Redis vs RabbitMQ - Key Differences

Key Features of Redis

• Scalability: In Redis, horizontal scaling is achieved by adding nodes and distributing data across them, ensuring high availability while handling more traffic.‍
• Additional Persistence: Redis provides two persistence options—RDB snapshot and write-ahead log—to save the in-memory data in durable storage.‍
• Data Replication: It offers data replication from the master instance to multiple replicas to overcome failures, as a replica can be promoted to master.‍
• Transaction: Redis supports transactions, allowing the sequential execution of multiple commands in a single step.‍
• Pub/Sub System: It leverages Pub/Sub system to allow effective communication. A publisher can send messages via the PUBLISH command, and a subscriber can subscribe or unsubscribe to a topic using the SUBSCRIBE and UNSUBSCRIBE commands.

Key Features of RabbitMQ

• Multi-Protocol Support: RabbitMQ supports multiple messaging protocols, either directly or through a plugin. The supported protocols include AMQP 0-9-1, MQTT, STOMP, AMQP 1.0, and RabbitMQ streams.‍
• Clustering: This feature allows you to connect multiple nodes to create a single logical broker, enabling high queue availability and increased throughput. Different elements, such as users, exchanges, virtual hosts, and permissions, are synchronized across all the nodes present in the cluster. Clients can connect to a node and view all its elements.‍
• Routing Capabilities: Routing is a critical feature that enables the transmission of messages from the producer to the consumer via exchange. The exchange receives messages from the producer and pushes them to the correct queues.‍
• Reliability: RabbitMQ is a highly reliable message broker. It provides features like delivery confirmation and message persistence while handling message failures.‍
• Scalability: It is a highly scalable tool that can handle high volumes of messages and, if required, scale horizontally to accommodate message traffic.

Working

Although both Redis and RabbitMQ facilitate microservices, software components, and applications to exchange messages, their working principles differ significantly. Let’s explore their working principle:

Redis Working Principle

Redis enables you to organize data in key-value pairs, which provides a clear structure. This structure allows client applications to subscribe to specific channels and receive messages. It also lets you separate and publish the data into different components according to the obtained keys from the key-value pairs.

When the data publisher sends a message through the channel, the Redis node verifies the message key to identify interested subscribers. In the next step, Redis sends the messages to all the associated subscribers.

RabbitMQ Working Principle

RabbitMQ, on the other hand, utilizes the Advanced Message Queuing Protocol (AMQP) to securely send and receive messages via a message broker containing exchanges and queues.

In this process, the data producer sends messages to RabbitMQ. The RabbitMQ exchange receives the message and routes it to the associated queue according to certain rules called bindings. The message resides in the queue until the consumer accesses it. After retrieval, the consumer replies with an acknowledgment confirming the delivery of the message so that the producer can push the next message.

RabbitMQ restricts the publisher from sending messages if the queue reaches maximum capacity. It removes the restrictions after the consumer handles the unread messages. RabbitMQ also allows message retrieval during exchange failure, which helps retain communication between the producer and the consumer.

Message Handling

While both support message distribution, their message handling mechanism differs significantly between both these tools.

‍Delivery

Redis sends messages to all connected subscribers without guaranteeing message delivery. Subscribers must be connected to the Redis server to receive messages. If the subscriber is not connected, it will not be able to receive messages.

RabbitMQ delivers messages point-to-point or from one publisher to many subscribers using AMQP, supporting complex routing logic. After each message is delivered, the consumer sends an acknowledgment to the producer confirming its successful delivery. If the producer doesn’t receive the confirmation message, it retries sending the same message again in regular periods.

‍Size‍

Redis does not define any upper limit on the size of messages. Still, latency can be seen for messages larger than 1MB, which is why most developers use it as a cache.

Contrarily, RabbitMQ can handle large messages up to 128 MB without experiencing any performance drop.

‍Persistence‍

Redis doesn’t support persistence by default. To support this feature, you can enable the Redis Database (RDB). RDB takes periodic snapshots of the RAM and stores them on disk. However, this process slows down message delivery as it adds overhead to data operations. To overcome this challenge, you can use alternative recovery methods like asynchronous replication.

RabbitMQ, on the other hand, supports both persistent and transient messages. When sending messages to persistence queues, it writes data to permanent storage as the data arrives. But if the memory capacity exceeds, RabbitMQ can also write transient messages to the disk.

‍Encryption‍

Redis 6.0 and later versions support Transport Layer Security (TLS), Internode, file system, private, and client-side encryption to encrypt information.

In contrast, RabbitMQ utilizes SSL to transmit encrypted data between different messaging system components, including producers, brokers, and consumers.

Speed

Redis is an in-memory data store with caching features that send millions of messages per second, making it an ideal platform for low-latency applications.

Alternatively, RabbitMQ waits for acknowledgment from each consumer before sharing the next message, which slows down the message exchange process.

Availability

Redis Clusters allows you to distribute data from a leader node to multiple follower nodes. When a leader node fails, any of the follower nodes takes control to offer high availability while delivering messages.

Conversely, in RabbitMQ, various data nodes are replicated in a cluster, preventing message queues from being duplicated across these nodes. Each node contains a copy of all the message queues it is responsible for in the cluster.

Performance

Performance is one of the most important factors in determining which platform is better than the other for processing data with growing demands. It includes the speed and availability offered by the tool.

If your application requires low latency and high throughput, then you must consider choosing Redis over RabbitMQ. RabbitMQ is not an ideal solution when speed is involved, as it waits for the acknowledgment message to arrive at the publisher.

However, if you need a tool that efficiently delivers messages to consumers, you can select RabbitMQ. When using Redis, there is a potential risk of the data being lost during transmission.

Scalability

Scalability determines the ease of handling increasing or decreasing demand by including or removing additional resources. In terms of scalability, both the options in RabbitMQ vs Redis provide high scalability, handling large amounts of data.

Redis offers high scalability, enabling you to scale horizontally by adding more servers to your resources. The process of splitting data between multiple servers to achieve scalability is also referred to as sharding.

Conversely, RabbitMQ’s clustering mechanism makes it suitable for large-scale deployments. This allows you to connect multiple nodes, offering high throughput and increased queue availability.

Reliability

Reliability ensures proper delivery of messages to the subscriber/consumer, eliminating the risk of data loss during communication.

Redis is a less reliable platform than RabbitMQ, as it does not guarantee delivery in the Pub/Sub system. The underlying process is based on sockets and event loops and does not involve queues. If the subscriber is not listening during publication, the message might be lost.

In contrast, RabbitMQ offers a reliable solution. With its acknowledgment mechanism, RabbitMQ waits for the consumer's confirmation message to reach the producer before allowing the next message transfer. This feature guarantees the delivery of each message to the consumers.