EMQ vs Kafka: What are the differences?

Introduction

EMQ and Kafka are two popular messaging systems that are used for data streaming and processing in real-time. While both systems serve similar purposes, they have key differences in their design and functionality. In this article, we will explore these differences in detail.

1. Scalability: EMQ is designed to be a highly scalable MQTT broker that can handle massive amounts of concurrent connections and messages. It is built on a distributed architecture, allowing it to scale horizontally as the number of connected clients and messages increase. On the other hand, Kafka is a distributed streaming platform that is built for horizontal scalability. It can handle high message throughput and is designed to handle large volumes of data in a fault-tolerant manner.

2. Message Persistence: EMQ stores messages in memory, providing low-latency message delivery. However, this also means that messages are not persisted on disk by default, which can be a limitation in certain use cases. Kafka, on the other hand, is built for durability and guarantees persistent storage of messages. Messages are stored on disk and replicated across multiple nodes in a Kafka cluster, ensuring fault-tolerance and durability.

3. Message Ordering: EMQ guarantees ordering of messages within a single MQTT session. This ensures that messages are processed in the order they are received by the broker. Kafka, on the other hand, provides a different model for message ordering. It allows messages to be written to multiple topics in parallel, which means that messages within a topic may not be consumed in the exact order they were produced. Kafka provides configurable mechanisms to ensure order preservation, such as partitioning and message timestamps.

4. Message Delivery Guarantees: EMQ provides at most once and at least once delivery guarantees. For QoS level 1 and 2, EMQ can ensure that messages are delivered exactly once to the subscribed clients. Kafka, on the other hand, provides configurable delivery semantics. It supports at most once, at least once, and exactly once delivery guarantees, allowing developers to choose the appropriate level of guarantee for their use case.

5. Protocol Support: EMQ is designed as a full-featured MQTT broker, providing extensive protocol support for MQTT clients and IoT devices. It supports features such as QoS levels, retained messages, last will and testament, and more. Kafka, on the other hand, is not limited to a specific protocol and provides a simple and efficient binary protocol for data streaming. It can be used with various client libraries and supports a wide range of programming languages.

6. Use Cases: EMQ is well-suited for applications that require real-time messaging, such as IoT applications, telemetry data processing, and chat applications. It provides low-latency message delivery, efficient protocol support, and high scalability. Kafka, on the other hand, is more suitable for applications that require high-throughput, fault-tolerant, and durable data streaming. It is commonly used for use cases such as log aggregation, event sourcing, stream processing, and real-time analytics.

In summary, EMQ and Kafka have key differences in terms of scalability, message persistence, message ordering, message delivery guarantees, protocol support, and use cases. These differences make them suitable for different applications and use cases in the real-time data streaming and processing domain.