📚 multi-processing w/ Node Cluster API

README.md

@@ -10,7 +10,7 @@ To deploy a frontend-only React app, use the static-site optimized
 
 ## Design Points
 
-A combo of two npm projects, the backend server and the frontend UI. So there are two `package.json` configs.
+A combo of two npm projects, the backend server and the frontend UI. So there are two `package.json` configs and thereforce two places to run `npm` commands:
 
   1. [`package.json`](package.json) for [Node server](server/) & [Heroku deploy](https://devcenter.heroku.com/categories/deployment)
       * `heroku-postbuild` script compiles the webpack bundle during deploy
@@ -18,6 +18,7 @@ A combo of two npm projects, the backend server and the frontend UI. So there ar
   2. [`react-ui/package.json`](react-ui/package.json) for [React web UI](react-ui/)
       * generated by [create-react-app](https://github.com/facebookincubator/create-react-app)
 
+Includes a minimal [Node Cluster](https://nodejs.org/docs/latest-v8.x/api/cluster.html) [implementation](server/index.js) to parallelize the single-threaded Node process across the available CPU cores.
 
 ## Demo
 

server/index.js

@@ -1,23 +1,41 @@
 const express = require('express');
 const path = require('path');
+const cluster = require('cluster');
+const numCPUs = require('os').cpus().length;
 
-const app = express();
 const PORT = process.env.PORT || 5000;
 
-// Priority serve any static files.
+// Multi-process to utilize all CPU cores.
-app.use(express.static(path.resolve(__dirname, '../react-ui/build')));
+if (cluster.isMaster) {
+  console.error(`Node cluster master ${process.pid} is running`);
 
-// Answer API requests.
+  // Fork workers.
-app.get('/api', function (req, res) {
+  for (let i = 0; i < numCPUs; i++) {
-  res.set('Content-Type', 'application/json');
+    cluster.fork();
-  res.send('{"message":"Hello from the custom server!"}');
+  }
-});
 
-// All remaining requests return the React app, so it can handle routing.
+  cluster.on('exit', (worker, code, signal) => {
-app.get('*', function(request, response) {
+    console.error(`Node cluster worker ${worker.process.pid} exited: code ${code}, signal ${signal}`);
-  response.sendFile(path.resolve(__dirname, '../react-ui/build', 'index.html'));
+  });
-});
 
-app.listen(PORT, function () {
+} else {
-  console.log(`Listening on port ${PORT}`);
+  const app = express();
-});
+
+  // Priority serve any static files.
+  app.use(express.static(path.resolve(__dirname, '../react-ui/build')));
+
+  // Answer API requests.
+  app.get('/api', function (req, res) {
+    res.set('Content-Type', 'application/json');
+    res.send('{"message":"Hello from the custom server!"}');
+  });
+
+  // All remaining requests return the React app, so it can handle routing.
+  app.get('*', function(request, response) {
+    response.sendFile(path.resolve(__dirname, '../react-ui/build', 'index.html'));
+  });
+
+  app.listen(PORT, function () {
+    console.error(`Node cluster worker ${process.pid}: listening on port ${PORT}`);
+  });
+}