Federation Supergraph

You can use GraphQL Mesh as a [Federation](https://the-guild.dev/graphql/hive/federation ] supergraph in multiple ways. You can either provide each source, and let Mesh build your supergraph, or you can provide prebuilt Supergraph SDL.

Consuming prebuilt Supergraph SDL

If you use Apollo Rover CLI or GraphQL Hive  to compose your subgraphs, you can easily consume the prebuilt supergraph SDL by using Supergraph handler;

npm i @graphql-mesh/supergraph

pnpm add @graphql-mesh/supergraph

yarn add @graphql-mesh/supergraph

bun add @graphql-mesh/supergraph

sources:
  - name: Supergraph
    handler:
      supergraph:
        source: http://some-source.com/supergraph.graphql # it can be a path from the file system `./supergraph.graphql`
        schemaHeaders:
          myTokenHeader: MY_TOKEN_VALUE

Configuring subgraphs within the supergraph

You can also configure subgraphs within the supergraph by providing the subgraph name in order to change the endpoint and headers for each subgraph.

sources:
  - name: Supergraph
    handler:
      supergraph:
        source: http://some-source.com/supergraph.graphql
        subgraphs:
          - name: accounts
            endpoint: http://localhost:9871/graphql
            operationHeaders: # You can use context variables here
              Authorization: "Bearer {context.headers['x-accounts-token']}"
          - name: reviews
            endpoint: '{env.REVIEWS_ENDPOINT:https://default-reviews.com/graphql}'
            operationHeaders:
              Authorization: "Bearer {context.headers['x-reviews-token']}"

Config API Reference

• source (type: String, required) - A url to your WSDL or generated SDL with annotations
• schemaHeaders (type: Any) - JSON object representing the Headers to add to the runtime of the API calls only for schema introspection You can also provide .js or .ts file path that exports schemaHeaders as an object
• operationHeaders (type: JSON) - JSON object representing the Headers to add to the runtime of the API calls only for operation during runtime
• bodyAlias (type: String) - The name of the alias to be used in the envelope for body components

default: body

• soapHeaders (type: Object) - SOAP Headers to be added to the request:
  • alias (type: String) - The name of the alias to be used in the envelope

default: header

• namespace (type: String, required) - The namespace of the SOAP Header For example: http://www.example.com/namespace
• headers (type: JSON, required) - The content of the SOAP Header For example: { “key”: “value” } then the content will be <key>value</key>
• soapNamespace (type: String) - The namespace of the SOAP envelope By default, SOAP handler detects the SOAP version and if SOAP version is 1.1, it uses http://schemas.xmlsoap.org/soap/envelope/ namespace If SOAP version is 1.2, it uses http://www.w3.org/2003/05/soap-envelope namespace

Using Mesh to build the supergraph

You can provide the existing subgraphs within GraphQL Mesh, or you can use Federation Subgraph to create subgraphs from regular sources.

sources:
  - name: accounts
    handler:
      graphql:
        endpoint: http://localhost:9871/graphql
    transforms:
      - federation:
          types:
            - name: User
              config:
                key:
                  - fields: id
                resolveReference:
                  queryFieldName: user
                  args:
                    id: '{root.id}'
  - name: reviews
    handler:
      graphql:
        endpoint: http://localhost:9872/graphql
  - name: products
    handler:
      graphql:
        endpoint: http://localhost:9873/graphql
  - name: inventory
    handler:
      graphql:
        endpoint: http://localhost:9874/graphql

You can check our working example on the repo.