Скачать или смотреть Resolving the Username should be an email Error in AWS Cognito with Lambda Function

Learn how to effectively handle the `Username should be an email` error when creating a Cognito user via a Lambda function in AWS. Follow our guide for a step-by-step solution!
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Troubleshooting AWS Cognito: The Username Should Be An Email Error

Setting up user authentication with Amazon Cognito can sometimes lead to confusing error messages, especially when you’re using AWS Lambda in conjunction with API Gateway. A common issue developers face is the error message: Username should be an email. In this post, we’ll dive deep into understanding why this error occurs and how to resolve it effectively.

Understanding the Error

When you attempt to register a user in Cognito, it expects the username to be in a specific format. If your Lambda function triggers this error, it generally indicates a mismatch between the expected username format and what is being passed.

In this specific case, the username is intended to be an email address, but the error suggests that the format being sent to Cognito is incorrect.

The Setup

You might have a snippet of code similar to this in your Lambda function:

[[See Video to Reveal this Text or Code Snippet]]

As you've detailed, you've validated that the email format is correct and that your Lambda function has necessary permissions. So, let's focus on the potential cause: how the username is being extracted from the event.

Solution: Correctly Extracting the Username

The primary issue lies in how the username is defined in the code. In your current setup, using json.dumps(event["body"]) converts the user data into a JSON string, which is not what Cognito requires. Here’s how you can properly handle the username extraction:

Step 1: Determine the Format of the Event Body

First, you need to understand whether the event body is being sent as a JSON string or as a raw string. Depending on this, you will need to use one of the following methods:

If the event is indeed JSON, convert it from JSON to an object using json.loads. This will give you a usable Python object.

[[See Video to Reveal this Text or Code Snippet]]

If the username is passed directly as a plain string, you can simply refer to it without converting it.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Implementing the Change

Simply replace the line for defining the username in your Lambda function. Here’s how your updated function might look:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

In conclusion, the Username should be an email error from AWS Cognito is typically related to how the username is being passed into the admin_create_user function. By ensuring that you correctly extract the username from your event, you can avoid this error and successfully register users in your Cognito user pool.

Remember to always validate the format of the body being sent to the Lambda function. If you run into more issues, double-check the structure of your input and adjust accordingly. With these insights, you're more equipped to troubleshoot and resolve similar issues in the future!