Iceberg REST Catalog Overview #1 — Introduction

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The Apache Iceberg project has become a cornerstone for modern data lakehouses, offering advanced table formats that improve performance, consistency, and interoperability. As Iceberg adoption has grown, so has the need for a standardized way for different catalog implementations to communicate with client applications seamlessly. This is where the Iceberg REST Catalog API comes into play.

Let’s explore each endpoint of the Iceberg REST Catalog API, discussing how it facilitates everyday table operations across different catalog implementations. But before diving into the individual endpoints, let’s first introduce the broader specification and its purpose.

Why a REST Catalog API?

Apache Iceberg has a diverse ecosystem of catalog implementations, from Hive Metastore and AWS Glue to standalone catalogs. However, managing Iceberg tables across different catalogs has historically required custom integrations, making interoperability a challenge.

The Iceberg REST Catalog API provides a universal standard for server-client communication, ensuring that Iceberg clients can interact with any compliant catalog, regardless of the server implementation's underlying technology or programming language.

By adopting this RESTful approach, Iceberg enables:

• Interoperability — A standard API that multiple catalog implementations can use, making it easier to switch between or integrate with different catalogs.
• Language Agnosticism — The REST API allows Iceberg clients to interact consistently with catalogs written in any language (Python, Java, etc.).
• Cloud-Native Flexibility — Since HTTP-based, the API is well-suited for cloud environments where RESTful interactions are standard.

The Foundation of the REST Catalog API

The API is formally defined using OpenAPI 3.1.1, ensuring a clear and structured specification that different catalog implementations can easily adopt. Below is the introductory section of the specification, highlighting the licensing and API metadata:

Licensed to the Apache Software Foundation (ASF) under one  
or more contributor license agreements. See the NOTICE file  
distributed with this work for additional information  
regarding copyright ownership. The ASF licenses this file  
to you under the Apache License, Version 2.0 (the "License");  
you may not use this file except in compliance with the License.  
You may obtain a copy of the License at:  

https://www.apache.org/licenses/LICENSE-2.0  
Unless required by applicable law or agreed to in writing, software  
distributed under the License is distributed on an "AS IS" BASIS,  
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
See the License for the specific language governing permissions and  
limitations under the License.        

This section ensures that the API follows Apache’s open-source licensing model, making it freely available for any organization to implement and extend.

Further, the API metadata defines:

• Title: Apache Iceberg REST Catalog API
• License: Apache 2.0
• Version: 0.0.1 (initial draft version)
• Description: Specification for the first version of the REST Catalog API, supporting both Iceberg v1 and v2 table formats, with a preference for v2.

How the API is Structured

The REST Catalog API is designed with flexibility in mind, allowing for different configurations depending on the environment:

Default Server URL

{scheme}://{host}/{basePath}        

• A generic format where the scheme (HTTP/HTTPS), host, and basePath are configurable.

Custom Port Support

{scheme}://{host}:{port}/{basePath}        

• Similar to the default, but explicitly allowing the specification of a port (e.g., 443 for HTTPS).

Security and Authentication

• Supports OAuth2 authentication (catalog scope).
• Supports Bearer token authentication for secure interactions.

These features make the API adaptable across cloud and on-prem environments, ensuring it can be implemented in traditional enterprise data warehouses and modern, distributed data lakehouses.

What’s Next?

Now that we’ve introduced the Iceberg REST Catalog API, the following blogs in this series will dive into each endpoint, explaining their role in managing namespaces, tables, transactions, and more.

Stay tuned as we explore:

• Namespace Management: Creating, listing, and modifying namespaces.
• Table Operations: Creating, updating, and deleting Iceberg tables.
• Transaction and Metadata Handling: How Iceberg catalogs track snapshots and commit changes.
• Scan Planning & Query Optimization: Enhancing query execution with efficient data retrieval strategies.

Each blog will provide practical examples and use cases, helping you understand how to work with the API in real-world scenarios.

Conclusion

The Apache Iceberg REST Catalog API makes Iceberg table management more accessible, portable, and standardized across catalogs. With this API, organizations can future-proof their data lakehouses by avoiding vendor lock-in and enabling smooth interoperability between different tools and platforms.

In the next installment, we’ll explore namespace management and how it helps structure datasets in Iceberg catalogs.