I'm trying to get a start with AWS by starting at the beginning, running the Build a Basic Web Application tutorial. I figured I'd be able to just follow it step by step and have a simple Hello World web page front end to a little database. But I'm running into a strange error: including the bare-bones, default aws-sdk module is failing!
Short version:
This code:
// Include the AWS SDK module
const AWS = require('aws-sdk');
generates this error: Error: Cannot find module 'aws-sdk'
Long Story:
I'm following the process step by step, creating all the pieces using the AWS online tools. The first hint of trouble happened when I created my Lambda function. I wasn't too worried that the Create Function tool shows a Node.js version of 18.x instead of the tutorial's Node.js 16.x, but I definitely noticed that the Lambda shell it generated was named index.mjs instead of index.js. No problem, I'll just use that file. I replaced the contents with Amazon's HelloWorld code.
// Define handler function, the entry point to our code for the Lambda service
// We receive the object that triggers the function as a parameter
exports.handler = async (event) => {
// Extract values from event and format as strings
let name = JSON.stringify(`Hello from Lambda, ${event.firstName} ${event.lastName}`);
// Create a JSON object with our response and store it in a constant
const response = {
statusCode: 200,
body: name
};
// Return the response constant
return response;
};
I set up the Test Event functionality using their data:
{
"firstName": "Ada",
"lastName": "Lovelace"
}
But running the code generated my first error: exports is not defined in ES module scope
Doing some searching on that error sent me down a rabbit hole far outside the scope of a basic tutorial, so I renamed the file from index.mjs to index.js. Rebuilt and poof, it worked just fine:
{
"statusCode": 200,
"body": ""Hello from Lambda, Ada Lovelace""
}
I won't go through the steps of creating the database, because that's not relevant. Everything was fine until I replaced the code with the code that would access the database - it errored with the message above. To simplify the issue, I deleted the Lambda and rebuilt it with the working code above, and the require statement:
// Include the AWS SDK module
const AWS = require('aws-sdk');
// Define handler function, the entry point to our code for the Lambda service
// We receive the object that triggers the function as a parameter
exports.handler = async (event) => {
// Extract values from event and format as strings
let name = JSON.stringify(`Hello from Lambda, ${event.firstName} ${event.lastName}`);
// Create a JSON object with our response and store it in a constant
const response = {
statusCode: 200,
body: name
};
// Return the response constant
return response;
};
Running that generates this output:
{
"errorType": "Runtime.ImportModuleError",
"errorMessage": "Error: Cannot find module 'aws-sdk'nRequire stack:n- /var/task/index.jsn- /var/runtime/index.mjs",
"trace": [
"Runtime.ImportModuleError: Error: Cannot find module 'aws-sdk'",
"Require stack:",
"- /var/task/index.js",
"- /var/runtime/index.mjs",
" at _loadUserApp (file:///var/runtime/index.mjs:1000:17)",
" at async UserFunction.js.module.exports.load (file:///var/runtime/index.mjs:1035:21)",
" at async start (file:///var/runtime/index.mjs:1200:23)",
" at async file:///var/runtime/index.mjs:1206:1"
]
}
The strangest thing I see in the dump: it still references index.mjs even though I deleted the file (or renamed it - I tried both ways). In the online IDE, I only have access to the file tree that shows only index.js. I assume that's /var/task so I don't know where /var/runtime is that still contains a reference to index.mjs.
I'm looking forward to the solution to this head-scratcher. It feels like it's simple enough that it should Just Work!
