AWS Lambda in NodeJS error: "Wrong arguments"

Question

Scenario

My React (Gatsby) application requests information from a database to display a list of products.
The database is a Postgres table on AWS RDS, in a VPC.
My aim is for the React application to trigger an AWS Lambda function to retrieve products from AWS RDS.

Error:

In writing my lambda function, I intend to request all products from my table.
The error message I get is TypeError: Wrong arguments

Code:

index.js

const rds = require('./connection.js');

exports.handler = async ( event, context, callback ) => {
    await callback(null, rds.getProducts);
};

connection.js

const Pool = require('pg').Pool;

const pool = new Pool({
    user: process.env.user,
    host: process.env.host,
    database: process.env.database,
    password: process.env.password,
    port: process.env.port,
});

const getProducts = ( request, response ) => {
    pool.query(`SELECT * FROM product_list ORDER by id ASC`, ( error, result ) => {
        if( error ) throw new Error(error);
        response.status(200).json(result.rows);
    })
};

module.exports = {
    getProducts,
};

package.json

{
  "name": "lambda3",
  "version": "1.0.0",
  "description": "lambda function access rds",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "scott",
  "license": "ISC",
  "dependencies": {
    "pg": "^7.14.0"
  }
}

Full error:

{
  "errorType": "TypeError",
  "errorMessage": "Wrong arguments",
  "trace": [
    "TypeError: Wrong arguments",
    "    at RAPIDClient.postInvocationResponse (/var/runtime/RAPIDClient.js:41:18)",
    "    at complete (/var/runtime/CallbackContext.js:34:12)",
    "    at callback (/var/runtime/CallbackContext.js:44:7)",
    "    at /var/runtime/CallbackContext.js:105:16",
    "    at Runtime.exports.handler (/var/task/index.js:9:11)",
    "    at Runtime.handleOnce (/var/runtime/Runtime.js:66:25)"
  ]
}

Thoughts: I followed the AWS guide on how to upload a NodeJS deployment package. There didn't seem to be an issue with connection.js when testing locally.

Unsure how to debug this as even "AWS Lambda wrong arguments" yields few relevant results.

are you sure about this, await callback(null, rds.getProducts); you are awaiting on the callback. — Arun Kamalanathan
– Arun Kamalanathan, Commented Nov 25, 2019 at 5:23
@ArunmainthanKamalanathan I think it should not matter as the callback is the only thing in the function block. I have tried with and without the async/await keywords, and there has been no difference in output. — Scott
– Scott, Commented Nov 25, 2019 at 5:26
Is it working in your local. you are passing "rds.getProducts" as a function reference. you are not calling the function for e.g "rds.getProducts()" . Also in the connection.js you are calling "response.status(200)", it looks like an express syntax to me. — Arun Kamalanathan
– Arun Kamalanathan, Commented Nov 25, 2019 at 5:39

Arun Kamalanathan · Accepted Answer · 2019-11-25 06:11:38Z

1

What I see as the main issue here is how you use the call back.

The callback function accepts two parameters error and the value.

https://docs.aws.amazon.com/lambda/latest/dg/nodejs-prog-model-handler.html

What I think that you are doing wrong here is, passing the function as reference instead of value for e.g rds.getProducts() to get the value.

answered Nov 25, 2019 at 6:11

Arun Kamalanathan

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