MQTT---HiveMQ源码详解(十一)Netty-Throttling

源博客地址:http://blog.csdn.net/pipinet123

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MQTT交流群:221405150

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实现功能

读取用户throttling配置，对broker的连接、消息进行限制，以保证broker在最健康、最效率的时间去serve

类图

它的流量限制是使用GlobalTrafficShapingHandler去完成的，由GlobalTrafficShapingHandlerProvider来提供。 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通过使用ThrottlingConfigurationService读取用户配置，来限制incoming和outgoing。

同时给ShutdownRegistry注册一个GlobalTrafficShapingExecutorShutdown，以当broker关闭时，能够关闭GlobalTrafficShapingHandler中的ScheduledExecutorService。

由于MQTT协议中对remainingLength的限制在256m，如此大的数据，如果发到服务端，如果数量再一多，再优秀的mqtt broker都扛不住，所以它还提供了自定义最大消息长度，以保证broker稳定运行，以及攻击，是一个阻拦。 在MqttMessageDecoder中，来判断最大消息长度，来限制连接。

LicenseConnectionLimiter是它读取license之后，根据license限制做的一个连接数限制，以及连接数占最大连接数限制的报警百分比限制。具体的license读取、license验证、license加密这一块由于不属于本章内容，所以不做过多细节介绍，并且由于它是商用软件，所以细节以后也不会不做透漏，请各位朋友谅解；因为本系列只是协助大家了解企业级的broker如何实现的，它考虑的思路是什么，而不是破坏别人知识产权的。