Demo of a federated graphql api with all services and gateway collocated.

A federated graph is one that is comprised of one or more subgraphs, which run in separate servers–essentially graphql microservices. The gateway is responsible for exposing a unified graph and ensuring that fields in queries and mutations reach the correct subgraphs.

The demo contains the following:

• gateway
• subgraphs
  • user subgraph
  • commit subgraph

Each subgraph, and the gateway, is exposed on a different port on the same host.

The user subgraph defines a User type:

type Query {
  me: User
  user(id: ID!): User
  users: [User]
}

type User @key(fields: "id") {
  id: ID!
}

The commit subgraph defines a new Commit type and extends the User type:

type Query {
  commit(id: ID!): Commit
  commits: [Commit]
}

type Mutation {
  commitCreate(input: CommitCreateInput!): CommitCreatePayload
}
input CommitCreateInput {
  message: String!
}
type CommitCreatePayload {
  commit: Commit
}

type Commit @key(fields: "id") {
  id: ID!
  sha: String
  short: String
  message: String
  user: User
}

type User @key(fields: "id") {
  id: ID!
  commits: [Commit]
}

Start the gateway by running npm run dev. You can then run queries against it like so: