Implementation of messaging protocols is a fundamental communication component for modern applications. Different application components require transmitting messages while ensuring reliable and efficient communication. A good example of ensuring reliable message exchange is implementing a pipeline. Once a message is assigned to the pipeline, its destination is already established. This message will always get delivered. Moreover, if the destination is busy or not connected to the queue, the pipeline will hold that message until the destination gets back. You require a message queueing system (pipeline) to implement these advanced queuing operations like message persistence, message priority, scheduled messages, time-to-live, etc.
A communication contains a payload of the actual data being transmitted or received. These messages are dispatched by a producer and received by a consumer. On the other side, a message queue is a line (MQ) that stores and manages the flow of these messages in a sequential first-in, first-out (FIFO) order until a consumer retrieves them. It holds the messages waiting to be processed. These messages will then be enqueued and dequeued in the order they are received to ensure asynchronous communication between the sender and the receiver.
In that context, it allows applications to exchange and receive messages through a queue. These messages are stored in a pipeline until the receiving application processes them. It allows asynchronous communication by ensuring a service can transmit a notification to the queue and continue processing. In contrast, another service can receive the message and process it in a timely approach.
A perfect hypothetical example of how message queues (MQ) can be used is an e-commerce app that uses a message queue to process orders. In this case, when a customer places an order, the app dispatches a notification to the queue with the order details. This message payload will include details such as the customer’s shipping address, the products being ordered, and the total cost of the order.
The same application will have another service (fulfillment service) that receives the message from the pipeline and processes the order. While using a message queue, the application can still process other consumers’ incoming orders while the fulfillment service takes care of the orders as they are received. The system remains scalable, as the order service doesn’t need to wait for the fulfillment service to complete the order before processing the incoming orders.
The same application will have another service (fulfillment service) that receives the message from the pipeline and processes the order. While using a message queue, the application can still process other consumers’ incoming orders while the fulfillment service takes care of the orders as they are received. The system remains scalable, as the order service doesn’t need to wait for the fulfillment service to complete the order before processing the incoming orders.
A queue manager functions as a software application that delivers messaging services to various applications. This is to guarantee the accurate delivery of messages to their designated pipelines or their redirection to a different manager if required.
A message queue uses a straightforward architecture:
When a consumer processes a task, it is removed from the queue. However, this process may differ based on the style of message pipeline being used.
Message queues style differs in characteristics. The major message queues types are:
Point-to-point queues send messages from a single producer to a single consumer. This method is commonly used for simple and one-to-one communication between services.
An excellent example of a point-to-point queue is communication between a web app and a backend server. In this case, the app sends a message containing a user request to the queue. The server then processes the request and sends a response back to the app. Messages are only produced by one consumer, received by one consumer, and then removed from the queue.
This approach dispatches messages from a producer (Publishers) to multiple consumers (subscribers). A consumer can subscribe to specific message categories and receive messages that match the respective subscription. The Pub/Sub pattern is essential whenever you want to distribute messages to multiple recipients.
A good example that fits the Pub/Sub pattern is news systems. For example, a financial news system can route messages to multiple subscribers based on specific subscriptions, such as stock prices and market trends. All subscribers who have subscribed to the relevant category will receive the news update.
Fanout queues are closely related to Pub/Sub patterns. Messages are sent from a single producer to multiple consumers. However, it uses a fan-out pattern. All connected consumers receive a message sent by the producer simultaneously.
Fanouts a commonly used to create real-time event-driven applications. Take an example of a Social media platform. Any post you add to your timeline is sent to all your followers in real time. The significant advantage of Fanouts is the ability to implement real-time communication. Chat application uses a real-time event-driven architecture to send in group chat communication. All group members receive a message sent by one member.
When a producer sends the message to the queue, the consumer may not be available to receive the dispatched message. In this case, the message will be stored in the queue until its receiver becomes available. Dead letter queues are used to store messages that cannot be delivered to the intended recipient at a given time.
Take an email application as an example, specifically the email delivery service. In this case, if you send an email that fails to be delivered to the intended recipient, it is stored in a dead letter queue for further examination or re-routed to a different recipient.
Messages stored in a queue are treated using a first-in, first-out (FIFO) approach. This means the first received messages will be processed first, and others will follow in the same order. However, you can use queues to treat messages based on priority levels.
Priority queues are used to store and manage messages with different priority levels. Messages are processed based on priority. Higher-priority messages are processed first, and lower-priority messages come last.
A priority queue allows you to handle time-sensitive and crucial messages. Take an example an app that sells VVIP, VIP, and regular products. In this case, a priority queue can be used to process orders based on the levels you have set.
Message queues provide tone benefits for modern application development. Based on this post, let’s check out a few advantages you can leverage:
Message queues can be applied based on the above benefits, and this post has discussed queue types. The everyday use cases examples where they are used include:
Message queues are a powerful tool for creating scalable, fault-tolerant applications. This goes in hand with their ability to decouple operations and enhance overall application reliability. You can use a message pipeline for flexibility and make it easier to scale your app. This makes pipelines a valuable addition to your application architecture.
For an even more solid knowledge, do check out our article on what is a message broker.