Enable Subgraphs in StepZen for Apollo Federation

Why Build Your Subgraphs with StepZen?

Whether you want to build new subgraphs quickly, or proxy existing subgraphs that you do not want to modify, StepZen can significantly accelerate your development and deliver subgraphs ready for the Apollo Federation layer.

While Apollo leaves the choice of how you build subgraphs up to you, there are advantages of doing it using StepZen.

• Speed of development A few lines of code gets you a subgraph against any backend.
• Optimized backend access StepZen is a specialized in-memory GraphQL query optimization engine, with in-memory JSON stitching, built by database experts.
• No code changes required to enable Apollo FederationSometimes the GraphQL backend that you want to federate is from a software provider that you do not have control over; sometimes your teams has build their subgraphs using libraries that have no support for Apollo Federation. Either way, a simplestepzen import graphql command allows you to create a proxy layer in StepZen that then easily enables your backend for Apollo Federation.
• Run your subgraphs in the StepZen cloud You get high performance because the REST, database and GraphQL calls are all optimized for efficiencies — with built-in caching, pushdowns and scaling.

How to Build & Enable Subgraphs for Apollo Federation

Whether you let StepZen introspect the backend service (REST, SOAP / XML, database or GraphQL), or you write your SDL and attach@rest, @dbquery or @graphqldirectives to it, you get a compact code that represents the GraphQL-ization of a backend or domain.

Build your subgraphs with a few lines of declarative code

StepZen’ s directives take away much of the heavy lifting for you, the entirety of the two blocks of code below(Customers subgraph and Orders subgraph) represents two GraphQL APIs :

Customers subgraph (equivalently created with thestepzen import curl https://api.acme.com/customerscommand

type User {
  id: ID
  name: String
  email: String
}
type Query {
  userByEmail (email: String): User
      @rest (endpoint: “https://api.acme.com/customers?email=$email”)
  userById (id: ID): User
      @rest (endpoint: “https://api.acme.com/customers/$id”)
}

Orders subgraph (equivalently created with thestepzen import postgresql command)

type Order {
  id: ID
  createdOn: Date
  carrier: String
  trackingId: String
}
type Query {
  orders (customerId: ID): [Order]
      @dbquery (type: “postgresql”, table: “orders”)
}

Extend your subgraphs with the @keydirective

StepZen’s non-root resolvers use a directive@materializer. To see how it works, let's extend our Customers and Orders subgraphs with the @key directive that Apollo Federation requires.The code looks like this:

Customers subgraph with @key annotation

type User @key (fields: “id”){
  id: ID
  name: String
  email: String
}
type Query {
  userByEmail (email: String): User
      @rest (endpoint: “https://api.acme.com/customers?email=$email”)
  userById (id: ID): User
      @rest (endpoint: “https://api.acme.com/customers/$id”)
}

Orders subgraph with@keyannotation

type User @key (fields: “id”) {
  id: ID
  orders: [Order]
    @materializer (query: “orders”,
                    arguments: [{name: “customerId”, field: “id”}])
}
type Order {
  id: ID
  createdOn: Date
  carrier: String
  trackingId: String
}
type Query {
  orders (customerId: ID): [Order]
      @dbquery (type: “postgresql”, table: “orders”)
}

The Orders subgraph shows that to populate User.orders, we issue the query orders and pass inUser.id as the argument customerIdfor that query. (You can also attach a series of transformations if needed.)

Non-root resolvers are created by @materializer that connects the data in the enclosing type (its scalar fields are always produced first in the execution step) with a query/mutation, which in turn returns the data of the type of that field being resolved.

Apollo Federation Subgraph Compatibility

In addition to @key, subgraphs created (or proxied) in StepZen support the following annotations for Apollo Federation 1 and Apollo Federation 2. See the Apollo Federation docs for latest compatability information and the StepZen & Apollo Federation Example for a tutorial with details about annotating StepZen subgraphs for Apollo Federation.