ThingsBoard 二次开发之源码分析 5-如何接收 MQTT 连接

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ThingsBoard源码分析5-如何接收MQTT连接

1. MQTT server

需要接收设备的MQTT连接，那么thingsboard中必然有MQTT服务器，MQTT服务器创建的类是MqttTransportService；

基于netty的mqtt server,添加了MqttTransportServerInitializer的处理类，并向ChannelPipeline添加了netty的MqttDecoder和MqttEncoder让我们可以忽略MQTT消息的编解码工作，重要的是添加了MqttTransportHandler；

2. MqttTransportHandler处理连接

此例中，我们首先需要创建租户，租户管理员，并添加设备，使用MQTT Box模拟硬件设备，拷贝ACCESS TOKEN做为MQTT Box的Username开始连接我们的thingsboard后台

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• 高清：https://p.pstatp.com/origin/137b60001339a846253dd

由于没有使用ssl,收到连接请求以后，便会调用

private void processAuthTokenConnect(ChannelHandlerContext ctx, MqttConnectMessage msg) {
    String userName = msg.payload().userName();
    log.info("[{}] Processing connect msg for client with user name: {}!", sessionId, userName);
    if (StringUtils.isEmpty(userName)) {
        ctx.writeAndFlush(createMqttConnAckMsg(CONNECTION_REFUSED_BAD_USER_NAME_OR_PASSWORD));
        ctx.close();
    } else {
        //取出userName,构造protobuf的类(方便传输与解析)，交给transportService处理。此时会使用到源码解析第三篇DefaultTransportService的解析的相关信息了解process的处理。参阅下方①的详细解析。
        transportService.process(ValidateDeviceTokenRequestMsg.newBuilder().setToken(userName).build(),
                new TransportServiceCallback<ValidateDeviceCredentialsResponseMsg>() {
                    @Override
                    public void onSuccess(ValidateDeviceCredentialsResponseMsg msg) {
                        onValidateDeviceResponse(msg, ctx);
                    }

                    @Override
                    public void onError(Throwable e) {
                        log.trace("[{}] Failed to process credentials: {}", address, userName, e);
                        ctx.writeAndFlush(createMqttConnAckMsg(MqttConnectReturnCode.CONNECTION_REFUSED_SERVER_UNAVAILABLE));
                        ctx.close();
                    }
                });
    }
}

1. DefaultTransportService的process方法构造了异步任务，成功调用onSuccess的Consumer,失败调用onFailure的Consumer；

2. 将验证用户的任务交由transportApiRequestTemplate.send

public ListenableFuture<Response> send(Request request) {
    if (tickSize > maxPendingRequests) {
        return Futures.immediateFailedFuture(new RuntimeException("Pending request map is full!"));
    }
    UUID requestId = UUID.randomUUID();
    request.getHeaders().put(REQUEST_ID_HEADER, uuidToBytes(requestId));
    //由第三篇文章的分析得出，此topic时tb_transport.api.responses.localHostName
    request.getHeaders().put(RESPONSE_TOPIC_HEADER, stringToBytes(responseTemplate.getTopic()));
    request.getHeaders().put(REQUEST_TIME, longToBytes(System.currentTimeMillis()));
    //参阅第一篇基础知识的介绍，来自谷歌的库，settableFuture，可设置结果的完成
    SettableFuture<Response> future = SettableFuture.create();
    ResponseMetaData<Response> responseMetaData = new ResponseMetaData<>(tickTs + maxRequestTimeout, future);
    //将future放到pendingRequests中②
    pendingRequests.putIfAbsent(requestId, responseMetaData);
    log.trace("[{}] Sending request, key [{}], expTime [{}]", requestId, request.getKey(), responseMetaData.expTime);
    //将消息发送给消息队列topic是tb_transport.api.requests
    requestTemplate.send(TopicPartitionInfo.builder().topic(requestTemplate.getDefaultTopic()).build(), request, new TbQueueCallback() {
        @Override
        public void onSuccess(TbQueueMsgMetadata metadata) {
            log.trace("[{}] Request sent: {}", requestId, metadata);
        }

        @Override
        public void onFailure(Throwable t) {
            pendingRequests.remove(requestId);
            future.setException(t);
        }
    });
    return future;
}

3. 根据第三篇TbCoreTransportApiService的分析，我们发现DefaultTbQueueResponseTemplate的成员变量requestTemplate即consumer刚好是订阅的tb_transport.api.requests的消息：

......
requests.forEach(request -> {
    long currentTime = System.currentTimeMillis();
    long requestTime = bytesToLong(request.getHeaders().get(REQUEST_TIME));
    if (requestTime + requestTimeout >= currentTime) {
        byte[] requestIdHeader = request.getHeaders().get(REQUEST_ID_HEADER);
        if (requestIdHeader == null) {
            log.error("[{}] Missing requestId in header", request);
            return;
        }
       	//获取response的topic，可以做到消息从哪来，处理好以后回哪里去，此时的topic是tb_transport.api.responses.localHostName
        byte[] responseTopicHeader = request.getHeaders().get(RESPONSE_TOPIC_HEADER);
        if (responseTopicHeader == null) {
            log.error("[{}] Missing response topic in header", request);
            return;
        }
        UUID requestId = bytesToUuid(requestIdHeader);
        String responseTopic = bytesToString(responseTopicHeader);
        try {
            pendingRequestCount.getAndIncrement();
            //调用handler进行处理消息
            AsyncCallbackTemplate.withCallbackAndTimeout(handler.handle(request),
                    response -> {
                        pendingRequestCount.decrementAndGet();
                        response.getHeaders().put(REQUEST_ID_HEADER, uuidToBytes(requestId));
                        //handler.hande处理的结果返回给发送方topic是tb_transport.api.responses.localHostName
                        responseTemplate.send(TopicPartitionInfo.builder().topic(responseTopic).build(), response, null);
                    },
                    e -> {
                        pendingRequestCount.decrementAndGet();
                        if (e.getCause() != null && e.getCause() instanceof TimeoutException) {
                            log.warn("[{}] Timeout to process the request: {}", requestId, request, e);
                        } else {
                            log.trace("[{}] Failed to process the request: {}", requestId, request, e);
                        }
                    },
                    requestTimeout,
                    timeoutExecutor,
                    callbackExecutor);
          .......

4. 具体验证逻辑：

@Override
public ListenableFuture<TbProtoQueueMsg<TransportApiResponseMsg>> handle(TbProtoQueueMsg<TransportApiRequestMsg> tbProtoQueueMsg) {
    TransportApiRequestMsg transportApiRequestMsg = tbProtoQueueMsg.getValue();
    // protobuf构造的类中判定是否包含需要验证的信息块
    if (transportApiRequestMsg.hasValidateTokenRequestMsg()) {
        ValidateDeviceTokenRequestMsg msg = transportApiRequestMsg.getValidateTokenRequestMsg();
        //调用validateCredentials，具体内容就是查询deviceInfo，并将结果交由第二个Function进行进一步处理
        return Futures.transform(validateCredentials(msg.getToken(), DeviceCredentialsType.ACCESS_TOKEN), value -> new TbProtoQueueMsg<>(tbProtoQueueMsg.getKey(), value, tbProtoQueueMsg.getHeaders()), MoreExecutors.directExecutor());
    } 
  ......

5. 当通过设备的acess token找到了deviceInfo,便会通过消息中间件将DeviceInfo发出来，topic是tb_transport.api.responses.localHostName，在第三篇的分析中，DefaultTransportService 的transportApiRequestTemplate即订阅此topic：

List<Response> responses = responseTemplate.poll(pollInterval);
if (responses.size() > 0) {
    log.trace("Polling responses completed, consumer records count [{}]", responses.size());
} else {
    continue;
}
responses.forEach(response -> {
    byte[] requestIdHeader = response.getHeaders().get(REQUEST_ID_HEADER);
    UUID requestId;
    if (requestIdHeader == null) {
        log.error("[{}] Missing requestId in header and body", response);
    } else {
        requestId = bytesToUuid(requestIdHeader);
        log.trace("[{}] Response received: {}", requestId, response);
        //参见上②，将验证的future放入到pendingRequests中，现在通过设置的requestId取出来
        ResponseMetaData<Response> expectedResponse = pendingRequests.remove(requestId);
        if (expectedResponse == null) {
            log.trace("[{}] Invalid or stale request", requestId);
        } else {
            //设置settableFuture的结果
            expectedResponse.future.set(response);
        }
    }
......

