Rapid Development Techniques for APIs with GraphQL on AWS [Graph Meetup @ Milan]

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Alex Casalboni Technical Evangelist, AWS @alex_casalboni Rapid Development Techniques for APIs with GraphQL on AWS @ 2019, Amazon Web Services, Inc. or its Affiliates. All rights reserved bit.ly/graphql-aws-milano

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About me • Software Engineer & Web Developer • Worked in a startup for 4.5 years • ServerlessDays Organizer • AWS Customer since 2013

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This talk is for developers < frontend | backend >

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How do you prototype an API? bit.ly/graphql-aws-milano

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Congratulations! You’ve just been hired.

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Today’s mobile experience is lacking Mobile website, no native apps Slow to book, low conversion rates Backend built for high-speed desktops !

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Your job is to define tomorrow’s experience Digital agency hired for design First prototype in 4 weeks Must use real data, no mockup !

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Our Goal Enable backend services for prototype Allow design to evolve Keeping up with day-to-day job !

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{ "_id": 3, "name": "ElastiLodge South Zanetown", "image": "https://placehold.it/300x300.png", "description": ” ... ", "location": "South Zanetown", "manager": { "name": ”Marco Rossi", "email": ”marco.rossi@elastilodge.com" }, "timeZone": "US/Central", "phoneNumber": "802-918-3262", "category": 5, "address": { "street": "410 Simonis Forest", "zip": "07545-2308", "city": "South Zanetown", "country": "Virgin Islands, British" }, "deskHours": "24 hours", "amenities": [ ... ], "restaurants": [ ... ] } Legacy REST API

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REST API challenges bit.ly/graphql-aws-milano

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/posts /comments /authors REST API Chatty & Over fetching { "posts" : [ { "id" : 1, "content" : "the quick brown fox jumps over the…", "author" : "/authors/123", "created" : 1550486509, "comments" : "/posts/1/comments", ... }, { "id" : 2, "content" : "the quick brown fox jumps over…", "author" : "/authors/123" "created" : 1550486509, "comments" : "/posts/2/comments", ... } ] }

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Why GraphQL bit.ly/graphql-aws-milano

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GraphQL is a query language for your API, and a server-side runtime for executing queries by using a type system you define for your data. https://graphql.org

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Why GraphQL? posts comments authors GraphQL API Type safe Contract-driven Efficient Easy to test Realtime

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How does GraphQL work? type Query { getTodos: [Todo] } type Todo { id: ID! name: String description: String priority: Int duedate: String } Model data with application schema query { getTodos { id name priority } } Client requests what it needs { "id": "1", "name": "Get Milk", "priority": "1" }, { "id": "2", "name": "Go to gym", "priority": "5" },… Only that data is returned

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GraphQL Operations Queries Read data Mutations Write data Subscriptions Listen for data query { search(q: “harry potter”) { title } } mutation { create(title: “new book”) { id } } subscription { onCreate { id title } }

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Is REST dead then? When data drives UI Structured data Query-driven Client-driven development Use GraphQL When you leverage HTTP Caching, Content types Hypermedia For resources (e.g. Amazon S3) Use REST Pick the appropriate protocol for your use case

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How to deploy a GraphQL API? bit.ly/graphql-aws-milano

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Welcome AWS AppSync! Managed & serverless Multiple data sources Data-sync, real-time, and offline Conflict detection in the cloud Enterprise security features

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Data Sources REST Endpoint /graphql Amazon Cognito Amazon DynamoDB AWS Lambda Amazon Elasticsearch Amazon RDS AWS Lambda

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Resolvers Amazon DynamoDB /graphql Request Resolver Maps payload to underlying data source via Velocity Template to execute query / mutation. Response Resolver Maps response from data source to GraphQL response via Velocity Template.

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KEEP CALM and WATCH the DEMO

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Let’s prototype! Phase #1: Hotel Detail bit.ly/graphql-aws-milano

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Hotel Detail: Design What data is required? Can we use existing data sources? How can we enable via AppSync? Challenges? Missing data?

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Mapping to Legacy API { "_id": 3, "image": "https://placehold.it/300x300.png", "name": "EL Resort & Spa", "description": "...", "location": "Fiji", "manager": { "name": "Florentino Jacobi", "email": "florentino.jacobi@elastilodge.com" }, "timeZone": "US/Central", "address": { "street": "123 Main St", ”postalcode": "07545", "city": "Momi Bay", "country": "Fiji" }, "phoneNumber": "1-888-123-4567", "category": 5, "deskHours": "24 hours", "amenities": [ ... ], "restaurants": [ ... ] }

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Hotel Detail: GraphQL Schema type Hotel { hotelId: ID! name: String! image: String location: String! phoneNumber: AWSPhone! address: Address! ... } type Query { listHotels(offset: String, limit: Int) getHotel(hotelId: ID!) }

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Hotel Detail: Resolvers ## Resolver: Request Mapping ## { "version": "2018-05-29", "method": "GET", "resourcePath": "/hotels/${ctx.args.hotelId}", "params": { "headers": { "Content-Type": "application/json" } }, } ## Resolver: Response Mapping ## #if($ctx.result.statusCode == 200) ## If response is 200, return the body. ## Could also filter result... $ctx.result.body #else ## If not 200, append response to error $utils.appendError($ctx.result.body) #end

