graphql-pubnub-subscriptions
v1.0.0
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A GraphQL Subscriptions PubSub Engine for PubNub
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graphql-pubnub-subscriptions
This package implements the PubSubEngine Interface from the graphql-subscriptions package and also the new AsyncIterator interface. It allows you to connect your subscriptions manager to a PubNub PubSub mechanism to support multiple subscription manager instances.
Installation
npm install graphql-pubnub-subscriptions
or
yarn add graphql-pubnub-subscriptions
Using as AsyncIterator
Define your GraphQL schema with a Subscription
type:
schema {
query: Query
subscription: Subscription
}
type Subscription {
messages: Result
}
type Result {
message: String!
}
Now, let's create a simple PNPubSub
instance:
import { PNPubSub } from '@pubnub/graphql-pubnub-subscriptions';
const pubsub = new PNPubSub();
Now, implement your Subscriptions type resolver, using the pubsub.asyncIterator
to map the event you need:
const SOME_CHANNEL = 'myChannel';
export const resolvers = {
Subscription: {
messages: {
subscribe: () => pubsub.asyncIterator(SOME_CHANNEL),
},
},
}
Subscriptions resolvers are not a function, but an object with
subscribe
method, that returnsAsyncIterable
.
Calling the method asyncIterator
of the PNPubSub
instance will subscribe to the topic provided and will return an AsyncIterator
binded to the PNPubSub instance and listens to any event published on that topic.
Now, the GraphQL engine knows that messages
is a subscription, and every time a message is published to that channel and subscribe key, the PNPubSub
will PUBLISH
the event to all other subscribed instances and those in their turn will emit the event to GraphQL using the next
callback given by the GraphQL engine.
The channel doesn't get created automatically, it has to be created beforehand.
If you publish non string data it gets stringified and you have to parse the received message data.
Receive Messages
The received message from PubNub gets directly passed as payload to the resolve/filter function.
Dynamically use a channel based on subscription args passed on the query:
Assuming you have a Subscription defined in the schema like this:
type Subscription {
messages(channel: String!): Result
}
You can use the passed in channel like so:
export const resolvers = {
Subscription: {
messages: {
subscribe: (_, args) => pubsub.asyncIterator(args.channel),
},
},
}
Using both arguments and payload to filter events
NOTE: This is currently not implemented. Feel free to add this capability!
import { withFilter } from 'graphql-subscriptions';
export const resolvers = {
Subscription: {
messages: {
subscribe: withFilter(
(_, args) => pubsub.asyncIterator(args.channel),
(payload, variables) => payload, // NOT IMPLEMENTED
),
},
},
}
Creating the PNPubSub Client
import { PNPubSub } from '@pubnub/graphql-pubnub-subscriptions';
const pubSub = new PNPubSub({
subscribeKey: 'some subscribe key',
publishKey: 'some publish key',
});
Options
These are the options which are passed to the internal PubNub JS SDK. Please Note that not all options are implemented at this time and therefore may not pass through.
Subscription Options
There's an additional option to send some console debugs during execution by passing a debug flag.
import { PNPubSub } from '@pubnub/graphql-pubnub-subscriptions';
const pubSub = new PNPubSub({
subscribeKey: 'some subscribe key',
publishKey: 'some publish key',
debug: true, // <-- Just add this flag!
});