Synchronous api calls in Node.js - node.js

Question

I've a cronjob that runs every 10 secs. It requests for machines for a single client and does computation based on the response and then has to update or create documents with those computations in a for loop. But, the api calls after '***' in the code don't happen until the for loop has executed and the data sent to the api calls is that of the last machine which is wrong. I want to solve this by this way or some other way possible. My code looks like this:
// index.js
const cron = require("node-cron");
const express = require("express");
const fs = require("fs");
const request = require("request");
app = express();
var clientId = 'ABCD';
var apiUrl = 'http://example.com:3001/';
var getMachines = apiUrl + 'getMachines/',
updateMachine = apiUrl + 'updateMachine/',
getControlRoomStatus = apiUrl + 'getControlRoomStatus/',
registerControlRoomStatus = apiUrl + 'registerControlRoomStatus/',
updateControlRoomStatus = apiUrl + 'updateControlRoomStatus/';
cron.schedule("*/10 * * * * *", function() {
APICall(getMachines, { 'clientId' : clientId }, 'POST', function(err, machines) {
if (err) {
console.log(err);
} else {
console.log('--------------------------------------------------------------------------------------------------');
var allMachines = machines;
var currentDateTime = IST();
for (var i = 0; i < 2; i++) {
var lastCycleTime = new Date(allMachines[i]['lastCycleTime']);
var lastHeartbeat = new Date(allMachines[i]['lastHeartbeat']);
var machineData;
var controlRoomData;
var machineId = {
'machineId' : allMachines[i]['machineId']
};
console.log(machineId);
if (allMachines[i]['downtimeStatus'] == '0') {
if ((currentDateTime - lastCycleTime)>300000) {
if ((currentDateTime - lastHeartbeat)>300000) {
console.log(allMachines[i]['machineId'] ,' No Internet');
controlRoomData = {
'clientId': clientId,
'lastTimeStamp': allMachines[i]['lastCycleTime'],
'status': 'Inactive',
'type': 'No Internet/Power'
};
} else {
console.log(allMachines[i]['machineId'] ,' No button pressed');
controlRoomData = {
'clientId': clientId,
'lastTimeStamp': allMachines[i]['lastCycleTime'],
'status': 'Inactive',
'type': 'No Button Pressed'
};
}
machineData = {
'status' : 'Inactive'
};
} else {
console.log(allMachines[i]['machineId'] ,' Active');
machineData = {
'status' : 'Active'
};
controlRoomData = {
'clientId': clientId,
'lastTimeStamp': allMachines[i]['lastCycleTime'],
'status': 'Active',
'type': 'N.A'
};
}
} else {
if ((currentDateTime - lastHeartbeat)>300000) {
console.log(allMachines[i]['machineId'] ,' button pressed ',' No Internet');
controlRoomData = {
'clientId': clientId,
'lastTimeStamp': allMachines[i]['lastCycleTime'],
'status': 'Inactive',
'type': 'No Internet/Power'
};
} else {
var downtimeLength = allMachines[i]['downtimeData'].length - 1;
console.log(allMachines[i]['machineId'] ,' button pressed ',allMachines[i]['downtimeData'][downtimeLength]['downtimeType']);
controlRoomData = {
'clientId': clientId,
'lastTimeStamp': allMachines[i]['lastCycleTime'],
'status': 'Inactive',
'type': allMachines[i]['downtimeData'][downtimeLength]['downtimeType']
};
}
machineData = {
'status' : 'Inactive'
};
}
***
APICall(getControlRoomStatus, machineId, 'POST', function(err, controlRoom) {
if (err) {
console.log(err);
} else {
console.log(machineId,controlRoomData);
if (controlRoom == null ) {
APICall(registerControlRoomStatus, controlRoomData, 'POST', function(err, body) {
if (err) {
console.log(err);
} else {
// console.log(body);
}
});
} else {
var updateControlRooomUrl = (updateControlRoomStatus+''+controlRoom['_id']+'');
// console.log(updateControlRooomUrl);
APICall(updateControlRooomUrl, controlRoomData, 'PUT', function(err, body) {
if (err) {
console.log(err);
} else {
// console.log(body);
}
});
}
}
});
var updateMachineUrl = (updateMachine+''+allMachines[i]['_id']+'');
// console.log(updateMachineUrl);
APICall(updateMachineUrl, machineData, 'PUT', function(err, body) {
if (err) {
console.log(err);
} else {
console.log(i,machineId);
// console.log(body);
}
});
}
}
});
});
function APICall(url, requestData, method, callback) {
request({
url: url,
form: requestData,
method: method
}, function (error, response, body) {
if (error || response.statusCode !== 200) {
return callback(error || {statusCode: response.statusCode});
}
callback(null, JSON.parse(body));
});
}
function IST(){
var dateUTC = new Date();
var dateUTC = dateUTC.getTime();
var dateIST = new Date(dateUTC);
dateIST.setHours(dateIST.getHours() + 5);
dateIST.setMinutes(dateIST.getMinutes() + 30);
return dateIST;
}
app.listen(3128);
Thank you in advance.

Answer 1

I used a different method to do things and now it's working just as it's supposed to. I used 'async' and replaced the for loop with the following:
var async = require('async');
...
async.map(allMachines , function(machine, callback) {
...
});
...

Answer 2

You can try the following package:
sync-request
You can find it here on NPM.
Here is an example how to use it (from the docs):
var request = require('sync-request');
var res = request('GET', 'http://example.com');
console.log(res.getBody());
As stated in the documentation, don't use it in production code, since this will terribly block your server and it will slow down considerably (if you are running a HTTP server which you are using express).
If you have asynchronous code and you want to execute some code after the asynchronous you also can use:
Observables (not native need to use a package, RxJS for example)
Promises (native ES6 JS)