AWS AppSync Construct Library

---

!cdk-constructs: Experimental

> The APIs of higher level constructs in this module are experimental and under active development.
> They are subject to non-backward compatible changes or removal in any future version. These are
> not subject to the Semantic Versioning model and breaking changes will be
> announced in the release notes. This means that while you may use them, you may need to update
> your source code when upgrading to a newer version of this package.

---

The @aws-cdk/aws-appsync package contains constructs for building flexible
APIs that use GraphQL.

``ts nofixture
import * as appsync from '@aws-cdk/aws-appsync-alpha';
`

Example

$3

Example of a GraphQL API with AWS_IAM authorization resolving into a DynamoDb
backend data source.

GraphQL schema file schema.graphql:

`gql
type demo {
id: String!
version: String!
}
type Query {
getDemos: [ demo! ]
}
input DemoInput {
version: String!
}
type Mutation {
addDemo(input: DemoInput!): demo
}
`

CDK stack file app-stack.ts:

`ts
const api = new appsync.GraphqlApi(this, 'Api', {
name: 'demo',
schema: appsync.SchemaFile.fromAsset(path.join(__dirname, 'schema.graphql')),
authorizationConfig: {
defaultAuthorization: {
authorizationType: appsync.AuthorizationType.IAM,
},
},
xrayEnabled: true,
});

const demoTable = new dynamodb.Table(this, 'DemoTable', {
partitionKey: {
name: 'id',
type: dynamodb.AttributeType.STRING,
},
});

const demoDS = api.addDynamoDbDataSource('demoDataSource', demoTable);

// Resolver for the Query "getDemos" that scans the DynamoDb table and returns the entire list.
// Resolver Mapping Template Reference:
// https://docs.aws.amazon.com/appsync/latest/devguide/resolver-mapping-template-reference-dynamodb.html
demoDS.createResolver('QueryGetDemosResolver', {
typeName: 'Query',
fieldName: 'getDemos',
requestMappingTemplate: appsync.MappingTemplate.dynamoDbScanTable(),
responseMappingTemplate: appsync.MappingTemplate.dynamoDbResultList(),
});

// Resolver for the Mutation "addDemo" that puts the item into the DynamoDb table.
demoDS.createResolver('MutationAddDemoResolver', {
typeName: 'Mutation',
fieldName: 'addDemo',
requestMappingTemplate: appsync.MappingTemplate.dynamoDbPutItem(
appsync.PrimaryKey.partition('id').auto(),
appsync.Values.projecting('input'),
),
responseMappingTemplate: appsync.MappingTemplate.dynamoDbResultItem(),
});

//To enable DynamoDB read consistency with the MappingTemplate:
demoDS.createResolver('QueryGetDemosConsistentResolver', {
typeName: 'Query',
fieldName: 'getDemosConsistent',
requestMappingTemplate: appsync.MappingTemplate.dynamoDbScanTable(true),
responseMappingTemplate: appsync.MappingTemplate.dynamoDbResultList(),
});
`

$3

AppSync provides a data source for executing SQL commands against Amazon Aurora
Serverless clusters. You can use AppSync resolvers to execute SQL statements
against the Data API with GraphQL queries, mutations, and subscriptions.

`ts
// Create username and password secret for DB Cluster
const secret = new rds.DatabaseSecret(this, 'AuroraSecret', {
username: 'clusteradmin',
});

// The VPC to place the cluster in
const vpc = new ec2.Vpc(this, 'AuroraVpc');

// Create the serverless cluster, provide all values needed to customise the database.
const cluster = new rds.ServerlessCluster(this, 'AuroraCluster', {
engine: rds.DatabaseClusterEngine.AURORA_MYSQL,
vpc,
credentials: { username: 'clusteradmin' },
clusterIdentifier: 'db-endpoint-test',
defaultDatabaseName: 'demos',
});

