Issue with AWS Lambda and EventBridge – Schedule not working as expected? Let’s Troubleshoot!

AWS Lambda and EventBridge are powerful tools that can help you build scalable and event-driven architectures. However, when things go wrong, it can be frustrating and difficult to troubleshoot. In this article, we’ll dive into a common issue with AWS Lambda and EventBridge – schedule not working as expected – and provide you with clear and direct instructions to resolve the problem.

What is AWS Lambda and EventBridge?

Before we dive into the issue, let’s quickly recap what AWS Lambda and EventBridge are.

AWS Lambda is a serverless compute service that runs your code in response to events. It’s a great way to build scalable and cost-effective applications without worrying about server management.

EventBridge, formerly known as CloudWatch Events, is a fully managed event bus service that allows you to respond to events from various sources, such as AWS services, SaaS applications, and your own applications. It provides a unified way to handle events across your entire application.

The Issue: Schedule not working as expected

You’ve set up an EventBridge rule to trigger your AWS Lambda function at a specific schedule, but for some reason, it’s not working as expected. You’ve double-checked your code, the Lambda function is working fine when triggered manually, and the EventBridge rule is set up correctly. So, what’s going on?

Let’s break down the possible reasons behind this issue and troubleshoot step-by-step.

Reason 1: Inaccurate Schedule Expression

The first thing to check is the schedule expression in your EventBridge rule. Make sure it’s accurate and follows the correct syntax.

 Rule:
  EventPattern:
    - schedule:
        - cron(0 12 * * ? *)

In the above example, the schedule expression is set to trigger the Lambda function every day at 12:00 PM (UTC). Check your schedule expression to ensure it’s correct and matches your intended schedule.

Reason 2: Time Zone Issues

Another common issue is related to time zones. Make sure you’re specifying the correct time zone in your schedule expression.

 Rule:
  EventPattern:
    - schedule:
        - cron(0 12 * * ? * America/New_York)

In this example, we’re specifying the America/New_York time zone. If you’re in a different time zone, make sure to update the schedule expression accordingly.

Reason 3: Lambda Function Execution Role

Check the execution role of your Lambda function to ensure it has the necessary permissions to be triggered by EventBridge.

Login to the AWS Management Console, navigate to the IAM dashboard, and check the role attached to your Lambda function. Ensure it has the following permissions:

• lambda:InvokeFunction
• events:PutEvents

If the role is missing these permissions, update the role and try again.

Reason 4: EventBridge Rule Target

Verify that the EventBridge rule is targeting the correct Lambda function.

Check the EventBridge rule and ensure it’s pointing to the correct Lambda function ARN.

 Rule:
  Targets:
    - Arn: arn:aws:lambda:REGION:ACCOUNT_ID:function:FUNCTION_NAME

Replace REGION, ACCOUNT_ID, and FUNCTION_NAME with your actual values.

Reason 5: Lambda Function Invocation

Check the Lambda function invocation settings to ensure it’s set up correctly.

Navigate to the Lambda function dashboard and check the invocation settings. Ensure the handler is set correctly, and the environment variables are configured as needed.

If you’re using a proxy integration, ensure the integration request is set up correctly.

Reason 6: EventBridge Rule Status

Verify that the EventBridge rule is enabled and not disabled.

Login to the AWS Management Console, navigate to the EventBridge dashboard, and check the rule status. Ensure it’s set to “Enabled” and not “Disabled”.

Reason 7: CloudWatch Logs

Check the CloudWatch logs to see if there are any errors or warnings related to the EventBridge rule or Lambda function.

Navigate to the CloudWatch dashboard, select the log group associated with your Lambda function, and check the logs for any errors or warnings.

If you find any errors, investigate the cause and resolve the issue accordingly.

Troubleshooting Checklist

To help you troubleshoot the issue, use the following checklist:

Reason	Check
Inaccurate Schedule Expression	Verify schedule expression syntax and accuracy
Time Zone Issues	Specify correct time zone in schedule expression
Lambda Function Execution Role	Check Lambda function execution role permissions
EventBridge Rule Target	Verify EventBridge rule targets correct Lambda function ARN
Lambda Function Invocation	Check Lambda function invocation settings and handler
EventBridge Rule Status	Verify EventBridge rule status is enabled
CloudWatch Logs	Check CloudWatch logs for errors or warnings

Conclusion

In this article, we’ve covered the common reasons behind the issue of AWS Lambda and EventBridge schedule not working as expected. By following the troubleshooting steps and checklist, you should be able to identify and resolve the problem.

Remember to double-check your schedule expression, time zone, Lambda function execution role, EventBridge rule target, Lambda function invocation settings, EventBridge rule status, and CloudWatch logs.

If you’re still having issues, feel free to reach out to AWS support or seek help from a certified AWS professional.

Happy troubleshooting!

Additional Resources

For further reading and learning, check out the following resources:

• AWS Lambda Documentation: https://docs.aws.amazon.com/lambda/latest/dg/welcome.html
• EventBridge Documentation: https://docs.aws.amazon.com/eventbridge/latest/userguide/what-is-amazon-eventbridge.html
• AWS CLI Command Reference: https://docs.aws.amazon.com/cli/latest/reference/index.html

Stay tuned for more articles and tutorials on AWS Lambda and EventBridge!

Frequently Asked Questions

Get answers to common issues with AWS Lambda and EventBridge scheduling.