Is there a way to read the MQ message without impacting the current producer and consumer?
We have a consumer already to read from a MQ, but we want to feed the same messages in the MQ to some other places. Is there way to do that without touching the MQ producer nor the existing consumer?
I searched around and found there's something called queue browse. Can I set up another consumer for this MQ and only do browsing? Will both the old and new consumer be able to get all messages?
The producer is not owned by us, so can't change the configuration of it.
So the best option is to not touch producer + consumer; But if no other choice, we can try modify a bit of the existing consumer.
Are there any ways? Thanks a lot!
Related
I am using Nifi to get data from IBM MQ. It is working fine. My question is once the message is read from an MQ queue, does it get deleted from the queue? How to just read messages from the queue without deleting them from the queue?
My question is once the message is read from an MQ queue, does it get
deleted from the queue?
Yes, that is the default behavior.
How to just read messages from the queue without deleting them from
the queue?
You use the option: MQGMO_BROWSE_FIRST followed by MQGMO_BROWSE_NEXT on the MQGET API calls.
You can also open the queue for browse only. i.e. MQOO_BROWSE option for MQOPEN API call.
It sounds as if you would like to use a "publish/subscribe" model rather than a "point-to-point" model.
From ActiveMQ:
Topics In JMS a Topic implements publish and subscribe semantics. When
you publish a message it goes to all the subscribers who are
interested - so zero to many subscribers will receive a copy of the
message. Only subscribers who had an active subscription at the time
the broker receives the message will get a copy of the message.
Queues A JMS Queue implements load balancer semantics. A single
message will be received by exactly one consumer. If there are no
consumers available at the time the message is sent it will be kept
until a consumer is available that can process the message. If a
consumer receives a message and does not acknowledge it before closing
then the message will be redelivered to another consumer. A queue can
have many consumers with messages load balanced across the available
consumers.
If you have a queue, when a consumer consumes that message, it is removed from the queue so that the next consumer consumes the next message. With a topic, multiple consumers can be subscribed to that topic and retrieve the same message without being exclusive.
If neither of these work for you, I'm not sure what semantics you're looking for -- a "queue" which doesn't delete the message when it is consumed will never let a consumer access any but the first message.
Is there any way you can control the order delivery of messages in a topic in EMS or Tibco (using a JMS Topic Subscriber)? Something like the message selector, but instead of filtering to do ordering.
I would like to use a header like JMSXDeliveryCount, so that new messages will get a higher priority. I know that there's RedeliveryDelay, but that works only for queues, not topics.
Even JMSPriority could be an option if I can set it after getting the message with a topic subscriber. Can I do that? Maybe with a Java Code activity?
The broker will deliver messages in order as it receives them, but re-ordering messages is a distributed computing / EIP problem (see sequencer). The issue is the broker does't know how many messages are coming or how long to keep the window open for re-ordering messages. This activity is best done outside the broker in your application where that information is understood.
EIP frameworks and ESB's have done a nice job of standardizing a handler for this type of workflow.
ref: EIP Sequencer http://www.enterpriseintegrationpatterns.com/patterns/messaging/MessageSequence.html
JMSPriority is indeed an option, but it cannot be set on an already received message. The solution is to confirm the message and republished it with a different priority.
I was wondering if there is a way for you to configure a queue to automatically clear messages? We are striving to partially implement a component of our architecture and want to be able to send to the queue, but have the queue automatically remove the messages that are being sent so that we don't have to run scripts, etc to perform the clean-up.
So far the only thing I have been able to find is to run CLEAR QLOCAL or set the messages to expire from the publishing application.
For you use case there are a few options in IBM MQ:
Create a QALIAS that points to a TOPIC object which has a topic string with no subscribers, messages put to the QA will just disappear.
Have the sending application set message expiry.
Use the IBM MQ CAPEXPRY feature to administratively force message expiry at the queue level.
Run a script to issue CLEAR QLOCAL against the queue. There can not be open handles on the queue for this to work.
Programmatically issue the equivalent PCF command to CLEAR QLOCAL against the queue. There cannot be open handles on the queue for this to work.
Run the IBM MQ dmpmqmsg utility against the queue to read and discard the messages.
