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GraphQLOverWebSocket

Coherent, zero-dependency, lazy, simple, GraphQL over WebSocket Protocol compliant server and client.

Continuous integration graphql-transport-ws


Getting started

Install

$ yarn add graphql-transport-ws

Create a GraphQL schema

import { buildSchema } from 'graphql';

// Construct a schema, using GraphQL schema language
const schema = buildSchema(`
  type Query {
    hello: String
  }
  type Subscription {
    greetings: String
  }
`);

// The roots provide resolvers for each GraphQL operation
const roots = {
  query: {
    hello: () => 'Hello World!',
  },
  subscription: {
    greetings: async function* sayHiIn5Languages() {
      for (const hi of ['Hi', 'Bonjour', 'Hola', 'Ciao', 'Zdravo']) {
        yield { greetings: hi };
      }
    },
  },
};

Start the server

import https from 'https';
import { execute, subscribe } from 'graphql';
import { createServer } from 'graphql-transport-ws';

const server = https.createServer(function weServeSocketsOnly(_, res) {
  res.writeHead(404);
  res.end();
});

createServer(
  {
    schema, // from the previous step
    roots, // from the previous step
    execute,
    subscribe,
  },
  {
    server,
    path: '/graphql',
  },
);

server.listen(443);

Use the client

import { createClient } from 'graphql-transport-ws';

const client = createClient({
  url: 'wss://welcomer.com/graphql',
});

// query
(async () => {
  const result = await new Promise((resolve, reject) => {
    let result;
    client.subscribe(
      {
        query: '{ hello }',
      },
      {
        next: (data) => (result = data),
        error: reject,
        complete: () => resolve(result),
      },
    );
  });

  expect(result).toEqual({ hello: 'Hello World!' });
})();

// subscription
(async () => {
  const onNext = () => {
    /**/
  };

  await new Promise((resolve, reject) => {
    client.subscribe(
      {
        query: 'subscription { greetings }',
      },
      {
        next: onNext,
        error: reject,
        complete: resolve,
      },
    );
  });

  expect(onNext).toBeCalledTimes(5); // we say "Hi" in 5 languages
})();

Recipes

Client usage with Promise 
import { createClient, SubscribePayload } from 'graphql-transport-ws';

const client = createClient({
  url: 'wss://hey.there/graphql',
});

async function execute<T>(payload: SubscribePayload) {
  return new Promise((resolve, reject) => {
    let result: T;
    client.subscribe<T>(payload, {
      next: (data) => (result = data),
      error: reject,
      complete: () => resolve(result),
    });
  });
}

// use
(async () => {
  try {
    const result = await execute({
      query: '{ hello }',
    });
    // complete
    // next = result = { data: { hello: 'Hello World!' } }
  } catch (err) {
    // error
  }
})();
Client usage with Observable 
import { Observable } from 'relay-runtime';
// or
import { Observable } from '@apollo/client';
// or
import { Observable } from 'rxjs';
// or
import Observable from 'zen-observable';
// or any other lib which implements Observables as per the ECMAScript proposal: https://github.com/tc39/proposal-observable

const client = createClient({
  url: 'wss://graphql.loves/observables',
});

function toObservable(operation) {
  return new Observable((observer) => client.subscribe(operation, observer));
}

const observable = toObservable({ query: `subscription { ping }` });

const subscription = observable.subscribe({
  next: (data) => {
    expect(data).toBe({ data: { ping: 'pong' } });
  },
});

// ⏱

subscription.unsubscribe();
Client usage with Relay 
import {
  Network,
  Observable,
  RequestParameters,
  Variables,
} from 'relay-runtime';
import { createClient } from 'graphql-transport-ws';

const subscriptionsClient = createClient({
  url: 'wss://i.love/graphql',
  connectionParams: () => {
    const session = getSession();
    if (!session) {
      return {};
    }
    return {
      Authorization: `Bearer ${session.token}`,
    };
  },
});

