Using a cronjob to update and display results of a MySQL query

Question

Im having some trouble how I could realize it to have a dynamic website where the data is fetched via ajax to the user.

At the end of the ajax is a simple php script which opens a MySQL connection to my db and fetching some results (which looks to all users the same, there aren't any user specific results) to display them later for example in a table.

This is what I come so far. It is working but when there thousands of users who open the website ... this wouldn't be good and I don't think my server would update it fast enough.

So my intention is to update the wanted results only once every x seconds serversided with a cronjob maybe, I would save a lot resources.

The problem is that I don't know how I could realize this part, could I please get some help? Or should I forget the ajax stuff and start using node.js?

I've got a pretty good root server which is my webspace aswell so it would be possible to install some extra applications.

Answer 1

A really basic Node.js solution using memory-cache and node-cron :

var cache = require('memory-cache');
var CronJob = require('cron').CronJob;

var job;
var jobStarted = false;
var rateLimitExceeded = false;

var job = new CronJob('5 * * * * *', function() {
    // Runs every 5 seconds
    doALongDataBaseOperation(function(err, data) {
        cache.put('cacheId', data);
    });
});

app.get('/path/that/needs/caching', function(req, res) {
    cache.get('cacheId', function(e, data) {
        if (data) {
            res.end(data);
        } else {
            // contingency in case the cache doesn't exist
            doALongDataBaseOperation(function(err, data) {
                res.end(data);
                cache.put('cacheId', data);
            });
        }
    });
});

Answer 2

You could cache the data using Memcache (or something similar). Your cronjob could run and refresh the cache as often as you would like.

Then your AJAX can call a simple PHP script to retrieve the data from your cache.