This is to showcase how GraphQL federation would be used in practice with Elixir.
Start each of the Elixir subgraph services in separate terminal windows.
$ cd <products|reviews|inventory>
$ mix deps.get
$ mix phx.server
Start the federated gateway.
$ cd gateway
$ yarn
$ yarn start
- Gateway http://localhost:4000
- Products http://localhost:4001
- Reviews http://localhost:4002
- Inventory http://localhost:4003
schema @link(url: "https:\/\/specs.apollo.dev\/federation\/v2.0", import: ["@key", "@extends", "@external"]) {
query: RootQueryType
mutation: RootMutationType
}
type Product @extends @key(fields: "upc") {
upc: String! @external
inStock: Boolean
}
type RootQueryType @extends {}
type RootMutationType {
decrementInventory(upc: String!, amount: Int): String
}schema @link(url: "https://specs.apollo.dev/federation/v2.0", import: ["@key"]) {
query: RootQueryType
mutation: RootMutationType
}
type Product @key(fields: "upc") {
upc: String!
name: String!
price: Int
}
type RootQueryType {
product(upc: String!): Product
}
type RootMutationType {
addDiscount(upc: String!, amount: Int!): String
}Note: The reviews schema does not import the Federation v2 directives but it will be converted to v2 schema by the gateway.
schema {
query: RootQueryType
}
type Product @extends @key(fields: "upc") {
upc: String! @external
reviews: [Review]
}
type Review @key(fields: "id") {
id: ID!
}
type RootQueryType @extends {
review(id: ID!): Review
}The meat of this PoC is in the schema.ex of each service and in the absinthe_federation library that pulls in some additional macros
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