6. DefaultTransportService的process异步请求获得了返回的结果，此时调用onSuccess回调，即调用MqttTransportHandler的onValidateDeviceResponse；

private void onValidateDeviceResponse(ValidateDeviceCredentialsResponseMsg msg, ChannelHandlerContext ctx) {
    if (!msg.hasDeviceInfo()) {
        ctx.writeAndFlush(createMqttConnAckMsg(CONNECTION_REFUSED_NOT_AUTHORIZED));
        ctx.close();
    } else {
        deviceSessionCtx.setDeviceInfo(msg.getDeviceInfo());
        sessionInfo = SessionInfoProto.newBuilder()
                .setNodeId(context.getNodeId())
                .setSessionIdMSB(sessionId.getMostSignificantBits())
                .setSessionIdLSB(sessionId.getLeastSignificantBits())
                .setDeviceIdMSB(msg.getDeviceInfo().getDeviceIdMSB())
                .setDeviceIdLSB(msg.getDeviceInfo().getDeviceIdLSB())
                .setTenantIdMSB(msg.getDeviceInfo().getTenantIdMSB())
                .setTenantIdLSB(msg.getDeviceInfo().getTenantIdLSB())
                .setDeviceName(msg.getDeviceInfo().getDeviceName())
                .setDeviceType(msg.getDeviceInfo().getDeviceType())
                .build();
        //创建SessionEvent.OPEN的消息，调用sendToDeviceActor方法，包含sessionInfo
        transportService.process(sessionInfo, DefaultTransportService.getSessionEventMsg(SessionEvent.OPEN), new TransportServiceCallback<Void>() {
           .......

7. sendToDeviceActor的实现：

protected void sendToDeviceActor(TransportProtos.SessionInfoProto sessionInfo, TransportToDeviceActorMsg toDeviceActorMsg, TransportServiceCallback<Void> callback) {
    //创建tpi，此时会选择一个固定的partition Id,组成的topic是tb_core, fullTopicName是tb_core.(int) 如： tb_core.1
    TopicPartitionInfo tpi = partitionService.resolve(ServiceType.TB_CORE, getTenantId(sessionInfo), getDeviceId(sessionInfo));
......
    //使用tbCoreMsgProducer发送到消息队列，设置了toDeviceActorMsg
    tbCoreMsgProducer.send(tpi,
            new TbProtoQueueMsg<>(getRoutingKey(sessionInfo),
                    ToCoreMsg.newBuilder().setToDeviceActorMsg(toDeviceActorMsg).build()), callback != null ?
                    new TransportTbQueueCallback(callback) : null);
}

8. 此时第二篇基于DefaultTbCoreConsumerService可以知道DefaultTbCoreConsumerService 的消费者订阅该主题的消息：

try {
    ToCoreMsg toCoreMsg = msg.getValue();
    if (toCoreMsg.hasToSubscriptionMgrMsg()) {
        log.trace("[{}] Forwarding message to subscription manager service {}", id, toCoreMsg.getToSubscriptionMgrMsg());
        forwardToSubMgrService(toCoreMsg.getToSubscriptionMgrMsg(), callback);
    } else if (toCoreMsg.hasToDeviceActorMsg()) {
        log.trace("[{}] Forwarding message to device actor {}", id, toCoreMsg.getToDeviceActorMsg());
        //交由此方法进行处理
        forwardToDeviceActor(toCoreMsg.getToDeviceActorMsg(), callback);
    }

9. forwardToDeviceActor对消息的处理

   private void forwardToDeviceActor(TransportToDeviceActorMsg toDeviceActorMsg, TbCallback callback) {
       if (statsEnabled) {
           stats.log(toDeviceActorMsg);
       }
       //创建type为TRANSPORT_TO_DEVICE_ACTOR_MSG的消息，并交给AppActor处理
       actorContext.tell(new TransportToDeviceActorMsgWrapper(toDeviceActorMsg, callback));
   }
   

