52 lines
1.8 KiB
Markdown
52 lines
1.8 KiB
Markdown
# Apollo Federation
|
|
|
|
`Apollo Federation` is a `GraphQL` API gateway which can combine multiple GraphQL services, allowing each service to implement the subset of the API it is responsible for. You can read more in the [official documentation](https://www.apollographql.com/docs/apollo-server/federation/introduction).
|
|
|
|
`Async-graphql` supports all the functionality of `Apollo Federation`, but some modifications to your `Schema` are required.
|
|
|
|
- You can use the `extends` property declaration on `async_graphql::Object` and `async_graphql::Interface` to extend a type offered by another implementing service.
|
|
|
|
- The `external` property declares that a field comes from another service。
|
|
|
|
- The `provides` property indicates the fields provided by a service.
|
|
|
|
## Entity lookup function
|
|
|
|
```rust
|
|
struct Query;
|
|
|
|
#[Object]
|
|
impl Query {
|
|
#[entity]
|
|
async fn find_user_by_id(&self, id: ID) -> User {
|
|
User { ... }
|
|
}
|
|
|
|
#[entity]
|
|
async fn find_user_by_id_with_username(&self, #[graphql(key)] id: ID, username: String) -> User {
|
|
User { ... }
|
|
}
|
|
|
|
#[entity]
|
|
async fn find_user_by_id_and_username(&self, id: ID, username: String) -> User {
|
|
User { ... }
|
|
}
|
|
}
|
|
```
|
|
|
|
**Notice the difference between these three lookup functions, which are all looking for the `User` object.**
|
|
|
|
- `find_user_by_id`
|
|
|
|
Use `id` to find an `User` object, the key for `User` is `id`.
|
|
|
|
- `find_user_by_id_with_username`
|
|
|
|
Use `id` to find an `User` object, the key for `User` is `id`, and the `username` field value of the `User` object is requested.
|
|
|
|
- `find_user_by_id_and_username`
|
|
|
|
Use `id` and `username` to find an `User` object, the keys for `User` are `id` and `username`.
|
|
|
|
For a complete example, refer to: <https://github.com/async-graphql/examples/tree/master/federation>.
|