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What Is Apache Kafka? Definition, Operation, Architecture, and Applications

With DigitalOcean Managed Kafka now available, I wanted to write a quick introduction guide on what Apache Kafka is in general and what you would need to know in order to get started using it.


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Bobby Iliev
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January 27, 2024
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Overview

Apache Kafka is an open-source stream-processing platform. It was originally developed at LinkedIn and then contributed to the Apache Software Foundation. Kafka is renowned for its high throughput, scalability, and durability. It’s commonly used for creating real-time data pipelines and streaming applications, serving as a backbone for handling massive streams of events or data.

Understanding Apache Kafka

Apache Kafka is a distributed streaming platform, which means it can handle the transmission of data across different nodes or machines. Its design allows for handling high volumes of data and enables real-time data processing. The platform is based on a publish-subscribe model and has three key functionalities:

  1. Publish and Subscribe to Streams of Records: Kafka allows you to publish and subscribe to streams of data, much like a message queue or enterprise messaging system. This makes it highly useful for building data pipelines that can transport and process data from various sources to different destinations.

  2. Store Streams of Records with Reliability: Kafka stores streams of records in a fault-tolerant way. This means that data is replicated and preserved in case of system failures, ensuring data integrity and availability.

  3. Process Streams of Records as They Occur: Kafka’s capability to process records in real-time makes it an excellent choice for scenarios where immediate data processing is crucial, such as in financial transactions or online recommendations.

Kafka’s Core Components

Kafka Producers and Consumers

  • Producers: They are applications or processes that send (publish) data to Kafka. A producer sends data to specific topics in the Kafka cluster.

  • Consumers: They are applications or processes that read (subscribe to) data from Kafka. Consumers read data from one or more topics in the Kafka cluster and process it accordingly.

Kafka Brokers and Clusters

  • Brokers: A Kafka cluster consists of one or more servers, known as brokers. Each broker is responsible for storing data and serving clients. To ensure high availability and fault tolerance, data is replicated across multiple brokers.

  • Clusters: A cluster refers to the group of Kafka brokers working together. The cluster configuration enhances scalability and reliability. As your data needs grow, you can add more brokers to the cluster to handle more data with minimal downtime.

Kafka Topics and Partitions

  • Topics: A topic is a category or feed name to which records are published. Producers write data to topics and consumers read from topics.

  • Partitions: Topics in Kafka are divided into partitions. Partitions allow Kafka to parallelize processing by splitting the data across multiple brokers. Each partition can be hosted on a different broker, enabling distributed processing and storage.

Kafka and Zookeeper

  • Zookeeper: In earlier versions of Kafka, Zookeeper was used for managing and coordinating Kafka brokers. It was responsible for cluster membership, topic configuration, and leader election among brokers.
  • Recent Changes: Newer versions of Kafka have started to reduce the dependency on Zookeeper, moving towards a self-managed metadata quorum that simplifies operations and improves performance.

Kafka in Action: A Node.js Example

Instead of a typical installation, let’s consider using DigitalOcean’s Managed Kafka clusters, which simplify the setup process and provide a robust environment for Kafka applications.

Simple Node.js Producer and Subscriber

In this section, we’ll explore how to create a basic Kafka producer and consumer using Node.js, leveraging the kafkajs library. This example demonstrates the fundamental operations of publishing messages to a Kafka topic and consuming them.

Node.js Producer

const { Kafka } = require('kafkajs');

// Initialize a new Kafka client
const kafka = new Kafka({
  clientId: 'my-app',
  brokers: ['your-broker:9092']
});

// Creating a producer instance
const producer = kafka.producer();

// Function to send message
const sendMessage = async () => {
  await producer.connect();
  await producer.send({
    topic: 'test-topic',
    messages: [{ value: 'Hello Kafka World!' }],
  });

  await producer.disconnect();
};

sendMessage();

Explanation:

  • Kafka Client: Initializes a Kafka client that connects to your Kafka cluster. Replace 'your-broker:9092' with the address of your Kafka broker.
  • Producer Creation: A producer is created to send messages to Kafka.
  • Sending Messages: The sendMessage function demonstrates connecting to Kafka, sending a single message to a specified topic (‘test-topic’), and then disconnecting.

Node.js Consumer

const { Kafka } = require('kafkajs');

// Initialize a new Kafka client
const kafka = new Kafka({
  clientId: 'my-app',
  brokers: ['your-broker:9092']
});

// Creating a consumer instance
const consumer = kafka.consumer({ groupId: 'test-group' });

// Function to receive messages
const receiveMessage = async () => {
  await consumer.connect();
  await consumer.subscribe({ topic: 'test-topic', fromBeginning: true });

  await consumer.run({
    eachMessage: async ({ topic, partition, message }) => {
      console.log({
        value: message.value.toString(),
      });
    },
  });
};

receiveMessage();

Explanation:

  • Consumer Creation: Similar to the producer, a consumer instance is created with a specific groupId.
  • Receiving Messages: The receiveMessage function shows how to connect to the Kafka topic, subscribe to it, and define the behavior for processing each received message. Messages are logged to the console in this example.

Integrating with DigitalOcean Managed Kafka Clusters

These examples assume you are using DigitalOcean’s Managed Kafka clusters. Make sure to replace 'your-broker:9092' with the actual broker information provided by DigitalOcean. This way, you can focus more on application development rather than on the setup and maintenance of Kafka infrastructure.

Practical Usage

This setup is ideal for applications that require real-time data processing and streaming capabilities. For example, you might use this configuration for real-time analytics, event sourcing, or as part of a larger microservices architecture.

The simplicity of kafkajs makes it an excellent choice for Node.js developers working with Kafka. By leveraging managed services like DigitalOcean’s Kafka clusters, you can efficiently run robust, scalable messaging and streaming applications.

Conclusion

Apache Kafka stands as a powerful solution for handling real-time data feeds, offering robust scalability and high throughput. Its architecture, which supports efficient data processing and streaming, makes it ideal for a variety of applications, from real-time analytics to log aggregation and messaging systems. With the evolution of Kafka, including the shift away from Zookeeper and the integration with modern managed services like DigitalOcean’s Managed Kafka clusters, it continues to adapt and remain relevant in the fast-paced world of big data and stream processing. Whether you’re a developer venturing into real-time data systems or an enterprise handling large volumes of data, Kafka offers a reliable and efficient platform worth exploring.

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