Evolving Your GraphQL API: Strategies for Managing Breaking Changes
As your application grows and user needs change, your GraphQL API must adapt to these changes. Introducing breaking changes to the schema can be risky, potentially causing bugs or unexpected behavior in the application. Breaking changes include removing types, fields, or directives, or modifying existing fields or directives.
Versioning vs. Evolution: Two Approaches to Managing Breaking Changes
There are two main strategies for managing breaking changes: versioning and evolution. REST APIs use versioning, where breaking changes are added to a new version of the API, and clients must explicitly point to the new version. GraphQL, on the other hand, encourages evolution, where changes are made incrementally and continuously.
The Evolution Process
When introducing breaking changes, fields must go through a process of re-implementation, deprecation, and eventual removal. This process allows clients to adapt to the changes without disruption.
Challenges of Evolution
While evolution is a more agile approach, it poses some challenges. One issue is finding optimal names for replaced fields, as the original name may be taken. Another challenge is dealing with deprecated fields, which can accumulate and clutter the schema.
Versioning Fields: A Solution to Evolution Challenges
One approach to overcome these challenges is to version fields independently. This can be achieved by adding a version argument to the field, allowing clients to specify which version to use. This approach keeps the contract of the schema hidden, preventing verbosity and clutter.
Providing Contextual Feedback
GraphQL currently lacks good contextual information when running queries. Providing deprecation information and warnings about versioned fields can help developers revise outdated queries. This can be achieved by adding a deprecations top-level entry to the response format.
Strategies for Versioning
There are several approaches to versioning, including making versionConstraint mandatory, using the old version by default until a certain date, and using the latest version by default. Each strategy has its advantages and disadvantages, and the best approach depends on the context.
Versioning Directives
Directives can also be versioned using the same methodology as fields. This allows for more flexibility and control over the API.
Combining Versioning and Evolution
By combining versioning and evolution, you can create an API that is both agile and flexible. This approach allows for continuous evolution of the schema while providing control over breaking changes.
Implementing Versioning in Your GraphQL Server
While this strategy is promising, its implementation may vary depending on the GraphQL server. Some servers may already support custom data under the extensions entry in the response format. Even without this enhanced feedback, you can still version fields and directives to avoid naming conflicts and clutter.