Cant insert data into DynamoDB using new nodejs 8.10 - node.js

Question

I want to use new nodejs 8.10 for developing my lambdas. A simple piece of code when written in node 6.10 style works but the same(similar) code doesn't work when I use node 8.10.
Below is working code which successfully inserts data into dynamodb table(nodejs 6.10)
var AWS = require('aws-sdk');
// Set the region
AWS.config.update({region: 'us-east-1'});
var documentClient = new AWS.DynamoDB.DocumentClient({apiVersion: '2012-08-10'});
exports.handler = (event, context, callback) => {
// TODO implement
var params = {
Item: {
client: 'client_'+Math.random(),
Type: 1,
Status: true,
json: { foo: 'bar', address:{ city:'Pune', street: 'ABC Nagar', pin:'411099'} }
},
TableName: 'clients'
};
documentClient.put(params, function(err, data) {
if (err) {
console.log("Error", err);
callback(err, null);
} else {
console.log("Success", data);
// return "Hi, insert data completed";
callback(null, data);
}
});
};
And below one which is node 8.10 style which doesn't work(means doesn't insert data into dynamodb table). I keep getting null as return value.
var AWS = require('aws-sdk');
// Set the region
AWS.config.update({region: 'us-east-1'});
var documentClient = new AWS.DynamoDB.DocumentClient({apiVersion: '2012-08-10'});
exports.handler = async (event) => {
// TODO implement
var params = {
Item: {
client: 'client_'+Math.random(),
Type: 1,
Status: true,
json: { foo: 'bar', address:{ city:'Pune', street: 'ABC Nagar', pin:'411099'} }
},
TableName: 'clients'
};
documentClient.put(params, function(err, data) {
if (err) {
console.log("Error", err);
} else {
console.log("Success", data);
return "Hi, insert data completed";
}
});
};
I spent searching 2-3 hours searching.. couldn't find any article or any question similar. Can anyone tell me what am I doing wrong?

Answer 1

Async / Await is a syntactical sugar for promise, Your documentClient.put should be wraped with promise. Since documentClient.put is based on callback appoach, you have to wrap it with promise
var AWS = require('aws-sdk');
// Set the region
AWS.config.update({region: 'us-east-1'});
var documentClient = new AWS.DynamoDB.DocumentClient({apiVersion: '2012-08-10'});
exports.handler = async (event) => {
// TODO implement
var params = {
Item: {
client: 'client_'+Math.random(),
Type: 1,
Status: true,
json: { foo: 'bar', address:{ city:'Pune', street: 'ABC Nagar', pin:'411099'} }
},
TableName: 'clients'
};
let putItem = new Promise((res, rej) => {
documentClient.put(params, function(err, data) {
if (err) {
console.log("Error", err);
rej(err);
} else {
console.log("Success", data);
res("Hi, insert data completed");
}
});
});
const result = await putItem;
console.log(result);
return result
};
Note: Its advisable to use DB operations in separate file,rather than using in handler function itself

Answer 2

Did you look in your table to see if it's inserting data? I think it is.
The problem with your async-style code is that you aren't returning a value. Returning "Hi, insert data completed" from the put callback doesn't return a value from handler.
You could manually create a promise and return that from handler, but I'd try using promisify.
This code is untested but should be close:
...
const util = require('util');
...
documentClient.putPromise = util.promisify(documentClient.put);
...
try {
const data = await documentClient.putPromise(params);
console.log("Success", data);
return "Hi, insert data completed";
}
catch (err) {
console.log("Error", err);
}
Here's more on promisify: http://2ality.com/2017/05/util-promisify.html

Answer 3

Calling await dynamo.put(params).promise(); is how I solved this issue after some googling. Specifically, it seems like calling foo.promise(); in the aws sdk is supported now.