Is there any possible customizations to requeue messages being processed while a stream undeploy operation is occuring?
Let's say I have 10 unacked messages in RabbitMQ being processed by a slow processor during an undeploy, how can I ensure those messages are not going to be delivered to the DLQ because of "dispatcher has no subscribers" but instead being re-queued in the input processor queue?
You shouldn't get such exceptions; modules are stopped left to right, so the inbound channel adapter should be stopped before the downstream components are unsubscribed from their input channels.
Is this a custom module?
Related
I am learning how DLQ works in Azure service bus queue. i.e., unconsumed messages will be in DLQ. I have enabled dead lettering (deadLetteringOnMessageExpiration) on message expiration.
References:
Azure Service Bus - Subscriptions and DLQ
Azure Service Bus - *move* message from DLQ to main
https://learn.microsoft.com/en-us/azure/service-bus-messaging/enable-dead-letter
AMR template:
https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-resource-manager-namespace-queue
Questions:
If deadLetteringOnMessageExpiration is enabled, would DLQ be available for that queue (like below screenshot)?
If yes, how can I process messages from DLQ? (I guess I can view such messages here but not sure what will happen next)
My goal is to create a queue with DLQ where unprocessed message can be processed at some point and what is the best way to achieve that.
If deadLetteringOnMessageExpiration is enabled, would DLQ be available for that queue?
Dead-letter queue is always there for queues and subscriptions, unrelated to how you configure your entity.
If yes, how can I process messages from DLQ?
Up to you. You can peek DLQ-ed messages, recieve and process, etc. It really depends on how you want to handle those dead-lettered messages in the context of your system.
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.
I have a Tibco EMS Message Queue on a production system that routes messages from a single producer to a single consumer application.
We are scaling the application vertically, but due to financial constraints, we cannot scale the two applications in pairs.
A single producer will route messages to the message broker and the message broker will need to bridge the message to 1 of 3 consumers based on a message selector.
I have set up a queue bridge and selector to route messages on the producer queue to consumer queues. This is a 1 to many queue bridge.
I noticed that the bridged consumer queues have consumers attached to them and they are receiving the messages correctly based on the selector, however the producer queue retains copies of the messages which must be manually purged at the end of day.
What is the best way to handle this scenario using bridges and selectors so that the message is retained on the broker until it is consumed (durable) but once a message is consumed by a consumer queue, the message is removed by the broker.
The easiest way to dispose those messages of the original queue is by introducing MaxMsgs and MaxBytes on the queue.
As for you requirement that the message on the original queue can only be disposes if it was consumed on one of the bridged queues, this is not possible.
That said, it also it not needed, since the bridged queue keep its own message copy, regardless of what happens to the message in the source queue. So expiring messages in the original queue has no effect on the already bridged messages
Let's suppose I have several subscribers consuming from a topic. After a message has been delivered to all the subscribers I'd like to trigger a job that would use this message in input.
So the easy way to do that would be to move messages that have been succesfully delivered to all the sucscribers to a queue from which my job would consume messages.
Is it part of JMS?
Is there any message broker able to do that directly?
If not is there a simple solution to solve this problem?
You should be able to do this using activemq's advisories.
See here for more about advisory messages: http://activemq.apache.org/advisory-message.html
So what you want to do, for the topic in question, is track:
the number of consumers
when a message is dispatched to them
when the message has been ack'd by each of the consumers
to get the number of consumers, listen to the "ActiveMQ.Advisory.Consumer.Topic." advisory topic
to get when a message is dispatched, listen to the "ActiveMQ.Advisory.MessageDelivered.Topic."
to get when a message has been ack'd, listen to "ActiveMQ.Advisory.MessageConsumed.Topic."
you could easily use Apache Camel to help out with this (listening to the topics) and aggregating whether or not all consumers have processed (ack'd) the message.. then that could kick off your further processing..
You could just create another durable subscription to route the message from the topic to queue directly. From that queue your job can consume messages. This is much easier than creating a trigger to route the messages to a queue.
So the easy way to do that would be to move messages that have been
succesfully delivered to all the sucscribers to a queue from which my
job would consume messages. Is it part of JMS?
No, this is not part of JMS specification.
I have a persistent queue, non-transacted, client-acknowledge, the consumers read with jms.prefetchPolicy.queuePrefetch=1&wireFormat.maxInactivityDuration=50000
and once a consumer processes a message, it ack's the message.
If the consumer reads the message, and before it can send an ack, the process terminates abruptly, what happens in ActiveMq? (What ActiveMq parameters come into play here?)
How is that different than if the the consumer will take 10 minutes to process the message (so the consumer task is alive and working), how does ActiveMq know the message is still being worked on? (Does it monitor the TCP/IP connection, if the connection dies, it assumes the message will not be Ack'ed?)
How do I determine if a message is a "poison pill", i.e. it makes the consumers crash? (the redelivery count seems to be valid if the consumer task does not die; is there an internal counter in the message that says "it was been read n times without being successfully ack'ed?")
As an experiment, I sent 6 messages, one of them being a "poison pill" (kills the consumer before the consumer can send the ack), with 2 simultaneous consumers running (and automatically restarting consumers to bring the count to 2 whenever a consumer dies). Looking at the queue (using jconsole, I enable jmx using broker.setUseJmx(true)), 4 messages were delivered, 2 are in-flight. Why would there be 2 in-flight instead of just one?
I've been reading the ActiveMq and JMS specs for a while without clear/conclusive answers, so any insights on what parameters come into play, and if there are any known bugs, will be greatly useful.
This is purely based on my understanding of JMS - may not be completely correct:
If the consumer reads the message, and before it can send an ack, the process terminates abruptly, what happens in ActiveMq
My understanding is that since this happens in the context of a session with the JMS provider, JMS provider knows if the session is no longer active or has failed and any message not acknowledged as part of the session will be redelivered when the session is re-established.
How do I determine if a message is a "poison pill", i.e. it makes the consumers crash?
Like you have mentioned, the JMS provider keeps track of the # of times the message was redelivered possibly in the header of the message
4 messages were delivered, 2 are in flight
Not sure about this point