聊聊artemis的individualAcknowledge

序

本文主要研究一下artemis的individualAcknowledge

acknowledge

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

public class ActiveMQMessage implements javax.jms.Message {

   //......

   public void acknowledge() throws JMSException {
      if (session != null) {
         try {
            if (session.isClosed()) {
               throw ActiveMQClientMessageBundle.BUNDLE.sessionClosed();
            }
            if (individualAck) {
               message.individualAcknowledge();
            }
            if (clientAck || individualAck) {
               session.commit(session.isBlockOnAcknowledge());
            }
         } catch (ActiveMQException e) {
            throw JMSExceptionHelper.convertFromActiveMQException(e);
         }
      }
   }

   //......
}

• ActiveMQMessage的acknowledge方法对于individualAck为true的会单独执行message.individualAcknowledge()

message.individualAcknowledge

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 individualAcknowledge() throws ActiveMQException {
      if (consumer != null) {
         consumer.individualAcknowledge(this);
      }

      return this;
   }

   //......
}

• ClientMessageImpl的individualAcknowledge方法会执行consumer.individualAcknowledge(this)

consumer.individualAcknowledge

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 void individualAcknowledge(ClientMessage message) throws ActiveMQException {
      if (lastAckedMessage != null) {
         flushAcks();
      }

      session.individualAcknowledge(this, message);
   }

   public void flushAcks() throws ActiveMQException {
      if (lastAckedMessage != null) {
         if (logger.isTraceEnabled()) {
            logger.trace(this + "::FlushACK acking lastMessage::" + lastAckedMessage);
         }
         doAck(lastAckedMessage);
      }
   }

   private void doAck(final ClientMessageInternal message) throws ActiveMQException {
      ackBytes = 0;

      lastAckedMessage = null;

      if (logger.isTraceEnabled()) {
         logger.trace(this + "::Acking message " + message);
      }

      session.acknowledge(this, message);
   }

   //......
}

• ClientConsumerImpl的individualAcknowledge，对于lastAckedMessage不为null的先执行flushAcks，最后执行session.individualAcknowledge

session.individualAcknowledge

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

public final class ClientSessionImpl implements ClientSessionInternal, FailureListener {

   //......

   public void individualAcknowledge(final ClientConsumer consumer, final Message message) throws ActiveMQException {
      // if we're pre-acknowledging then we don't need to do anything
      if (preAcknowledge) {
         return;
      }

      checkClosed();

      startCall();
      try {

         sessionContext.sendACK(true, blockOnAcknowledge, consumer, message);
      } finally {
         endCall();
      }
   }

   //......
}

• ClientSessionImpl的individualAcknowledge方法通过sessionContext.sendACK来发送ack

sessionContext.sendACK

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

public class ActiveMQSessionContext extends SessionContext {

   //......

   public void sendACK(boolean individual,
                       boolean block,
                       final ClientConsumer consumer,
                       final Message message) throws ActiveMQException {
      PacketImpl messagePacket;
      if (individual) {
         messagePacket = new SessionIndividualAcknowledgeMessage(getConsumerID(consumer), message.getMessageID(), block);
      } else {
         messagePacket = new SessionAcknowledgeMessage(getConsumerID(consumer), message.getMessageID(), block);
      }

      if (block) {
         sessionChannel.sendBlocking(messagePacket, PacketImpl.NULL_RESPONSE);
      } else {
         sessionChannel.sendBatched(messagePacket);
      }
   }

   //......
}   

• ActiveMQSessionContext的sendACK方法对于individual为true的创建的是SessionIndividualAcknowledgeMessage，最后通过sessionChannel.sendBlocking或者sessionChannel.sendBatched方法发送消息

ServerConsumerImpl

activemq-artemis-2.11.0/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/ServerConsumerImpl.java

public class ServerConsumerImpl implements ServerConsumer, ReadyListener {

   //......

   public synchronized void acknowledge(Transaction tx, final long messageID) throws Exception {
      if (browseOnly) {
         return;
      }

      // Acknowledge acknowledges all refs delivered by the consumer up to and including the one explicitly
      // acknowledged

