What is a Pub Sub Queue? | A Comprehensive Guide

Today, organizations are building applications based on microservices architecture to make solutions lightweight and scalable. Since microservices applications are composed of small components, it is essential to have effective connectivity for performance. Therefore, you need a message broker or a message queuing mechanism with message patterns for the seamless functioning of these micro-services applications.

The Pub Sub queue (or Pub/Sub) is a message pattern of message brokers and it is used to communicate between the various components of microservices. It is used to provide program-to-program and asynchronous communication between the micro-services.

Also known as Publish-Subscribe, Pub Sub queue offers exchange message services using scaling and loose coupling methods between the sender and receiver. The Pub Sub queue is beneficial when you require many subscribers to a single source. This article discusses the Pub/Sub message pattern in message Queue and different frameworks that use this pattern.

Table of Contents

• Prerequisites
• What is a Message Queue?
• What is Pub/Sub?
• Key Features of Pub/Sub Queue
• Advantages and Disadvantages of Pub Sub Queue
• Use Cases of Pub Sub Queue
  • Messaging Frameworks with a Pub/Sub Message Queue Feature
    • Apache Kafka
    • Google Pub/Sub
    • Redis
    • Amazon SNS
    • Azure Service Bus
• Conclusion

Prerequisites

Understanding Pub Sub queue requires basic knowledge of integrations.

What is a Message Queue?

Message queues are used to provide communication between micro-service applications that consists of many architectural components. It provides a type of asynchronous service-to-service connectivity in the applications. Message queues ensure that messages are queued until they have been processed. Messages in message queues can be queries, responses, errors, data, or any information. 

The message queue consists of a producer responsible for sending messages to the queue based on the queue name. It also consists of a consumer subscribing to these messages and receiving messages from the producer. Therefore, a message queue can be used by multiple consumers and producers. 

Several organizations use many famous message queues, such as IBM MQ, RabbitMQ, Azure Scheduler, Azure Queue Storage, Apache Kafka, Apache Qpid, and more.

What is Pub/Sub?

Pub/Sub is a message pattern in a message queue, where the publisher supplies information in the form of messages and the subscriber consumes messages. When the producer publishes this message, it specifies a topic that identifies the subject of data inside the message. And the subscriber is the consumer of this message based on the interest in the message.

When a message is published, one of the primary aspects of Pub/Sub is that it specifies a subject. The Pub Sub queue, however, does not acknowledge the subscribers. And no application will receive the message in the queue if a message is published on a topic with no subscribers.

The rise in popularity of microservices applications and effective connectivity between the services and components is essential for the operation of applications. For this, Pub/Sub messaging provides two solutions:

1. It allows Developers to create applications with the decoupled and reliable communication methods between them.
2. It helps Developers to create event-driven architectures with simple steps.

Messages in message queues can be broadcast asynchronously across different components of applications using the Pub/Sub concept. The topic is the core component in the Pub Sub queue that makes the messaging functionality seamless. The Pub/Sub pattern defines the publisher for sending the messages to the topic, where the topic will send messages to all the subscribers. This concept separates Pub/Sub pattern from other traditional messaging brokers, in which single messages are sent in a batch format where users or services have to request and get messages. 

Key Features of Pub/Sub Queue

• The Pub/Sub pattern separates publishers from subscribers so that publishers don’t know the application consuming the messages, and subscribers know who is sending it. This process helps secure the messages and improve the security firewalls of applications.
• The exception in Pub/Sub is user-created policies; any information in the Pub Sub queue will be sent to all subscribers immediately.
• The Pub/Sub queue method allows event-driven applications to be built without repeatedly searching a message queue for information.
• Further, it enables Developers to design distinct isolated processes that can be performed in parallel and serve countless subscribers with the same message.
• It uses push-based delivery to send messages to subscribers in real-time, making it the best connectivity solution. It removes the requirement of the poll, which helps to check messages and lowers the application’s delivery time.

Advantages and Disadvantages of Pub Sub Queue

Here are some key advantages of implementing the Pub/Sub messaging queue.

