What is Kafka?

Apache Kafka is an open-source distributed streaming platform designed to handle high volumes of real-time data. LinkedIn originally developed it and later donated it to the Apache Software Foundation, where it became an Apache top-level project.

At its core, Kafka is a publish-subscribe messaging system that allows producers to publish messages to a topic and consumers to subscribe to one or more topics to consume those messages. Unlike traditional message brokers, Kafka is designed to handle high-throughput data streams, making it an option for building real-time chat and messaging applications.

Kafka is known for its fault-tolerant and scalable data processing. It’s built upon a distributed architecture, which can be deployed across multiple servers or clusters, allowing it to handle large amounts of incoming data and distribute the workload among the available resources.

Another feature of Kafka is its durability. Kafka stores all the messages it receives in a distributed commit log, allowing reliable data retention and replayability. This means that even if a consumer goes offline or a failure occurs, it can resume processing from where it left off, ensuring data consistency and reliability.

How does Apache Kafka work?

Kafka operates as a distributed publish-subscribe system, and it uses a distributed commit log to store streams of records, allowing multiple producers and consumers to read and write data concurrently.

Kafka follows a client-server architecture, where the server is called a Kafka broker. Producers are responsible for writing data to Kafka topics, essentially categories or feeds to which records can be published. Each record consists of a key, a value, and optional metadata. Producers can choose to publish records synchronously or asynchronously.

Consumers, on the other hand, read data from Kafka topics. They subscribe to one or more topics and consume records in the order they were written. Kafka allows multiple consumers to form consumer groups, where each consumer within a group processes a subset of the partitions in a topic. This enables parallel processing and load balancing.

Kafka stores the published records in a distributed commit log divided into multiple partitions. Each partition is an ordered, immutable sequence of records. The partitions allow Kafka to scale horizontally by distributing the load across multiple servers or brokers.

To ensure fault tolerance and durability, Kafka replicates partitions across multiple brokers. Each partition has a leader and one or more followers. The leader handles all read and write requests for the partition, while the followers replicate the data and serve as backups. If the leader fails, one of the followers is elected as the new leader to ensure continuous operation.

Kafka also provides strong durability guarantees by storing data on disk and allowing configurable replication factors to ensure data redundancy. This means that even if a broker or disk fails, the data is still available and can be recovered.

To achieve high throughput and low latency, Kafka uses a combination of batching, compression, and zero-copy techniques. Producers can batch multiple records together before sending them to Kafka, reducing network overhead. Kafka also supports data compression to further minimize network bandwidth usage. Additionally, Kafka leverages kernel-level page cache and file system cache to enable zero-copy data transfers, avoiding unnecessary data copies and improving performance.

Kafka's architecture also supports fault tolerance and scalability through Kafka Connect and Kafka Streams. Kafka Connect allows easy integration with external systems, enabling data ingestion and egress from Kafka. Kafka Streams provides a high-level API for building stream processing applications on top of Kafka, allowing developers to process and transform data in realtime.

What are some of the features of Apache Kafka?

Apache Kafka is a distributed streaming platform that offers a wide range of features, making it highly suitable for building real-time chat and messaging applications. Some of the notable features of Apache Kafka are:

• High Throughput: Kafka is designed to handle large data streams efficiently.

• Scalability: Kafka scales horizontally, allowing you to add more brokers to the cluster to handle increasing data loads.

• Fault Tolerance: Kafka provides fault tolerance by replicating data across multiple brokers in a cluster. If any broker fails, other replicas can seamlessly access the data.

• Durability: Kafka persists data on disk, ensuring data integrity and durability. It allows you to configure the retention period for data, meaning you can store data for as long as you need.

• Message Retention: Kafka provides configurable retention policies, allowing you to decide how long to retain messages in the system. This feature is crucial for applications that require historical data analysis.

• Flexibility: Kafka supports various data formats and protocols, making it flexible for different use cases. It can handle both structured and unstructured data and supports various integration patterns.

• Monitoring and Management: Kafka provides a robust set of tools and APIs for monitoring and managing clusters, including metrics, logs, and administrative APIs. This makes it easier to monitor the health and performance of Kafka clusters.

