Handling promises inside the forEach loop - node.js

Question

I am trying to run a series of tasks. Each task is dynamic, and could have different rules to follow. This will be executed on AWS-Lambda.
I have an array of JSON. It has a body with task name in it, and it also has attributes.
I need to dynamically load a javascript file with the name inside the body.
I need to wait until all is finished inside that task. Or it failed (regardless where). If the fail happens, I will need to write that data inside the current record inside the forEach loop.
I have old issue, where my forEach is finished first without waiting for the task to complete.
This is the forEach loop:
const jobLoader = require('./Helpers/jobLoader');
event.Records.forEach(record => {
const { body: jobName } = record;
const { messageAttributes } = record;
const job = jobLoader.loadJob(jobName);
job.runJob(messageAttributes).then(res => {
console.log('Show results');
return; // resume another record from forEach
}).catch(err => {
record.failed = true;
record.failureMessage = err.message;
console.log('I errored');
});
console.log('All Done');
});
The problem is that message All Done is printed, and then the message show results is printed. I get results from the database once it comes for execution.
This is the file that loads a task:
exports.loadJob = (jobName) => {
const job = require(`../Tasks/${jobName}`);
return job;
};
This is the file that contains actual task:
const mySqlConnector = require('../Storage/mySql');
exports.runJob = async (params) => {
let payload = {};
let dataToSend = await getUserName(params.userId.stringValue);
payload.dataToSend = dataToSend;
let moreDataToSend = await getEvenMoreData(params.userId.stringValue);
payload.moreDataToSend = moreDataToSend;
return await sendData(payload);
};
const getUserName = async (userId) => {
const query = 'SELECT * FROM user_data';
return await mySqlConnector.handler(query);
};
const getEvenMoreData = async (userId) => {
const query = 'SELECT * FROM user_data';
return await mySqlConnector.handler(query);
};
const sendData = (payload) => {
//this should be Axios sending data
};
And this is the mySql connector itself:
const mysql = require('promise-mysql');
exports.handler = async (query) => {
return mysql.createConnection({
host : '127.0.0.1',
user : 'root',
password : '',
database: 'crm'
}).then(conn =>{
let result = conn.query(query);
conn.end();
return result;
}).then(rows => {
//console.log("These are rows:" + rows);
return rows;
}).catch(error => {
return error;
});
};
The task file can have any number of things it needs to complete, which will be different when I start adding tasks.
I need that job.runJob completes, or that it catches an error, from whatever location it originated, so I can continue with the forEach.
I have tried using map and what not, but the end result is always the same.
What am I doing wrong?

Answer 1

You can use Promise.all method :
const promises = event.Records.map(record => {
const { body: jobName } = record;
const { messageAttributes } = record;
const job = jobLoader.loadJob(jobName);
return job.runJob(messageAttributes).then(res => {
console.log('Show results', res);
}).catch(err => {
record.failed = true;
record.failureMessage = err.message;
console.log('I errored');
throw new Error('Your error !');
});
});
try {
const results = await Promise.all(promises);
console.log('All done');
} catch (e) {
console.log('Something has an error', e);
}
don't forget to make your function async !

Answer 2

I managed to solve it, and still keep details about the execution:
Something like this:
for (let prop in event.Records){
const { body: jobName } = event.Records[prop];
const { messageAttributes } = event.Records[prop];
const job = jobLoader.loadJob(jobName);
await job.runJob(messageAttributes).then(res => {
console.log('Show results', res);
}).catch(err => {
event.Records[prop].failed = true;
event.Records[prop].failed = err.message;
console.log('I errored');
});
}