聊聊artemis JMSBridge的QualityOfServiceMode

序

本文主要研究一下artemis JMSBridge的QualityOfServiceMode

QualityOfServiceMode

activemq-artemis-2.11.0/artemis-jms-server/src/main/java/org/apache/activemq/artemis/jms/bridge/QualityOfServiceMode.java

public enum QualityOfServiceMode {
   AT_MOST_ONCE(0), DUPLICATES_OK(1), ONCE_AND_ONLY_ONCE(2);

   private final int value;

   QualityOfServiceMode(final int value) {
      this.value = value;
   }

   public int intValue() {
      return value;
   }

   public static QualityOfServiceMode valueOf(final int value) {
      if (value == AT_MOST_ONCE.value) {
         return AT_MOST_ONCE;
      }
      if (value == DUPLICATES_OK.value) {
         return DUPLICATES_OK;
      }
      if (value == ONCE_AND_ONLY_ONCE.value) {
         return ONCE_AND_ONLY_ONCE;
      }
      throw new IllegalArgumentException("invalid QualityOfServiceMode value: " + value);
   }

}

• QualityOfServiceMode定义了三个枚举值，分别是AT_MOST_ONCE、DUPLICATES_OK、ONCE_AND_ONLY_ONCE

sendBatchNonTransacted

activemq-artemis-2.11.0/artemis-jms-server/src/main/java/org/apache/activemq/artemis/jms/bridge/impl/JMSBridgeImpl.java

public final class JMSBridgeImpl implements JMSBridge {

   //......

   private void sendBatchNonTransacted() {
      try {
         if (qualityOfServiceMode == QualityOfServiceMode.ONCE_AND_ONLY_ONCE || (qualityOfServiceMode == QualityOfServiceMode.AT_MOST_ONCE && maxBatchSize > 1)) {
            // We client ack before sending

            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acking source session");
            }

            messages.getLast().acknowledge();

            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acked source session");
            }
         }

         boolean exHappened;

         do {
            exHappened = false;
            try {
               sendMessages();
            } catch (TransactionRolledbackException e) {
               ActiveMQJMSBridgeLogger.LOGGER.transactionRolledBack(e);
               exHappened = true;
            }
         }
         while (exHappened);

         if (maxBatchSize > 1) {
            // The sending session is transacted - we need to commit it

            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Committing target session");
            }

            targetSession.commit();

            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Committed target session");
            }
         }

         if (qualityOfServiceMode == QualityOfServiceMode.DUPLICATES_OK) {
            // We client ack after sending

            // Note we could actually use Session.DUPS_OK_ACKNOWLEDGE here
            // For a slightly less strong delivery guarantee

            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acking source session");
            }

            messages.getLast().acknowledge();

            if (ActiveMQJMSBridgeLogger.LOGGER.isTraceEnabled()) {
               ActiveMQJMSBridgeLogger.LOGGER.trace("Client acked source session");
            }
         }
      } catch (Exception e) {
         if (!stopping) {
            ActiveMQJMSBridgeLogger.LOGGER.bridgeAckError(e, bridgeName);
         }

         // We don't call failure otherwise failover would be broken with ActiveMQ
         // We let the ExceptionListener to deal with failures

         if (connectedSource) {
            try {
               sourceSession.recover();
            } catch (Throwable ignored) {
            }
         }

      } finally {
         // Clear the messages
         messages.clear();

      }
   }

   //......
}

• JMSBridgeImpl的sendBatchNonTransacted方法在qualityOfServiceMode为ONCE_AND_ONLY_ONCE或者AT_MOST_ONCE且maxBatchSize大于1的时候先执行messages.getLast().acknowledge()；之后使用一个while循环执行sendMessages，循环在没有TransactionRolledbackException异常时会终止；最后在qualityOfServiceMode为DUPLICATES_OK的时候执行messages.getLast().acknowledge()

小结

QualityOfServiceMode定义了三个枚举值，分别是AT_MOST_ONCE、DUPLICATES_OK、ONCE_AND_ONLY_ONCE；JMSBridgeImpl的sendBatchNonTransacted方法在qualityOfServiceMode为ONCE_AND_ONLY_ONCE或者AT_MOST_ONCE(且maxBatchSize大于1)的时候在sendMessages之前先执行ack(如果异常在ack与sendMessages之间，则消息可能丢失；由于ONCE_AND_ONLY_ONCE需要local transaction或者JTA处理，在没有事务情况下与AT_MOST_ONCE相同)；而对于qualityOfServiceMode为DUPLICATES_OK的在sendMessages之后执行ack(如果异常在sendMessages与ack之间，则异常之后，client端由于没有收到ack会再次发送消息，可能造成重复)

doc

• JMSBridgeImpl

来源：oschina

链接：https://my.oschina.net/go4it/blog/3162322