基于MQTT协议实现Broker
写在前面:
前一篇文字<<基于MQTT协议谈谈物联网开发-华佗写代码>>主要叙述了MQTT协议的编解码以及基于MQTT协议的一些常见应用场景,并以一个简单的消息推送系统作为例子阐述具体MQTT应用的开发,这篇文字继续叙述上述应用中Mqtt Broker部分的实现.
1.Mqtt Broker开源产品:
Mqtt Broker简单来说就是基于MQTT协议的Server实现,并且github上有很多开源实现,如下图:
各种Mqtt Broker开源实现的几个关键技术指标对比如下图:
可以根据业务的需求不同选用不同的broker开源实现,总体来说,对Mqtt Broker来说,要求高可用,无状态,易扩容,可靠传输等,下面就以Mqtt Broker的实现作为例子,讲讲基于MQTT协议的Broker具体开发,不考虑太复杂的业务逻辑,仅以最简洁的方式,阐述整个流程,基于Golang和RabbitMQ开发.
2.Mqtt Broker具体实现:
2.1Mqtt Broker架构草图:
2.2Mqtt Broker实现细节说明:
(1)Broker与RabbitMQ建立TCP连接,实现断线重连逻辑以及断线通知机制;
(2)Broker声明与RabbitMQ相关的exchanger, amqp队列,以及rpc队列;
(3)Broker监听APP端mqttclient的tcp连接,对应每个连接,Broker实例化一个appClient;
(4)每个appClient处理与之对应的APP业务请求,包括发布,订阅,取消订阅,心跳等;
(5)每个appClient获取一个channel,通过channel与RabbitMQ进行通信;
(6)若Broker与RabbitMQ发生断连,则channel不可用,必须等待重连成功,然后重新获取channel;
(7)若RabbitMQ发生重启,之前对应APP需要订阅的数据,每个appClient必须重新订阅;
(8)若APP断开连接,则对应的appClient必须释放所有资源并结束生命周期,不再服务;
(9)其他...
2.3Mqtt Broker代码实现:
根据上述的架构草图以及细节说明,就整个架构比较关键的几个环节,用具体代码实现加以阐述,以求透彻.
(1)Broker与RabbitMQ连接:
定义相关数据结构以及方法如下:
package rabbit var ( RabbitServerAddr = flag.String("rabbitserveraddr", "amqp://guest:guest@localhost:5672", "") ) const ( CONNECT_INTERVAL = 3 ) var _rabbit *Rabbit = nil var _once sync.Once //定义Rabbit结构 type Rabbit struct { wg *sync.WaitGroup rabbitconn *amqp.Connection rabbitconnListeners map[string]chan bool _mutex sync.Mutex } //获取Rabbit单例 func GetRabbitInstance(_wg *sync.WaitGroup, listenerID string, rabbitconnChan chan bool) *Rabbit { _once.Do(func() { _rabbit = &Rabbit{ wg: _wg, } _rabbit.rabbitconnListeners = make(map[string]chan bool) _rabbit.initConn() }) if listenerID != "" && rabbitconnChan != nil { _rabbit._mutex.Lock() _rabbit.rabbitconnListeners[listenerID] = rabbitconnChan _rabbit._mutex.Unlock() } return _rabbit } //建立RabbitMQ连接 func (r *Rabbit) initConn() { if r.rabbitconn != nil { return } conn, err := amqp.Dial(*RabbitServerAddr) if err != nil { time.Sleep(time.Second * CONNECT_INTERVAL) U.FailOnError(err) } r.rabbitconn = conn r.wg.Add(1) go r.checkConn() } //RabbitMQ断线重连 func (r *Rabbit) checkConn() { defer r.wg.Done() for { <-r.rabbitconn.NotifyClose(make(chan *amqp.Error)) U.GetLog().Printf("r.conn.NotifyClose") r.broadcastConnStatus(false) for { conn, err := amqp.Dial(*RabbitServerAddr) if err == nil { r.rabbitconn = conn r.broadcastConnStatus(true) break } U.GetLog().Printf("amqp.Dial failed") r.broadcastConnStatus(false) time.Sleep(time.Second * CONNECT_INTERVAL) } } }
(2)Broker声明exchanger, amqp队列,以及rpc队列:
定义相关数据结构以及方法如下:
package mqtt type TOPIC_CHAN_TYPE map[string]chan ExchangeMessage //定义BrokerExchanger结构 type BrokerExchanger struct { wg *sync.WaitGroup channel *amqp.Channel exchangerChan chan *MqttClientCmd amqpqueueName string amqpDeliveryChan <-chan amqp.Delivery amqpTopicChan map[string]TOPIC_CHAN_TYPE rpcqueueName string rpcDeliveryChan <-chan amqp.Delivery rpcClientChan map[string]chan ExchangeMessage } //实例化BrokerExchanger func NewBrokerExchanger(_wg *sync.WaitGroup) *BrokerExchanger { _be := &BrokerExchanger{ wg: _wg, } _be.once() return _be } //声明Exchange,区分amqp与rpc类型 func (be *BrokerExchanger) declareExchange(exctype string) error { if be.channel == nil { return fmt.Errorf("[BrokerExchanger::declareExchange] channel not ready") } var defaultExchange string var exchangeType string switch exctype { case defaultAMQPExchange: defaultExchange = defaultAMQPExchange exchangeType = "topic" case defaultRPCExchange: defaultExchange = defaultRPCExchange exchangeType = "direct" default: U.GetLog().Printf("unexpected exchange type:%s", exctype) return fmt.Errorf("[BrokerExchanger::declareExchange] unexpected exchange type:%s", exctype) } err := be.channel.ExchangeDeclare( defaultExchange, // name