graphql-multiplex-subscriptions


If you need to use multiple PubSubEngines in your Apollo server (e.g.
graphql-redis-subscriptions and graphql-postgres-subscriptions), use this
package to coordinate which PubSubEngine handles a given topic.

Usage

Imagine you're currently using graphql-redis-subscriptions, and you set up
your pubsub like this:

``js
// Before
import { RedisPubSub } from 'graphql-redis-subscriptions'

export const pubsub = new RedisPubSub()
`

But then you decide you want to use graphql-postgres-subscriptions for some
topics. All you have to do is create a MultiplexPubSub with a selectEngine
function that returns which engine you'd like to use for a given topic. For
example, you could use postgres for all topics beginning with pg/:

`js
import { RedisPubSub } from 'graphql-redis-subscriptions'
import { PostgresPubSub } from 'graphql-postgres-subscriptions'
import { MultiplexPubSub } from 'graphql-multiplex-subscriptions'

const redisPubSub = new RedisPubSub()
const postgresPubSub = new PostgresPubSub()

export const pubsub = new MultiplexPubSub({
selectEngine: topic =>
topic.startsWith('pg/') ? postgresPubSub : redisPubSub,
})
`

WARNING: selectEngine should always return a PubSubEngine. If it doesn't,
you will get TypeErrors!

Since you use a function to select the engine you can use whatever logic you
want. So you could just map specific topics to a specific engine:

`js
import { RedisPubSub } from 'graphql-redis-subscriptions'
import { PostgresPubSub } from 'graphql-postgres-subscriptions'
import { MultiplexPubSub } from 'graphql-multiplex-subscriptions'

const redisPubSub = new RedisPubSub()
const postgresPubSub = new PostgresPubSub()

export const pubsub = new MultiplexPubSub({
selectEngine: topic =>
topic.matches(/^(user|organization)\//) ? postgresPubSub : redisPubSub,
})
``