Working with supergraphs

A supergraph (also called a federated graph) is a graph composed of multiple subgraphs:

Rover commands that interact with supergraphs begin with rover supergraph. These commands primarily deal with composition of a supergraph schema that adheres to the core schema specification.

Composing a supergraph schema

You can use the supergraph compose command to compose a supergraph schema based on a provided subgraph configuration file:

rover supergraph compose --config ./supergraph.yaml

Configuration

The supergraph compose command's --config option expects the path to a YAML file that contains a list of all subgraphs:

subgraphs:
  films:
    routing_url: https://films.example.com
    schema: 
      file: ./films.graphql
  people:
    routing_url: https://people.example.com
    schema: 
      file: ./people.graphql

In the above example, The YAML file specifies each subgraph's public-facing URL (routing_url), along with the path to its schema (schema.file).

It's also possible to pull subgraphs from various sources and specify them in the YAML file. For example, here is a configuration that specifies schema using Apollo Registry refs (subgraph, graphref) and subgraph introspection (subgraph_url):

subgraphs:
  films:
    routing_url: https://films.example.com
    schema: 
      file: ./films.graphql
  people:
    routing_url: https://example.com/people
    schema: 
      subgraph_url: https://example.com/people
  actors:
    routing_url: https://localhost:4005
    schema: 
      graphref: mygraph@current 
      subgraph: actors 

Output format

By default, supergraph compose outputs a supergraph schema document to stdout. This will be useful for providing the schema as input to other Rover commands in the future.

You can also save the output to a local .graphql file like so:

# Creates prod-schema.graphql or overwrites if it already exists
rover supergraph compose --config ./supergraph.yaml > prod-schema.graphql

For more on passing values via stdout, see Using stdout.