Exposing our hit counter table

Add a table property to our hit counter #

Edit hitcounter.ts and modify it as such table is exposed as a public property.

import * as lambda from "aws-cdk-lib/aws-lambda";
import * as dynamodb from "aws-cdk-lib/aws-dynamodb";
import { Construct } from "constructs";
import { NodejsFunction } from "aws-cdk-lib/aws-lambda-nodejs";
import * as path from "path";

export interface HitCounterProps {
  /** the function for which we want to count url hits **/
  downstream: lambda.IFunction;
}

export class HitCounter extends Construct {
  /** allows accessing the counter function */
  public readonly handler: lambda.Function;

  /** the hit counter table */
  public readonly table: dynamodb.Table;

  constructor(scope: Construct, id: string, props: HitCounterProps) {
    super(scope, id);

    const table = new dynamodb.Table(this, "Hits", {
      partitionKey: { name: "path", type: dynamodb.AttributeType.STRING },
      billingMode: dynamodb.BillingMode.PAY_PER_REQUEST,
    });
    this.table = table;

    this.handler = new NodejsFunction(this, "HitCounterHandler", {
      runtime: lambda.Runtime.NODEJS_20_X,
      handler: "handler",
      entry: path.join(__dirname, "../lambda/hitcounter.ts"),
      environment: {
        DOWNSTREAM_FUNCTION_NAME: props.downstream.functionName,
        HITS_TABLE_NAME: table.tableName,
      },
    });

    // grant the lambda role read/write permissions to our table
    table.grantReadWriteData(this.handler);

    // grant the lambda role invoke permissions to the downstream function
    props.downstream.grantInvoke(this.handler);
  }
}

Now we can access the table from our stack #

Go back to cdk-workshop-stack.ts and assign the table property of the table viewer:

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as apigw from 'aws-cdk-lib/aws-apigateway';
import { HitCounter } from './hitcounter';
import { TableViewer } from 'cdk-dynamo-table-viewer';

export class CdkWorkshopStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const hello = new lambda.Function(this, 'HelloHandler', {
      runtime: lambda.Runtime.NODEJS_20_X,
      code: lambda.Code.fromAsset('lambda'),
      handler: 'hello.handler'
    });

    const helloWithCounter = new HitCounter(this, 'HelloHitCounter', {
      downstream: hello
    });

    // defines an API Gateway REST API resource backed by our "hello" function.
    new apigw.LambdaRestApi(this, 'Endpoint', {
      handler: helloWithCounter.handler
    });

    new TableViewer(this, 'ViewHitCounter', {
      title: 'Hello Hits',
      table: helloWithCounter.table
    });
  }
}

We’re finished making code changes, so once you save this file, you can close the npm run watch command with Ctrl-C.