• Any supported message broker may be readily incorporated into Pub/Sub using any programming language, as it is not dependent on a programming language, protocol, or specialized technology.

• While handling inter-component interactions, Pub/Sub can be used as a bridge to improve connectivity between components developed in various languages. Pub/Sub messaging allows for simple integrations with other systems without worrying about security issues and creating functionalities that enhance communications. 

• In a Pub/Sub queue, you send a message to the topic, and later the topic will be sent to the subscriber directly without any external application interference. This helps eliminate direct interaction with applications and increases transparency and security.

• Since you do not need to pre-define a certain number of publishers or subscribers using the Pub/Sub message queueing, it allows flexibility in exchanging messages. Depending on the usage, the publishers or subscribers can be added or removed from the topics. 

• In Pub Sub queue, the segregation of connection and functionality makes debugging easier because developers can concentrate on the individual component without bothering about the rest of the program being affected. 

• Even with complicated architectural modifications, a new Pub/Sub messaging system is as simple as changing the subject if the message formats are compatible.

Here are some limitations of the Pub/Sub messaging queue.

• When dealing with media (music or video), Pub/Sub is not ideal since they require seamless synchronized streaming between the host and the receiver. Pub/Sub messaging is unsuitable for video conferencing and media streaming applications since it does not provide synchronous end-to-end communications.

• If decoupled structures aren’t an essential aspect of your app, implementing Pub/Sub will be a waste of resources, leading to extra complexity for smaller systems.

Use Cases of Pub Sub Queue

A typical technological difficulty is sending events to big groups of applications at the same time. You need to have a system that quickly sends information to your customers while avoiding adverse outcomes as the number of recipients grows dramatically.

With Pub/Sub, events, whether raw or processed, can be made accessible in real-time to numerous apps throughout your team and company. For instance, change events from Databases are routinely sent via Pub/Sub. In BigQuery and other Data Storage Systems, these events may be utilized to build a view of the Database state and history.

Messaging Frameworks with a Pub/Sub Message Queue Feature

Here is a list of popular messaging frameworks that implement the Pub Sub queue feature.

• Apache Kafka
• Google Pub/Sub
• Redis
• Amazon SNS
• Azure Service Bus

Apache Kafka

Kafka is an Apache-developed Pub/Sub messaging system with communication logging. All information is stored in the partitions established for topics by Kafka Brokers, guaranteeing communications are distributed evenly throughout divisions. If a producer delivers two messages with 2 sections, Kafka will keep one statement in the first partition and the second message in the second partition.

Google Pub/Sub 

Cloud Pub/Sub offers asynchronous, many-to-many communications between system applications. Publisher apps can send messages to a “subject,” and other applications can subscribe to that topic to get the information. 

Redis

Redis is an in-memory data structure store that may be used as a Database, Cache, Message Broker, or Streaming Engine. This supports standard message queues and Pub/Sub pattern applications, making it one of the most prominent message brokers. Redis Pub Sub is the one in which senders (publishers) send messages and receivers (subscribers) receive them.

Amazon SNS

The Amazon Web Services Simple Notification Service is a web service that streamlines the process of transferring alerts to the subscribers who have signed up for messages. It is a fully controlled Pub Sub messaging service that uses topics to send messages among large numbers of applications at once.

Azure Service Bus

Azure Service Bus is a Cloud messaging service that connects any Cloud-based services, machines, and applications. Azure Service Bus provides a fully managed enterprise message broker with message queues and publish-subscribe topics. Azure bus topic works as a broker, but each subscriber can only view messages that meet particular requirements.

Conclusion

This article helped you understand the Pub/Sub messaging pattern in message queues and its functionalities, advantages, and disadvantages. The Pub/Sub messaging pattern is a powerful yet straightforward communication medium to send critical messages among applications.

Managing all connections is the foundation for building real-time global microservices-based systems. Due to many advantages over conventional message brokers, Pub Sub queue is utilized to establish asynchronous and extensible message flows with minimum delay.

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