index.ts

/**
 *  Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
 *  with the License. A copy of the License is located at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  or in the 'license' file accompanying this file. This file is distributed on an 'AS IS' BASIS, WITHOUT WARRANTIES
 *  OR CONDITIONS OF ANY KIND, express or implied. See the License for the specific language governing permissions
 *  and limitations under the License.
 */

import * as lambda from '@aws-cdk/aws-lambda';
import * as dynamodb from '@aws-cdk/aws-dynamodb';
import * as defaults from '@aws-solutions-constructs/core';
import { Construct } from '@aws-cdk/core';
import { overrideProps } from '@aws-solutions-constructs/core';

/**
 * @summary The properties for the LambdaToDynamoDB Construct
 */
export interface LambdaToDynamoDBProps {
  /**
   * Whether to create a new lambda function or use an existing lambda function.
   * If set to false, you must provide a lambda function object as `existingObj`
   *
   * @default - true
   */
  readonly deployLambda: boolean,
  /**
   * Existing instance of Lambda Function object.
   * If `deploy` is set to false only then this property is required
   *
   * @default - None
   */
  readonly existingLambdaObj?: lambda.Function,
  /**
   * Optional user provided props to override the default props.
   * If `deploy` is set to true only then this property is required
   *
   * @default - Default props are used
   */
  readonly lambdaFunctionProps?: lambda.FunctionProps,
  /**
   * Existing instance of dynamodb table object.
   * If this is set then the dynamoTableProps is ignore.
   *
   * @default - None
   */
  readonly existingTableObj?: dynamodb.Table,
  /**
   * Optional user provided props to override the default props
   *
   * @default - Default props are used
   */
  readonly dynamoTableProps?: dynamodb.TableProps
}

export class LambdaToDynamoDB extends Construct {
  public readonly lambdaFunction: lambda.Function;
  public readonly dynamoTable: dynamodb.Table;

  /**
   * @summary Constructs a new instance of the LambdaToDynamoDB class.
   * @param {cdk.App} scope - represents the scope for all the resources.
   * @param {string} id - this is a a scope-unique id.
   * @param {LambdaToDynamoDBProps} props - user provided props for the construct
   * @since 0.8.0
   * @access public
   */
  constructor(scope: Construct, id: string, props: LambdaToDynamoDBProps) {
    super(scope, id);

    this.lambdaFunction = defaults.buildLambdaFunction(this, {
      deployLambda: props.deployLambda,
      existingLambdaObj: props.existingLambdaObj,
      lambdaFunctionProps: props.lambdaFunctionProps
    });


    if (!props.existingTableObj) {
      // Set the default props for DynamoDB table
      if (props.dynamoTableProps) {
        const dynamoTableProps = overrideProps(defaults.DefaultTableProps, props.dynamoTableProps);
        this.dynamoTable = new dynamodb.Table(this, 'DynamoTable', dynamoTableProps);
      } else {
        this.dynamoTable = new dynamodb.Table(this, 'DynamoTable', defaults.DefaultTableProps);
      }
    } else {
      this.dynamoTable = props.existingTableObj;
    }


    this.lambdaFunction.addEnvironment('DDB_TABLE_NAME', this.dynamoTable.tableName);

    this.dynamoTable.grantReadWriteData(this.lambdaFunction.grantPrincipal);

    // Conditional metadata for cfn_nag
    if (props.dynamoTableProps?.billingMode === dynamodb.BillingMode.PROVISIONED) {
      const cfnTable: dynamodb.CfnTable = this.dynamoTable.node.findChild('Resource') as dynamodb.CfnTable;
      cfnTable.cfnOptions.metadata = {
          cfn_nag: {
              rules_to_suppress: [{
                  id: 'W73',
                  reason: `PROVISIONED billing mode is a default and is not explicitly applied as a setting.`
              }]
          }
      };
    }
  }
}