• Native Deployment: Kafka is well-suited for cloud-native deployments, as it can be easily deployed and managed in cloud environments such as AWS, Azure, and Google Cloud Platform. It can also integrate with cloud-native services for data processing and analytics.

Disadvantages of using Apache Kafka

While Apache Kafka offers many advantages, there are also considerable disadvantages to consider:

• Complexity of Configuration and Management: Setting up and managing a Kafka cluster can be complex and require expertise in distributed systems. Developers need to configure various parameters, such as replication factor, partition count, and retention policies, to optimize the performance and reliability of their Kafka deployments. Monitoring and troubleshooting Kafka can also be challenging, especially in large-scale production environments.

• Potentially High Latency: While Kafka is known for its high throughput, it may introduce latency in certain scenarios. This can be due to network congestion, message serialization, and deserialization, or the processing time of consumers. Developers must carefully design and optimize their applications to minimize latency and ensure real-time performance.

• Lack of Real-time Messaging Features: While Kafka excels at handling large volumes of data and providing fault-tolerant data pipelines, it may not offer the same real-time messaging features as specialized messaging platforms like PubNub. PubNub, for example, provides additional features like presence detection and mobile push notifications.

• Limited Support for Non-Java Languages: While Kafka provides client libraries for several programming languages, its core functionality and ecosystem primarily focus on Java. Developers working with other languages may face limited support and documentation, making integrating Kafka into their existing tech stack harder.

• Resource Intensive: Kafka can be resource-intensive, especially when dealing with high message throughput or large data volumes. It requires a dedicated infrastructure to handle the storage and processing requirements.

• Operational Overhead: Running a Kafka cluster requires ongoing maintenance and monitoring. This includes managing partitions, handling replication, and monitoring performance. This can add operational overhead and require dedicated resources.

• Learning Curve: Apache Kafka has a steep learning curve, particularly for developers unfamiliar with distributed systems or event-driven architectures. Understanding its concepts and best practices may take time and effort.

• High Initial Setup Cost: Implementing Kafka can require significant upfront costs, especially for organizations that must invest in dedicated hardware or cloud infrastructure to support the Kafka cluster. This can be a barrier for smaller companies or startups with limited resources.

• Complex Monitoring and Troubleshooting: Monitoring and troubleshooting Kafka can be challenging due to its distributed nature. Identifying and resolving partitioning, replication, or performance issues can require deep technical expertise and specialized tools.

• Dependency on ZooKeeper: Kafka relies heavily on ZooKeeper for cluster coordination and metadata management. This introduces an additional layer of complexity and potential points of failure. Any issues with ZooKeeper can impact the overall stability and availability of the Kafka cluster.

• Inflexible Schema Evolution: Kafka's schema evolution capabilities are relatively limited compared to other data streaming platforms. Modifying the schema of existing topics can be challenging and may require complex migration strategies, which can be time-consuming and prone to errors.

• Lack of Native Analytics and Querying Capabilities: Kafka is designed as a distributed messaging system and does not provide native analytics or querying capabilities. Developers need to integrate Kafka with other tools or platforms, such as Apache Spark or Elasticsearch, to perform complex data analysis or search operations on the stream of messages.

• Limited Support for Message Ordering: Kafka guarantees message ordering within a single partition but not across multiple partitions. This can be challenging for applications that rely on strict message ordering, such as financial systems or event-driven workflows. Developers must carefully design their partitioning strategy to ensure the desired ordering semantics.

• Potential Data Duplication: In some scenarios, Kafka may introduce data duplication. This can happen when a producer retries sending a message after a failure, resulting in multiple copies of the message stored in different partitions. Developers need to handle duplicate messages on the consumer side to ensure data consistency and avoid processing the same data multiple times.

• Limited Backward Compatibility: Kafka's backward compatibility is limited to a certain extent. Upgrading to a newer version of Kafka may require changes to the client code to accommodate any breaking changes or new features. This can be time-consuming and may introduce compatibility issues if not handled properly. Developers should carefully plan and test the upgrade process to ensure a smooth transition without impacting the stability of their applications.

• Limited Support for Complex Routing and Transformation: Kafka's routing and transformation capabilities are relatively limited compared to other message queuing systems. Developers may need to implement custom logic or integrate with external tools to perform complex routing, filtering, or data transformation operations on the stream of messages. This can add complexity to the application architecture and require additional development effort.

