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This code snippet demonstrates how to set up a database stack using AWS CDK with TypeScript. It includes the creation of a VPC, security groups, and an RDS instance. The roles to be used by Lambdas to access the database are also defined here. Also included Lambda functions to initialize the database with a user and permissions and function to create tables on the database. The initialize function is triggered via a custom resource to ensure it runs after the RDS instance is created. The function to create tables is also defined and should be invoked as needed from AWS Console or other mechanisms.

    
export class DatabaseStack extends Stack {
  constructor(scope: Construct, id: string, props: WebStackProps) {
    super(scope, id, props);
    const { environment } = props;
    const { secretArn } = props.env;
    // VPC for RDS and lambda resolvers
    const { vpc, securityGroupResolvers, securityGroupRDS } = createVPCAndSecurityGroups(this);
    // IAM role
    const rdsRole = createRDSRole(this);
    // RDS Postgresql instance
    const rdsInstance = createRDSInstance(this, {
      vpc,
      securityGroupRDS,
      rdsRole
    });
    const lambdaRole = createLambdaRole(this, [secretArn, rdsInstance.secret!.secretArn], rdsInstance.instanceArn);
    // Secrets for database credentials
    const credentials = Secret.fromSecretCompleteArn(this, 'Credentials', secretArn);
    credentials.grantRead(rdsRole);

    // Returns functions to connect with RDS instance
    const paramsForResolver = {
      vpc,
      securityGroupResolvers,
      securityGroupRDS,
      role: lambdaRole,
      rdsInstance,
      credentials
    };

    // Instantiate a new db with user and permissions also add table
    const instantiate = createInstantiateFunction({
      creator: createResolverSuperUser(this, paramsForResolver)
    });
    const tables = createTablesFunction({
      creator: createResolverUser(this, paramsForResolver)
    });
    instantiate.node.addDependency(rdsInstance);
    tables.node.addDependency(rdsInstance);

    const triggerName = 'ti-function';
    const lambdaRoleWithTrigger = createLambdaRoleWithTrigger(this, [secretArn, rdsInstance.secret!.secretArn], rdsInstance.instanceArn, instantiate.functionArn);
    // Custom resource to execute instantiate function
    const customResource = new AwsCustomResource(this, triggerName, {
      functionName: triggerName,
      role: lambdaRoleWithTrigger,
      onUpdate: {
        service: 'Lambda',
        action: 'invoke',
        parameters: { FunctionName: instantiate.functionName },
        physicalResourceId: PhysicalResourceId.of(triggerName)
      },
      policy: AwsCustomResourcePolicy.fromSdkCalls({
        resources: [instantiate.functionArn]
      })
    });
    customResource.node.addDependency(instantiate);

    // You can add CfnOutput to share the RDS Endpoint or other resources if needed
  }
}