ASG
IBM
Zystems
Cressida
Icon
Netflexity
 
  MQSeries.net
Search  Search       Tech Exchange      Education      Certifications      Library      Info Center      SupportPacs      LinkedIn  Search  Search                                                                   FAQ  FAQ   Usergroups  Usergroups
 
Register  ::  Log in Log in to check your private messages
 
RSS Feed - WebSphere MQ Support RSS Feed - Message Broker Support

MQSeries.net Forum IndexGeneral IBM MQ SupportHelp with pub/sub

Post new topicReply to topic
Help with pub/sub View previous topic :: View next topic
Author Message
hrengifo
PostPosted: Mon Feb 03, 2014 6:50 pm Post subject: Help with pub/sub Reply with quote

Newbie

Joined: 03 Feb 2014
Posts: 2

hi everybody.
i have a technical question that i can not work out.
my solution have two components, the first one is a broker flow and the other one is a jee app.
1. my jee app publish a message on a MQ topic
2. when the broker flow are executed, reads (browse) the message on a queue that are listening the topic
3. broker flow modifies the message with some content of the queue read in the point 2

my issue is that i always need to read the last message published, without using message priority. it is like if the new publications overrides the old one.
Back to top
View user's profile Send private message
exerk
PostPosted: Tue Feb 04, 2014 12:51 am Post subject: Re: Help with pub/sub Reply with quote

Jedi Council

Joined: 02 Nov 2006
Posts: 6318

hrengifo wrote:
...my issue is that i always need to read the last message published, without using message priority. it is like if the new publications overrides the old one.

That's generally how pub/sub works - who would want 'old' information?
_________________
It's puzzling, I don't think I've ever seen anything quite like this before...and it's hard to soar like an eagle when you're surrounded by turkeys.

Back to top
View user's profile Send private message
zpat
PostPosted: Tue Feb 04, 2014 3:08 am Post subject: Reply with quote

Jedi Council

Joined: 19 May 2001
Posts: 5831
Location: UK

Queues don't listen. They only hold messages.

Active and matching subscriptions are passed messages. If you define an administrative durable subscription with a destination of a queue, that queue will get all the messages sent.

You can read that queue until the last message on the queue which will be the last one published.

However the classic model of picking up just the last one published is called "retained publication". In this case the pub/sub engine keeps the most recent message available, so if someone then subscribes after the time it was published - they can still pick it up.

In this case the application dynamically subscribes whenever it wants to collect the last published message. No queues are necessarily used.

This requires the publisher to set the "retained publication" flag. However WMB nodes do not dynamically subscribe to publications (as far as I know). If you think about it - how would the flow know when to subscribe?

Usually WMB input nodes are active all the time, in which case you can use an administrative subscription to feed the flow via a queue. But the flow would get invoked for every message.

So you need to decide what criteria would cause you to look for the most recent publication. I.e. When is this needed? At intervals perhaps?

Read the pub/sub documentation for WMQ first, then see how (or if) the WMB broker can fit into that.
_________________
Well, I don't think there is any question about it. It can only be attributable to human error. This sort of thing has cropped up before, and it has always been due to human error.
Back to top
View user's profile Send private message
Display posts from previous:
Post new topicReply to topic Page 1 of 1

MQSeries.net Forum IndexGeneral IBM MQ SupportHelp with pub/sub
Jump to:



You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Protected by Anti-Spam ACP


Theme by Dustin Baccetti
Powered by phpBB 2001, 2002 phpBB Group

Copyright MQSeries.net. All rights reserved.