GraphQL `Context` and Services

Simple example showing how to use Context as a class within GraphQL, along with context.services for abstracting away downstream API complexity.

For extra credit, this also shows off Apollo's REST Data Source with built in caching!

Demo

Use the following example query:

query MyGitHubRateLimit {
  # Example of getting properties from context
  ip

  # Example of using context.services.GitHub
  github {
    rateLimit {
      limit
      # 👇 Cached automatically!
      remaining
    }
  }

  # Returning the app version is handy 🤷‍♂️
  version
}

Rationale

Using Context (instead of a plain {...} object) moves complexity from within your middleware to a separate, testable layer:

.use(
  "/graphql",
  graphql((req, res) => {
    const context = new Context({ req })

    return {
      context,
      graphiql: true,
      pretty: true,
      schema,
    }
  })

Context can have a strict, testable API for your resolvers to use, instead of ad-hoc reliance on req.query or req.body:

// Before
ip: (parent, args, context, info) => {
  if (req.header("x-forwarded-for")) {
    return req.header("x-forwarded-for").split(",").shift()
  }

  if (req.connection.remoteAddress) {
    return req.connection.remoteAddress
  }

  return req.ip
}

// After
ip: (parent, args, context, inf0) => {
  return context.ip
}

API calls within resolvers are simplified:

rateLimit: (parent, args, context, info) => {
  const { GitHub } = context.services

  return GitHub.getRateLimit()
}

The same as Apollo's dataSources, but works with the standard express-graphql library:

https://www.apollographql.com/docs/apollo-server/features/data-sources.html#Accessing-data-sources-from-resolvers

chris-jin-g/graphql-context-services

GraphQL Context and Services

Demo

Rationale

GraphQL `Context` and Services