Introduzione a GraphQL

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Introduzione a GraphQL
AWS AppSync & Amplify

Brief intro to Serverless

What is serverless?
No infrastructure provisioning,
no management
Automatic scaling
Pay for value Highly available and secure

AWS
Lambda
AWS
Fargate
Amazon
API Gateway
Amazon
SNS
Amazon
SQS
AWS
Step Functions
COMPUTE
DATA STORES
INTEGRATION
Amazon Aurora
Serverless
Amazon
S3
Amazon
DynamoDB
AWS
AppSync

GraphQL

/posts /comments /authors
REST API
posts comments authors
GraphQL API
What is GraphQL?

GraphQL APIs
Open, declarative data-fetching specification
!= Graph database
Use NoSQL, Relational, HTTP, etc.
Traditional data-fetching GraphQL
/posts
/postInfo
/postJustTitle
/postsByAuthor
/postNameStartsWithX
/commentsOnPost
/posts

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

GraphQL
Int: A signed 32‐bit integer.
Float: A signed double-precision floating-point value.
String: A UTF‐8 character sequence.
Boolean: true or false.
ID: The ID scalar type represents a unique identifier, often
used to refetch an object or as the key for a cache. The ID
type is serialized in the same way as a String; however,
defining it as an ID signifies that it is not intended to be
human‐readable.
Scalar types
GraphQL + AppSync
AWSDate: accepts date strings of the form YYYY-MM-DD.
AWSTime: accepts time strings of the form hh:mm:ss.sss.
AWSDateTime: accepts datetime strings of the form YYYY-MM-
DDThh:mm:ss.sssZ.
AWSTimestamp: represents the number of seconds that have
elapsed since 1970-01-01T00:00Z.
AWSEmail: represents an Email
AWSJSON: represents a JSON string that complies with RFC
8259.
AWSURL: represents a valid URL string.
AWSPhone: represents a valid Phone Number
AWSIPAddress: scalar type represents a valid IPv4 or IPv6
address string.

GraphQL Spec - Types
Schema
type Event {
id: ID!
name: String
where: String
when: String
description: String
comments: [Comment]
}
type Comment {
commentId: String!
eventId: ID!
content: String!
createdAt: String!
}

GraphQL Spec - Mutation
Schema
Mutation
type Mutation {
createEvent(
name: String!,
when: String!,
where: String!,
description: String!
): Event
deleteEvent(id: ID!): Event
commentOnEvent(
eventId: ID!,
content: String!,
createdAt: String!
): Comment
}

GraphQL Spec - Query
Schema
Mutation
Query
type Query {
getEvent(id: ID!): Event
listEvents(
limit: Int,
nextToken: String
): EventConnection
}

GraphQL Spec - Subscription
Schema
Mutation
Query
Subscription type Subscription {
onComments(eventId: String!): Comment
@aws_subscribe(mutations: ["commentOnEvent"])
}

GraphQL Spec - Subscription
Schema
Mutation
Query
Subscription type Subscription {
onComments(eventId: String!): Comment
@aws_subscribe(mutations: ["commentOnEvent"])
}
type Mutation {
…
commentOnEvent(
eventId: ID!,
content: String!,
createdAt: String!
): Comment
}

GraphQL - Summary
Schema
Mutation
Query
Subscription
Realtime? YES
Batching? YES
Pagination? YES
Relations? YES
Aggregations? YES
Search? YES
Offline? YES

What are the GraphQL benefits?
• Rapid prototyping and iteration
• Co-location of data requirements & application views
o Implementations aren’t encoded in the server
• Data behavior control
o Batching, request/response and real-time
• Bandwidth optimization (N+1 problem)

I want to run my own GraphQL server!!

AWS AppSync – Intro

What is AWS AppSync?
AWS AppSync is a managed service for application data
using GraphQL with real-time capabilities and an offline
programming model.
Real-time
Collaboration
Offline Programming
Model with Sync
Flexible Database
Options
Fine-grained
Access Control

AWS AppSync Benefits
Get many resources from
many data sources with a
single request
Self-documenting APIs with
Introspection
Clients receive the data
they ask for. Nothing
more, nothing less
React Native, Android,
iOS, and Web (JS) using
the Apollo GraphQL client
Data persistence across
application restarts
Write-through mutations with
optimistic UI

How does AWS AppSync work?

