Insert to DynamoDB if item doesn't exits - node.js

Question

I'm setting up an attendance check on a streaming video with aws-rekognition, when a person is identified then a lambda should write it to a DynamoDB. the insertDynamo()works fine alone(when I'm not calling it as function),but when I put it inside a function, it doesn't write to the DynamoDB table. Any idea on what am doing wrong?
var AWS = require('aws-sdk');
var today = new Date();
var date = today.getFullYear()+'-'+(today.getMonth()+1)+'-'+today.getDate();
var hour = today.getHours() + ":" + today.getMinutes() + ":" + today.getSeconds();
exports.handler = async (event, context) => {
//console.log('Received event:', JSON.stringify(event, null, 2));
event.Records.forEach((record) => {
// Kinesis data is base64 encoded so decode here
const load = new Buffer(record.kinesis.data, 'base64').toString('ascii');
const payload = JSON.parse(load);
if(payload.FaceSearchResponse != null)
{
payload.FaceSearchResponse.forEach((face) => {
if(face.MatchedFaces != null &&
Object.keys(face.MatchedFaces).length > 0)
{
var id = JSON.stringify(face.MatchedFaces[0].Face.ExternalImageId, null, 4);
//this is hard code it ---needs to split string from kinesis(id)
insertDynamo(date,hour,'0001');
}
else
{
//do nothing
}
});
}
});
return `Successfully processed ${event.Records.length} records.`;
};
var insertDynamo = function(date,hour,id){
exports.handler = async (event,context) => {
const documentClient = new AWS.DynamoDB.DocumentClient();
let responseBody = "";
let statusCode = 0;
const params = {
TableName: "users",
Item:{
badgeNumber: id,
assistance:{
date:date,
hour:hour
}
},
ConditionExpression: 'attribute_not_exists(badgenumber)'
};
try {
const data = await documentClient.put(params).promise();
responseBody = JSON.stringify(data);
statusCode = 201;
} catch (err) {
responseBody = `Unable to put product: ${err}`;
statusCode = 403;
}
const response = {
statusCode: statusCode,
headers: {
"Content-Type": "application/json"
},
body:responseBody
}
return response
}
};

Answer 1

Your lambda function will finish immediate when it has been called, because you use .forEach to loop through all the records. This mean all your requests to insert to DynamoDB will be cancel before they finish their yobs.
I have 2 solutions for your case:
Wait until lambda callback stack is clear
Just prepend a "config" line to your lambda function
context.callbackWaitsForEmptyEventLoop = true;
Use old school for loop instead of forEach (recommended). forEach use callback style to solve each item, then it will not work as our expectly with async/await keyword.
var AWS = require('aws-sdk');
var today = new Date();
var date = today.getFullYear() + '-' + (today.getMonth() + 1) + '-' + today.getDate();
var hour = today.getHours() + ":" + today.getMinutes() + ":" + today.getSeconds();
exports.handler = async (event, context) => {
//console.log('Received event:', JSON.stringify(event, null, 2));
for (const record of event.Records) { // for of instead of forEach
const load = new Buffer(record.kinesis.data, 'base64').toString('ascii');
const payload = JSON.parse(load);
if (payload.FaceSearchResponse != null) {
for (const face of payload.FaceSearchResponse) { // for of instead of forEach
if (face.MatchedFaces != null &&
Object.keys(face.MatchedFaces).length > 0) {
var id = JSON.stringify(face.MatchedFaces[0].Face.ExternalImageId, null, 4);
//this is hard code it ---needs to split string from kinesis(id)
await insertDynamo(date, hour, '0001'); // wait until task finish then solve next item
}
else {
//do nothing
}
}
}
}
return `Successfully processed ${event.Records.length} records.`;
};
var insertDynamo = function (date, hour, id) {
// What is this?????????
// exports.handler = async (event, context) => {
// }
const documentClient = new AWS.DynamoDB.DocumentClient();
const params = {
TableName: "users",
Item: {
badgeNumber: id,
assistance: {
date: date,
hour: hour
}
},
ConditionExpression: 'attribute_not_exists(badgenumber)'
};
return documentClient.put(params).promise(); // enough for us
};