API logic to get latest weather information - node.js

Question

I'm writing weather API which fetches METAR and TAFS data from aviation weather stations.
Data changes once an hour.
Need to fetch latest weather information, but in my code I cannot make it to fetch it after an hour.
var express = require('express');
var router = express.Router();
const ADDS = require('adds');
var moment = require('moment');
// adds moment to the locals
router.use((req, res, next)=>{
res.locals.moment = moment;
next();
});
const avWet = Promise.all([
ADDS('metars', {
stationString: 'KCRX,KMSL,KSNH,KTUP',
hoursBeforeNow: 1,
mostRecentForEachStation: true
}),
ADDS('tafs', {
stationString: 'KTUP,KMSL',
hoursBeforeNow: 1,
mostRecentForEachStation: true
})
])
.then(results => {
const parsedData = results;
/* GET home page. */
router.get('/', function(req, res, next) {
res.render('wet_av', {
parsedData
})
})
});
module.exports = router;

Answer 1

You don't have to restart Your app to get data, so You don't have to use nodemon or another watcher which will restart the app too.
Simply write Your method which will get data and store it in variable
Schedule it to check for new data
Call that method to get data and push to render
const express = require('express');
const router = express.Router();
const ADDS = require('adds');
const moment = require('moment');
// adds moment to the locals
router.use((req, res, next)=>{
res.locals.moment = moment;
next();
});
let weatherInformation = null;
let weatherInformationParsedAt = 0;
async function getWeatherInformation() { // [1] method that will get data from api
const startOfHour = moment().startOf('hour').format('YYYY-MM-DD hh:')+'00';
const currentTimeString = moment().startOf('minute').format('YYYY-MM-DD hh:mm');
// if there is no data then need to parse
let needToParse = !weatherInformation;
// forcing to parse if it's 00'th minute of hour
if (startOfHour === currentTimeString &&
Date.now() - weatherInformationParsedAt > 30000
) { // if start of hour
needToParse = true;
}
// forcing to parse if data is old more than 2 mins, making sure we have fresh data
if (!needToParse &&
weatherInformation &&
Date.now() - weatherInformationParsedAt > 120000
) {
needToParse = true;
}
try {
// if need to parse so let's fetch again (that's for caching)
if (needToParse) {
const query = {
hoursBeforeNow: 1,
mostRecentForEachStation: true,
};
const results = await Promise.all([
ADDS('metars', {
...query,
stationString: 'KCRX,KMSL,KSNH,KTUP',
}),
ADDS('tafs', {
...query,
stationString: 'KTUP,KMSL',
}),
]);
weatherInformation = results;
weatherInformationParsedAt = Date.now();
}
}
catch (error) {
console.error(error);
}
return weatherInformation;
}
setInterval(getWeatherInformation, 1000); // [2] every second call method which checks for changes
router.get('/', async (req, res, next) => {
const parsedData = await getWeatherInformation(); // [3] calling method to get weather information
res.render('wet_av', {
parsedData,
});
});
module.exports = router;