// yes, both fetch AND subscribe handled in one implementation
function fetchOrSubscribe(operation: RequestParameters, variables: Variables) {
  return Observable.create((sink) => {
    if (!operation.text) {
      return sink.error(new Error('Operation text cannot be empty'));
    }
    return subscriptionsClient.subscribe(
      {
        operationName: operation.name,
        query: operation.text,
        variables,
      },
      {
        ...sink,
        error: (err) => {
          if (err instanceof Error) {
            sink.error(err);
          } else if (err instanceof CloseEvent) {
            sink.error(
              new Error(
                `Socket closed with event ${err.code}` + err.reason
                  ? `: ${err.reason}` // reason will be available on clean closes
                  : '',
              ),
            );
          } else {
            // GraphQLError[]
            sink.error(new Error(err.map(({ message }) => message).join(', ')));
          }
        },
      },
    );
  });
}

export const network = Network.create(fetchOrSubscribe, fetchOrSubscribe);
Client usage with Apollo 
import { ApolloLink, Operation, FetchResult, Observable } from '@apollo/client';
import { createClient, Config, Client } from 'graphql-transport-ws';

class WebSocketLink extends ApolloLink {
  private client: Client;

  constructor(config: Config) {
    super();
    this.client = createClient(config);
  }

  public request(operation: Operation): Observable<FetchResult> {
    return new Observable((sink) => {
      return this.client.subscribe<FetchResult>(operation, {
        ...sink,
        error: (err) => {
          if (err instanceof Error) {
            sink.error(err);
          } else if (err instanceof CloseEvent) {
            sink.error(
              new Error(
                `Socket closed with event ${err.code}` + err.reason
                  ? `: ${err.reason}` // reason will be available on clean closes
                  : '',
              ),
            );
          } else {
            // GraphQLError[]
            sink.error(new Error(err.map(({ message }) => message).join(', ')));
          }
        },
      });
    });
  }
}

const link = new WebSocketLink({
  url: 'wss://where.is/graphql',
  connectionParams: () => {
    const session = getSession();
    if (!session) {
      return {};
    }
    return {
      Authorization: `Bearer ${session.token}`,
    };
  },
});
Client usage in Node 
const WebSocket = require('ws'); // yarn add ws
const Crypto = require('crypto');
const { createClient } = require('graphql-transport-ws');

const client = createClient({
  url: 'wss://no.browser/graphql',
  webSocketImpl: WebSocket,
  /**
   * Generates a v4 UUID to be used as the ID.
   * Reference: https://stackoverflow.com/a/2117523/709884
   */
  generateID: () =>
    ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, (c) =>
      (c ^ (Crypto.randomBytes(1)[0] & (15 >> (c / 4)))).toString(16),
    ),
});

// consider other recipes for usage inspiration
Server usage with Express GraphQL 
import https from 'https';
import express from 'express';
import { graphqlHTTP } from 'express-graphql';
import { createServer } from 'graphql-transport-ws';
import { execute, subscribe } from 'graphql';
import { schema } from 'my-graphql-schema';

// create express and middleware
const app = express();
app.use('/graphql', graphqlHTTP({ schema }));

// create a http server using express
const server = https.createServer(app);

server.listen(443, () => {
  createServer(
    {
      schema,
      execute,
      subscribe,
    },
    {
      server,
      path: '/graphql', // you can use the same path too, just use the `ws` schema
    },
  );
});
Server usage with console logging 
import https from 'https';
import { execute, subscribe } from 'graphql';
import { createServer } from 'graphql-transport-ws';

const server = https.createServer(function weServeSocketsOnly(_, res) {
  res.writeHead(404);
  res.end();
});

createServer(
  {
    schema,
    execute: async (args) => {
      console.log('Execute', args);
      const result = await execute(args);
      console.debug('Execute result', result);
      return result;
    },
    subscribe: async (args) => {
      console.log('Subscribe', args);
      const subscription = await subscribe(args);
      // NOTE: `subscribe` can sometimes return a single result, I dont consider it here for sake of simplicity
      return (async function* () {
        for await (const result of subscription) {
          console.debug('Subscribe yielded result', { args, result });
          yield result;
        }
      })();
    },
    onConnect: (ctx) => {
      console.log('Connect', ctx);
      return true; // default behaviour - permit all connection attempts
    },
    onComplete: (ctx, msg) => {
      console.debug('Complete', { ctx, msg });
    },
  },
  {
    server,
    path: '/graphql',
  },
);

server.listen(443);

Documentation

Check the docs folder out for TypeDoc generated documentation.

How does it work?

Read about the exact transport intricacies used by the library in the GraphQL over WebSocket Protocol document.

Want to help?

File a bug, contribute with code, or improve documentation? Read up on our guidelines for contributing and drive development with yarn test --watch away!