• Lack of Built-in Stream Processing: Kafka primarily focuses on message storage and delivery and does not provide built-in capabilities for stream processing. Developers need to use external frameworks or libraries such as Spark or Elasticsearch to perform complex data analysis or search operations on the stream of messages. This can add overhead and complexity to the application architecture, as these external tools need integration.

What are some Kafka use cases?

Apache Kafka is used in various use cases, such as:

• Real-time stream processing: Kafka allows applications to process and analyze real-time data streams, making it suitable for use cases such as fraud detection, real-time analytics, and online machine learning.

• Log aggregation: Kafka's ability to handle high-throughput data ingestion makes it an ideal choice for log aggregation use cases. It can collect logs from multiple sources and centralize them for further analysis, monitoring, and debugging.

• Commit log for distributed systems: Kafka's durability and fault-tolerance features make it an option for building distributed systems. It can serve as a commit log, storing events and ensuring they are replicated across multiple nodes, thus ensuring data integrity and fault tolerance.

• Change data capture (CDC): Kafka's ability to capture and stream real-time data changes from databases allows applications to react to data modifications in near realtime. CDC use cases include data synchronization, data warehousing, and building materialized views.

• Event sourcing: Kafka's log-based architecture and ability to store and replay events make it a good fit for event sourcing patterns. It can capture and store events in a system, enabling audit trails, temporal queries, and state reconstruction.

• Metrics and monitoring: Kafka can be a reliable and scalable data pipeline for collecting and processing metrics and monitoring data. It can ingest data from various sources, perform real-time processing, and forward it to monitoring systems for analysis and visualization.

• Microservices communication: Kafka's publish-subscribe model and support for message partitioning enable efficient communication between microservices. It can be used as a communication channel for asynchronous and event-driven architectures, facilitating decoupling and scaling of microservices.

What is Kafka’s architecture?

The architecture of Apache Kafka is designed to handle large-scale, real-time data streams with high throughput. It follows a distributed and scalable design, allowing it to handle large amounts of data and support high data ingestion rates.

At the core of Kafka's architecture are the following components:

• Topics: Topics are the primary data organization unit in Kafka. They represent a category or feed name to which messages are published. Messages published to a topic are stored in an append-only log structure.

• Producers: Kafka Producers are the entities responsible for publishing messages to Kafka topics. They write data to Kafka as records consisting of a key, value, and optional metadata. Producers can choose which topic to publish to and specify a partition key to control how records are distributed across partitions.

• Brokers: Brokers form the cluster of servers in Kafka. They are responsible for storing and handling the publish-subscribe messaging system. Each broker manages one or more partitions of each topic. Brokers are stateless and can scale horizontally, allowing for high availability and fault tolerance.

• Partitions: Topics are divided into multiple partitions, which are ordered, immutable sequences of records. Each partition is hosted on a single broker within the cluster, and multiple partitions allow for parallel processing and increased throughput.

• Consumers: Kafka Consumers read messages from Kafka topics. They can subscribe to one or more topics and consume data at their own pace. Consumer groups enable parallel processing of messages, where each consumer within a group reads from a unique partition. This allows for scalable and efficient processing of data.

• Connectors: Kafka Connect is a framework for building and running connectors that enable the integration of Kafka with external systems. Connectors allow for easily ingesting data from and outputting data to various sources and sinks.

• Streams: Kafka Streams is a client library that allows for building real-time streaming applications that process data in Kafka. It provides an API for consuming, processing, and producing data streams, enabling the creation of applications such as event-driven architectures and real-time analytics.

Integrating PubNub with Kafka

Enterprise technologies such as Kafka are generating more insights than ever, but how do you turn these into actions?

The PubNub Bridge for Kafka runs side-by-side with your other on-premise enterprise systems to provide a secure, scalable, and highly available mechanism to integrate with PubNub. By connecting PubNub with your Kafka instance, you can:

• Integrate mobile app event notifications without writing code or opening firewalls, allowing you to interface with mobile workers and enable Bring your own Device (BYOD) use cases for your enterprise employees

• Grant access to your shared event stream across teams, without additional business routing logic or segmentation, enabling collaboration across your organization with data access audit trails.

For more information on our PubNub bridge for Kafka, see our developers page.