mathieumg/graphql-redis-subscriptions

A graphql subscriptions implementation using redis and apollo's graphql-subscriptions

graphql-redis-subscriptions

This package implements the PubSubEngine Interface from the graphql-subscriptions package. It allows you to connect your subscriptions manger to a redis Pub Sub mechanism to support multiple subscription manager instances.

Basic Usage

import { RedisPubSub } from 'graphql-redis-subscriptions';
const pubsub = new RedisPubSub();
const subscriptionManager = new SubscriptionManager({
  schema,
  pubsub,
  setupFunctions: {},
});

Using Trigger Transform

Recently, graphql-subscriptions package added a way to pass in options to each call of subscribe. Those options are constructed via the setupFunctions object you provide the Subscription Manager constructor. The reason for graphql-subscriptions to add that feature is to allow pub sub engines a way to reduce their subscription set using the best method of said engine. For example, meteor's live query could use mongo selector with arguments passed from the subscription like the subscribed entity id. For redis, this could be a bit more simplified, but much more generic. The standard for redis subscriptions is to use dot notations to make the subscription more specific. This is only the standard but I would like to present an example of creating a specific subscription using the channel options feature.

First I create a simple and generic trigger transform

const triggerTransform = (trigger, {path}) => [trigger, ...path].join('.');

Then I pass it to the RedisPubSub constructor.

const pubsub = new RedisPubSub({
  triggerTransform,
});

Lastly, I provide a setupFunction for commentsAdded subscription field. It specifies one trigger called comments.added and it is called with the channelOptions object that holds repoName path fragment.

const subscriptionManager = new SubscriptionManager({
  schema,
  setupFunctions: {
    commentsAdded: (options, {repoName}) => ({
      'comments.added': {
        channelOptions: {path: [repoName]},
      },
    }),
  },
  pubsub,
});

When I call subscribe like this:

const query = `
  subscription X($repoName: String!) {
    commentsAdded(repoName: $repoName)
  }
`;
const variables = {repoName: 'graphql-redis-subscriptions'};
subscriptionManager.subscribe({query, operationName: 'X', variables, callback});

The subscription string that Redis will receive will be comments.added.graphql-redis-subscriptions. This subscription string is much more specific and means the the filtering required for this type of subscription is not needed anymore. This is one step towards lifting the load off of the graphql api server regarding subscriptions.

Creating the Redis Client

For production usage, it is recommended to send a redis client from the using code.

import { RedisPubSub } from 'graphql-redis-subscriptions';
import * as Redis from 'ioredis';

const options = {
  host: REDIS_DOMAIN_NAME,
  port: PORT_NUMBER,
  retry_strategy: options => {
    // reconnect after
    return Math.max(options.attempt * 100, 3000);
  }
};

const pubsub = new RedisPubSub({
  ...,
  publisher: new Redis(options),
  subscriber: new Redis(options)
});

You can learn more on ioredis package here.

Passing redis options object

The basic usage is great for development and you will be able to connect to a redis server running on your system seamlessly. But for any production usage you should probably pass in a redis options object

import { RedisPubSub } from 'graphql-redis-subscriptions';

const pubsub = new RedisPubSub({
  connection: {
    host: REDIS_DOMAIN_NAME,
    port: PORT_NUMBER,
    retry_strategy: options => {
      // reconnect after
      return Math.max(options.attempt * 100, 3000);
    }
  }
});

You can learn more on the redis options object here.