Simple App

package.json

{
    "name": "simpleapp",
    "description": "simple application",
    "version": "0.0.1",
    "author": {
        "name": "Tim Douglas"
    },
    "dependencies": {
        "express": "3.4.8",
        "moment": "2.5.1"
    }
}

server.js

var CONFIG = {
    port: 9000, // Port to listen on
    cacheUnits: 'seconds', // Cache units, 'days', 'minutes', 'seconds'. See momentjs documentation
    cacheValue: 10, // Cache value, e.g. 10 (seconds), 5 (days)
    cachePath: 'cache.json' // Path where cached response will be saved and restored
};

var express = require('express')
    , moment = require('moment')
    , fs = require('fs');


var cached = {};
var app = express();

/**
 * Return JSON with a structure which includes the current time.
 */
app.get('/api/sample/', function (req, res) {
    // If there is no cache timestamp set, or we have exceeded the cache duration, get the result.
    if (!cached.timeStamp || moment().diff(cached.timeStamp, CONFIG.cacheUnits) > CONFIG.cacheValue) {
        getResults(function (err, results) {
            cached.results = results;
            cached.timeStamp = moment();
            fs.writeFileSync(CONFIG.cachePath, JSON.stringify(cached));
            res.json(200, results);
        });
    } else {
        // Otherwise, we will used the cached result.
        process.nextTick(function () {
            res.json(200, cached.results);
        });
    }

});


/**
 * Gets the results asynchronously.
 * @param callback - function(err, results)
 */
function getResults(callback) {
    // TODO: Fake a result which includes the current time.
    var results = {
        currentTime: moment().toString()
    }
    process.nextTick(function () {
        callback(null, results);
    });
}

/**
 * Do initialization and invoke the callback once it has finished.
 * @param callback - function(err)
 */
function doInitialization(callback) {
    if (fs.existsSync(CONFIG.cachePath)) {
        cached = JSON.parse(fs.readFileSync(CONFIG.cachePath, 'utf8'));
    }
    process.nextTick(function () {
        // TODO: Error handling here. Hardcoding null for no error.
        callback(null);
    });
}


/**
 * Do any initialization which is required before the app can begin taking requests.
 */
doInitialization(function (err) {
    if (err) {
        console.log('Error: ' + err);
        process.exit(1);
    } else {
        console.log('Listening on port: ' + CONFIG.port);
        app.listen(CONFIG.port);
    }
});