Is it possible to avoid sending the same messages (data) to the certain queue using RabbitMQ configuration?
Or should I do this programmatically?
RabbitMQ does not offer message de-duplication out of the box.
There is a plugin which offers a certain level of de-duplication.
You can also implement de-duplication yourself at either the producers or consumers by checking if the sent/received message was already seen against a cache.
Related
Is it possible to implement the aggregator pattern in RabbitMQ?
I have A … N messages that I need to wait for/aggregate before sending off to another queue X.
So I'm thinking I will have some kind of unique ID that ensures that messages are routed exclusively to the same consumer and then wait for all the messages to arrive.
Is this possible in RabbitMQ?
Yes, it is possible.
But this is not RabbitMQ specific. Understanding what to aggregate and how to do it is beyond the responsibility of the message broker.
You need to write a service to subscribe to the relevant messages and then publish the result back. In the context of RabbitMQ, you could use routing keys to ensure the right consumer gets the messages, but that is not the only way.
If I have two queues from which I want to consume messages, and I use a single SimpleMessageQueueListenerContainer for it, in which order would the listeners be invoked/messages consumed when both queues have messages?
I will try to be more specific of the problem I am working on:
I have a consumer application which needs to consume messages from 2 queues – say regular-jobs-queue and infrequent-jobs-queue. If there are any messages in ‘infrequent-jobs-queue’ I want to consume those before consuming messages from ‘regular-jobs-queue’. I might not be able to combine these and put all messages into a single rabbitmq level priority queue and assign higher priority to infrequent-job message because of some upcoming use-cases like purging regular-jobs without affecting infrequent-jobs and others.
I am aware that RabbitMQ has support for consumer priority but I am not very sure if it will be applicable here. I want all instances of my consumer application to first consume messages of infrequent-jobs-queue if any and not prioritize amongst these consumers.
Or should I like have 2 containers, with dedicated consumer thread(s) per queue and have an internal priority-queue data structure into which I can put messages as and when consumed from rabbitmq queue.
Any help would be really appreciated. Thanks.
~Rashida
You can't do what you want; messages will be delivered with equal priority.
Moving them to an internal in-memory queue will risk message loss.
You might want to consider using one of the RabbitTemplate.receive() or receiveAndConvert() methods instead of a message-driven container.
That way you have complete control.
I am putting together a queue based distributed system, all standard stuff. We are using the latest version of RabbitMQ to provide our messaging transport tier.
I have some questions regarding achieving high availability (for my applications and not actually RabbitMQ) that I couldn't answer by reading the documentation. Would appreciate some advice, it's very likely my lack of understanding of Rabbit/AMQP that is causing the problem :)
Problem: I have a message producer (called the primary). There is one and only 1 message producer. There is a secondary producer (called the backup) which should take over from the primary should it fail.
How could I achieve this using existing RabbitMQ capabilities?
Thoughts: Use an "exclusive" queue, to which the primary will be connected to. The backup will attempt to connect to to this queue. When the primary fails, the backup will gain connectivity to the queue and establish control over the process.
What is the correct pattern I should be using to achieve this? I couldn't find any documentation on competing producers etc, would appreciate your advice! How do others do this?
Kind regards
TM
If you want to have only one producer at a time - you can't afford it with RabbitMQ mechanism (unless you'll get some plugin but I don't know such of a kind). You can gain control on producers number on application level.
P.S.:
Looks like you don't get AMQP idea well, producers publish messages to exchanges, while consuming get them from queue. The broker (RabbitMQ) route messages from exchange to on or more queues (in fact, it can also route messages to other exchange, but that's another story).
I am starting with ActiveMQ and I have a usecase. i have n producers sending messages into a Queue Q1. I want to stop the delivery of messages (i.e. i do not want consumers to consume those messages). I want to store the messages for sometime without those being consumed.
I was looking at ways this can be achieved. These two things came into my mind based on what i browsed through.
Using Mirrored queues, so that I can wiretap the messages and save into a virtual queue.
Possibly stop consumers from doing a PULL on the queue.
Another dirty way of doing this is by making consumers not send ack messages once its consumed a message from the queue.
We are currently not happy with either of these.
Any other way you can suggest.
Thanks in advance.
If you always want message delivery to be delayed you can use the scheduler feature of ActiveMQ to delay delivery until a set time or a fixed delay etc.
Other strategies might also work but it really up to you to design something that fits your use case. You can try to use Apache Camel to define a route that implements the logic of your use case to either dispatch a message to a Queue or send it to the scheduler for delayed processing. It all really depends on your use case and requirements.
I'm using NServiceBus 4.x with RabbitMQ 3.2.x as my transport.
I made the assumption that by using RabbitMQ as my transport I would be given the competing consumer model as an option. I understand that NServiceBus employs the "Fannout" exchange type for all exchanges and does not support round robin at this time. However is there a way to configure NServiceBus to take advantage of the levels of indirection via Exchanges and channels that RabbitMQ offers.
I have several consumers I would like to compete for messages from a given queue. What I am observing is subscribers' blocking access to further message retrieval from the queue until the message is consumed. So having more then one consumer at this point does me no good other then redundancy.
After reading some documentation on RabbitMQ I'm assuming that it's normal to block until the Ack receipt is sent from the subscriber. But I had assumed that subscriber #2 would have free access to the queue to fetch another message.
There is mention of increasing the prefetch count on RabbitMQ channel.
Example:
channel.BasicQos(0,prefetchcount,false)
I don't see anywhere that I can change this setting via configuration in NServiceBus. Furthermore as I read what prefetch does I'm really not sure this what i'm looking for.
Is it possible to use RabbitMQ with out a distirbutor type pattern used with MSMQ? Or should I move to MassTransit or Rebus?
Put prefetchcount=2 in your connection string. Any value above 1 will tell the broker to allow more than X unacked message to go out. You need to fiddle with this setting to find the optimum for your scenario.