Apollo Federation v2 — Overview

fastql.federation adds Apollo Federation v2 support to any FastQL schema: federation directives as applied-directive metadata, a federated-SDL printer with the @link import header, and the _service / _entities machinery for entity resolution.

Installation

Federation support is built into FastQL — no extra install required. Import from fastql.federation:

from fastql.federation import (
    key, shareable, reference_resolver, print_federated_schema,
)

Defining a federated schema

Decorate types with federation directives and build a regular Schema. FastQL injects the _service { sdl } root, the _Any / _Entity / _Service types, and the _entities(representations:) root field automatically.

from fastql import Field, Query, Schema, Type
from fastql.federation import key, shareable, print_federated_schema


@Type(directives=[key("id"), shareable()])
class Product:
    id: str
    name: str


@Query
class QueryRoot:
    @Field
    def product(self, id: str) -> Product | None:
        return PRODUCTS.get(id)


schema = Schema(query=QueryRoot)
sdl = print_federated_schema(schema)   # includes the @link(url: ...) header

print_federated_schema produces the federation-annotated SDL that the Apollo Router ingests as the subgraph SDL.

Available directive helpers

Helper	SDL directive	Placement
`key(fields)`	`@key(fields: ...)`	`@Type(directives=[...])`
`shareable()`	`@shareable`	`@Type` or `@Field`
`external()`	`@external`	`@Field`
`requires(fields)`	`@requires(fields: ...)`	`@Field`
`provides(fields)`	`@provides(fields: ...)`	`@Field`
`inaccessible()`	`@inaccessible`	`@Type` or `@Field`
`override(from_subgraph)`	`@override(from: ...)`	`@Field`
`tag(name)`	`@tag(name: ...)`	`@Type` or `@Field`

All helpers are applied via @Type(directives=[...]) or @Field(directives=[...]).

Next: Entity resolution — @key and reference resolvers.

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Apollo Federation v2 — Overview

Installation

Defining a federated schema

Available directive helpers

​Installation

​Defining a federated schema

​Available directive helpers

Installation

Defining a federated schema

Available directive helpers