What the hell is GraphQL?

It's an alternative way to design APIs... that's all

It all starts with the Schema

Instead of loads of endpoints like this

GET http://api.com/users/1
POST http://api.com/users

Quick Recap

• Schema - Definition of Data + queries & mutations
• Resolver - A function that implements a query or mutation
• Nested Resolvers - very powerful way to resolve (mostly relational) data
• Subscription - subscribe to events over websockets
  • Fire events (e.g. 'messageAdded') on a pubsub instance
  • Subscription resolver listens for those events and sends them back down to clients
  • Can add filtering on subscriptions

Aerogear Data Sync Server

• Schema is defined in UI by end user. Saved in the metadata db (postgres)
• DataSources allow users to specify where data comes from. (Postgres, InMemory, Mongo, etc)
• Resolver Mappings tell the server how to perform the particular query/mutation (e.g. run an SQL statement)
• As part of resolver definition, end user can define a 'publish' field for subscriptions

Aerogear Data Sync Server (continued)

• We are using Apollo Server V1. Be very aware that most docs on Apollo's website are for V2.
• Pubsub - using Notify/Listen mechanism in Postgres
• Schema Changes are Hot Reloaded - when a change is made via UI, a message is published on the pubsub. Server picks this up and reloads schema without restarting
• Subscriptions use the Postgres Pubsub mechanism. This allows subscriptions to work across several server instances