- What is message queuing ?
- What is RabbitMQ and how does it work?
- How to install RabbitMQ?
- What programming languages are supported by RabbitMQ?
- What are queues, exchanges, bindings and routing keys?
- How to create a queue in RabbitMQ?
- How does RabbitMQ ensure high availability and fault tolerance?
- How to handle consumer acknowledgement in RabbitMQ?
- Can RabbitMQ be used for pub-sub messaging?
- Are there any alternatives to RabbitMQ for message queuing?
What is message queuing?
Message Queuing allows applications to communicate by sending messages to each other. The Message Queue provides temporary message storage when the destination program is busy or not connected.
- Message Queuing enables asynchronous communication between different components or systems. This increases system reliability, scalability, and flexibility.
- This is achieved by adding a message broker (like RabbitMQ or LavinMQ) to pass messages or data between processes or systems.
- Messages are sent by a producer to the Message Queue, where they are held until consumed by a consumer.
- This decouples the producer from the consumer, allowing them to operate independently.
- Message Queuing can be used for distributed computing, task scheduling, and workflow management.
Here is a video that explains the basic concepts of message queueing. Also read our blog on the same subject.
What is RabbitMQ and how does it work?
RabbitMQ is a message queueing system - it enables communication between systems. It receives messages from a producer, stores them, and transfers them to a consumer. But how does RabbitMQ store and transfer these messages?
If intentionally simplified, we can say that producers publish messages to exchanges in RabbitMQ. Exchanges route these messages to the right queues, where they are stored. Consumers subscribe to queues to receive and process these messages.
The diagram below provides a simplified view of how a message moves from the producer, via RabbitMQ, to a consumer.
This blog introduces the basics of RabbitMQ and explains why developers are increasingly opting for a microservice architecture over a monolithic system. Additionally, this other blog offers an explanation of RabbitMQ from a non-developer's perspective.
How to install RabbitMQ?
You can install and run RabbitMQ in various environments:
- Local Installation: Install directly on various operating systems like Ubuntu, Windows and macOS.
- Docker: You can also run RabbitMQ in a docker container.
- Kurbenetes: RabbitMQ can also be deployed on container orchestration platforms like Kurbenetes.
- Package Managers: Some operating systems offer RabbitMQ via package managers like APT for Ubuntu or Homebrew for macOS.
You can find more information on each installation option in the documentation.
While these installation methods are viable, we recommend creating and running your RabbitMQ instance on the cloud with CloudAMQP — It’s the easiest way. This is mostly because the installation and operational challenges of managing RabbitMQ on your own could be significant. A cloud-based RabbitMQ service like CloudAMQP could make things easier for you.
CloudAMQP can be used for free with the plan Little Lemur. Go to the CloudAMQP plan page and sign up for any plan.
What programming languages are supported by RabbitMQ?
RabbitMQ server is built using the Erlang programming language. That notwithstanding, you can communicate with the broker using client libraries, which work with all main programming languages. Some of the supported languages are, but not limited to:
- Java
- Spring Framework
- C#
- Ruby
- Python
- PHP
- Javascript and Node
- Swift
- Objective-C
- Golang
- Elixir
What are queues, exchanges, bindings and routing keys?
- A queue in RabbitMQ is the data structure that stores messages sent by producers. Producers send messages to the queue, and consumers retrieve them for processing. Messages are not published directly to a queue. Instead, they first go to an exchange.
- An exchange routes messages to various queues, utilising header attributes, bindings, and routing keys to determine the proper “path”.
- A binding acts as a connection, establishing a link between a queue and an exchange.
- The routing key is an attribute of a message that an exchange uses to identify the correct queues to send the message to, based on the type of exchange.
This video explains the different types of exchanges in RabbitMQ. You can also read our blog on queues, exchanges, bindings and routing keys.
How to create a queue in RabbitMQ?
Take the following steps to create a queue from the RabbitMQ Management console - you can also create queues programmatically. Please note that you'll need a RabbitMQ server running. Again, the easiest way to spin up a RabbitMQ instance is to create one on CloudAMQP(refer to installation).