I used the Subscriber SYSTEM.JMS.D.SUBSCRIBER.QUEUE and Client ID as setClientID("USER1") and used topicSubscriber = topicSession.createDurableSubscriber(topic,"SUB1");
The topicSubscriber is created and while trying to receive using this topicSubscriber.receive(); , it is not receiving the messages from topic , but there are messages in topic.
Can any one say why its not receiving messages and whether i need to chek any queue configurations.
Any help is appreciated.
Thanks in advance.
I already had topicConnection.Start() in my coding , also i checked in TopicSession there is no Start() Method.
The same code with Non durable subscriber method topicSession.createSubscriber(topic); is working , but for durable it is not working.
Thanks
Sorry, yes I meant topicConnection.Start(). It was worth a check.
I got the answer for durable subscriber not working ,
My queue depth has reached the max queue depth , so the subscriber is not able to subscribe the message.
Eg . my max queue depth for queue SYSTEM.JMS.D.SUBSCRIBER.QUEUE is set to 100 , and if we check our current queue depth and if it reaches 100 the subscriber will not work.
As an alternative way iam trying to create with Temporary Topic , here iam getting an error while creating the durable subscriber topicSession.createDurableSubscriber(topic,"SUB1");
JMS Exception :: javax.jms.InvalidDestinationException: MQJMS0003:
Destination not understood or no longer valid
Can anyone help to solve this error.
Thanks in Advance.
The problem seems to be how you are using SYSTEM.JMS.D.SUBSCRIBER.QUEUE. You appear to be directing messages and subscribers to this queue as the destination for a durable subscription. IBM MQ uses that queue to manage durable subscriptions.
As a general rule, queues whose names begin with SYSTEM are for internal system use by MQ. Some of them, such as SYSTEM.ADMIN.*.EVENT are OK to get messages from but you would not use these as a subscription destination for unrelated messages either.
Many tutorials use SYSTEM.DEFAULT.LOCAL.QUEUE as a destination for messages but this is only because the queue is known to exist on all versions of MQ and MQ uses only the definition of the queue and never the content of that queue. It is easier for the tutorial writer (and IBM is just as guilty here) to point at SYSTEM.DEFAULT.LOCAL.QUEUE then to walk the student through the need for and means to create their own queue. So although best practices suggest it should not be an exception to the "do not use SYSTEM objects" rule, common usage makes SYSTEM.DEFAULT.LOCAL.QUEUE the de facto exception.
The other exceptions are, of course, the command queues for MQ, MFT and IIB. These are also names SYSTEM.* but are designed for users to communicate with the software listening on the queue.
Note that all the exceptions "do not use SYSTEM objects" rule are interfaces between applications and MQ system resources. The event queues are MQ sending information to the user. The command queues are the user sending information to the system components. A subscription is neither of these categories. A destination for a subscription is considered an application-owned object, even when the system manages it on behalf of the subscriber.
When you want a durable subscription, either let the system assign a permanent queue and use that, or else pre-define a queue (that is not named SYSTEM.*) and use that. Whatever else you do, please do NOT try to hijack MQ's internal system queues for application-level purposes.
I have a .NET application that needs to monitor a queue in WebSphere MQ. I need to react to each message without impacting the current process. The client application can't explicity send me the same message.
Can I read a message without removing it from the queue? Can I be notified for each message? Can I configure the MQ to duplicate the current queue?
Is there another solution?
If you are using WMQ v7 then you can do this without any impact to the existing applications other than to change the queue name for one of them.
Currently the message producer and consumer use the same queue. In v7 of WMQ you can create an alias over a topic so that the message producer thinks it's a queue. Then you can create two administrative, durable subscriptions such that one points to the existing input queue and another points to a queue dedicated to your new application.
Of course you are already using v7 since v6 goes out of service next year, right? You can upgrade the QMgr to v7 which enables this behavior while still using v6 client code for the apps.
If you are using WMQ v6 then the MirrorQ program might work for you.
You could change from using a queue to a durable topic and have both your reader and your browser subscribe to it.
You could also create a distribution list on your queue manager. A distribution list is used to send a copy of the same message to multiple queues. You would then have a processing queue and a browsing/monitoring queue.