Scheduling in AWS using time zone 📅

Scheduling

Sometimes you need to schedule an AWS service based on your local time zone. As of now, that's possible! In this tutorial, we will schedule a lambda using an EventBridge schedule. We will use CDK to create the infrastructure. Check out the architecture 🏛 below.

Architecture

First, we need a lambda. In this example we're using a Node.js lambda.

const func = new NodejsFunction(this, 'func-id', {
  runtime: Runtime.NODEJS_18_X
});

Then, we need a role 👷 so the EventBridge schedule can invoke the lambda.

const role = new Role(this, 'role-id', {
  managedPolicies: [{ managedPolicyArn: 'arn:aws:iam::aws:policy/service-role/AWSLambdaRole' }],
  assumedBy: new ServicePrincipal('scheduler.amazonaws.com')
});

Finally, we need to create an EventBridge schedule 📅.

new CfnSchedule(this, 'schedule-id', {
  flexibleTimeWindow: {
    mode: 'OFF',
  },
  scheduleExpression: 'cron(0 6,8 ? * MON-FRI *)',
  scheduleExpressionTimezone: 'Europe/Amsterdam',
  target: {
    arn: func.functionArn,
    roleArn: role.roleArn,
  },
});

Let's go over some of the fields in the CfnSchedule construct.

• target: here you can find a reference 📙 to both the ARN of the lambda and of the role.
• scheduleExpressionTimezone: here you can pick your time zone of choice 👆.
• scheduleExpression: here you can add a cron schedule. The easiest way to test your cron is to enter it in the AWS console when creating a schedule. You will get instant validation feedback if your cron is not correct ❌.

Cron validation

You will also see the upcoming trigger 🔫 dates, which allows you to verify your scheduling.

Upcoming trigger dates

Example code

Here's the entire CDK code that's already working. First, the stack.

import { Stack, StackProps } from 'aws-cdk-lib';
import { Role, ServicePrincipal } from 'aws-cdk-lib/aws-iam';
import { Runtime } from 'aws-cdk-lib/aws-lambda';
import { NodejsFunction } from 'aws-cdk-lib/aws-lambda-nodejs';
import { CfnSchedule } from 'aws-cdk-lib/aws-scheduler';
import { Construct } from 'constructs';
import { join } from 'path';

export class SchedulingStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);
    const func = new NodejsFunction(this, 'func-id', {
      entry: join(__dirname, '../src/lambda/func.ts'),
      runtime: Runtime.NODEJS_18_X,
    });
    const role = new Role(this, 'role-id', {
      managedPolicies: [{ managedPolicyArn: 'arn:aws:iam::aws:policy/service-role/AWSLambdaRole' }],
      assumedBy: new ServicePrincipal('scheduler.amazonaws.com'),
    });
    new CfnSchedule(this, 'schedule-id', {
      flexibleTimeWindow: {
        mode: 'OFF',
      },
      scheduleExpression: 'cron(0 6,8 ? * MON-FRI *)',
      scheduleExpressionTimezone: 'Europe/Amsterdam',
      target: {
        arn: func.functionArn,
        roleArn: role.roleArn,
      },
    });
  }
}

Then, the CDK lambda code.

export async function handler(): Promise<void> {
  console.log('Func-y!');
}

If you execute a cdk deploy, this code should deploy a EventBridge schedule, IAM role and lambda function to your account.

You're all set now! Good luck writing your own time zone based schedule 📅.