// Build a data source for AppSync to access the database.
declare const api: appsync.GraphqlApi;
const rdsDS = api.addRdsDataSource('rds', cluster, secret, 'demos');

// Set up a resolver for an RDS query.
rdsDS.createResolver('QueryGetDemosRdsResolver', {
typeName: 'Query',
fieldName: 'getDemosRds',
requestMappingTemplate: appsync.MappingTemplate.fromString(
{
"version": "2018-05-29",
"statements": [
"SELECT * FROM demos"
]
}
),
responseMappingTemplate: appsync.MappingTemplate.fromString(
$utils.toJson($utils.rds.toJsonObject($ctx.result)[0])
),
});

// Set up a resolver for an RDS mutation.
rdsDS.createResolver('MutationAddDemoRdsResolver', {
typeName: 'Mutation',
fieldName: 'addDemoRds',
requestMappingTemplate: appsync.MappingTemplate.fromString(
{
"version": "2018-05-29",
"statements": [
"INSERT INTO demos VALUES (:id, :version)",
"SELECT * WHERE id = :id"
],
"variableMap": {
":id": $util.toJson($util.autoId()),
":version": $util.toJson($ctx.args.version)
}
}
),
responseMappingTemplate: appsync.MappingTemplate.fromString(
$utils.toJson($utils.rds.toJsonObject($ctx.result)[1][0])
),
});
`

$3

GraphQL schema file schema.graphql:

`gql
type job {
id: String!
version: String!
}

input DemoInput {
version: String!
}

type Mutation {
callStepFunction(input: DemoInput!): job
}
`

GraphQL request mapping template request.vtl:

`json
{
"version": "2018-05-29",
"method": "POST",
"resourcePath": "/",
"params": {
"headers": {
"content-type": "application/x-amz-json-1.0",
"x-amz-target":"AWSStepFunctions.StartExecution"
},
"body": {
"stateMachineArn": "",
"input": "{ \"id\": \"$context.arguments.id\" }"
}
}
}
`

GraphQL response mapping template response.vtl:

`json
{
"id": "${context.result.id}"
}
`

CDK stack file app-stack.ts:

`ts
const api = new appsync.GraphqlApi(this, 'api', {
name: 'api',
schema: appsync.SchemaFile.fromAsset(path.join(__dirname, 'schema.graphql')),
});

const httpDs = api.addHttpDataSource(
'ds',
'https://states.amazonaws.com',
{
name: 'httpDsWithStepF',
description: 'from appsync to StepFunctions Workflow',
authorizationConfig: {
signingRegion: 'us-east-1',
signingServiceName: 'states',
}
}
);

httpDs.createResolver('MutationCallStepFunctionResolver', {
typeName: 'Mutation',
fieldName: 'callStepFunction',
requestMappingTemplate: appsync.MappingTemplate.fromFile('request.vtl'),
responseMappingTemplate: appsync.MappingTemplate.fromFile('response.vtl'),
});
`

$3

AppSync has builtin support for Amazon OpenSearch Service (successor to Amazon
Elasticsearch Service) from domains that are provisioned through your AWS account. You can
use AppSync resolvers to perform GraphQL operations such as queries, mutations, and
subscriptions.

`ts
import * as opensearch from 'aws-cdk-lib/aws-opensearchservice';

const user = new iam.User(this, 'User');
const domain = new opensearch.Domain(this, 'Domain', {
version: opensearch.EngineVersion.OPENSEARCH_1_3,
removalPolicy: RemovalPolicy.DESTROY,
fineGrainedAccessControl: { masterUserArn: user.userArn },
encryptionAtRest: { enabled: true },
nodeToNodeEncryption: true,
enforceHttps: true,
});

declare const api: appsync.GraphqlApi;
const ds = api.addOpenSearchDataSource('ds', domain);

ds.createResolver('QueryGetTestsResolver', {
typeName: 'Query',
fieldName: 'getTests',
requestMappingTemplate: appsync.MappingTemplate.fromString(JSON.stringify({
version: '2017-02-28',
operation: 'GET',
path: '/id/post/_search',
params: {
headers: {},
queryString: {},
body: { from: 0, size: 50 },
},
})),
responseMappingTemplate: appsync.MappingTemplate.fromString([
#foreach($entry in $context.result.hits.hits)
#if( $velocityCount > 1 ) , #end
$utils.toJson($entry.get("_source"))
#end
]),
});
`

Custom Domain Names

For many use cases you may want to associate a custom domain name with your
GraphQL API. This can be done during the API creation.

