Allow custom PubSubEngine for GraphQL PubSub

[dzhelezov]

By default ApolloServer uses an EventEmitter-based PubSubEngine, and in general it is recommended to use a more scalable (like Redis-based) one. However, it doesn't seem to be possible to provide a custom implementation since as thepubSub implementation should be passed to the buildSchema call here :

warthog/src/core/server.ts

Line 161 in b464981

async buildGraphQLSchema(): Promise<GraphQLSchema> {

Here's a relevant example from type-graphql:
https://github.com/MichalLytek/type-graphql/blob/d5e3403f7610ce8f53b919a3dd490806685570c7/examples/redis-subscriptions/index.ts#L27

[goldcaddy77]

Good call. Will take a crack at it this week.

[metmirr]

@goldcaddy77 what is the status of this issue?

[goldcaddy77]

Hi @metmirr , this is not implemented yet. If you want to put in a PR I'm happy to review and get it integrated.

[goldcaddy77]

This has been implemented. See https://github.com/goldcaddy77/warthog/blob/main/src/core/server.ts#L185