Grafbase and Strawberry federation

Mobilis can generate a local Federation v2 graph with a Grafbase Gateway and FastAPI subgraphs. Strawberry defines each subgraph in Python; Mobilis copies that source into the generated service's installable package. The gateway composes the running subgraphs and serves the resulting supergraph schema.

ruby

sites = fastapi("sites", publish_port: false) do |service|
  service.graphql_subgraph("sites", source: "schemas/sites_schema.py")
end
deployments = fastapi("deployments", publish_port: false) do |service|
  service.graphql_subgraph("deployments", source: "schemas/deployments_schema.py")
end
gateway = grafbase("gateway", port: 5000)
connect(from: gateway, to: sites)
connect(from: gateway, to: deployments)

The supplied Python module must export a strawberry.federation.Schema named schema. Mobilis installs strawberry-graphql[fastapi] and mounts GraphQLRouter at /graphql. Query fields, mutations, entity keys, resolve_reference, and application behavior live in that module. The generator does not create placeholder business resolvers or translate SDL into Python. Service routes.py and other packaged source files remain available for custom logic.

Connect a subgraph to PostgreSQL using the usual connect edge. Its GraphQL context receives a request-scoped SQLAlchemy session that closes at the end of the request. graphql_support.py supplies load_by_ids and grouped_loader for bounded batch queries; a resolver can keep a loader in info.context["loaders"] so multiple entity fields share one batch per request. Synchronous SQLAlchemy work should run through starlette.concurrency.run_in_threadpool in async Strawberry resolvers. Exceptions propagate as GraphQL errors. Database migrations and schema ownership remain the application's responsibility.

The gateway connection graph is the subgraph registry. Only connected FastAPI services with a declared subgraph are composed. Each subgraph must be healthy before a short-lived composer service invokes grafbase compose; composition failure stops gateway startup and leaves Grafbase's diagnostics in ./dc_dev logs gateway-composer. On success, the generated supergraph.graphql is stored in a Compose volume and the official Grafbase Gateway image starts in air-gapped mode with that file. No Grafbase account or hosted registry is needed. The DSL's port: is the published host port; the gateway listens internally on 5000. Its default health endpoint is /health. The generated project uses pinned versions from ContainerVersions.

Run the numbered example and its generated integration test:

bundle exec ruby -Ilib scripts/24_grafbase_federation.rb
cd generate
./sites/demo/integration

The script seeds two PostgreSQL databases, validates a query traversing Site.name from Sites and Site.deployments from Deployments, tests a mutation and malformed entity key, and proves that incompatible Site.id types fail real Grafbase composition. After startup, execute the federated query directly against the published gateway port:

curl -fsS http://localhost:5000/graphql \
  -H 'Content-Type: application/json' \
  --data '{"query":"{ sites { id name deployments { id status } } }"}'

The generated project runs without Mobilis after generation. The demonstration uses local credentials and data; do not treat its two databases or one gateway as a production availability design.

Set FEDERATION_DEMO_OTEL=1 before generating to connect the gateway and both subgraphs to an OpenTelemetry collector. Grafbase exports spans and propagates W3C traceparent to subgraphs; FastAPI instruments incoming HTTP requests and SQLAlchemy operations using the existing connection-based telemetry setup. Without collector connections, no exporter endpoint is configured and the services run normally. The generated schema source remains independent of telemetry.

This integration was tested with Strawberry Federation 2.5, Grafbase Gateway 0.53.5, and the published Grafbase CLI 0.105.1. It does not imply that all Federation v2 directives or newer Strawberry defaults are supported by this combination. Validate additional directives with the pinned composer and gateway before adopting them. Grafbase's repository says its hosted platform has sunsetted and the gateway and CLI are in maintenance mode; the local, air-gapped path here does not depend on that platform. REST wrapping and broader resolver generation are future work.

Grafbase and Strawberry federation ​

Grafbase and Strawberry federation