react-express-mysql: split backend code

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

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

@@ -0,0 +1,48 @@
+const app = require("./server");
+const { port } = require("./config");
+
+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.exit(1);
+    }
+    process.exit(0);
+  });
+}
+//
+// need above in docker container to properly exit
+//