IBM MQ message groups

Question

I'm currently faced with a use case where I need to process multiple messages in parallel, but related messages should only be processed by one JMS consumer at a time.

As an example, consider the messages ABCDEF and DEFGHI, followed by a sequence number:

• ABCDEF-1
• ABCDEF-2
• ABCDEF-3
• DEFGHI-1
• DEFGHI-2
• DEFGHI-3

If possible, I'd like to have JMS consumers process ABCDEF and DEFGHI messages in parallel, but never two ABCDEF or DEFGHI messages at the same time across two or more consumers . In my use case, the ordering of messages is irrelevant. I cannot use JMS filters because I would not know the group name ahead of time, and having a static list of group names is not feasible. . Messages are sent via a system which is not under my control, and the group name always consists of 6 letters.

ActiveMQ seems to have implemented this via their message groups feature, but I can't find equivalent functionality in IBM MQ. My understanding is that this behaviour is driven by JMSXGroupId and JMSXGroupSeq headers, which are only defined in an optional part of the JMS specification.

As a workaround, I could always have a staging ground (a database perhaps), where all messages are placed and then have a fast poll on this database, but adding an extra piece of infrastructure seems overkill here. Moreover, it would also not allow me to use JMS transactions for reprocessing in case of failures.

To me this seems like a common use case in messaging architecture, but I can't find a simple yes/no answer anywhere online, and the IBM MQ documentation isn't very clear about whether this functionality is supported or not.

Thanks in advance

Answer 1

IBM MQ also has the concept of message groups.

The IBM MQ message header, called the Message Descriptor (MQMD) has a couple of fields in it that the JMS Group fields map to:-

• JMSXGroupID -> MQMD GroupID field
• JMSXGroupSeq -> MQMD MsgSeqNumber field

Read more here

• IBM MQ docs: Mapping JMS property fields
• IBM MQ docs: Message groups