10. 通过第四篇的总结3，我们可以直接去看AppActor的doProcess方法对此类型消息的处理,跟踪发现AppActor将消息转给了TenantActor, TenantActor创建了DeviceActor,并将消息转给了DeviceActor;

11. DeviceActor拿到此类型的消息，进行了如下的处理：

    protected boolean doProcess(TbActorMsg msg) {
        switch (msg.getMsgType()) {
            case TRANSPORT_TO_DEVICE_ACTOR_MSG:
                //包装成TransportToDeviceActorMsgWrapper交由processor处理，并继续调用processSessionStateMsgs
                processor.process(ctx, (TransportToDeviceActorMsgWrapper) msg);
                break;
            case DEVICE_ATTRIBUTES_UPDATE_TO_DEVICE_ACTOR_MSG:
    

12. processSessionStateMsgs的处理：

    private void processSessionStateMsgs(SessionInfoProto sessionInfo, SessionEventMsg msg) {
        UUID sessionId = getSessionId(sessionInfo);
        if (msg.getEvent() == SessionEvent.OPEN) {
         .....
            sessions.put(sessionId, new SessionInfoMetaData(new SessionInfo(SessionType.ASYNC, sessionInfo.getNodeId())));
            if (sessions.size() == 1) {
               // 将调用pushRuleEngineMessage(stateData, CONNECT_EVENT);
                reportSessionOpen();
            }
            //将调用pushRuleEngineMessage(stateData, ACTIVITY_EVENT);
            systemContext.getDeviceStateService().onDeviceActivity(deviceId, System.currentTimeMillis());
            dumpSessions();
        }
    ....
    

13. 由于CONNECT_EVENT和ACTIVITY_EVENT仅仅类型不同，以下暂时只分析CONNECT_EVENT

    public void pushMsgToRuleEngine(TenantId tenantId, EntityId entityId, TbMsg tbMsg, TbQueueCallback callback) {
        if (tenantId.isNullUid()) {
            if (entityId.getEntityType().equals(EntityType.TENANT)) {
                tenantId = new TenantId(entityId.getId());
            } else {
                log.warn("[{}][{}] Received invalid message: {}", tenantId, entityId, tbMsg);
                return;
            }
        }
        //和第7点类似，创建的tpi的fullTopicName的例子 tb_rule_engine.main.1
        TopicPartitionInfo tpi = partitionService.resolve(ServiceType.TB_RULE_ENGINE, tenantId, entityId);
        log.trace("PUSHING msg: {} to:{}", tbMsg, tpi);
        ToRuleEngineMsg msg = ToRuleEngineMsg.newBuilder()
                .setTenantIdMSB(tenantId.getId().getMostSignificantBits())
                .setTenantIdLSB(tenantId.getId().getLeastSignificantBits())
                .setTbMsg(TbMsg.toByteString(tbMsg)).build();
        producerProvider.getRuleEngineMsgProducer().send(tpi, new TbProtoQueueMsg<>(tbMsg.getId(), msg), callback);
        toRuleEngineMsgs.incrementAndGet();
    }
    

14. 通过第二篇的分析DefaultTbRuleEngineConsumerService订阅了此topic: tb_rule_engine.main.1的消息，收到消息以后，调用forwardToRuleEngineActor方法，包裹成QUEUE_TO_RULE_ENGINE_MSG类型的消息，交由AppActor进行分发处理；

15. AppActor交给TenantActor处理，TenantActor交给RootRuleChain处理，RuleChainActor交给firstRuleNode处理，也就是某一个RuleNodeActor;

16. 打开前端RULE CHAINS的界面，会发现，MESSAGE TYPE SWITCH是接收input的第一个节点，其实数据库的配置中，rule_chain表中配置的first_rule_node_id就是TbMsgTypeSwitchNode；

17. 进入TbMsgTypeSwitchNode的onMsg方法(实际上所有的ruleNode处理消息的方法都是onMsg),发现根据messageType（此时是CONNECT_EVENT）定义了relationtype并调用ctx.tellNext(msg, relationType);

18. 此时DefaultTbContext创建一个RuleNodeToRuleChainTellNextMsg，类型是RULE_TO_RULE_CHAIN_TELL_NEXT_MSG，交给RuleChainActor处理；

