index.js

// simple node web server that displays hello world
// optimized for Docker image
const express = require('express');
// this example uses express web framework so we know what longer build times
// do and how Dockerfile layer ordering matters. If you mess up Dockerfile ordering
// you'll see long build times on every code change + build. If done correctly,
// code changes should be only a few seconds to build locally due to build cache.

const mongoose = require('mongoose');
const morgan = require('morgan');
// morgan provides easy logging for express, and by default it logs to stdout
// which is a best practice in Docker. Friends don't let friends code their apps to
// do app logging to files in containers.

// Constants
const PORT = process.env.PORT || 8080;
// if you're not using docker-compose for local development, this will default to 8080
// to prevent non-root permission problems with 80. Dockerfile is set to make this 80
// because containers don't have that issue :)

// App
const app = express();

mongoose.connect(process.env.MONGO_URI)
    .then(function () {
        console.log("Connected to MongoDB");
        // Seed the example product table
        require('./models/seeds/product.js')();
    }).catch(err => console.error(err));

app.use(morgan('common'));

app.get('/', function (req, res) {
    res.send('Hello Docker World\n');
});

app.get('/healthcheck', function (req, res) {
    // do app logic here to determine if app is truly healthy
    // you should return 200 if healthy, and anything else will fail
    // if you want, you should be able to restrict this to localhost (include ipv4 and ipv6)
    res.send('I am happy and healthy\n');
});

const server = app.listen(PORT, function () {
    console.log('Webserver is ready');
});


//
// need this in docker container to properly exit since node doesn't handle SIGINT/SIGTERM
// this also won't work on using npm start since:
// https://github.com/npm/npm/issues/4603
// https://github.com/npm/npm/pull/10868
// https://github.com/RisingStack/kubernetes-graceful-shutdown-example/blob/master/src/index.js
// if you want to use npm then start with `docker run --init` to help, but I still don't think it's
// a graceful shutdown of node process
//

// quit on ctrl-c when running docker in terminal
process.on('SIGINT', function onSigint() {
    console.info('Got SIGINT (aka ctrl-c in docker). Graceful shutdown ', new Date().toISOString());
    shutdown();
});

// quit properly on docker stop
process.on('SIGTERM', function onSigterm() {
    console.info('Got SIGTERM (docker container stop). Graceful shutdown ', new Date().toISOString());
    shutdown();
});

// shut down server
function shutdown() {
    server.close(function onServerClosed(err) {
        if (err) {
            console.error(err);
            process.exitCode = 1;
        }
        process.exit();
    })
}

module.exports = app;