`ts
import * as acm from 'aws-cdk-lib/aws-certificatemanager';
import * as route53 from 'aws-cdk-lib/aws-route53';

const myDomainName = 'api.example.com';
const certificate = new acm.Certificate(this, 'cert', { domainName: myDomainName });
const schema = new appsync.SchemaFile({ filePath: 'mySchemaFile' })
const api = new appsync.GraphqlApi(this, 'api', {
name: 'myApi',
schema,
domainName: {
certificate,
domainName: myDomainName,
},
});

// hosted zone and route53 features
declare const hostedZoneId: string;
declare const zoneName = 'example.com';

// hosted zone for adding appsync domain
const zone = route53.HostedZone.fromHostedZoneAttributes(this, HostedZone, {
hostedZoneId,
zoneName,
});

// create a cname to the appsync domain. will map to something like xxxx.cloudfront.net
new route53.CnameRecord(this, CnameApiRecord, {
recordName: 'api',
zone,
domainName: api.appSyncDomainName,
});
`

Log Group

AppSync automatically create a log group with the name /aws/appsync/apis/ upon deployment with
log data set to never expire. If you want to set a different expiration period, use the logConfig.retention property.

To obtain the GraphQL API's log group as a logs.ILogGroup use the logGroup property of the
GraphqlApi construct.

`ts
import * as logs from 'aws-cdk-lib/aws-logs';

const logConfig: appsync.LogConfig = {
retention: logs.RetentionDays.ONE_WEEK,
};

new appsync.GraphqlApi(this, 'api', {
authorizationConfig: {},
name: 'myApi',
schema: appsync.SchemaFile.fromAsset(path.join(__dirname, 'myApi.graphql')),
logConfig,
});
`

Schema

You can define a schema using from a local file using SchemaFile.fromAsset

`ts
const api = new appsync.GraphqlApi(this, 'api', {
name: 'myApi',
schema: appsync.SchemaFile.fromAsset(path.join(__dirname, 'schema.graphl')),
});
`

$3

Alternative schema sources can be defined by implementing the ISchema
interface. An example of this is the CodeFirstSchema class provided in
awscdk-appsync-utils

Imports

Any GraphQL Api that has been created outside the stack can be imported from
another stack into your CDK app. Utilizing the fromXxx function, you have
the ability to add data sources and resolvers through a IGraphqlApi interface.

`ts
declare const api: appsync.GraphqlApi;
declare const table: dynamodb.Table;
const importedApi = appsync.GraphqlApi.fromGraphqlApiAttributes(this, 'IApi', {
graphqlApiId: api.apiId,
graphqlApiArn: api.arn,
});
importedApi.addDynamoDbDataSource('TableDataSource', table);
`

If you don't specify graphqlArn in fromXxxAttributes, CDK will autogenerate
the expected arn for the imported api, given the apiId. For creating data
sources and resolvers, an apiId is sufficient.

Authorization

There are multiple authorization types available for GraphQL API to cater to different
access use cases. They are:

- API Keys (AuthorizationType.API_KEY)
- Amazon Cognito User Pools (AuthorizationType.USER_POOL)
- OpenID Connect (AuthorizationType.OPENID_CONNECT)
- AWS Identity and Access Management (AuthorizationType.AWS_IAM)
- AWS Lambda (AuthorizationType.AWS_LAMBDA)

These types can be used simultaneously in a single API, allowing different types of clients to
access data. When you specify an authorization type, you can also specify the corresponding
authorization mode to finish defining your authorization. For example, this is a GraphQL API
with AWS Lambda Authorization.

