Message Queue vs. Publish-Subscribe

If you're trying to tie distributed systems together, you're likely considering implementing a message queue or perhaps a publish-subscribe pattern. Here's the difference between these two options and information to help you choose the right solution.

The flexibility and scalability of IronMQ allows you to have both in one platform. Book a free demo and see Iron's message queues in action first-hand.

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What is a Messaging System?

Multiple messaging systems exist, but they all serve the purpose of maintaining a stream of incoming messages and transferring them across your applications. A messaging system maintains a queue in its disks or memory, allowing it to store the messages producers add to the system while deleting messages that consumers have consumed/executed.

Messaging systems may follow one of two patterns: message queuing or a pub-sub pattern.

Countless solutions exist that were originally designed to act as message queuing systems, like RabbitMQ, RocketMQ, Apache ActiveMQ, Amazon SQS, and IBM MQ. Other technologies, like Apache Kafka, were designed to support pub-sub patterns. However, newer solutions like IronMQ meet the needs of both. So, let's explore message queue vs pub-sub systems side by side so you can decide which pattern best suits your environment.

IronMQ offers the option of both queuing and publish-subscribe so you can set up the perfect message broker. Book a free demo to get started.

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What Is the Message Queueing Pattern?

The message queuing pattern takes on a point-to-point approach. A message within the queue will be deleted once consumed, similar to the Post Office Protocol, where a message is deleted from the server once it is delivered. These queues enable asynchronous messaging.

In the event of a network issue that causes a delay in a message's delivery, like if a consumer is unreachable, that message will stay in the queue until it can be delivered. This means messages aren't necessarily delivered in any particular order. They are instead delivered on a first-available basis, which can boost efficiency in certain environments.

What Is the Pub/Sub Pattern?

The publish-subscribe pattern, often called the pub-sub pattern involves publishers that produce ("publish") messages in different categories and subscribers who consume published messages from various categories they are subscribed to. Unlike point-to-point messaging, a message will only be deleted if it's consumed by all subscribers to the category.

Some message systems, such as Kafka, have a retention policy that ensures messages stay in the queue for a specified amount of time, even after they are consumed by all subscribers. Other providers include Google Cloud Pub/Sub messaging, which offers similar functionality. Both are examples of middleware message delivery services that offer scalability and decoupling potential for real-time data streams and workflows.

Pros and Cons of Message Queuing

Message queues, or MQs, have a number of use cases. An MQ ensures that each message is consumed by only one consumer, so it's ideal for task lists and work queues because it eliminates redundancy.

The benefits of a message queue include its ability to support fast, high-volume consumption rates since you can add multiple consumers for a topic but still only have a single consumer process each message. Who consumes the message is dependent on the MQ's design.

If you have a setup where a message should be processed quickly, but only one time and in no particular order, a message queue would be the ideal solution. A common example would be a system managing paychecks. Everyone should only receive a paycheck once, but it doesn't necessarily matter who processes it or in what order.

Pros and Cons of Pub/Sub

Publish-subscribe messaging enables multiple consumers to receive each message in a given topic and also ensures that messages are received by consumers in the same order they were produced.

Pub-sub systems are ideal for stateful applications since these applications care about the order in which messages are received. The order of messages determines the state of the app and the correctness of its processing logic.

Given its specific order and multiple-recipient design, the pub-sub pattern is ideal for an environment where it's important that multiple consumers get the same message and in the right order. Think of a stock ticker, where many people would want to know the latest price changes on the stocks they're following and where it's also important that they get their information in the right order. For instance, it'd make a big difference to know if a low price came in before a high price and vice versa.

Message Queue vs. Publish-Subscribe

How Iron.io Can Help

Deciding between message queue vs pub-sub will ultimately come down to your specific use case, but what if you have systems that could use both? Iron offers you the flexibility to choose between a message queuing pattern and a publish-subscribe pattern, depending on what best suits your needs.

On top of that, Iron offers the fastest messaging solution on the market, outperforming RabbitMQ and other popular alternatives, providing you with the most available, scalable, and application-ready messaging system out there.

Are you interested in learning more about Iron? Book a free demo and see for yourself what IronMQ can do for your business.

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