聊聊artemis消息的推拉模式

序

本文主要研究一下artemis消息的推拉模式

拉模式

receive

activemq-artemis-2.11.0/artemis-jms-client/src/main/java/org/apache/activemq/artemis/jms/client/ActiveMQMessageConsumer.java

public final class ActiveMQMessageConsumer implements QueueReceiver, TopicSubscriber {

   //......

   @Override
   public Message receive() throws JMSException {
      return getMessage(0, false);
   }

   @Override
   public Message receive(final long timeout) throws JMSException {
      return getMessage(timeout, false);
   }

   @Override
   public Message receiveNoWait() throws JMSException {
      return getMessage(0, true);
   }

   private ActiveMQMessage getMessage(final long timeout, final boolean noWait) throws JMSException {
      try {
         ClientMessage coreMessage;

         if (noWait) {
            coreMessage = consumer.receiveImmediate();
         } else {
            coreMessage = consumer.receive(timeout);
         }

         ActiveMQMessage jmsMsg = null;

         if (coreMessage != null) {
            ClientSession coreSession = session.getCoreSession();
            boolean needSession = ackMode == Session.CLIENT_ACKNOWLEDGE ||
               ackMode == ActiveMQJMSConstants.INDIVIDUAL_ACKNOWLEDGE ||
               coreMessage.getType() == ActiveMQObjectMessage.TYPE;

            if (coreMessage.getRoutingType() == null) {
               coreMessage.setRoutingType(destination.isQueue() ? RoutingType.ANYCAST : RoutingType.MULTICAST);
            }
            if (session.isEnable1xPrefixes()) {
               jmsMsg = ActiveMQCompatibleMessage.createMessage(coreMessage, needSession ? coreSession : null, options);
            } else {
               jmsMsg = ActiveMQMessage.createMessage(coreMessage, needSession ? coreSession : null, options);
            }

            try {
               jmsMsg.doBeforeReceive();
            } catch (IndexOutOfBoundsException ioob) {
               ((ClientSessionInternal) session.getCoreSession()).markRollbackOnly();
               // In case this exception happen you will need to know where it happened.
               // it has been a bug here in the past, and this was used to debug it.
               // nothing better than keep it for future investigations in case it happened again
               IndexOutOfBoundsException newIOOB = new IndexOutOfBoundsException(ioob.getMessage() + "@" + jmsMsg.getCoreMessage());
               newIOOB.initCause(ioob);
               ActiveMQClientLogger.LOGGER.unableToGetMessage(newIOOB);
               throw ioob;
            }

            // We Do the ack after doBeforeReceive, as in the case of large messages, this may fail so we don't want messages redelivered
            // https://issues.jboss.org/browse/JBPAPP-6110
            if (session.getAcknowledgeMode() == ActiveMQJMSConstants.INDIVIDUAL_ACKNOWLEDGE) {
               jmsMsg.setIndividualAcknowledge();
            } else if (session.getAcknowledgeMode() == Session.CLIENT_ACKNOWLEDGE) {
               jmsMsg.setClientAcknowledge();
               coreMessage.acknowledge();
            } else {
               coreMessage.acknowledge();
            }
         }

         return jmsMsg;
      } catch (ActiveMQException e) {
         ((ClientSessionInternal) session.getCoreSession()).markRollbackOnly();
         throw JMSExceptionHelper.convertFromActiveMQException(e);
      } catch (ActiveMQInterruptedException e) {
         ((ClientSessionInternal) session.getCoreSession()).markRollbackOnly();
         throw JMSExceptionHelper.convertFromActiveMQException(e);
      }
   }

   //......
}

• ActiveMQMessageConsumer的receive方法最后调用的是getMessage方法，它对于session.getAcknowledgeMode()为ActiveMQJMSConstants.INDIVIDUAL_ACKNOWLEDGE执行jmsMsg.setIndividualAcknowledge()，其余的都执行coreMessage.acknowledge()

acknowledge

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/client/impl/ClientMessageImpl.java

public class ClientMessageImpl extends CoreMessage implements ClientMessageInternal {

   //......