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Hotel Detail: Result query { getHotel(hotelId: 3) { name location image phoneNumber address { street city } amenities } } { "name": "ElastiLodge North Rodgerstad", "location": "North Rodgerstad", "image": "/300x300.png", "phoneNumber": "(214) 210-4674", "address": { "street": "123 Main St", "city": "North Rodgerstad" }, "amenities": [ ... ] } (from 8KB to 312B -> 93% lighter response)

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Mobile Code – Initialize App Sync Client do { // create app sync configuration (cache, service config etc) let config = … // client initialization let appSyncClient = try AWSAppSyncClient(appSyncConfig: config) } catch { fatalError("Error initializing appsync client. \(error)") }

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Mobile Code – Run a Query // call a GraphQL Query appSyncClient?.fetch(query: GetHotelQuery(hotelId: hotelId), cachePolicy: .fetchIgnoringCacheData) {(result, error) in guard let r = result, error == nil else { print(error?.localizedDescription ?? "") return } // use the data in the GUI self.hotelDetails = r.data?.getHotel … }

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KEEP CALM and WATCH the DEMO

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Let’s prototype! Phase #2: Reservations bit.ly/graphql-aws-milano

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Reservations: Design What data is required? Can we use existing data sources? How can we enable via AppSync? Challenges?

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Reservations: GraphQL Schema type Reservation { confirmationNumber: ID! hotel: Hotel! guest: User! startDate: AWSDate! endDate: AWSDate! rate: Int! } type Query { ... reservations(guestId : ID!):[Reservation] } type Mutation { createReservation(input:ReservationInput) deleteReservation(confNum: ID!) }

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Reservations: Query Resolver - Input #set( $todayString = $util.time.nowISO8601().substring(0, 10) ) { "version": "2017-02-28", "operation": "Query", "query": { "expression": "guestId = :gId AND startDate > :startDate", "expressionValues": { ":gId": $util.dynamodb.toDynamoDBJson($ctx.identity.sub), ":startDate": $util.dynamodb.toDynamoDBJson($todayString) } } }

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Reservations: Query Resolver - Output $util.toJson($ctx.result.items)

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Reservations: Result query { guestReservations { confirmationNumber hotel { hotelId name image phoneNumber } startDate endDate } }

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Extending Reservation Workflow Legacy System /graphql Subscription (MQTT) Mutate reservation record, modifying record in DynamoDB and triggering subscription DynamoDB Stream: Put event in queue for processing AWS Lambda AWS Lambda Amazon DynamoDB Amazon SNS Amazon SNS

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Subscription Query subscription ReservationSubscription { createReservationEvent(guestId:1) { confirmationNumber } }

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Mobile Code – Subscribe to changes let sub = CreateReservationEventSubscription(guestId: userId) newReservationSubscription = try appSyncClient?.subscribe(subscription: sub, resultHandler: { (result, transaction, error) in // check for error // store a reference to the new booking into our cache transaction?.update(query: GuestReservationsQuery(guestId: userId)) { (data: inout GuestReservationsQuery.Data) in data.guestReservations?.append(bookingToAdd) // consume the data in the UI self.bookingDetails?.append(bookingToAdd) } }

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KEEP CALM and WATCH the DEMO

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Let’s prototype! Phase #3: Adaptive rates bit.ly/graphql-aws-milano

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Adaptive Rates: Design R&D is building an adaptive rate capability Delivered via Amazon SageMaker API How do we add today’s rate to our existing API?

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How to evolve our GraphQL API GraphQL supports multiple data sources per query: 1. Add new field 2. Configure new Data Source and Resolvers

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Adaptive Rates: GraphQL Types and Resolvers type Hotel { hotelId: ID! name: String! location: String! ... rate: Rate } type Rate { hotelId: ID! rate: Int! currency: String! date: AWSDate! } ## rate Field Resolver: Request Mapping ## { "version": "2018-05-29", "method": "GET", "resourcePath": "/rd/rates/${ctx.source.hotelId}", "params": { "headers": { "Content-Type": "application/json" } } }

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Adaptive Rates: Result query { getHotel(hotelId: 3) { name location image phoneNumber address { street city } amenities rate { currency rate } } } { "name": "ElastiLodge North Rodgerstad", "location": "North Rodgerstad", "image": "https://placehold.it/300x300.png", "phoneNumber": "(214) 210-4674", "address": { "street": “...", "city": “..." }, "amenities": [ ... ], "rate": { "currency": "USD", "rate": 312 } }

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KEEP CALM and WATCH the DEMO

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What did we just do? bit.ly/graphql-aws-milano

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What did we accomplish today? Built a rich, flexible, mobile-ready API Incorporated legacy, new, and prototype features in a single endpoint Evolved API as requirements changed No coding required! Well, there were a few Velocity Templates AWS Console includes starter / boilerplate templates

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AWS Amplify CLI Toolchain for developers Enables you to prototype and build quickly Built-in GraphQL Transformer Converts schema to CloudFormation templates and builds cloud resources $ amplify api add # create GraphQL schema # for example: type Hotel @model @searchable { name: String! location: String! ... } github.com/aws-amplify/amplify-cli

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Backend Dev: Hmm. So you’re saying this “GraphQL” will allow any web/mobile developer to arbitrarily query basically any field in any backend service, recursively, however they want, without any backend developers involved? Frontend Dev: Yeah, right? It’s amazing! […silence…] Backend Dev: Guards, seize this person.

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Real-world pitfalls Cost of queries on the backend Authentication and authorization