AWS Lambda stops execution in the middle of the code - mysql

Question

I am trying to trigger csv file upload in s3 and insert the data from the file to database using lambda.
Most of the times code executes successfully if i run the code back to back in couple of seconds gap.
But sometimes the problem i face is the code stops execution at console console.log('about to get the data'); and ignore rest of the code and sometimes mysql connection gets time out.
I can find that the problem occurs only when i test the lambda code with more than 20 seconds of gap. So, i guess this is a cold start problem.
I don't want to miss even a single s3 trigger. So, i need help to find flaw in my code that is causing this problem.
const AWS = require('aws-sdk');
const s3 = new AWS.S3({region: 'ap-south-1', apiVersion: '2006-03-01'});
var mysql= require('mysql');
var conn = mysql.createPool({
connectionLimit: 50,
host: 'HOST',
user: 'USER',
password: 'PASSWORD',
database: 'DATABASE'
})
async function mainfunc (event, context, callback) {
console.log("Incoming Event: ", JSON.stringify(event));
const bucket = event.Records[0].s3.bucket.name;
const filename = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
const params = {
Bucket: bucket,
Key: filename
};
console.log('about to get the data'); //Code stops here some times
return await getresult(params);
};
async function getresult(params){
var result = await s3.getObject(params).promise();
var recordList = result.Body.toString('utf8').split(/\r?\n/).filter(element=>{
return element.length> 5;
})
recordList.shift()
var jsonValues = [];
var jsonKeys = result.Body.toString('utf8').split(/\r?\n/)[0]
recordList.forEach((element) => {
element = element.replace(/"{2,}/g,'"').replace(/, /g,"--").replace(/"{/, "{").replace(/}"/, "}").replace(/,/g, ';').replace(/--/g,', ').split(';');
jsonValues.push(element)
});
var lresult = await query(jsonKeys, jsonValues);
return lresult;
}
async function query(jsonKeys, jsonValues){
var qresult = await conn.getConnection(function(err, connection) {
if (err){
console.log(err,'------------------------------------');// Sometimes i get Sql Connection timeout error here
} else {
console.log("Connected!");
var sql = "INSERT INTO reports ("+jsonKeys+") VALUES ?";
connection.query(sql, [jsonValues], function (err, result) {
if (err){
console.log(err);
connection.release()
return err;
} else {
console.log("1 record inserted");
console.log(result);
connection.release()
return result;
}
});
}
})
}
exports.handler = mainfunc

Answer 1

I have solved the issue by using promise in the "query" function
function query(jsonKeys, jsonValues){
return new Promise(function(resolve, reject) {
conn.getConnection(function (err, connection) {
if (err) {
console.log(err, '------------------------------------');
}
else {
console.log("Connected!");
var sql = "INSERT INTO principal_reports (" + jsonKeys + ") VALUES ?";
connection.query(sql, [jsonValues], function (err, result) {
if (err) {
console.log(err);
connection.release();
reject(err)
}
else {
console.log("1 record inserted");
console.log(result);
connection.release();
resolve(result)
}
});
}
})
})
}
and changed the code
var lresult = await query(jsonKeys, jsonValues);
to
var lresult = await query(jsonKeys, jsonValues).then(data =>{
return data;
}).catch(error =>{
return error;
});