eclipse mqttclient 性能&MQTT(32202): 正在發佈過多的消息

mqttclient性能&MQTT(32202): 正在發佈過多的消息

org.eclipse.paho.client.mqttv3

2.2 GHz Intel Core i7 mac系統

publish性能，注意請使用單線程的 mqttclinet

1萬條 341毫秒
4萬條 1163毫秒
5萬 1450毫秒
10萬條 2700毫秒

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多線程的 mqttclinet MQTT(32202): 正在發佈過多的消息 問題

異常信息

[15:07:21]: publish failed, message: aaaa
正在進行過多的發佈 (32202)
 at org.eclipse.paho.client.mqttv3.internal.ClientState.send(ClientState.java:496)
 at org.eclipse.paho.client.mqttv3.internal.ClientComms.internalSend(ClientComms.java:132)
 at org.eclipse.paho.client.mqttv3.internal.ClientComms.sendNoWait(ClientComms.java:156)
 at org.eclipse.paho.client.mqttv3.MqttAsyncClient.publish(MqttAsyncClient.java:1027)
 at org.eclipse.paho.client.mqttv3.MqttClient.publish(MqttClient.java:399)
 at io.communet.ichater.emq.util.MqttUtil.publishMsg(MqttUtil.java:171)
 at io.communet.ichater.emq.util.MqttUtil.publishMsg(MqttUtil.java:161)
 at io.communet.ichater.emq.sub.MqttSendMsgEventSubscribe.onEvent(MqttSendMsgEventSubscribe.java:28)
 at java.lang.reflect.Method.invoke(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:372)
 at org.greenrobot.eventbus.EventBus.invokeSubscriber(EventBus.java:507)
 at org.greenrobot.eventbus.EventBus.invokeSubscriber(EventBus.java:501)
 at org.greenrobot.eventbus.AsyncPoster.run(AsyncPoster.java:46)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
 at java.lang.Thread.run(Thread.java:818)

解決辦法

1. 消息發送發送限流
2. 用單獨的一個線程來完成 MQ 消息的推送 (不用這個MqttAsyncClient ，使用MqttClient 就沒有事)
3. options.setMaxInflight(1000) 增加 actualInFlight 的值;

反思

筆者出現這個錯誤是因爲使用 EventBus, 之前使用單獨線程的 Handler 是沒有問題的, 調查發現, 使用 EventBus 是新建線程運行的, 而 Handler 是單獨一個線程.
所以當發送大量消息的時候, EventBus 幾乎是同一個點發出去, 就會造成這個錯誤

原因

根據堆棧信息找到報錯地方

if (actualInFlight >= this.maxInflight) {
    //@TRACE 613= sending {0} msgs at max inflight window
    log.fine(CLASS_NAME, methodName, "613", new Object[]{new Integer(actualInFlight)});

    throw new MqttException(MqttException.REASON_CODE_MAX_INFLIGHT);
}

其中 actualInFlight 如下

// processed until the inflight window has space. 
if (actualInFlight < this.maxInflight) {
    // The in flight window is not full so process the 
    // first message in the queue
    result = (MqttWireMessage)pendingMessages.elementAt(0);
    pendingMessages.removeElementAt(0);
    actualInFlight++;
    
    //@TRACE 623=+1 actualInFlight={0}
    log.fine(CLASS_NAME,methodName,"623",new Object[]{new Integer(actualInFlight)});
}

從 pendingMessages 中取出消息時, actualInFlight 加 1, maxInflight 可以自己設定, 默認值爲 10.

public class ClientState {
  ...
  volatile private Vector pendingMessages;
  ...
}

在 ClientState 中：

public void send(MqttWireMessage message, MqttToken token) throws MqttException {
        ... 
        if (message instanceof MqttPublish) {
            synchronized (queueLock) {
                if (actualInFlight >= this.maxInflight) {
                    //@TRACE 613= sending {0} msgs at max inflight window
                    log.fine(CLASS_NAME, methodName, "613", new Object[]{new Integer(actualInFlight)});

                    throw new MqttException(MqttException.REASON_CODE_MAX_INFLIGHT);
                }
                
                MqttMessage innerMessage = ((MqttPublish) message).getMessage();
                //@TRACE 628=pending publish key={0} qos={1} message={2}
                log.fine(CLASS_NAME,methodName,"628", new Object[]{new Integer(message.getMessageId()), new Integer(innerMessage.getQos()), message});

                switch(innerMessage.getQos()) {
                    case 2:
                        outboundQoS2.put(new Integer(message.getMessageId()), message);
                        persistence.put(getSendPersistenceKey(message), (MqttPublish) message);
                        break;
                    case 1:
                        outboundQoS1.put(new Integer(message.getMessageId()), message);
                        persistence.put(getSendPersistenceKey(message), (MqttPublish) message);
                        break;
                }
                tokenStore.saveToken(token, message);
                pendingMessages.addElement(message);
                queueLock.notifyAll();
            }
        } else {
        ...
        }
    }

可以看到 pendingMessages 中添加元素的時候並沒有做 qos 類型的判斷

private void decrementInFlight() {
    final String methodName = "decrementInFlight";
    synchronized (queueLock) {
        actualInFlight--;
        //@TRACE 646=-1 actualInFlight={0}
        log.fine(CLASS_NAME,methodName,"646",new Object[]{new Integer(actualInFlight)});
            
        if (!checkQuiesceLock()) {
            queueLock.notifyAll();
        }
    }
}

當收到消息反饋時 actualInFlight 減 1.