Microservice architectures have been the preferred choice for designing software solutions for quite some time. In general, the idea is to have a system, consisting of multiple small applications performing different tasks. So, here comes the question – how are these different applications communicating in order to form a whole and complete software product? In this article, we’ll explain the difference between a message queue and a message broker. We’re going to discuss their use cases and tell you whether you can use them together as a means of communication between software applications.
What is a message queue?
A queue is a data structure where the piece of information that enters the queue first is also transmitted first. This programming concept is also known as FIFO, or First-In-First-Out.
Imagine you have a pipe. You’re holding one end, while your friend’s holding the other one.
You start adding little stones to the pipe. The first one you added will be the first to arrive at the other end and into your friend’s hands. A pretty simple concept, isn’t it? A message queue works in the exact same way, only with messages instead of stones.
Messages are the bits of information that we want to transmit. Services can have message queues, which contain an array of sequentially sorted calls, sent to the desired destinations. The information in the queue is stored until it is received by the correct service. The applications that create messages and push them into the queue are called producers. . On the other hand, the applications that go through the queue and receive those messages are called consumers. The message queue also enables asynchronous communication between different services. When sending information, the producer can keep working without interruption, allowing the consumer application to process the information at its own pace.
What is a message broker?
A message broker is simply software that provides a means for stable and reliable communication between different applications.
But what if those applications and services are in different languages and don’t use the same technology stack? Not to worry – translating the information between messaging protocols is part of the message broker’s job.
What else are message brokers responsible for? Well, they store, route, and deliver information to the desired destination. In general, their purpose is to allow applications to communicate internally thus playing the part of a communications layer. Senders can issue messages even without knowing who the receivers of those messages are, how many of them there are, and even if those receivers are active at the moment or not.
Different messaging styles
Now that we know what a message broker is, let’s look at the different messaging styles, more specifically point-to-point messaging and publish-subscribe messaging.
Point-to-point messaging uses message queues in such a way that the messages’ sender and receiver have a one-to-one relationship. This type of messaging style is used when a guarantee is needed that each message will be sent and consumed only once. For example, this is the preferred style to use when working with financial transactions.
The publish-subscribe messaging style enables the producer of the message to send it toward a topic. Consumers subscribe to these topics and receive the information sent by the producers. This is a one-to-many relationship between sender and receiver. When a message is published on a topic, it reaches everyone who has subscribed to it. So, when is it appropriate to use publish-subscribe messaging? Imagine a truck driver sends out an update about a delay between certain borders. Everyone along the truck’s route will get the message and can plan accordingly. Furthermore, if the update is sent on a system that includes drivers, they’d be able to plan their trips around these new circumstances.
Message queue vs message broker: The differences
A message queue facilitates communication between applications by sending, receiving, and storing messages using the queue data structure. Even though we use message queues for data transfer, they can’t read the information they are carrying.
A message broker is simply a mechanism that extends the usage of message queues. Unlike message queues, message brokers can read the contents of the information carried through them. Also, message brokers can process information from all sorts of sources. For example, information read from files or HTTP requests.In short, the message broker is responsible for:
- The conversion between data transport protocols
- The transformation of message formats between services
- The routing of the communication between services
- The distribution of events from various sources
As it turns out, message brokers use message queues to transmit information between all interested parties. Simply put, the message queue is a structure that stores the produced data until its consumption, and the message broker is a software component that manages the message queues.
In a microservice architecture, every microservice offers different functionality than the rest. However, they cannot perform those functionalities without keeping in touch with the other services. Message queues provide a means for applications to push information to the queue. The message broker simply takes the information from the sender, translates it between different messaging protocols, if needed, and delivers the message to the correct receiver.
So go ahead and use a message broker in your next project! If you have any questions, please feel free to contact us at Dreamix and we’ll be more than happy to help you out!