      // We use a transaction here as if the message is not found, we should rollback anything done
      // This could eventually happen on retries during transactions, and we need to make sure we don't ACK things we are not supposed to acknowledge

      boolean startedTransaction = false;

      if (tx == null) {
         startedTransaction = true;
         tx = new TransactionImpl(storageManager);
      }

      try {

         MessageReference ref;
         do {
            synchronized (lock) {
               ref = deliveringRefs.poll();
            }

            if (logger.isTraceEnabled()) {
               logger.trace("ACKing ref " + ref + " on tx= " + tx + ", consumer=" + this);
            }

            if (ref == null) {
               ActiveMQIllegalStateException ils = ActiveMQMessageBundle.BUNDLE.consumerNoReference(id, messageID, messageQueue.getName());
               tx.markAsRollbackOnly(ils);
               throw ils;
            }

            ref.acknowledge(tx, this);

            acks++;
         }
         while (ref.getMessageID() != messageID);

         if (startedTransaction) {
            tx.commit();
         }
      } catch (ActiveMQException e) {
         if (startedTransaction) {
            tx.rollback();
         } else {
            tx.markAsRollbackOnly(e);
         }
         throw e;
      } catch (Throwable e) {
         ActiveMQServerLogger.LOGGER.errorAckingMessage((Exception) e);
         ActiveMQException activeMQIllegalStateException = new ActiveMQIllegalStateException(e.getMessage());
         if (startedTransaction) {
            tx.rollback();
         } else {
            tx.markAsRollbackOnly(activeMQIllegalStateException);
         }
         throw activeMQIllegalStateException;
      }
   }

   public synchronized void individualAcknowledge(Transaction tx, final long messageID) throws Exception {
      if (browseOnly) {
         return;
      }

      boolean startedTransaction = false;

      if (logger.isTraceEnabled()) {
         logger.trace("individualACK messageID=" + messageID);
      }

      if (tx == null) {
         if (logger.isTraceEnabled()) {
            logger.trace("individualACK starting new TX");
         }
         startedTransaction = true;
         tx = new TransactionImpl(storageManager);
      }

      try {

         MessageReference ref;
         ref = removeReferenceByID(messageID);

         if (logger.isTraceEnabled()) {
            logger.trace("ACKing ref " + ref + " on tx= " + tx + ", consumer=" + this);
         }

         if (ref == null) {
            ActiveMQIllegalStateException ils = new ActiveMQIllegalStateException("Cannot find ref to ack " + messageID);
            tx.markAsRollbackOnly(ils);
            throw ils;
         }

         ref.acknowledge(tx, this);

         acks++;

         if (startedTransaction) {
            tx.commit();
         }
      } catch (ActiveMQException e) {
         if (startedTransaction) {
            tx.rollback();
         } else if (tx != null) {
            tx.markAsRollbackOnly(e);
         }
         throw e;
      } catch (Throwable e) {
         ActiveMQServerLogger.LOGGER.errorAckingMessage((Exception) e);
         ActiveMQIllegalStateException hqex = new ActiveMQIllegalStateException(e.getMessage());
         if (startedTransaction) {
            tx.rollback();
         } else if (tx != null) {
            tx.markAsRollbackOnly(hqex);
         }
         throw hqex;
      }

   }

   //......
}   

• ServerConsumerImpl的individualAcknowledge方法先根据messageID将该消息从deliveringRefs中移除，然后执行ref.acknowledge(tx, this)；而普通的acknowledge方法则是不断循环执行deliveringRefs.poll()，然后执行ref.acknowledge(tx, this)，直到取到指定messageID的ref才跳出循环

小结

ActiveMQMessage的acknowledge方法对于individualAck为true的会单独执行message.individualAcknowledge()；ClientMessageImpl的individualAcknowledge方法会执行consumer.individualAcknowledge(this)；ClientConsumerImpl的individualAcknowledge，对于lastAckedMessage不为null的先执行flushAcks，最后执行session.individualAcknowledge；ClientSessionImpl的individualAcknowledge方法通过sessionContext.sendACK来发送ack；ActiveMQSessionContext的sendACK方法对于individual为true的创建的是SessionIndividualAcknowledgeMessage，最后通过sessionChannel.sendBlocking或者sessionChannel.sendBatched方法发送消息

doc

• ClientMessageImpl

来源：oschina

链接：https://my.oschina.net/go4it/blog/3162562