add react-express-mysql application sample

Signed-off-by: Anca Iordache <anca.iordache@docker.com>

samples/react-express-mysql/backend/index.js

@@ -0,0 +1,78 @@
+// simple node web server that displays hello world
+// optimized for Docker image
+
+var 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.
+
+var 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 :)
+
+// Appi
+var app = express();
+
+app.use(morgan('common'));
+
+app.get('/', function (req, res) {
+  res.send('Hello Docker World\n');
+});
+
+app.get('/healthz', 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');
+});
+
+var 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();
+  })
+}
+//
+// need above in docker container to properly exit
+//
+
+module.exports = app;