Subscriptions: Getting Started

Subscriptions allow GraphQL clients to observe specific events and receive updates from the server when those events occur.

NOTE Much of the credit should be given to the [Ruby implementation](https://github.com/rmosolgo/graphql-ruby/blob/master/guides/subscriptions/overview.md) as they provided a great overview of how the backend should work. :::

Setup

Install the Pusher PHP Library (opens new window) for interacting with the Pusher HTTP API.

composer require pusher/pusher-php-server

Add the service provider to your config/app.php

'providers' => [
    \Nuwave\Lighthouse\Subscriptions\SubscriptionServiceProvider::class,
],

Pusher Webhook

Subscriptions do not expire by themselves. Unless a subscription is deleted, it will continue to broadcast events after the client has disconnected.

Using a Presence webhook will mitigate this problem. When a Pusher channel is abandoned (ie. unsubscribed), it will trigger the webhook, which will instruct Lighthouse to delete the subscription.

The webhook URL will typically be:

/graphql/subscriptions/webhook

You can add the webhook in the Pusher Dashboard. Select the type Presence.