subscriptions-transport-ws

(Work in progress!)

A GraphQL WebSocket server and client to facilitate GraphQL subscriptions.

subscriptions-transport-ws is an extension for GraphQL, and you can use it with any GraphQL client and server (not only Apollo).

See GitHunt-API and GitHunt-React for an example server and client integration.

Getting Started

Start by installing the package, using Yarn or NPM:

Using Yarn:
$ yarn add subscriptions-transport-ws

Or, using NPM:
$ npm install --save subscriptions-transport-ws

This command also installs this package's dependencies, including graphql-subscriptions.

Server

Starting with the server, create a new simple SubscriptionsManager, with a PubSub implementation:

import { SubscriptionManager, PubSub } from 'graphql-subscriptions';

const schema = {}; // Replace with your GraphQL schema object
const pubsub = new PubSub();

const subscriptionManager = new SubscriptionManager({
  schema,
  pubsub
});

Now, use your subscriptionManager, and create your SubscriptionServer:

import { createServer } from 'http';
import { SubscriptionServer } from 'subscriptions-transport-ws';

const WS_PORT = 5000;

// Create WebSocket listener server
const websocketServer = createServer((request, response) => {
  response.writeHead(404);
  response.end();
});

// Bind it to port and start listening
websocketServer.listen(WS_PORT, () => console.log(
  `Websocket Server is now running on http://localhost:${WS_PORT}`
));

const subscriptionManager = new SubscriptionServer(
  {
    onConnect: async (connectionParams) => {
      // Implement if you need to handle and manage connection
    },
    subscriptionManager: subscriptionManager
  },
  {
    server: websocketServer,
    path: '/'
  }
);

Client (browser)

For client side, we will use SubscriptionClient, and we also need to extend our network interface to use this transport for GraphQL subscriptions:

import {SubscriptionClient, addGraphQLSubscriptions} from 'subscriptions-transport-ws';
import ApolloClient, {createNetworkInterface} from 'apollo-client';

// Create regular NetworkInterface by using apollo-client's API:
const networkInterface = createNetworkInterface({
 uri: 'http://localhost:3000' // Your GraphQL endpoint
});

// Create WebSocket client
const wsClient = new SubscriptionClient(`ws://localhost:5000/`, {
    reconnect: true,
    connectionParams: {
        // Pass any arguments you want for initialization
    }
});

// Extend the network interface with the WebSocket
const networkInterfaceWithSubscriptions = addGraphQLSubscriptions(
    networkInterface,
    wsClient
);

// Finally, create your ApolloClient instance with the modified network interface
const apolloClient = new ApolloClient({
    networkInterface: networkInterfaceWithSubscriptions
});

Now, when you want to use subscriptions in client side, use your ApolloClient instance, with subscribe or subscribeToMore (according to your apollo-client usage):

apolloClient.subscribeToMore({
    document: gql`
        subscription onNewItem {
            newItemCreated {
                id
            }
        }`,
    variables: {},
    updateQuery: (prev, {subscriptionData}) => {
        return; // Modify your store and return new state with the new arrived data
    }
});

If you don't use any package/modules loader, you can still use this package, by using unpkg service, and get the client side package from:

https://unpkg.com/subscriptions-transport-ws@VERSION/browser/client.js

Replace VERSION with the latest version of the package.

API

SubscriptionClient

Constructor(url, options, connectionCallback)

• url: string : url that the client will connect to
• options?: Object : optional, object to modify default client behavior
  • timeout?: number : how long the client should wait in ms for a subscription to be started (default 5000 ms)how long the client should wait in ms for a subscription to be started (default 5000 ms)
  • connectionParams?: Object : object that will be available as first argument of onConnect (in server side)
  • reconnect?: boolean : automatic reconnect in case of connection error
  • reconnectionAttempts?: number : how much reconnect attempts
  • connectionCallback?: (error) => {} : optional, callback that called after the first init message, with the error (if there is one)
• webSocketImpl: Object - optional, WebSocket implementation. use this when your environment does not have a built-in native WebSocket (for example, with NodeJS client)

Methods

subscribe(options, handler) => id

• options: {SubscriptionOptions}
  • query: string : GraphQL subscription
  • variables: Object : GraphQL subscription variables
  • operationName: string : operation name of the subscription
• handler: (errors: Error[], result?: any) => void : function to handle any errors and results from the subscription response

unsubscribe(id) => void - unsubscribes from a specific subscription

• id: string : the subscription ID of the subscription to unsubscribe from

unsubscribeAll() => void - unsubscribes from all active subscriptions.

on(eventName, callback, thisContext) => Function

• eventName: string: the name of the event, available events are: connect, reconnect and disconnect
• callback: Function: function to be called when websocket connects and initialized.
• thisContext: any: this context to use when calling the callback function.
• => Returns an off method to cancel the event subscription.

onConnect(callback, thisContext) => Function - shorthand for .on('connect', ...)

