APW - Apollo Phoenix Websocket

Apollo is a feature rich GQL client, APW implements an Apollo GraphQL Network Layer for it over Phoenix Channels allowing you to re-use a single bidirectional connection for executing your queries and mutations, the backend can send new data via subscriptions, and the Apollo client can update its internal store and update your views accordingly.

Since version 0.6.0, all Apollo operations are supported: queries, mutations, watchQueries (pooling) and subscriptions.

Using the Apollo Client, queries and mutations resolve to promises, and watchQueries and subscriptions resolve to observables.

See the Apollo client documentation for more info on how to invoke your GQL backend.

Installation

npm install --save apollo-phoenix-websocket

Usage

Just import the createNetworkInterface from APW and use it to create an ApolloClient.

The createNetworkInterface function takes an options object, the only required property is uri which specifies your endpoint websocket address.

import ApolloClient from 'apollo-client'
import {createNetworkInterface} from 'apollo-phoenix-websocket'

// Nothing to configure if you are using an Absinthe backend
// Otherwise take a look at the Options section.
const networkInterface = createNetworkInterface({uri: 'ws://localhost:4000/socket'})

const apollo = new ApolloClient({networkInterface})

Options

Most likely, (as you are looking for a phoenix-websocket transport) you might be using the Absinthe library to implement your Elixir GQL server. APW is configured by default to work out of the box with an Absinthe backend.

But if need araises, you can supply some advanced options to customize how it works. Here's is a commented example of the options that you can set for APW, with their respective default values:

createNetworkInterface({

  // The websockets endpoint to connect to, like ws://example.com:4000/socket
  uri: WS_URI,

  // how to send queries and mutations
  channel: {
    topic: '__absinthe__:control',
    event: 'doc',
  },

  // for using websocket subscriptions
  subscription: (subscriptionResponse) => ({
    topic: subscriptionResponse.subscriptionId,
    event: 'subscription:data',

    // extract the data from the event payload
    map: payload => payload.result.data,

    // what to do when unsubscribing
    off: controlChannel => {
      controlChannel.push('unsubscribe', {
        subscriptionId: subscriptionResponse.subscriptionId
      })
    }
  }),

  // If you want to reuse an existing Phoenix Socket, just provide a function
  // for APW to get it. By default, it will use the Phoenix Socket module.
  Socket: options => new Socket(options),
})

Middlewares

You can use middlewares with use just like with the standard apollo network interface. For example, a middleware can set authorization token on every request.

networkInterface.use([{
  applyMiddleware({request, options}, next) {
    // Here you can modify the interface options, for example
    // you can change the socket/channel that will handle the request
    // For example for a channel expecting authenticated queries
    options.channel.topic = "gql:restricted"
    options.channel.params = {...paramsForTopicJoin}

    // Or Modify the request
    request.variables = {name: 'Luke'}
    
    // Or Just add authorization token
    options.params = {
      ...options.params,
      auth_token: 'my-secret-token',
    }

    next()
  }
}])

Afterware

You can use afterwares with useAfter just like the standard apollo network interface. An example use-case is for error handling:

networkInterface.useAfter([{
  applyAfterware({response, options}, next) {
    // throw an error that will trigger your error handler
    if (response.error) {
      throw new Error(response.error)
    }
    next();
  }
}])

Absinthe backend

Absinthe is an amazing project (kudos to @benwilson512 et al.). It's actually very simple to create a GQL backend with it.

Take a look at the following places for more information:

• The Absinthe guide itself for getting started.
• Absinthe Phoenix for implementing websocket subscriptions on your endpoint.
• Absinthe.Schema#subscription/2 docs for how to setup your schema

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