How to set different header for different subgraph via ApolloGateway?

Question

I am using Apollo gateway to build a graphql federation service. Below is the demo code:

const gateway = new ApolloGateway({
  supergraphSdl: new IntrospectAndCompose({
    subgraphs: [
      { name: 'products', url: 'https://products-service.dev/graphql' },
      { name: 'reviews', url: 'https://reviews-service.dev/graphql' },
    ],
    introspectionHeaders: {
      Authorization: 'Bearer abc123',
    },
  }),
});

As you can see there are 2 subgraphs products and reviews, and there is also a introspectionHeaders which gives authorization. My questions is:

• How can I specify different header for different subgraph? In above example, the header applies on both subgraph

Answer 1

you can use use buildService...something this:

  const authMap = {
    'products': 'abc',
     'reviews': 'xyz'
  }

  const gateway = new ApolloGateway({
    supergraphSdl: new IntrospectAndCompose({
      subgraphs: [
         { name: 'products', url: 'https://products-service.dev/graphql' },
         { name: 'reviews', url: 'https://reviews-service.dev/graphql' },
      ]
    }),
    buildService (item: ServiceEndpointDefinition) {
      const { url, name } = item
      return new RemoteGraphQLDataSource({
        url,
        willSendRequest (options: any) {
          const { request } = options
          request.http.headers.set('Authorization' `Bearer ${authMap[name]}`)
        }
      })
    }
  })