I am using rabbitmq in spring boot application. I am using aws ecs for deployment. Now suppose multiple instance is running of my service. and rabbitmq listening for order create is registered with direct exchange.. So what happen when order is placed? will my both the instance of service will get same message? If yes, How to prevent duplicate message on those 2 listeners?
If the service creates multiple Listeners/Consumers for same queue on a direct exchange below mechanism is applicable:
By default, RabbitMQ will send each message to the next consumer, in sequence. On average every consumer will get the same number of messages. This way of distributing messages is called round-robin.
Best Tutorial for this topic: https://www.rabbitmq.com/tutorials/tutorial-two-java.html
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Using Spring boot #RabbitListener, we are able to process the AMQP messages.
Whenever a message sent to queue its immediately publish to destination exchange.
Using #RabbitListener we are able to process the message immediately.
But we need to process the message only between specific timings example 1AM to 6AM.
How to achieve that ?
First of all you can take a look into Delayed Exchange feature of RabbitMQ: https://docs.spring.io/spring-amqp/docs/current/reference/html/#delayed-message-exchange
So, this way on the producer side you should determine how long the message should be delayed before it is routed to the main exchange for the actual consuming afterwards.
Another way is to take a look into Spring Integration and its Delayer component: https://docs.spring.io/spring-integration/docs/5.2.0.BUILD-SNAPSHOT/reference/html/messaging-endpoints.html#delayer
This way you will consume messages from the RabbitMQ, but will delay them in the target application logic.
And another way I see like start()/stop() the listener container for consumption and after according your timing requirements. This way the message is going to stay in the RabbitMQ until you start the listener container: https://docs.spring.io/spring-amqp/docs/current/reference/html/#containerAttributes
We are using microservice architecture in our project. We deploy each service to a cluster by using Kubernetes. Services are developed by using Java programming language and Spring Boot framework.Three replicas exist for each service. Services communicate with each other using only events. RabbitMQ is used as a message queue. One of the services is used to send an email. The details of an email are provided by another service with an event. When a SendingEmail event is published by a service, three replicas of email service consume the event and the same email is sent three times.
How can I prevent that sending emails by other two services?
I think it depends on how you work with Rabbit MQ.
You can configure the rabbit mq with one queue for these events and make spring boot applications that represent the sending servers to be "Competing" Consumers.
If you configure it like this, only one replica will get an event at a time and only if it fails to process it the message will return to the queue and will become available to other consumers.
From what you've described all of them are getting the message, so it works like a pub-sub (which is also a possible way of work with rabbit mq, its just not good in this case).
When using RabbitMQ + Spring cloud stream you can define the following properties in application.properties file:
spring.cloud.stream.bindings.input1.destination=someDest
spring.cloud.stream.bindings.input1.group=someGroup
I guess that "destination" means the RabbitMQ queue, but what does it mean "group" here?
Thanks!
The destination means topic exchange. The group means a queue bound to that exchange. So, several apps may subscribe to the same destination and get the same message if they use different groups. If group is the same, only one consumer instance it going to get one message.
See documentation for more info: http://cloud.spring.io/spring-cloud-static/spring-cloud-stream-binder-rabbit/2.1.0.RC4/single/spring-cloud-stream-binder-rabbit.html#_rabbitmq_binder_overview
Actually, the destination is the exchange name; the queue someDest.someGroup will be bound to the exchange someDest.
When a group is provided, multiple instances of the app will compete for messages.
If there is no group, the queue will be an anonymous auto-delete queue.
Iam new to Rabbitmq.i want to implement Rabbitmq in my Application to send Emails.for that i need to configure multiple queues then connecting my Email messages to that Queues.for single queue based on Exchange name Application working perfectly but,i tried with multiple queues on that case facing issue while configuring in Spring-context.xml.
Thanks in advance,can any one share sample project of SpringMVC with RabbitMq along multiple queues.
Regards,
Balaji
I have a couple of queues and I need to do the following with ONE of them:
A producer should send a message to this queue, but ALL consumers should receive it. So, if I have 5 spring listeners on this queue, each of them should receive the message, but not the producer. I do that because I have a tomcat cluster and rabbitmq asynchronous messages, and if I get response from the worker, I don't know how to dispatch it to the correct tomcat node. So I decided to broadcast all worker replies to all tomcat nodes. Each tomcat cluster node listens the same output queue. Then, if it's a correct tomcat instance, it will be processed, all other copies will be lost, and it's ok. How to implement it? How make consumers on tomcat's end to receive the same message the same time?
Ok, found the solution here:
RabbitMQ / AMQP: single queue, multiple consumers for same message?
It's impossible to do in rabbitmq, need to create a couple of queues for each consumer.