TL;DR

In this article you will learn how to add logs in an Express workflow in Step Functions with the CDK because it is not enabled by default. Since they are enabled by default on a Standard State Machine, it can be misleading going from a Standard to an Express workflow.

Here is the snippet of code you need.

import { App, RemovalPolicy, Stack } from 'aws-cdk-lib';
import { LogGroup, RetentionDays } from 'aws-cdk-lib/aws-logs';
import { LogLevel, Pass, StateMachine, StateMachineType } from 'aws-cdk-lib/aws-stepfunctions';

export class ArticleStack extends Stack {
  constructor(scope: App, id: string) {
    super(scope, id);

    const expressLogGroup = new LogGroup(this, 'ExpressLogs', {
      retention: RetentionDays.ONE_DAY,
      removalPolicy: RemovalPolicy.DESTROY,
    });

    new StateMachine(this, 'ExpressWithLogs', {
      definition: new Pass(scope, 'ExampleStepForExpressWithLogs', {
        parameters: {
          bar: 'foo',
        },
      }),
      stateMachineType: StateMachineType.EXPRESS,
      logs: {
        destination: expressLogGroup,
        level: LogLevel.ALL,
        includeExecutionData: true,
      },
    });
  }
}

Standard workflows have logs enabled by default inside AWS Step Functions 💡

📙 Read this to better grasp what is happening with these log groups in Step Function or skip to the next section for the tutorial you came for

AWS explains it really clearly in its documentation, here is a quote describing the default logs behaviors of both Standard and Express types of State Machine.

Standard Workflows record execution history in AWS Step Functions, although you can optionally configure logging to Amazon CloudWatch Logs.

Unlike Standard Workflows, Express Workflows don't record execution history in AWS Step Functions. To see execution history and results for an Express Workflow, you must configure logging to Amazon CloudWatch Logs. Publishing logs doesn't block or slow down executions.

The following images show three different State Machines: one Express configured with logs, one Express configured without logs and one Standard. The only one that has a log group associated is the Express one configured with a log group.

The logs available for the Standard workflow are inside the AWS Step Functions service but there is no log group associated.

CDK is your best friend 💻

All you need is to create a log group, configure it and then attach it to the State Machine via the logs prop. If you want to jump directly to the snippet here is a shortcut.

The CDK handles all the work of creating the role for the State Machine to write inside CloudWatch.

The LogLevel allows you to select what kind of information you want to have. The four levels are: OFF, ALL, ERROR and FATAL. It is recommended by AWS to choose ALL because to have logs of all executions and not only the failed ones in this documentation.

But the includeExecutionData property of the CDK construct makes all the difference. Thanks to this property set to true, you have all step transition data displayed in the Step Functions console.

Express with NO logs execution data

Express with logs execution data because includeExecutionData is set to true

How to configure logs in an Express workflow in CDK ✅

Here is the snippet of code that you need to make it happen. 🧑‍💻

import { App, RemovalPolicy, Stack } from 'aws-cdk-lib';
import { LogGroup, RetentionDays } from 'aws-cdk-lib/aws-logs';
import { LogLevel, Pass, StateMachine, StateMachineType } from 'aws-cdk-lib/aws-stepfunctions';

export class ArticleStack extends Stack {
  constructor(scope: App, id: string) {
    super(scope, id);

    const expressLogGroup = new LogGroup(this, 'ExpressLogs', {
      retention: RetentionDays.ONE_DAY,
      removalPolicy: RemovalPolicy.DESTROY,
    });

    new StateMachine(this, 'ExpressWithLogs', {
      definition: new Pass(scope, 'ExampleStepForExpressWithLogs', {
        parameters: {
          bar: 'foo',
        },
      }),
      stateMachineType: StateMachineType.EXPRESS,
      logs: {
        destination: expressLogGroup,
        level: LogLevel.ALL,
        includeExecutionData: true,
      },
    });
  }
}

For this snippet of code, I used the V2 of the CDK (2.56 to be more precise)

Conclusion

You are all set to have logs on all your State Machines in CDK.