`ts
import * as lambda from 'aws-cdk-lib/aws-lambda';
declare const authFunction: lambda.Function;

new appsync.GraphqlApi(this, 'api', {
name: 'api',
schema: appsync.SchemaFile.fromAsset(path.join(__dirname, 'appsync.test.graphql')),
authorizationConfig: {
defaultAuthorization: {
authorizationType: appsync.AuthorizationType.LAMBDA,
lambdaAuthorizerConfig: {
handler: authFunction,
// can also specify resultsCacheTtl and validationRegex.
},
},
},
});
`

Permissions

When using AWS_IAM as the authorization type for GraphQL API, an IAM Role
with correct permissions must be used for access to API.

When configuring permissions, you can specify specific resources to only be
accessible by IAM authorization. For example, if you want to only allow mutability
for IAM authorized access you would configure the following.

In schema.graphql:

`gql
type Mutation {
updateExample(...): ...
@aws_iam
}
`

In IAM:

`json
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"appsync:GraphQL"
],
"Resource": [
"arn:aws:appsync:REGION:ACCOUNT_ID:apis/GRAPHQL_ID/types/Mutation/fields/updateExample"
]
}
]
}
`

See documentation for more details.

To make this easier, CDK provides grant API.

Use the grant function for more granular authorization.

`ts
const role = new iam.Role(this, 'Role', {
assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
});
declare const api: appsync.GraphqlApi;

api.grant(role, appsync.IamResource.custom('types/Mutation/fields/updateExample'), 'appsync:GraphQL');
`

$3

In order to use the grant functions, you need to use the class IamResource.

- IamResource.custom(...arns) permits custom ARNs and requires an argument.

- IamResouce.ofType(type, ...fields) permits ARNs for types and their fields.

- IamResource.all() permits ALL resources.

$3

Alternatively, you can use more generic grant functions to accomplish the same usage.

These include:

- grantMutation (use to grant access to Mutation fields)
- grantQuery (use to grant access to Query fields)
- grantSubscription (use to grant access to Subscription fields)

`ts
declare const api: appsync.GraphqlApi;
declare const role: iam.Role;

// For generic types
api.grantMutation(role, 'updateExample');

// For custom types and granular design
api.grant(role, appsync.IamResource.ofType('Mutation', 'updateExample'), 'appsync:GraphQL');
`

Pipeline Resolvers and AppSync Functions

AppSync Functions are local functions that perform certain operations onto a
backend data source. Developers can compose operations (Functions) and execute
them in sequence with Pipeline Resolvers.

`ts
declare const api: appsync.GraphqlApi;

const appsyncFunction = new appsync.AppsyncFunction(this, 'function', {
name: 'appsync_function',
api,
dataSource: api.addNoneDataSource('none'),
requestMappingTemplate: appsync.MappingTemplate.fromFile('request.vtl'),
responseMappingTemplate: appsync.MappingTemplate.fromFile('response.vtl'),
});
`

AppSync Functions are used in tandem with pipeline resolvers to compose multiple
operations.

`ts
declare const api: appsync.GraphqlApi;
declare const appsyncFunction: appsync.AppsyncFunction;

const pipelineResolver = new appsync.Resolver(this, 'pipeline', {
api,
dataSource: api.addNoneDataSource('none'),
typeName: 'typeName',
fieldName: 'fieldName',
requestMappingTemplate: appsync.MappingTemplate.fromFile('beforeRequest.vtl'),
pipelineConfig: [appsyncFunction],
responseMappingTemplate: appsync.MappingTemplate.fromFile('afterResponse.vtl'),
});
``

Learn more about Pipeline Resolvers and AppSync Functions here.