Lambda function completes, but query to RDS is incomplete - node.js

Question

I was trying to make a post query the db (RDS) using handler.async.
However, I ran into the following issues.
Half of the time, the lambda function completes but the query is not successfully sent to RDS. The other half of the time, it will be completely send to lambda. Tried adding a setTimeout function to increase lambda execution time by 3 secs and the query will be sent all the time.
Also the log will shows the error:
INFO Error: Cannot enqueue Query after fatal error.
The following are my code:
var mysql = require('mysql');
var connection = mysql.createConnection({
host : '***',
user : '***',
password : '***',
database : '***'
});
exports.handler = async (event) => {
const sql = `INSERT INTO forms VALUES(777,2,3,4,5,6,7,8,9,10,11);`;
const query = (x) => {
return new Promise ((resolve,reject)=>{
resolve(connection.query(x, function (error, results, fields) {
console.log(error)
console.log(results)
console.log(fields)
}))})}
await query(sql)
}
With the timeout function,
var mysql = require('mysql');
var connection = mysql.createConnection({
host : '***',
user : '***',
password : '***',
database : '***'
});
exports.handler = async (event) => {
const sql = `INSERT INTO forms VALUES(777,2,3,4,5,6,7,8,9,10,11);`;
const query = (x) => {
return new Promise ((resolve,reject)=>{
resolve(connection.query(x, function (error, results, fields) {
console.log(error)
console.log(results)
console.log(fields)
}))})}
await query(sql)
await wait(3000)
}
const wait = (x) => {
return new Promise ((resolve,reject)=>{
setTimeout(()=>{resolve(console.log("delay"))}, x);
})
}
The first value is a primary key. A constant 777 is sent to check, if error shows duplicate primary key, it will mean that the query is successfully sent. If there is no error, it means that the query is unsuccessfully sent although lambda finishes.
execution result succeeded but shows:
START RequestId: e541fe4b-6927-4fbb-90b4-750f77e5f460 Version: $LATEST
2019-12-19T01:54:45.212Z e541fe4b-6927-4fbb-90b4-750f77e5f460 INFO Error: **Cannot enqueue Query after fatal error**.
at Protocol._validateEnqueue (/var/task/node_modules/mysql/lib/protocol/Protocol.js:212:16)
at Protocol._enqueue (/var/task/node_modules/mysql/lib/protocol/Protocol.js:138:13)
at Connection.query (/var/task/node_modules/mysql/lib/Connection.js:201:25)
at /var/task/index.js:14:24
at new Promise (<anonymous>)
at query (/var/task/index.js:13:10)
at Runtime.exports.handler (/var/task/index.js:20:7)
at Runtime.handleOnce (/var/runtime/Runtime.js:66:25) {
code: 'PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR',
fatal: false
}2019-12-19T01:54:45.213Z e541fe4b-6927-4fbb-90b4-750f77e5f460 INFO undefined2019-12-19T01:54:45.213Z e541fe4b-6927-4fbb-90b4-750f77e5f460 INFO undefined2019-12-19T01:54:45.262Z e541fe4b-6927-4fbb-90b4-750f77e5f460 INFO delayEND RequestId: e541fe4b-6927-4fbb-90b4-750f77e5f460
REPORT RequestId: e541fe4b-6927-4fbb-90b4-750f77e5f460 Duration: 51.09 ms Billed Duration: 100 ms Memory Size: 128 MB Max Memory Used: 80 MB
May you please advise and also tell me which is the best way to execute it??

Answer 1

Managing RDBMS connections in any environment is not a trivial task. Lambda adds a layer of complexity here. You need to understand the distinction between warm and cold restarts, what it means for resources created outside of your handler function, when connection pools are appropriate, and when and how to release connections.
Persistent connections to a database are not particularly suitable in a microservices, FaaS environment like Lambda. That's one reason that Aurora Serverless supports an HTTP Data API (and hopefully other DB engines will too at some point).
Read How To: Manage RDS Connections from AWS Lambda Serverless Functions.
Also be aware of the new Amazon RDS Proxy with AWS Lambda.
In your particular case, the most obvious concern is that you are repeatedly creating DB connections but never releasing them (unless that is a built-in feature of the mysql package's query function that I'm not aware of).

Answer 2

You can increase the lambda timeout upto 15 minutes. But if you are calling the lambda through api gateway, the timeout is 29 seconds.
here is the code working for me.
const mysql = require('mysql');
const con = mysql.createConnection({
host: process.env.RDS_HOSTNAME,
user: process.env.RDS_USERNAME,
password: process.env.RDS_PASSWORD,
port: process.env.RDS_PORT,
connectionLimit: 10,
multipleStatements: true,// Prevent nested sql statements
debug: true
// ,database:'testdb1'
});
exports.handler = async (event) => {
try {
const data = await new Promise((resolve, reject) => {
con.connect(function (err) {
if (err) {
reject(err);
}
const sql = `INSERT INTO forms VALUES(777,2,3,4,5,6,7,8,9,10,11);`;
con.query(sql, function (err, result) {
if (err) {
console.log("Error->" + err);
reject(err);
}
resolve(result);
});
})
});
return {
statusCode: 200,
body: JSON.stringify(data)
}
} catch (err) {
return {
statusCode: 400,
body: err.message
}
}
};
reference: aws lambda with rds mysql DDL command not working