Graphql Schema update rollback

Question

We are moving some of our API's to graphql and would like to know to handle the rollback of the deployed package (Schema)and the best practice to the same.

To be more specific let's say we have a Schema S with 3 fields and then we added 4th field "A" . Now for some reason we cannot go forward with this package and field "A". So we have to perform roll back of the package so that now the Schema doesn't have field "A".

Now some consumer might ask for this field "A" and he might get an error. We could of course ask our clients to update but there is a time gap during which we might have failed request.

How do we handle this scenario,specifically an urgent rollback with in few hours or a day?

Answer 1

In general, you should avoid removing fields without warning to avoid the exact scenario you describe.

As your schema evolves, it's not uncommon to have some fields that are no longer needed. For example, rather than introducing a drastic change to a particular field (moving from a nullable to a non-nullable return type, adding required arguments, etc.), we may opt to add another field and encourage clients to transition to using that one instead. In such scenarios, we want to eventually remove the original field. The safest way to do so is to deprecate the field first. Using SDL, we can do so using a directive:

fieldA: String @deprecated(reason: "Use fieldB instead!")

After a certain amount of time, you can then remove the field entirely. How long you wait to remove the field depends on your team and the expectations you've communicated around handling deprecated fields. For example, you may find it helpful to set a deadline, by which point all clients are expected to have stopped using any deprecated fields. This works well as long as your client teams have the bandwidth to handle such technical debt.

A deprecated field's resolver can be changed to return a null value (if the field itself is nullable) or some minimal mock data. This prevents making unnecessary API or database calls, while still ensuring client requests don't result in an error.

In the context of your question, this means you should probably avoid rolling back to a previous release and instead follow the process outlined above for the fields you want to remove.

Alternatively, you could consider versioning. GraphQL generally shies away from the concept of versioning. As the official site explains:

Why do most APIs version? When there's limited control over the data that's returned from an API endpoint, any change can be considered a breaking change, and breaking changes require a new version. If adding new features to an API requires a new version, then a tradeoff emerges between releasing often and having many incremental versions versus the understandability and maintainability of the API.

In contrast, GraphQL only returns the data that's explicitly requested, so new capabilities can be added via new types and new fields on those types without creating a breaking change. This has led to a common practice of always avoiding breaking changes and serving a versionless API.

With that in mind, it's also feasible to still implement versioning with GraphQL by serving different schemas from different endpoints. While it's costly and usually unnecessary to go that route, it may be the right solution for you and your team, particularly if you expect to have to do similar rollbacks in the future.

Answer 2

You cannot do anything w.r.t GraphQL. Since you need to have the field present in the GraphQL type system. There may be libraries available, which will allow you to specify whether the field should be present in the query or not. But, there's no way of allowing non-existent field in the Query.

But what you can do is opt for a Blue-Green deployment strategy. In this strategy, you have both the versions running at the same time.

Let's say: Green is the version with Field A and Blue is the version without Field A. So when your clients are updated they start requesting the Blue version. And once all your clients are updated, shut-down the Green (with Field A).