• callback: Function: function to be called when websocket connects and initialized.
• thisContext: any: this context to use when calling the callback function.
• => Returns an off method to cancel the event subscription.

onReconnect(callback, thisContext) => Function - shorthand for .on('reconnect', ...)

• callback: Function: function to be called when websocket re-connects and initialized.
• thisContext: any: this context to use when calling the callback function.
• => Returns an off method to cancel the event subscription.

onDisconnect(callback, thisContext) => Function - shorthand for .on('disconnect', ...)

• callback: Function: function to be called when websocket disconnects.
• thisContext: any: this context to use when calling the callback function.
• => Returns an off method to cancel the event subscription.

Client-side helpers

addGraphQLSubscriptions(networkInterface, wsClient) => void

• networkInterface: any - network interface to extend with subscribe and unsubscribe methods.
• wsClient: SubscriptionClient - network interface to extend with subscribe and unsubscribe methods.

A quick way to add the subscribe and unsubscribe functions to the network interface

SubscriptionServer

Constructor(options, socketOptions)

• options: {ServerOptions}
  • subscriptionManager: SubscriptionManager : GraphQL subscription manager
  • onSubscribe?: (message: SubscribeMessage, params: SubscriptionOptions, webSocket: WebSocket) : optional method to create custom params that will be used when resolving this subscription
  • onUnsubscribe?: (webSocket: WebSocket) : optional method that called when a client unsubscribe
  • onConnect?: (connectionParams: Object, webSocket: WebSocket) : optional method that called when a client connects to the socket, called with the connectionParams from the client, if the return value is an object, its elements will be added to the context. return false or throw an exception to reject the connection. May return a Promise.
  • onDisconnect?: (webSocket: WebSocket) : optional method that called when a client disconnects
  • keepAlive?: number : optional interval in ms to send KEEPALIVE messages to all clients
• socketOptions: {WebSocket.IServerOptions} : options to pass to the WebSocket object (full docs here)
  • server?: HttpServer - existing HTTP server to use (use without host/port)
  • host?: string - server host
  • port?: number - server port
  • path?: string - endpoint path

Client-server communication

Each message has a type field, which defined in the protocol of this package, as well as associated fields depending on the message type.

Client -> Server

INIT

Client sends this message after connecting, this triggers onConnect on the server.

• payload: Object : optional parameters that the client specifies in connectionParams

SUBSCRIPTION_START

Client sends this message to start a subscription for a query.

• query: GraphQLDocument : GraphQL subscription
• variables: Object : GraphQL subscription variables
• operationName: string : operation name of the subscription
• id: string : subscription ID

SUBSCRIPTION_END

Client sends this message to end a subscription.

• id: string : subscription ID of the subscription to be terminated

Server -> Client

INIT_FAIL

The server sends this message if onConnect callback returns false or throws an exception. after sending this message, the server disconnects the client.

• payload: Object: the server side error

INIT_SUCCESS

The server sends this message if onConnect callback returns any other value then false.

SUBSCRIPTION_SUCCESS

The server sends this message to confirm that it has validated the subscription query and is subscribed to the triggers.

• id: string : ID of the subscription that was successfully set up

SUBSCRIPTION_FAIL

Server sends this message upon failing to register a subscription. It may also send this message at any point during the subscription to notify the client the the subscription has been stopped.

• payload: { errors: Array<Object> } : payload with an array of errors attributed to the subscription failing on the server
• id: string : subscription ID of the subscription that failed on the server

SUBSCRIPTION_DATA

GraphQL result sent periodically from server to client according to subscription.

• payload: GraphQLResult : GraphQL result from running the subscription
• id: string : subscription ID

KEEPALIVE

Server message sent periodically to keep the client connection alive.

Messages Flow

This is a demonstration of client-server communication, in order to get a better understanding of the protocol flow:

• Client creates a WebSocket instane using SubscriptionsClient object.
• Client sends INIT message to the server.
• Server calls onConnect callback with the init arguments and waits for init to finish, and return it's return value with INIT_SUCCESS, or INIT_FAIL in case of false or thrown exception from onConnect callback.
• Client gets INIT_SUCCESS and waits for the client's app to create subscriptions.
• App creates a subscription using subscribe client's API, and the SUBSCRIPTION_START message sent to the server.
• Server calls onSubscribe callback, and respondes with SUBSCRIPTION_SUCCESS in case of zero errors, or SUBSCRIPTION_FAIL if there is an problem with the subscription.
• Client get SUBSCRIPTION_SUCCESS and waits for data.
• App triggers PubSub's publication method, and the server published the event, passing it through the graphql-subscriptions package for filtering and resolving.
• Client recieves SUBSCRIPTION_DATA with the data, and handles it with apollo-client instance.