I have a dead-letter queue which stores failed messages. Is there have a way to manually trigger a listener to process the messages in the dead-letter queue? I’m using Spring AMQP.
Like I said, it depends on your use case, but I can assume you are looking for something from spring amqp out-of-the-box.
just have a look at BlockingQueueConsumer, you can i.e. prefetch one message if you want, then start it manually.
Please be aware that you need choose solution according to your case, maybe you just need a flag in db to mark the job is failed, or save the msg in db.
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I created a SpringBoot/Spring AMQP project where I configured a listener on a RabbitMQ queue. Question: Is there any way to leave the message in the queue? Let me explain: I consume the message and do some things (eg save on db), if something goes wrong I would like to be able to reconsume the message.
Thanks in advance
You need to think about configuring your listener container with transactions, so when DB call fails, the transaction is going to be rolled back and an AMQP message will not be acked on RabbitMQ.
See docs for more info: https://docs.spring.io/spring-amqp/docs/current/reference/html/#transactions
I don't know about the "Spring" way of accomplishing this, but what you describe is the normal behavior for AMQP consumers that do not automatically acknowledge.
From the documentation:
In automatic acknowledgement mode, a message is considered to be successfully delivered immediately after it is sent.
When you turn off automatic acknowledgment, your consumer must explicitly acknowledge the message, otherwise it will not be dequeued (or as you put it, it will be left "in the queue"). You will then need to simply ACK the message at the very end of your operation, when you are certain that your operation succeeded (and perhaps coordinated with your database transaction).
There is always the question of what to do first; acknowledge first or commit your database transaction first? Without adding complexity, you must choose what's best depending on what failure mode is less problematic for you, i.e. Would you rather tolerate a duplicated message or a missing message?
I have several jobs that each have multiple messages queued.
The messages for each job are randomly interleaved.
If a user decides to cancel a job I want to remove all the messages that are part of that job from the queue.
I have been able to use browse()to find all the messages to remove but haven't been able to figure out how to remove them.
I tried getting rid of them by using receiveSelected() but it just hangs.
(I am using JmsTemplate)
JMS does not define administration type functions, such as deleting a message from the queue.
The programmatic way is to consume the message. Alternatively, there are messaging management tools that allow you to do this without programming.
There is no any JMS API to remove message. However seems you can invoke purge removeMessage or other operation as per your requirement on MBean org.apache.activemq:type=Broker,brokerName=amq,destinationType=Queue,destinationName=testQ to delete messages.
You are on the right track. Consuming those messages using a selector is the way to go - such as with JmsTemplate receiveSelected.
If it "hangs", it likely means you have no matching messages on the queue. Can you identify your messages on some Property, such as JMSType or other StringProperty? Make sure you can and supply a JMS Selector.
I.e. if your jobs are initiated by user X, then set some property such as "initiatingUser" to "x". Then to consume all messages, use the selector initiatingUser='X'.
I am creating a hosted system where multiple customers can send messages. I am receiving thoses messages on a JMS queue.
Now, all processing is done in a similar way and I want my process to poll all incoming queues for messages and handle them. Is there a way in WSO2 ESB to subscribe to multiple queues?
If not possible, the workaround would be to create a seperate listener process for each queue and have this post the message to a central processing queue. But that seems to be a less clean solution (and I think it will scale worse than listening to multiple queues).
Any ideas on this?
If changes to activeMQ server is possible ie. if OP is able to influence the configuration to the server, something like ActiveMQ diverts could do the trick.
<divert name="prices-divert">
<address>jms.queue.ABC</address>
<forwarding-address>jms.queue.theone</forwarding-address>
<exclusive>true</exclusive>
</divert>
<divert name="prices-divert">
<address>jms.queue.xyz</address>
<forwarding-address>jms.queue.theone</forwarding-address>
<exclusive>true</exclusive>
</divert>
Basically, multiple diverts that converge the messages from multiple queues to the single queue. This method has advantage over the reading and writing to single queue-as mentioned by the OP and would in my view scale well as it is inbuilt feature.
You can define a sequence with all the required logic in it and then call it from multiple proxy services (each listening to a specific queue). Otherwise you can try something similar to this sample.
Currently I'm using bluelock's camel-spring-amqp component for my application.
What I want to achieve is:
Pull a message from RabbitMQ server.
Persist it to a database on successful processing / Send it to another "Error" queue on Exception
Tell the original queue that it is now safe to remove the message from the queue.
As of this writing, I'm able to pull from rabbit and persist to database using camel routes. What I don't really know how to do is acknowledge that my processing is done to the original queue. Here is my current route:
from("spring-amqp:EXCHANGE:queuename?autodelete=false&durable=true&type=direct&routingKey=")
.bean(Transform.class, "transform(byte[])")
.to("jpa:com.my.company.models.MyModel?entityType=java.util.ArrayList")
I realize I can set the acknowledgmentMode to NONE. But I don't know how to "manually" acknowledge once I have persisted my message.
Thanks for any help!
I'm new in Camel but I know a thing or two about RabbitMQ.
With RabbitMQConsumer the message is acknowledged if the processor doesn't throw any exception (line 133 at RabbitMQConsumer source).
So I suppose if you let your processor propagate the exception, the message won't be acknowledged. I haven't used spring-amqp but I guess it should have a similar behaviour.
I am working on an existing Spring jms application that pulls messages from ActiveMQ using jms:inbound-gateway. This application is a job processor that takes jobs off a queue and sends results back to the queue. Everything currently works great.
I would like to modify this application to accept one and only one job, process it, and then exit, but I have not been able to find a way to cleanly do this. The method that is called must return the results, and the results are automatically placed back onto the queue by Spring. Is there any way to tell Spring to stop accepting messages at 1? How would you know when it's done sending the reply message so you can exit.
In a more general case, if you had an application that wanted to stop accepting messages and finish processing them all so you could exit cleanly, how can that be done?
Thanks in advance for any advice.
It sounds like you should be using JmsTemplate.receive . Inbound gateway is meant for a message driven model. It sounds like while you are using a message queue for transport, you're not really doing a message driven model of processing. Obviously that's not a problem but if your aim is to process a single message you should just use JmsTemplate.
Another way to do this is to use the default message listener container, ensure threads is set to one and then make sure your activemq setup has no read-ahead setup (i.e. reads one message at a time and no more). Then, at the end of your onMessage method, call the DMLC.stop method.