exchangeType, // type true, // durable false, // auto-deleted false, // internal false, // no-wait nil, // arguments ) return err } //声明Queue,区分amqp与rpc类型 func (be *BrokerExchanger) declareQueue(exctype string) error { if be.channel == nil { return fmt.Errorf("[BrokerExchanger::declareQueue] channel not ready") } q, err := be.channel.QueueDeclare( "", // name true, // durable true, // delete when usused true, // exclusive false, // no-wait nil, // arguments ) if err != nil { return err } switch exctype { case defaultAMQPExchange: be.amqpqueueName = q.Name case defaultRPCExchange: be.rpcqueueName = q.Name default: U.GetLog().Printf("unexpected exchange type:%s", exctype) return fmt.Errorf("[BrokerExchanger::declareQueue] unexpected exchange type:%s", exctype) } return nil } //绑定Queue,区分amqp与rpc类型 func (be *BrokerExchanger) queueBind(exctype string) error { var queueName string switch exctype { case defaultAMQPExchange: return nil case defaultRPCExchange: queueName = be.rpcqueueName default: U.GetLog().Printf("unexpected exchange type:%s", exctype) return fmt.Errorf("[BrokerExchanger::queueBind] unexpected exchange type:%s", exctype) } err := be.channel.QueueBind( queueName, // queue name queueName, // routing key defaultRPCExchange, // exchange false, nil, ) return err } //消费Queue,区分amqp与rpc类型 func (be *BrokerExchanger) consume(exctype string) error { var queueName string switch exctype { case defaultAMQPExchange: queueName = be.amqpqueueName case defaultRPCExchange: queueName = be.rpcqueueName default: U.GetLog().Printf("unexpected exchange type:%s", exctype) return fmt.Errorf("[BrokerExchanger::consume] unexpected exchange type:%s", exctype) } deliveryChan, err := be.channel.Consume( queueName, // queue "", // consumer true, // auto-ack false, // exclusive false, // no-local false, // no-wait nil, // args ) if err != nil { return err } switch exctype { case defaultAMQPExchange: be.amqpDeliveryChan = deliveryChan case defaultRPCExchange: be.rpcDeliveryChan = deliveryChan default: U.GetLog().Printf("unexpected exchange type:%s", exctype) return fmt.Errorf("[BrokerExchanger::consume] unexpected exchange type:%s", exctype) } return nil }
说明:amqp发布订阅类型与rpc类型,在声明exchange时,exchange type字段不同,一个是topic,一个direct;
(3)MqttBroker定义及实现:
定义相关数据结构以及方法如下:
package mqtt //定义MqttBroker结构 type MqttBroker struct { wg *sync.WaitGroup addr string serverid string rabbit *rabbit.Rabbit channel *amqp.Channel brokerexchanger *BrokerExchanger mqttconnChan chan net.Conn rabbitconnChan chan bool connListeners map[string]chan bool mqttClientChan chan *MqttClientCmd clientMap map[string]*MqttClient Authenticate AuthenticateFunc AuthorizePublish AuthorizePublishFunc AuthorizeSubscribe AuthorizeSubscribeFunc } //监听RabbitMQ连接状态 func (mb *MqttBroker) handleRabbitConnChan() { defer mb.wg.Done() for connStatus := range mb.rabbitconnChan { U.GetLog().Printf("serverid:%s, rabbitmq connection status:%v", mb.serverid, connStatus) if !connStatus { mb.reset() } if connStatus { mb.rabbitConnSuccessCallback() } } } //初始化Broker Exchanger func (mb *MqttBroker) rabbitConnSuccessCallback() error { err := mb.initChannel() if err != nil { U.GetLog().Printf("initChannel error:%v", err) return err } err = mb.initBrokerExchanger() if err != nil { U.GetLog().Printf("mb.brokerexchanger.Init error:%v", err) return err } mb.broadcastRabbitConnStatus(true) return err } //监听APP连接 func (mb *MqttBroker) ListenAndServe() { defer mb.wg.Done() var listener net.Listener var err error listener, err = net.Listen("tcp", mb.addr) U.FailOnError(err) U.GetLog().Printf("listen and serve mqtt broker on %s", mb.addr) for { conn, err := listener.Accept() if err != nil { U.GetLog().Printf("accepting new connection error:%v", err) continue } mb.wg.Add(1) mb.mqttconnChan <- conn } } //针对每个APP连接,实例化MqttClient处理相关业务数据 func (mb *MqttBroker) handleMqttConnection() { defer mb.wg.Done() for conn := range mb.mqttconnChan { mqttclient, err := NewMqttClient(mb.wg, conn, mb) if err != nil { U.GetLog().Printf("NewMqttClient error:%v", err) continue } mb.clientMap[mqttclient.GetClientID()] = mqttclient mb.wg.Add(1) go mqttclient.Serve() } }