-
Access the RabbitMQ Management Console:
Login to your CloudAMQP account → Click the
Create New Instance
button to create a new RabbitMQ instance → Click the
RabbitMQ Manager
button to navigate to the RabbitMQ Management console of your instance. See image below:
- Navigate to Queues: On the RabbitMQ Management Console, go to the Queues and Streams tab. This section provides information about existing queues and allows you to create new ones.
-
Create a New Queue:
- Click on the Add a new queue button.
- Provide a name for your queue in the "Name" field. Queue names are case-sensitive.
- You can leave other settings at their default values for a basic queue.
- Click the Add queue button to create the new queue.
How does RabbitMQ ensure high availability and fault tolerance?
RabbitMQ supports high availability and fault-tolerance via clustering — which essentially involves linking two or more RabbitMQ instances together.
High availability in a RabbitMQ cluster is implemented at the queue level — using a variety of replicated queue types, namely: Quorum Queues, Stream Queues, and Classic Mirrored Queues (scheduled for deprecation in RabbitMQ 4.0).
- Quorum queues: Quorum queues in RabbitMQ consist of a leader and followers (replicas) distributed across the nodes in the cluster, with client interactions managed solely by the leader. The leader replicates commands to followers, which serve for redundancy. If a broker fails, a follower takes over as leader, maintaining service continuity.
- Stream queues: RabbitMQ's stream queues, designed for use cases like large fan-outs and replay, offer replication for high availability. Though they operate as quorum systems similar to Quorum Queues, allowing leader election by a majority and enabling reading from follower replicas, they prioritize higher throughput by not waiting for write confirmations from a majority of replicas, thus offering weaker consistency guarantees. In case of a node failure, a replica node takes over as leader, ensuring continuous operation.
How to handle consumer acknowledgement in RabbitMQ?
In RabbitMQ, consumer acknowledgement is a mechanism for ensuring reliable message delivery— it is a way for consumers to confirm that they have received and processed a message from a queue. If a consumer successfully processes a message and acknowledges it, RabbitMQ removes the message from the queue. A related concept to consumer acknowledgement in RabbitMQ is publisher confirms.
RabbitMQ supports two consumer acknowledgement modes:
- Automatic Acknowledgement (Default): By default, RabbitMQ assumes automatic acknowledgement (auto-ack). In this mode, as soon as a message is delivered to a consumer, it is considered acknowledged. This is suitable for scenarios where you can afford potential message loss, such as with fire-and-forget scenarios.
- Manual Acknowledgement: For scenarios where message reliability is critical, you can use manual acknowledgement. In this mode, the consumer explicitly sends an acknowledgement to RabbitMQ after successfully processing a message.
Using manual acknowledgement provides more control over message processing and ensures messages are not lost even if an error occurs during processing. However, it also requires careful handling of acknowledgements to avoid unintentional message loss.
If you're interested in learning more, CloudAMQP has a blog on RabbitMQ's best practices.
Can RabbitMQ be used for pub sub messaging?
Yes, RabbitMQ can be used for pub-sub (publish-subscribe) messaging, which is a messaging pattern where a single message is broadcasted to multiple subscribers.
You can implement the pub-sub pattern in RabbitMQ in one of two ways:
- A fanout exchange and a queue: Here, multiple queues are bound to a fanout exchange — the fanout exchange in turn forwards every message it receives to all the queues bound to it and by extension, to all the consumers bound to the queues.
- Using a stream queue: Because the stream queue is immutable — messages read are not deleted from the queue, the same message could be read by multiple consumers.
Stream queues were introduced in RabbitMQ 3.9. You can read our blog on stream queues to learn more about this queue type.
Are there any alternatives to RabbitMQ for message queuing?
Yes, there are several alternatives to RabbitMQ for message queuing, each with its own strengths and features — ActiveMQ is one popular alternative.
Additionally, At CloudAMQP, in addition to RabbitMQ, we also offer LavinMQ. This is our in-house developed message broker, that is focused on performance and ease of use.
Does this information seem a bit complex or intriguing? Interested in learning more about CloudAMQP’s offerings? Please feel free to reach out to support@cloudamqp.com.