19. 接下来将会进入到RuleChainActorMessageProcessor的onTellNext方法：

    private void onTellNext(TbMsg msg, RuleNodeId originatorNodeId, Set<String> relationTypes, String failureMessage) {
        try {
            checkActive(msg);
            //消息来源
            EntityId entityId = msg.getOriginator();
            //创建一个tpi，可能会使用
            TopicPartitionInfo tpi = systemContext.resolve(ServiceType.TB_RULE_ENGINE, msg.getQueueName(), tenantId, entityId);
           //查询有关系的RuleNode,其实就是从relation表中查询，该消息来源的id，relation_type和在TbMsgTypeSwitchNode定义的relationType一直的节点id,如上Connect Event就没有找到相应的relation的RuleNodeId
            List<RuleNodeRelation> relations = nodeRoutes.get(originatorNodeId).stream()
                    .filter(r -> contains(relationTypes, r.getType()))
                    .collect(Collectors.toList());
            int relationsCount = relations.size();
           //Connect Event就没有找到相应的relation的RuleNodeId,消息通过规则引擎，已经处理完成
            if (relationsCount == 0) {
                log.trace("[{}][{}][{}] No outbound relations to process", tenantId, entityId, msg.getId());
                if (relationTypes.contains(TbRelationTypes.FAILURE)) {
                    RuleNodeCtx ruleNodeCtx = nodeActors.get(originatorNodeId);
                    if (ruleNodeCtx != null) {
                        msg.getCallback().onFailure(new RuleNodeException(failureMessage, ruleChainName, ruleNodeCtx.getSelf()));
                    } else {
                        log.debug("[{}] Failure during message processing by Rule Node [{}]. Enable and see debug events for more info", entityId, originatorNodeId.getId());
                        msg.getCallback().onFailure(new RuleEngineException("Failure during message processing by Rule Node [" + originatorNodeId.getId().toString() + "]"));
                    }
                } else {
                    msg.getCallback().onSuccess();
                }
             //举例:Post telemetry的type可以找到相应的ruleNode,实现类是：TbMsgTimeseriesNode，那么此消息将会交给TbMsgTimeseriesNode处理
            } else if (relationsCount == 1) {
                for (RuleNodeRelation relation : relations) {
                    log.trace("[{}][{}][{}] Pushing message to single target: [{}]", tenantId, entityId, msg.getId(), relation.getOut());
                    pushToTarget(tpi, msg, relation.getOut(), relation.getType());
                }
            } else {
                MultipleTbQueueTbMsgCallbackWrapper callbackWrapper = new MultipleTbQueueTbMsgCallbackWrapper(relationsCount, msg.getCallback());
                log.trace("[{}][{}][{}] Pushing message to multiple targets: [{}]", tenantId, entityId, msg.getId(), relations);
                for (RuleNodeRelation relation : relations) {
                    EntityId target = relation.getOut();
                    putToQueue(tpi, msg, callbackWrapper, target);
                }
            }
        } catch (RuleNodeException rne) {
            msg.getCallback().onFailure(rne);
        } catch (Exception e) {
            msg.getCallback().onFailure(new RuleEngineException("onTellNext - " + e.getMessage()));
        }
    }
    

    What's more:

    如上面的举例，比如是遥测数据Post telemetry，将会使用TbMsgTimeseriesNode的onMsg做进一步的处理，比如存储数据，再通过webSocket进行数据的更新如果有webSocket的session的话，或者其他通知消息，就不详细展开了。

总结：

1. 处理MQTT的连接其实就是走完了整个规则引擎的逻辑，其他类型的消息，比如遥测数据，属性更新，RPC请求发送与接收，大体流程大同小异；

2. 在处理消息流向的时候，我们一定要清楚其订阅或者发布的主题是什么，这样我们才不会丢失方向；

3. Actor的模型就是根据消息的类型，使用AppActor进行一步步的分发，最终交由合适的RuleNode进行处理；

4. Protobuf类型的消息容易序列化传输与解析，所以在thingsboard中大量使用，但是生成的类可读性不是很高，可以选择直接读queue.proto文件，对类有感性的认知。

   ​ 由于作者水平有限，只是梳理了大致的流程，文章难免出现纰漏，望谅解并指正。