⚡️ Pro Feature ⚡️ This feature is bundled with GraphQL-Pro.

Pusher Implementation

GraphQL Pro includes a subscription system based on Redis and Pusher which works with any Ruby web framework.

After creating an app on Pusher and configuring the Ruby gem, you can hook it up to your GraphQL schema.

How it Works

This subscription implementation uses a hybrid approach:

So, the lifecycle goes like this:

Here’s another look:

1. Subscription is created in your app

          HTTP POST
        .---------->   write to Redis
      📱            ⚙️ -----> 💾
        X-Subscription-ID: 1234

2. Client opens a connection to Pusher

      📱 <---------> ☁️

3. The app sends updates via Pusher

      ⚙️ ---------> ☁️ ------> 📱
        POST           update
      (via gem)   (via websocket)

4. When the client unsubscribes, Pusher notifies the app

      ⚙️ <-------- ☁️  (disconnect) 📱

By using this configuration, you can use GraphQL subscriptions without hosting a push server yourself!

Database setup

Subscriptions require a persistent Redis database, configured with:

maxmemory-policy noeviction
# optional, more durable persistence:
appendonly yes

Otherwise, Redis will drop data that doesn’t fit in memory (read more in “Redis persistence”).

If you’re already using Redis in your application, see “Storing Data in Redis” for options to isolate data and tune your configuration.

Schema configuration

Add redis to your Gemfile:

gem 'redis'

and bundle install. Then create a Redis instance:

# for example, in an initializer:
$graphql_subscriptions_redis = Redis.new # default connection

Then, that Redis client is passed to the Subscription configuration:

class MySchema < GraphQL::Schema
  use GraphQL::Pro::PusherSubscriptions, redis: $graphql_subscriptions_redis

That connection will be used for managing subscription state. All writes to Redis are prefixed with graphql:sub:.

There are also two configurations for managing persistence:

Connection Pool

For better performance reading and writing to Redis, you can pass a connection_pool: instead of redis:, using the connection_pool gem:

  use GraphQL::Pro::PusherSubscriptions,
    connection_pool: ConnectionPool.new(size: 5, timeout: 5) { Redis.new },

Execution configuration

During execution, GraphQL will assign a subscription_id to the context hash. The client will use that ID to listen for updates, so you must return the subscription_id in the response headers.

Return result.context[:subscription_id] as the X-Subscription-ID header. For example:

result = MySchema.execute(...)
# For subscriptions, return the subscription_id as a header
if result.subscription?
  response.headers["X-Subscription-ID"] = result.context[:subscription_id]
render json: result

This way, the client can use that ID as a Pusher channel.

For CORS requests, you need a special header so that clients can read the custom header:

if result.subscription?
  response.headers["X-Subscription-ID"] = result.context[:subscription_id]
  # Required for CORS requests:
  response.headers["Access-Control-Expose-Headers"] = "X-Subscription-ID"

Read more here: “Using CORS”.

Payload Compression

To mitigate problems with Pusher’s 10kb message limit, you can specify compress_pusher_payload: true in the context of your subscription. For example:

# app/controllers/graphql_controller.rb
def execute
  # ...
  # Somehow detect whether the client supports compressed payloads,
  # for example, User-Agent, query param, or request header:
  if client_supports_compressed_payloads?
    context[:compress_pusher_payload] = true
  # ...

This will cause subscription payloads to include compressed_result: "..." instead of result: "..." when they’re sent over Pusher. See docs for Apollo Client or Relay Modern to read about preparing clients for compressed payloads.

By configuring compress_pusher_payload: true on a query-by-query basis, the subscription backend can continue to support clients running old client code (by not compressing) while upgrading new clients to compressed payloads.

Batched Deliveries

By default, PusherSubscriptions sends updates in batches of up to 10 at a time, using batch triggers. You can customize the batch size by passing batch_size: when installing it, for example:

use GraphQL::Pro::PusherSubscriptions, batch_size: 1, ...

batch_size: 1 will make PusherSubscriptions use the single trigger API instead of batch triggers.

Webhook configuration

Your server needs to receive webhooks from Pusher when clients disconnect. This keeps your local subscription database in sync with Pusher.

In the Pusher web UI, Add a webhook for “Channel existence”

Pusher Webhook Configuration

Then, mount the Rack app for handling webhooks from Pusher. For example, on Rails:

# config/routes.rb

# Include GraphQL::Pro's routing extensions:
using GraphQL::Pro::Routes

Rails.application.routes.draw do
  # ...
  # Handle Pusher webhooks for subscriptions:
  mount MySchema.pusher_webhooks_client, at: "/pusher_webhooks"

This way, we’ll be kept up-to-date with Pusher’s unsubscribe events.

Alternatively, you can configure the routes to load your schema lazily, during the first request:

# Provide the fully-qualified class name of your schema:
lazy_routes = GraphQL::Pro::Routes::Lazy.new("MySchema")
mount lazy_routes.pusher_webhooks_client, at: "/pusher_webhooks"


To ensure the privacy of subscription updates, you should use a private channel for transport.

To use a private channel, add a channel_prefix: key to your query context:

  context: {
    # If this query is a subscription, use this prefix for the Pusher channel:
    channel_prefix: "private-user-#{current_user.id}-",
    # ...
  # ...

That prefix will be applied to GraphQL-related Pusher channel names. (The prefix should begin with private-, as required by Pusher.)

Then, in your auth endpoint, you can assert that the logged-in user matches the channel name:

if params[:channel_name].start_with?("private-user-#{current_user.id}-")
  # success, render the auth token
  # failure, render unauthorized

Serializing Context

Since subscription state is stored in the database, then reloaded for pushing updates, you have to serialize and reload your query context.

By default, this is done with GraphQL::Subscriptions::Serialize’s dump and load methods, but you can provide custom implementations as well. To customize the serialization logic, create a subclass of GraphQL::Pro::PusherSubscriptions and override #dump_context(ctx) and #load_context(ctx_string):

class CustomSubscriptions < GraphQL::Pro::PusherSubscriptions
  def dump_context(ctx)
    context_hash = ctx.to_h
    # somehow convert this hash to a string, return the string

  def load_context(ctx_string)
    # Given the string from the DB, create a new hash
    # to use as `context:`

Then, use your custom subscriptions class instead of the built-in one for your schema:

class MySchema < GraphQL::Schema
  # Use custom subscriptions instead of GraphQL::Pro::PusherSubscriptions
  # to get custom serialization logic
  use CustomSubscriptions, redis: $redis

That gives you fine-grained control of context reloading.


You can monitor subscription state in the GraphQL-Pro Dashboard:

Redis Subscription Dashboard

Redis Subscription Detail

Development Tips

Clear subscription data

At any time, you can reset your subscription database with the “Reset” button in the GraphQL-Pro Dashboard, or in Ruby:

# Wipe all subscription data from the DB:

Developing with Pusher webhooks

To receive Pusher’s webhooks in development, Pusher suggests using ngrok. It gives you a public URL which you can setup with Pusher, then any hooks delivered to that URL will be forwarded to your development environment.

Client configuration

Install the Pusher JS client then see docs for: