NodeJS AWS Lambda, DynamoDB not writing result and not logging - node.js

Question

I'm having some trouble with DynamoDB. I've set up my Lambda permissions for full CRUDL (administrator access, so no restrictions). The following is the handler, and it's based on the doca
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GettingStarted.NodeJs.03.html
const uuidv4 = require("uuid/v4");
const services = require("./services/services");
var AWS = require("aws-sdk");
AWS.config.update({ region: "eu-west-2" });
var docClient = new AWS.DynamoDB.DocumentClient();
var tableName = "usersTable";
module.exports = {
registerUser: async (event, context) => {
const id = uuidv4();
let body;
if (event.body !== null && event.body !== undefined) {
body = JSON.parse(event.body);
}
const isValid = await services.validateUser(body);
if (isValid) {
var params = {
TableName: tableName,
Item: {
userId: "123abc",
firstName: "finn",
lastName: "murtons",
email: "email#email.com",
password: "secret"
}
};
console.log("Adding a new item...");
console.log(" Adding params", params);
docClient.put(params, function(err, data) {
if (err) {
console.error(
"Unable to add item. Error JSON:",
JSON.stringify(err, null, 2)
);
} else {
console.log("Added item:", JSON.stringify(data, null, 2));
}
});
}
},
... other functions
For this example, I'm hardcoding the params for clarity, but obviously I would usually get them from the event.body.
When I make a post request to this Lambda, I get a 502 error.
Looking at the cloudwatch logs, it gets as far as:
INFO Adding params { TableName: 'usersTable',
Item:
{ userId: '123abc',
firstName: 'finn',
lastName: 'murtons',
email: 'email#email.com',
password: 'secret' } }
Then there are no more logs after that. Ignore the isValid function, it's just checking that the request event body has the required fields.
Anybody have any ideas where I might be going wrong?

Answer 1

It's likely that the lambda is exiting before the DynamoDB call is made. You should make the call a Promise and await it:
await docClient.put(params).promise();