react-express-mysql: split backend code

Signed-off-by: Jérémie Drouet <jeremie.drouet@gmail.com>

react-express-mysql/backend/src/server.js

@@ -0,0 +1,31 @@
+// 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 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.
+
+// Appi
+const app = express();
+
+app.use(morgan("common"));
+
+app.get("/", function(req, res) {
+  res.json({ message: "Hello Docker World!" });
+});
+
+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");
+});
+
+module.exports = app;