Help Needed: Runtime.ImportModuleError for AWS Lambda Node.js Function

Question

Hello AWS Community,

I'm encountering a persistent issue with my AWS Lambda function written in Node.js, and I'm hoping to get some insights or suggestions on how to resolve it. Despite following AWS documentation and troubleshooting guides, the issue remains unresolved.

Issue Description:
When invoking my Lambda function, I receive a Runtime.ImportModuleError indicating that the module 'index' cannot be found. The exact error message is as follows:

Runtime.ImportModuleError: Error: Cannot find module 'index'
Require stack:
- /var/runtime/index.mjs

Steps Taken:

Confirmed that the index.js file is at the root level of my ZIP deployment package.
Ensured the handler configuration in the Lambda console is set to index.handler, matching the file name and export method in my code.
Simplified the index.js file to a basic function to eliminate potential issues with the function code itself.
Attempted to deploy the function code via both the AWS Management Console and the AWS CLI.
Function Details:

Runtime: Node.js 16.x
Region: eu-west-2
Deployment Method: ZIP upload through AWS Management Console and AWS CLI

Additional Context:

The function is intended to send emails using Amazon SES and logs to Amazon CloudWatch.
I'm currently on the AWS Basic Support plan, so direct technical support from AWS is not available.
I'm looking for any advice on what might be causing this issue or any additional troubleshooting steps I could take. Has anyone else encountered this error or have any insights on what might be going wrong?

The error manifests when I attempt to test the function using the "Test" feature in the AWS Lambda console.

Thank you in advance for your help!

index.js Code:
// Example of a simplified index.js file
exports.handler = async (event) => {
    console.log("Event:", event);
    return { statusCode: 200, body: "Hello from Lambda!" };
};

Note: This is a simplified version of my index.js to test the Lambda deployment and execution process. The actual function is intended to send emails using Amazon SES and log messages to Amazon CloudWatch.

I'm looking for insights into what might be causing this ImportModuleError and how to resolve it. Specifically, I'm curious if there are known issues with the Node.js 16.x runtime or if there are additional logs or diagnostics that I can enable to get more detailed information about the error.

Answer

Hi, 
The fact that the error occurs even with a simplified index.js suggests the issue likely lies with deployment or configuration.
While no widespread issues with Node.js 16.x in Lambda are known, trying a different runtime temporarily could help rule out any potential runtime-specific problems.
Below are few things which I suggest: 
* **Inspect Deployment Package Content:** Extract the ZIP file locally and verify that index.js is indeed present at the root level.
* **Address Potential Caching Issues:** Clear your browser cache and try deploying the function again.
* **Increase Function Version:** Create a new version of the function to force a fresh deployment.
* **Switch Runtime (Temporarily):** Try temporarily switch to a different Node.js runtime (e.g., 14.x) to isolate any potential runtime-specific issues.
* **Additional Logs:** Enable detailed logs and examine CloudWatch Logs for your function which should provide more comprehensive error information.

Hope this helps.

Help Needed: Runtime.ImportModuleError for AWS Lambda Node.js Function

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