.h2 Platforms

• Native Mobile (iOS, Android, React Native)
• Web Apps (JavaScript)

.h2 Features & API

• specify data requirements with code statements (graphql), using the console editor
• only needed data is fetched
• auto update data in app in realtime
• data can be added & updated locally while offline
• updates data for offline uses as soon as reconnect
• integration with Amazon Cognito & AWS IAM for setting fine grained permissions on graphql operations
  • OIDC token based
  • authz based on fields e.g. only author can update
• data stored in DynamoDB
• AWS Lambda functions can be triggered
• Run elasticsearch queries on the data
• auto resolve conflicts (default rules & define own business logic via Lambda)
• API Key, IAM, Cognito & OpenID Connect https://docs.aws.amazon.com/appsync/latest/devguide/security.html
• logs can be viewed in the web consoel & written to CloudWatch https://docs.aws.amazon.com/appsync/latest/devguide/monitoring.html#cwl
• default metrics for Latency, 4XX & 5XX errors https://docs.aws.amazon.com/appsync/latest/devguide/monitoring.html#cw-metrics

.h2 GraphQL & Querying

• not a graph DB
• db could be anything e.g. mongodb, mysql, dynamodb
• client sends its request 1 time, parses it and fetches/returns the data to the client in 1 round trip
• model the data and app state of what you need to arrive at
• define a schema defintion language (SDL) e.g.
• benefits
  • Type introspection https://en.wikipedia.org/wiki/Type_introspection
    • ability of a program to examine the type or properties of an object at runtime
    • A.instance_of?, a.class, A > B, B <= B
  • rapid prototyping
  • co-location of data requirements & app views (impl isn't encoded in the server)
  • data behaviour control (batching, request/response & real-time)
  • bandwidth optimisation
• integrates with apollographql client (plugins for platforms)
  • JS for mobile web & hybrid (react native/ionic)
  • offline support (automatically persisted data for queries)
  • read & write to local disk (dep on platform), fetch to server happens async (no latency from App pov) (Optimistic UI)
  • can add a callback for the fetch
• Event driven (handshake auth) for graphQL subscriptions
• auto websocket negotiation
• aws-amplify https://github.com/aws/aws-amplify
  • js lib for frontend & mobile dev (for JS frameworks & React + React Native)
  • Authentication (OOB uses cognito)
  • Analytics
  • API
  • Storage
  • Cache
• example schema available when creating an API via the console
• aws_subscibe to trigger notification to clients
• starter apps e.g
  • git clone https://github.com/aws-samples/aws-mobile-appsync-events-starter-android
  • download AppSync.json file
  • download graphql schema (.json or .graphql)
• Get an API URL & API Key (7 days valid, can be extended to 365 days)
• subscriptions listen for changes to a specific resource
• Java src is generated based on schema & events.graphql, allowing code completion when querying, mutating or subscribing
• uses MQTT over websocket
• each subscription has its own client (MqttSubscriptionClient)

User defined type. (types of Mutation (change) Subscription (subscribe to data))

type Query {

  getTodos: [Todo]

}

type Todo {

  id: ID!

  name: String

  description: String

  priority: Int

  duedate: String

}

{/noformat}

Query sent over network (client requests the shape of the data it wants)

query {
getTodos

}

Example client init

const client = new AWSAppSyncClient({

  url: awsconfig.ENDPOINT,

  region: AWS.config.region,

  auth: {

    type: AUTH_TYPE.AWS_IAM,

    credentials: Auth.currentCredentials()

  }

});

const WithProvider = () => (

  <ApolloProvider client={client}>

    <Rehydrated>

      <AppWithData />

    </Rehydrated>

  </ApolloProvider>

);

{/noformat}

Example Optimistic UI

options:

,
props: (props) => ({
onAdd: post => props.mutate({
optimisticResponse: () => ({
addPost:

}),
})
}),
update: (dataProxy, {data: {addPost}}) => {
const data = dataProxy.readQuery(

);
data.posts.push(addPost);
dataProxy.writeQuery(

);
}