Adapting Shopify API Code for Cursor-Based Pagination

Introduction

Shopify’s API is constantly evolving to provide better performance and functionality for developers. One significant change that has impacted many developers is the shift from page-based pagination to cursor-based pagination. This transition has brought about new challenges and opportunities for those working with Shopify’s API. In this blog post, we’ll explore the reasons behind this change, how it affects API calls, and how to adapt your code to work with the new pagination system.

The Shift from Page-Based to Cursor-Based Pagination

Why the Change?

Shopify made the decision to replace page-based pagination with cursor-based pagination for several reasons:

1. Improved Performance: Cursor-based pagination is more efficient, especially when dealing with large datasets.
2. Consistency: It provides a more consistent way to navigate through API results.
3. Scalability: As Shopify continues to grow, cursor-based pagination offers better scalability for handling increasing amounts of data.

When Did This Change Occur?

The transition to cursor-based pagination was implemented gradually:

• Some endpoints switched to cursor-based pagination in the 2019-07 API version.
• The remaining endpoints made the switch in the 2019-10 API version.

It’s important to note that older API versions (like 2019-04) still support page-based pagination, but these versions will eventually be phased out.

How Cursor-Based Pagination Works

Understanding the Link Header

With cursor-based pagination, the key to navigating through API results lies in the Link header of the API response. This header contains the URLs for the next and previous pages of results.

Here’s what you need to know about the Link header:

1. It’s included in the HTTP response headers, not in the JSON body of the response.
2. It contains links to both the next and previous pages (if they exist).
3. The format follows the RFC 5988 standard for web linking.

Parsing the Link Header

To work with cursor-based pagination, you’ll need to parse the Link header. Here’s an example of what it might look like:

Link: <https://your-store.myshopify.com/admin/api/2019-07/products.json?page_info=eyJsYXN0X2lkIjozOTc2...>; rel="next"

The important parts to extract are:

• The URL for the next (or previous) page
• The rel attribute, which indicates whether it’s a link to the “next” or “previous” page

Implementing Cursor-Based Pagination in Your Code

Making the Initial Request

When making your first API call, you can still use parameters like limit to control the number of results per page. For example:

GET /admin/api/2019-07/products.json?limit=50

Navigating to Subsequent Pages

To get the next page of results:

1. Check the Link header in the response.
2. Extract the URL for the “next” page.
3. Make a new API call using this URL.

Code Examples

Here’s a simple PHP function to extract the “next” URL from the Link header:

function getNextPageUrl($linkHeader) {
    if (preg_match('/<([^>]*)>;s*rel="next"/', $linkHeader, $matches)) {
        return $matches[1];
    }
    return null;
}

And here’s how you might use it in a loop to fetch all pages:

$url = "https://your-store.myshopify.com/admin/api/2019-07/products.json?limit=50";

do {
    $response = makeApiCall($url); // Your function to make API calls
    processResults($response->body); // Process the current page of results
    
    $linkHeader = $response->headers['Link'];
    $url = getNextPageUrl($linkHeader);
} while ($url !== null);

Common Issues and Solutions

Error: “page cannot be passed”

If you’re seeing an error like {"errors":{"page":"page cannot be passed."}}, it’s likely because you’re using an API version that no longer supports the page parameter. To resolve this:

1. Check which API version you’re using.
2. If you’re using 2019-07 or later, switch to cursor-based pagination.
3. If you need to use page-based pagination, consider using an older API version temporarily (e.g., 2019-04).

Missing Link Header

If you’re not seeing the Link header in your API responses:

1. Ensure you’re including the API version in your URL (e.g., /admin/api/2019-07/products.json).
2. Check that you have more than one page of results. If there’s only one page, there won’t be a “next” link.
3. Verify that you’re correctly accessing the headers in your API response.

Best Practices for Working with Cursor-Based Pagination

Use the Latest Stable API Version

While it may be tempting to stick with older versions that support page-based pagination, it’s best to adapt to the latest stable version to ensure you have access to the most up-to-date features and optimizations.

Implement Proper Error Handling

When working with cursor-based pagination, implement robust error handling to deal with scenarios such as:

• Missing Link headers
• Network errors when fetching subsequent pages
• Rate limiting issues

Optimize for Performance

While cursor-based pagination is generally more performant, you can further optimize your API usage by:

• Using appropriate limit values to balance between number of API calls and data processed per call
• Implementing caching mechanisms where appropriate
• Considering async requests for non-blocking operations

Conclusion

The transition from page-based to cursor-based pagination in Shopify’s API represents a significant improvement in terms of performance and scalability. While it may require some adjustments to your existing code, embracing this change will ultimately lead to more efficient and reliable integrations with Shopify’s platform.

By understanding how cursor-based pagination works, implementing proper parsing of the Link header, and following best practices, you can ensure that your Shopify integrations are robust and future-proof. As Shopify continues to evolve its API, staying informed about these changes and adapting your code accordingly will be crucial for maintaining successful e-commerce solutions.