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 mongoose Pub Sub mechanism to support multiple subscription manager instances.
At first, install the graphql-mongoose-subscriptions
package:
npm install graphql-mongoose-subscriptions
As the graphql-subscriptions package is declared as a peer dependency, you might receive warning about an unmet peer dependency if it's not installed already by one of your other packages. In that case you also need to install it too:
npm install graphql-subscriptions
Define your GraphQL schema with a Subscription
type:
schema {
query: Query
mutation: Mutation
subscription: Subscription
}
type Subscription {
somethingChanged: Result
}
type Result {
id: String
}
Now, let's create a simple MongoosePubSub
instance:
import { MongoosePubSub } from 'graphql-mongoose-subscriptions';
const pubsub = new MongoosePubSub();
Now, implement your Subscriptions type resolver, using the pubsub.asyncIterator
to map the event you need:
const SOMETHING_CHANGED_TOPIC = 'something_changed';
export const resolvers = {
Subscription: {
somethingChanged: {
subscribe: () => pubsub.asyncIterator(SOMETHING_CHANGED_TOPIC),
},
},
}
Subscriptions resolvers are not a function, but an object with
subscribe
method, that returnsAsyncIterable
.
Calling the method asyncIterator
of the MongoosePubSub
instance will send mongoose a SUBSCRIBE
message to the topic provided and will return an AsyncIterator
binded to the MongoosePubSub instance and listens to any event published on that topic.
Now, the GraphQL engine knows that somethingChanged
is a subscription, and every time we will use pubsub.publish
over this topic, the MongoosePubSub
will PUBLISH
the event over mongoose 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.
pubsub.publish(SOMETHING_CHANGED_TOPIC, { somethingChanged: { id: "123" }});
export const resolvers = {
Subscription: {
somethingChanged: {
subscribe: (_, args) => pubsub.asyncIterator(`${SOMETHING_CHANGED_TOPIC}.${args.relevantId}`),
},
},
}
export const resolvers = {
Subscription: {
somethingChanged: {
subscribe: (_, args) => pubsub.asyncIterator(`${SOMETHING_CHANGED_TOPIC}.${args.relevantId}.*`, { pattern: true })
},
},
}
import { withFilter } from 'graphql-subscriptions';
export const resolvers = {
Subscription: {
somethingChanged: {
subscribe: withFilter(
(_, args) => pubsub.asyncIterator(`${SOMETHING_CHANGED_TOPIC}.${args.relevantId}`),
(payload, variables) => payload.somethingChanged.id === variables.relevantId,
),
},
},
}
The basic usage is great for development and you will be able to connect to a mongoose server running on your system seamlessly. For production usage, it is recommended to send a mongoose client from the using code and pass in any options you would like to use. e.g: Connection retry strategy.
import { MongoosePubSub } from 'graphql-mongoose-subscriptions';
import mongoose from 'mongoose';
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/test', {useNewUrlParser: true, useUnifiedTopology: true});
const pubsub = new MongoosePubSub();
const pubsub = new MongoosePubSub({mongooseOptions:{url:'mongodb://localhost:27017/test',options:{useNewUrlParser: true, useUnifiedTopology: true}}})