API Versioning for the Bookshop API

Versioning is essential for maintaining and evolving the Bookshop API while ensuring backward compatibility. This page explains how to use versioning in the Bookshop API, recommended practices, and how to handle breaking changes.

Why Versioning Matters

Versioning helps to manage changes to the API without disrupting existing users. It allows the API to evolve with new features, improvements, or bug fixes, while ensuring that applications built on older versions continue to function correctly.

Versioning Strategy

The Bookshop API follows semantic versioning principles: vMAJOR.MINOR.PATCH, where:

• MAJOR: Increases when there are breaking changes that are not backward compatible.
• MINOR: Increases when adding new functionality in a backward-compatible manner.
• PATCH: Increases when making backward-compatible bug fixes.

Example Versions

• v1.0.0: Initial release of the Bookshop API.
• v1.1.0: Added a new endpoint for searching books by genre (non-breaking change).
• v2.0.0: Changed the data format returned by the GET /api/books endpoint (breaking change).

Specifying the API Version

The Bookshop API supports versioning via the URL path. The version is included at the beginning of the URL path, like so:

Example: Making a Versioned API Request

To fetch all books using version 1 of the API, you can make a request like this:

fetch('/api/v1/books', {
      method: 'GET',
      headers: {
          'Content-Type': 'application/json'
      }
  })
.then(response => response.json())
.then(data => console.log('Books:', data))
.catch(error => console.error('Error:', error));

Handling Breaking Changes

When making breaking changes, the version number should be incremented in the MAJOR position. For example, if the data format or required parameters change in a way that existing clients will not be able to handle, a new major version should be released.

Best Practices for Handling Breaking Changes

1. Deprecate Endpoints Gracefully Provide a deprecation notice in the API response headers (e.g., Deprecation: true) or in the response body. Give developers time to migrate to the new version.

2. Use Clear Documentation Clearly document changes in new versions and provide migration guides. Include information about deprecated features and recommended alternatives.

3. Support Multiple Versions Concurrently Keep supporting the previous major version(s) for a period of time to allow clients to transition to the new version.

4. Version All Endpoints Ensure that every endpoint includes the version number in the URL. This helps avoid ambiguity about which version is being accessed.

Deprecation Policy

The Bookshop API will maintain deprecated versions for a minimum of 6 months after a new major version is released. During this time, the older version will continue to receive critical bug fixes but will not receive new features.

• Notification: Deprecation notices will be added to the API documentation and responses for deprecated endpoints.
• End-of-Life: After the 6-month period, deprecated versions will be retired, and requests to retired versions will return a 410 Gone status.

Using Headers for Versioning (Alternative)

In addition to URL path versioning, the Bookshop API also supports versioning via custom request headers:

fetch('/api/books', {
      method: 'GET',
      headers: {
          'Content-Type': 'application/json',
          'Accept-Version': 'v1'
      }
  })
.then(response => response.json())
.then(data => console.log('Books:', data))
.catch(error => console.error('Error:', error));

While header-based versioning can be useful, URL path versioning is recommended for consistency and clarity.

Versioning Best Practices

1. Start with URL Path Versioning

   Including the version in the URL path is the most common approach and makes the API version explicit.

2. Use Semantic Versioning for Clarity

   Following the MAJOR.MINOR.PATCH pattern makes it easier for developers to understand the significance of each version change.

3. Communicate Changes Clearly

   When releasing a new version, update the documentation and provide release notes detailing the changes, especially if they are breaking.

4. Maintain Backward Compatibility Where Possible

   Try to avoid breaking changes, or if necessary, provide a clear migration path for users.

By following these versioning practices, you can ensure that the Bookshop API remains stable, reliable, and easy for developers to integrate with as it evolves.