(4)MqttClient定义及实现:
定义相关数据结构以及方法如下:
package mqtt //定义MqttClient结构 type MqttClient struct { wg *sync.WaitGroup tcpconn net.Conn broker *MqttBroker keepalive int lastheartbeat int clientid string rabbit *rabbit.Rabbit channel *amqp.Channel exchangers map[string]Exchanger topicMap map[string]chan ExchangeMessage brokerChan chan *MqttClientCmd rabbitconnChan chan bool needDisConn bool } //监听处理APP的业务请求 func (mc *MqttClient) Serve() { defer mc.wg.Done() defer mc.commonDefer() mc.wg.Add(1) go mc.timer() for { if mc.needDisConn { break } packet, err := MP.ReadPacket(mc.tcpconn) if err != nil { U.GetLog().Printf("ReadPacket error:%v", err) mc.needDisConn = true break } switch packet.GetMqttType() { case MP.Connect: err = mc.handleConn(packet) case MP.Disconnect: err = mc.handleDisConn(packet) case MP.Pingreq: err = mc.handlePing(packet) case MP.Publish: err = mc.handlePublish(packet) case MP.Subscribe: err = mc.handleSubscibe(packet) case MP.Unsubscribe: err = mc.handleUnSubscribe(packet) default: U.GetLog().Printf("unexpected packet type:%v", packet.GetMqttType()) } if err != nil { U.GetLog().Printf("handle packet error:%v", err) } if err == amqp.ErrClosed { mc.channel = nil U.GetLog().Printf("handle packet error amqp.ErrClosed:%v", amqp.ErrClosed) continue } mc.lastheartbeat = 0 } } //处理mqtt连接报文 func (mc *MqttClient) handleConn(packet MP.ControlPacket) error { U.GetLog().Printf("receive connect request...") p := packet.(*MP.ConnectPacket) pA := MP.NewControlPacket(MP.Connack).(*MP.ConnackPacket) pA.ReturnCode = p.Validate() mc.keepalive = int(p.KeepaliveTimer) //mc.keepalive == 10 if mc.broker != nil && mc.broker.Authenticate != nil { authRet := mc.broker.Authenticate(mc, string(p.Username), string(p.Password)) if !authRet { pA.ReturnCode = MP.ErrRefusedBadUsernameOrPassword } } if pA.ReturnCode != MP.Accepted { mc.needDisConn = true } err := mc.trySendPacket(pA) return err } //给APP发送mqtt连接报文的回包 func (mc *MqttClient) trySendPacket(packet MP.ControlPacket) error { // U.GetLog().Printf("try send packet:%v", packet.GetMqttType()) return packet.Write(mc.tcpconn) }
说明:作为例子,以上仅以mqtt连接报文叙述了相关连接请求处理,包括用到了前一篇文字<<基于MQTT协议谈谈物联网开发-华佗写代码>>中讲到的mqtt协议编解码方法;
3.运行测试
针对上述Mqtt Broker的具体实现,简单用nodejs编写了两个测试程序,一个是subscribe.js模拟订阅者,一个是publisher.js模拟生产者,如下:
生产者publisher.js:
var mqtt = require('mqtt'); var client = mqtt.createClient(6666, '127.0.0.1', {clientId:'xixi', username:'hello', password: 'world', clean:false}); var num = 0; setInterval(function () { for(var i = 0; i < 1; i++) { client.publish('someonelikeyou', 'hello mqtt ' + num,{qos:1, retain: true}); console.log("publish topic someonelikeyou, num:", num++); } }, 1000);
订阅者subscriber.js:
var mqtt = require('mqtt'); var client = mqtt.createClient(6666, '127.0.0.1', {clientId:'haha', username:'hello', password: 'world', clean:false}); client.subscribe('someonelikeyou',{qos:1}); console.log("subscribe topic someonelikeyou"); var num = 0; client.on('message', function (topic, message) { console.log(message.toString()); num++ });
运行结果如下图所示:
生产者运行结果:
订阅者运行结果:
MqttBroker运行结果:
出于篇幅考虑,上述使用到的具体一些函数,如broadcastConnStatus,handlePing等,其具体实现就不一一列举出来了,也有一些成员变量,用到了也不一一具体注释了,主要通过代码关键路径叙述实现的一些细节,如有错误,恳请指出,转载也请注明出处!!!
未完待续...
参考文字:mqtt
