graphql-pub-sub-with-initial-value

GraphQLPupSubWithIntialValue is a simple npm package that extends GraphQLPubSub with an asyncIteratorWithInitialState method. It lets you define an async function how to get the initial value.

Additionally it provides the possibilty to execute some cleanup work, when a client disconnects or the AsynIterator is closed. For that you can use the exported withCancel or the pubSub.withCancel function.

For more information checkout the GraphQL-Subscriptions

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Installation

npm install graphql-pub-sub-with-initial-value or yarn add graphql-pub-sub-with-initial-value

This package has peerDependencies to "graphql": "^14.3.1 || ^15.3.0" and "graphql-subscriptions": "^1.1.0", which you have to install yourself.

Usage

Easy & Simple

const asyncInititalValueFn = () => {
  // grab initial values somewhere else. Read from file, memory, 🤷
  return Promise.resolve(['test'])
}

import { PubSubWithIntialValue } from 'graphql-pub-sub-with-initial-value'

const pubSubWithInitialValue = new PubSubWithIntialValue()

const asyncIterator = pubSubWithInitialValue.asyncIteratorWithInitialValue<string[]>('TOPIC', asyncInititalValueFn)

pubSubWithInitialValue.withCancel(asyncIterator, () => console.log('on close/disconnect'))
// triggers cancel/disconnect
asyncIterator.return()

In a resolver of subsciption (ApolloServer)

It is recommended to put the pubSub on the context object during the ApolloServer creation or use PubSubs in combination with datasources or create it in a seperated file to reuse the instance.

import { GraphQLList, GraphQLNonNull, GraphQLObjectType, GraphQLString } from 'graphql'
import { PubSubWithIntialValue } from 'graphql-pub-sub-with-initial-value'

export const subscription = new GraphQLObjectType({
  fields: {
    callings: {
      resolve(payload) {
        return payload
      },
      subscribe(_obj, _args, context: { pubSub: PubSubWithIntialValue }): AsyncIterable<any> {
        return context.pubSub.asyncIteratorWithInitialValue<string[]>(() => Promise.resolve(['test']))
      },
      type: GraphQLNonNull(GraphQLList(GraphQLNonNull(GraphQLString)))
    }
  },
  name: 'Subscription'
})