AWS AppSync and GraphQL Subscription
Near Realtime updates of data
Event based mode, triggered by Mutations
- Scalable model, designed as a platform for common use-cases
Can be used with ANY data source in AppSync
- Lambda, DynamoDB, Elasticsearch
mutation addPost(
id: 123
title: ”New post!”
author: ”Nadia”)
{
id
title
author
}
data: [{
id: 123,
title: ”New Post!”
author: ”Nadia”
}]
Websockets over MQTT

AWS AppSync – Data Sources, Auth and more
DynamoDB
Lambda
Function Elasticsearch
Service
GraphQL
Schema
Upload
Schema
GraphQL
Query
Mutation
Subscription
Real-time
Offline
AppSync
API
Cognito
User Pool
Legacy
Application
Amazon RDS
HTTPS
endpoint

How does AppSync connect to my data sources?
{
"version": "2017-02-28",
"operation": "GetItem",
"key": {
"company_id": $util.dynamodb.toDynamoDBJson($ctx.args.id),
}
}

AWS AppSync – Debug Resolver Flow
Amazon CloudWatch logs

What about Offline access?

AppSync Client Storage
• Offline is a write-through "Store"
• Persistent storage mediums back the Apollo normalized
cache
• Local Storage for web
• AsyncStorage for React Native
• SQLite on native platforms
• Database can be preloaded
• Offline client can be configured
• WiFi only
• WiFi and cellular

AWS AppSync – Conflict Resolution
Conflict resolution in the cloud
a. Server wins
b. Client wins
c. Silent reject
d. Custom logic (AWS Lambda)
- Optimistic version check
- Extend with your own checks
Optional
• Client callback for Conflict Resolution is
still available as a fallback
{
"version" : "2017-02-28",
"operation" : "PutItem",
"key" : {
"id" : { "S" : "1" }
},
"condition" : {
"expression" : "attribute_not_exists(id)"
}
}
Example: Check that an ID doesn’t already exist:
"condition" : {
"expression" : "someExpression"
"conditionalCheckFailedHandler" : {
"strategy" : "Custom",
"lambdaArn" : "arn:..."
}
}
Run Lambda if version wrong:

Amplify Framework

Amplify Framework
ü CLI
ü Client libraries (native and JS support)
ü Console – Continuous deployment
and hosting
ü Prebuilt UI components
ü Toolchain
ü JS framework support

• Create, update, and delete cloud services
• Manage multiple environments
• GraphQL Transform
• GraphQL Codegen
Amplify Framework
CLI

Categories
Authentication
Analytics
Interactions (chat bots)
API (REST)
API (GraphQL)
Amplify CLI
Serverless functions
Storage
XR
Push notifications
Video
AI/ML

$ amplify add auth
$ amplify push
$ amplify configure auth
$ amplify delete
$ amplify codegen add
Amplify CLI

$ amplify add api
–
# schema.graphql
type Post @model {
id: ID!
title: String!
}

@model
Top-level entity; creates DynamoDB table, resolvers, and additional schema (queries,
mutations, and subscriptions) for base type
@connection
Enables relationships between @model types
@auth
Enables set of authorization rules
@searchable
Handles streaming the data of an @model object type to Amazon Elasticsearch Service
and configures search resolvers
@versioned
Enables versioning
@function
Enables adding a Lambda function as a data source
–

GraphQL Transform: Mix and match data sources
type Post {
id: ID!
content: String
description: String
ups: Int
downs: Int
}

createPost
readPost
updatePost
deletePost
type Post
@model {
id: ID!
content: String
description: String
ups: Int
downs: Int
}

mutations
queries
createPost
readPost
updatePost
deletePost
type Post
@model
@auth(rules: [{allow:
owner}]){
id: ID!
content: String
description: String
ups: Int
downs: Int
}

searchPosts
mutations
queries
createPost
readPost
updatePost
deletePost
type Post
@model
@auth(rules: [{allow: owner}])
@searchable{
id: ID!
content: String
description: String
ups: Int
downs: Int
}

searchPosts
mutations
queries
createPost
readPost
updatePost
deletePost
type Post
@model
@auth(rules: [{allow:
owner}])
@searchable{
id: ID!
content: String
description: String
ups: Int
downs: Int
}

Resources
• https://docs.aws.amazon.com/appsync/lates
t/devguide/
• https://github.com/aws-amplify/amplify-js
• https://github.com/aws/aws-appsync-
community
• https://github.com/awslabs
• https://www.amplify.com/

Introduzione a GraphQL

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