/**
- GraphQL Federation Gateway (federation_gateway.ts)
- Minimal gateway prototype that merges two simple schemas and forwards requests.
- For a production gateway use Apollo Federation or GraphQL Mesh.
- Usage:
- ts-node src/federation_gateway.ts */ import express from 'express'; import fetch from 'node-fetch'; import { buildSchema, graphql } from 'graphql';
// Demo schemas (in reality these are remote services)
const schemaA = buildSchema(type User { id: ID!, name: String! } type Query { userById(id: ID!): User });
const rootA = {
userById: ({ id }: any) => ({ id, name: User-${id} })
};
const schemaB = buildSchema(type Post { id: ID!, authorId: ID!, title: String! } type Query { postsByAuthor(authorId: ID!): [Post] });
const rootB = {
postsByAuthor: ({ authorId }: any) => ([{ id: 'p1', authorId, title: 'Hello World' }])
};
// Gateway composes: Query userAndPosts(id) -> fetch from both
const gatewaySchema = buildSchema(type User { id: ID!, name: String! } type Post { id: ID!, authorId: ID!, title: String! } type UserAndPosts { user: User, posts: [Post] } type Query { userAndPosts(id: ID!): UserAndPosts });
const gatewayRoot = {
userAndPosts: async ({ id }: any) => {
const u = (await graphql(schemaA, { userById(id: "${id}") { id name } }, rootA)).data?.userById;
const p = (await graphql(schemaB, { postsByAuthor(authorId: "${id}") { id authorId title } }, rootB)).data?.postsByAuthor;
return { user: u, posts: p };
}
};
const app = express(); app.use(express.json()); app.post('/graphql', async (req, res) => { const q = req.body.query; const r = await graphql(gatewaySchema, q, gatewayRoot); res.json(r); });
app.listen(8081, () => console.log('Federation gateway listen :8081'));