   public ClientMessageImpl acknowledge() throws ActiveMQException {
      if (consumer != null) {
         consumer.acknowledge(this);
      }

      return this;
   }

   //......
}

• ClientMessageImpl的acknowledge方法执行的是consumer.acknowledge(this)

推模式

handleMessage

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/client/impl/ClientConsumerImpl.java

public final class ClientConsumerImpl implements ClientConsumerInternal {

   //......

   public synchronized void handleMessage(final ClientMessageInternal message) throws Exception {
      if (closing) {
         // This is ok - we just ignore the message
         return;
      }

      if (message.getBooleanProperty(Message.HDR_LARGE_COMPRESSED)) {
         handleCompressedMessage(message);
      } else {
         handleRegularMessage(message);
      }
   }

   private void handleRegularMessage(ClientMessageInternal message) {
      if (message.getAddress() == null) {
         message.setAddress(queueInfo.getAddress());
      }

      message.onReceipt(this);

      if (!ackIndividually && message.getPriority() != 4 && !message.containsProperty(ClientConsumerImpl.FORCED_DELIVERY_MESSAGE)) {
         // We have messages of different priorities so we need to ack them individually since the order
         // of them in the ServerConsumerImpl delivery list might not be the same as the order they are
         // consumed in, which means that acking all up to won't work
         ackIndividually = true;
      }

      // Add it to the buffer
      buffer.addTail(message, message.getPriority());

      if (handler != null) {
         // Execute using executor
         if (!stopped) {
            queueExecutor();
         }
      } else {
         notify();
      }
   }

   private void queueExecutor() {
      if (logger.isTraceEnabled()) {
         logger.trace(this + "::Adding Runner on Executor for delivery");
      }

      sessionExecutor.execute(runner);
   }

   //......

}

• ClientConsumerImpl的handleRegularMessage会执行buffer.addTail(message, message.getPriority())以及queueExecutor()，queueExecutor通过sessionExecutor执行Runner

callOnMessage

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/client/impl/ClientConsumerImpl.java

public final class ClientConsumerImpl implements ClientConsumerInternal {

   //......

   private final PriorityLinkedList buffer = new PriorityLinkedListImpl<>(ClientConsumerImpl.NUM_PRIORITIES);

   //......   

   private class Runner implements Runnable {

      @Override
      public void run() {
         try {
            callOnMessage();
         } catch (Exception e) {
            ActiveMQClientLogger.LOGGER.onMessageError(e);

            lastException = e;
         }
      }
   }

   private void callOnMessage() throws Exception {
      if (closing || stopped) {
         return;
      }

      session.workDone();

      // We pull the message from the buffer from inside the Runnable so we can ensure priority
      // ordering. If we just added a Runnable with the message to the executor immediately as we get it
      // we could not do that

      ClientMessageInternal message;

      // Must store handler in local variable since might get set to null
      // otherwise while this is executing and give NPE when calling onMessage
      MessageHandler theHandler = handler;

      if (theHandler != null) {
         if (rateLimiter != null) {
            rateLimiter.limit();
         }

         failedOver = false;

         synchronized (this) {
            message = buffer.poll();
         }

         if (message != null) {
            if (message.containsProperty(ClientConsumerImpl.FORCED_DELIVERY_MESSAGE)) {
               //Ignore, this could be a relic from a previous receiveImmediate();
               return;
            }

            boolean expired = message.isExpired();

            flowControlBeforeConsumption(message);

            if (!expired) {
               if (logger.isTraceEnabled()) {
                  logger.trace(this + "::Calling handler.onMessage");
               }
               final ClassLoader originalLoader = AccessController.doPrivileged(new PrivilegedAction() {
                  @Override
                  public ClassLoader run() {
                     ClassLoader originalLoader = Thread.currentThread().getContextClassLoader();

                     Thread.currentThread().setContextClassLoader(contextClassLoader);

                     return originalLoader;
                  }
               });

               onMessageThread = Thread.currentThread();
               try {
                  theHandler.onMessage(message);
               } finally {
                  try {
                     AccessController.doPrivileged(new PrivilegedAction