I am using RabbitMQ to queue up all the messages and send the messages as SMS to respective consumers. I am using a Direct exchange and I have correctly created a binding to a queue with a routing key. The problem is, when I try to publish a message, I get some activity in the Message rates chart, but the message doesn't show up in the queue
Could certainly use some help here. I am sure the binding is done correctly.
Am I missing some other configuration?
I would recommend to "use specific exchanges", not sending message without specified exchange. I had same issue, when I published it to amq.direct or amq.fanout it worked as I wanted to.
If your configuration is correct, and you also have an active consumer that listens to that queue, I don't think anything is wrong. Doesn't those metrics depicts that the event was published and then delivered and acknowledged by the consumer ? So of course you won't have any queued events since it was consumed as soon as it was published.
It looks like the message is delivered to a consumer (as you can see in the chart). Remove the consumer and try to publish the message again, and you will see that it ends up in the queue instead.
In my case I was creating custom queue so I had to provide custom queue ID as a routing key.
Related
Is there any way to check a published message if no consumers are created? Now I just have a project which publishes events and I can see that they are published by checking exchanges created in RabbitMQ. But I'm not sure if there is a way to check the message content from the Rabbit MQ interface if there are no consumers. Maybe is it better to cover a publish logic with a unit test to check that a message with correct content is published?
You can specify an alternate exchange for published messages, and those messages will be delivered to the alternate exchange if no other exchanges are bound. You can then bind that an exchange to a queue to retain those messages if there are no subscribers.
Alternatively, you can specify the Mandatory flag on the published message, and the Publish call with throw an exception if there are no exchanges bound.
Alternate Exchange Unit Test
Mandatory Unit Test
Validation ("checking") of message content is a client function, and cannot be performed in the message queue itself. It either must be performed prior to publish (trust the publisher) or it must be performed immediately after dequeue but before processing (don't trust the publisher).
My problem:
I pull off a message from a RabbitMQ-Queue. I try to process this message and realize that it can't be processed yet. So i would like to add it back to the queue and let it return only on a specific time + 5000ms. Unfortunately that is more challenging than i thought.
What i've tried:
RabbitMQ Dead Letter Attributes -> My issue here is, even though the manual says that the default exchange is binded to every queue it doesnt forward it according to the routing criteria. I've tried to add expires = "5000" and x-dead-letter-routing-key = "queuename" also "x-dead-letter-exchange = "" as the default exchange should work. The only part which works is the expires part. The message will disappear and go into the dark. This also occurs with the dead-letter-exchange beeing amq.direct including the binding on the targeted queue.
Open gaps for me:
Where i'm a bit left in the dark is if the receivers have to be dead letter queues and if i the dead letter queue is a basic queue with extended functionality. It is also not clear if those parameters (x-dead-letter..) are only for DLX Queues. I would like to do this delayed delivery persistent and purely via. the message attributes and not via. queue configurations (only if required).
I've searched on the web and checked many different dead-letter infos. Im trying to build a micro-service like architecture while using RabbitMQ as the delivery mechanism (i use processes which take their work from the queue and forward it). I would believe other people here have the same running already but i couldn't find any blogs about this.
I had to come to the conclusion that on the message level it is not possible.
I've created now for each queue which is in use a separate queue ("name.delayed") , where i can add the message with the argument "expiration" = 5000
The queue settings itself has to be a dead letter queue routing it to the queue "name"
I have implemented the example from the RabbitMQ website:
RabbitMQ Example
I have expanded it to have an application with a button to send a message.
Now I started two consumer on two different computers.
When I send the message the first message is sent to computer1, then the second message is sent to computer2, the thrid to computer1 and so on.
Why is this, and how can I change the behavior to send each message to each consumer?
Why is this
As noted by Yazan, messages are consumed from a single queue in a round-robin manner. The behavior your are seeing is by design, making it easy to scale up the number of consumers for a given queue.
how can I change the behavior to send each message to each consumer?
To have each consumer receive the same message, you need to create a queue for each consumer and deliver the same message to each queue.
The easiest way to do this is to use a fanout exchange. This will send every message to every queue that is bound to the exchange, completely ignoring the routing key.
If you need more control over the routing, you can use a topic or direct exchange and manage the routing keys.
Whatever type of exchange you choose, though, you will need to have a queue per consumer and have each message routed to each queue.
you can't it's controlled by the server check Round-robin dispatching section
It decides which consumer turn is. i'm not sure if there is a set of algorithms you can pick from, but at the end server will control this (i think round robin algorithm is default)
unless you want to use routing keys and exchanges
I would see this more as a design question. Ideally, producers should create the exchanges and the consumers create the queues and each consumer can create its own queue and hook it up to an exchange. This makes sure every consumer gets its message with its private queue.
What youre doing is essentially 'worker queues' model which is used to distribute tasks among worker nodes. Since each task needs to be performed only once, the message is sent to only one node. If you want to send a message to all the nodes, you need a different model called 'pub-sub' where each message is broadcasted to all the subscribers. The following link shows a simple pub-sub tutorial
https://www.rabbitmq.com/tutorials/tutorial-three-python.html
I'm using ActiveMQ and I would like to know how to solve this specific case.
When the consumer is down, the producer sends a message to the queue. The message will remain in the queue until the consumer is running to consume it.
Now imagine I shutdown the producer, the message will STILL remain in the queue. Now i run the consumer and it will try to consume that message, but won't be able to reply back to the producer since its down.
I would like to solve this problem by cleaning the messages if the producer is out.
The ActiveMQ Broker cleans the Queue after stopping. I would like to do the same for the messages of a respective producer.
Thanks.
Based on what I understand now from your question and additional comments I propose to add a Message Property to your messages to identify the Producer, and write a small utility that uses a Message Selector to read all messages matching the Producer from the queue. You can run that utility straight after the Producer is stopped (or crashes), and that should quite accurately do what you want to achieve.
EDIT: although primarily focused on EE, the Sun/Oracle JavaEE Tutorial contains a very good chapter on general JMS programming that starts off with standalone producers and consumers. The accompanying source code bundle can be downloaded here, the ready to comoile samples in that bundle should get you started very quickly.
You can solve it a couple of ways. One is to set a TTL on the message so it goes away. The other is to connect via JMX and purge the Queue or remove the specific message using a selector statement or with the Message's specific MessageId value.
See this article for some hints.
I am getting a little confused with NServiceBus. It seems like a lot of examples that I see, they always use publish() and subscribe(). What I am trying to do is that I have a publisher that polling from its queue and distributes the message to subscriber’s queue. The messages are being generated by other application and the body of message will contain a text, which will be parsed later.
Do I still need to call publish() and subsribe() to transfer the messages from publisher's queue to subscriber's queue? The way I understood was that I only need to configure the queue names in both config file and call LoadAllMessages() on subscriber side, will take above scenario. I don't even have to handle the message on the subscriber side.
Thanks.
Your Publisher will still need to call Publish. What this does is the Publisher then looks into Subscription Storage to find out who is interested in that message type. It then will send a message to each Subscriber. On the Subscriber side you need to implement message handlers to do something with those messages. This is done via implementing the IHandleMessages<T> interface in the Subscriber assembly. NSB will discover this and autowire everything up. Be aware by default, the Subscriber will subscriber to all message types. If you want to only subscribe to certain messages, use the .DoNotAutoSubscribe setting in the manual configuration.