联邦GraphQLschema验证（FederatedGraphQLschemavalidation）

1. 安装相应的库

npm install @apollo/federation graphql

2. 在每个子服务的 schema 中添加 @key 指令

type Product @key(fields: "id") {
  id: ID!
  name: String!
  price: Float!
}

type Query {
  product(id: ID!): Product
}

3. 在网关服务中使用 federatedSchema 方法创建 schema

const { ApolloServer } = require('apollo-server');
const { ApolloGateway, RemoteGraphQLDataSource } = require('@apollo/gateway');
const { federatedSchema } = require('@apollo/federation');

const gateway = new ApolloGateway({
  serviceList: [
    { name: "products", url: "http://localhost:4001" },
    { name: "users", url: "http://localhost:4002" }
  ],
  buildService({ url }) {
    return new RemoteGraphQLDataSource({
      url,
      willSendRequest({ request, context }) {
        request.http.headers.set('user-id', context.userId || '');
      }
    });
  }
});

const server = new ApolloServer({
  schema: federatedSchema({ gateway }),
  context: ({ req }) => {
    const userId = req.headers.authorization || '';
    return { userId };
  }
});

server.listen().then(({ url }) => {
  console.log(`� Server ready at ${url}`);
});

4. 运行服务

node services/products.js
node services/users.js
node gateway.js

5. 对 schema 进行验证

npx graphql-cli validate --rules @apollo/federation/no-circular-references schema.graphql