurationService.outgoingLimit(),
this.throttlingConfigurationService.incomingLimit());
}
}
}
GlobalTrafficShapingHandlerProvider通過使用ThrottlingConfigurationService讀取用戶配置，來限制incoming和outgoing。
同時給ShutdownRegistry注冊一個GlobalTrafficShapingExecutorShutdown，以當broker關閉時，能夠關閉GlobalTrafficShapingHandler中的ScheduledExecutorService。
由于MQTT協議中對remainingLength的限制在256m，如此大的數據，如果發到服務端，如果數量再一多，再優秀的mqtt broker都扛不住，所以它還提供了自定義最大消息長度，以保證broker穩定運行，以及攻擊，是一個阻攔。 在MqttMessageDecoder中，來判斷最大消息長度，來限制連接。
LicenseConnectionLimiter是它讀取license之后，根據license限制做的一個連接數限制，以及連接數占最大連接數限制的報警百分比限制。具體的license讀取、license驗證、license加密這一塊由于不屬于本章內容，所以不做過多細節介紹，并且由于它是商用軟件，所以細節以后也不會不做透漏，請各位朋友諒解；因為本系列只是協助大家了解企業級的broker如何實現的，它考慮的思路是什么，而不是破壞別人知識產權的。
