GraphQL on Rails

GraphQL on Rails Marc-Andre Giroux @__xuorig__

@__xuorig__

@__xuorig__ therakiasite.blogspot.com

@__xuorig__ Montreal, Canada

@__xuorig__

@__xuorig__ A simple UI component

@__xuorig__

@__xuorig__ What kind of data is needed?

@__xuorig__ Cart Product ProductImage

@__xuorig__ Reusable endpoints (REST)

@__xuorig__ /carts/1 /products/1 /products/2 /products/3 /product_images/1 /product_images/2 /product_images/3

@__xuorig__ Too many round trips!

@__xuorig__ /carts/1?expand=products

@__xuorig__ /carts/1?ﬁelds=products(name, description, price)

@__xuorig__ /carts/1?ﬁelds=products/name,description,price

@__xuorig__ Custom Endpoints

@__xuorig__ /cart_with_all_the_stuff_i_need

@__xuorig__

@__xuorig__ /cart_with_all_the_stuff_i_need /cart_version_2_with_all_the_things /cart_with_products_and_images /cart_with_products_and_images_with_price_and_taxes my_tightly_coupled_custom_endpoint_including_only_the_things_i_need_bla_bla_bla_bla /cart_with_products_and_images_with_price_and_taxes_but_no_description /cart_with_products_and_images_with_price_and_taxes_but_no_description_v2

@__xuorig__

@__xuorig__ Server Client Updates a view Creates a new view
New view version Model changes Update endpoints Create new endpoint

@__xuorig__ yo, give me the resource with id = abc
OK, here’s the resource with id = abc Client Server

@__xuorig__ yo, give me the resource v2 with id =
abc OK, here’s the resource v2 with id = abc Client Server

@__xuorig__ yo, give me the resource v3 with id =
abc OK, here’s the resource v3 with id = abc Client Server

@__xuorig__ GraphQL

@__xuorig__ What GraphQL is NOT

@__xuorig__ What GraphQL IS

@__xuorig__ { myShop { name } } Field Selection Set

@__xuorig__ { myShop { name } } Lexed Parsed Validated
Executed { “myShop” { “name”: “GitHub” } }

@__xuorig__ { myShop { name } }

@__xuorig__

@__xuorig__ { shop(id: 1) { name } }

@__xuorig__ { myShop { name location { city address }
products(orderby: POPULARITY) { name price } } }

@__xuorig__ { “myShop”: { “name”: “Euruko 2016” “location” { “city”:
“Sofia” “address”: “Av. Diagonal 547” } “products”: [{ “name”: “Conference Ticket” “price”: 500000 }, { “name”: “Cool T-Shirt” “price”: 20000 }] } }

@__xuorig__ Type System

@__xuorig__ type QueryRoot { myShop: Shop shop(id: Int): Shop }

@__xuorig__ type Shop { name: String location: Address products(orderby: OrderEnum):
[Product] } enum ProductOrderEnum { PRICE, POPULARITY, ALPHABETICAL }

@__xuorig__ type Address { city: String address: String }

@__xuorig__ type Product { name: String price: Int }

@__xuorig__ { myShop { name yolo { swag } }
}

@__xuorig__ { myShop { name yolo { swag } }
} type Shop { name: String location: Address }

@__xuorig__ Introspection

@__xuorig__ query { __schema { … } }

@__xuorig__ Static Validation Code Generation IDE Integration Auto Documentation

@__xuorig__

products(orderby: POPULARITY) { id name price } } }

@__xuorig__

products(orderby: POPULARITY) { id name price } } }

@__xuorig__ Fragments

@__xuorig__ fragment productFields on Product { id name price }

products(orderby: POPULARITY) { ...productFields } } }

@__xuorig__ query Fragment Fragment Fragment Fragment

@__xuorig__ Mutations

@__xuorig__ mutation { createProduct(name: “Nice Mug”, price: 10000) { id
name } }

@__xuorig__ Resolving ﬁelds

@__xuorig__ github.com/rmosolgo/graphql-ruby

@__xuorig__ ProductType = GraphQL::ObjectType.define do name "Product" description “A product
sold at a shop” # … end

@__xuorig__ field :name do type types.String resolve -> (obj, args,
ctx) { obj.name } end

@__xuorig__ field :price do type types.Int resolve -> (obj, args,
ctx) do obj.subtotal + obj.taxes + obj.shipping_price end end

@__xuorig__ ShopType = ObjectType.define do name “Shop" description "A Shop"
field :products, [ProductType] end

@__xuorig__ QueryType = ObjectType.define do name “Query" description “The Root
of my Schema" field :myShop, ShopType end

@__xuorig__ MySchema = GraphQL::Schema.new( query: QueryRoot, mutation: MutationRoot )

@__xuorig__ POST /graphql

@__xuorig__ module Api class GraphqlController < ApiController def query query_string
= params[:query] variables = params[:variables] context = { current_user: current_user } # ... end end end

@__xuorig__ module Api class GraphqlController < ApiController def query #
... result = MySchema.query( query_string, variables: variables, context: context ) render json: result end end end

@__xuorig__ Drawbacks and solutions

@__xuorig__ N+1 Queries

@__xuorig__ # Product Type field :image do type ImageType resolve
-> (product, args, ctx) do product.image end end # Shop Type field :products do type [ProductType] resolve -> (shop, args, ctx) do shop.products end end

@__xuorig__ Product Load (1.0ms) SELECT "products".* FROM "products" WHERE "products"."shop_id"
= … Image Load (0.9ms) SELECT "images".* FROM "images" WHERE "images"."product_id" = … Image Load (0.2ms) SELECT "images".* FROM "images" WHERE "images"."product_id" = … Image Load (0.1ms) SELECT "images".* FROM "images" WHERE "images"."product_id" = …

@__xuorig__ Solution: Batching + Caching

@__xuorig__ field :image do type ImageType resolve -> (product, args,
ctx) do RecordLoader.for(Image).load(product.image_id) end end

@__xuorig__ HTTP Caching

@__xuorig__ Solution: Client Side Cache

@__xuorig__ Normalized Cache

@__xuorig__ query { shop { products { price } }
} query { shop { product(id: 1) { price } } }

@__xuorig__ { root: { shop: { products: [ Link.new(1) ]
} }, 1: { price: 1000 } }

@__xuorig__ https://github.com/facebook/relay http://www.apollostack.com/

@__xuorig__ Security

@__xuorig__ Query Depth Timeouts Query Complexity

@__xuorig__ Future

@__xuorig__ Subscriptions

@__xuorig__ subscription { productInventorySubscribe { products { inventory } }
}

@__xuorig__ Deferred Queries

@__xuorig__ query { shop { name description products { name
price } } }

@__xuorig__ query { shop { name description products @defer {
name price } } }

@__xuorig__

@__xuorig__ yo, give me the resource with id = abc
OK, here’s the resource with id = abc Client Server

@__xuorig__ Client Server yo, give me the resource with id
= 1 yo, give me the resource with id = 2 yo, give me the resource with id = 3 yo, give me the resource with id = 4

@__xuorig__ oh boy :( Client Server

@__xuorig__ I need that exact data shape (requirements) Here is
everything you can do! (capabilities) Client Server

@__xuorig__ Eﬃciency

@__xuorig__ Predictability

@__xuorig__ Thank you! Marc-Andre Giroux @__xuorig__

GraphQL on Rails

GraphQL on Rails

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