graphql-sse

import express from 'express'; import { createHandler } from 'graphql-sse'; import { useServer } from 'graphql-sse/use/express'; // Or use/fastify, use/koa, etc. import { makeExecutableSchema } from '@graphql-tools/schema'; import { createClient } from 'graphql-sse'; // --- Server Setup --- const typeDefs = ` type Query { hello: String } type Subscription { countdown(from: Int!): Int! } `; const resolvers = { Query: { hello: () => 'world', }, Subscription: { countdown: { subscribe: async function* (_, { from }: { from: number }) { for (let i = from; i >= 0; i--) { await new Promise((resolve) => setTimeout(resolve, 1000)); yield { countdown: i }; } }, }, }, }; const schema = makeExecutableSchema({ typeDefs, resolvers }); const handler = createHandler({ schema }); const app = express(); app.use('/graphql/sse', useServer({ handler })); // Mount the SSE handler app.get('/health', (req, res) => res.send('OK')); const PORT = process.env.PORT || 4000; app.listen(PORT, () => { console.log(`Server listening on http://localhost:${PORT}/graphql/sse`); }); // --- Client Setup --- const client = createClient({ url: `http://localhost:${PORT}/graphql/sse` }); async function runSubscription() { const query = ` subscription Countdown($from: Int!) { countdown(from: $from) } `; const input = { from: 5 }; console.log('\nClient: Subscribing to countdown...'); try { for await (const result of client.iterate(query, input)) { console.log('Client: Received:', result.data?.countdown); if (result.data?.countdown === 0) { console.log('Client: Countdown finished.'); break; } } } catch (error) { console.error('Client: Subscription error', error); } } // Start the client subscription after a short delay to allow server to boot setTimeout(runSubscription, 2000);