Update index.ts

src/index.ts

@@ -1,17 +1,109 @@
 import 'reflect-metadata';
 import { createConnection } from 'typeorm';
+import chalk from 'chalk';
+
+import cluster from 'cluster';
+const numCores = require('os').cpus().length;
 
 import logger from './config/logger';
 import app from './config/express';
 const PORT = process.env.PORT || 5000;
 
-createConnection()
-  .then(() => {
-    logger.info('database connection created');
-    app.listen(PORT, () => {
-      logger.info(`Server running at ${PORT}`);
+// Handle uncaught exceptions
+process.on('uncaughtException', (uncaughtExc) => {
+  // Won't execute
+  console.log(chalk.bgRed('UNCAUGHT EXCEPTION! 💥 Shutting down...'));
+  console.log('uncaughtException Err::', uncaughtExc);
+  console.log('uncaughtException Stack::', JSON.stringify(uncaughtExc.stack));
+  process.exit(1);
+});
+
+// Setup number of worker processes to share port which will be defined while setting up server
+const workers = [];
+const setupWorkerProcesses = () => {
+  // Read number of cores on system
+  console.log(`Master cluster setting up ${numCores} workers`);
+
+  // Iterate on number of cores need to be utilized by an application
+  // Current example will utilize all of them
+  for (let i = 0; i < numCores; i++) {
+    // Creating workers and pushing reference in an array
+    // these references can be used to receive messages from workers
+    workers.push(cluster.fork());
+
+    // Receive messages from worker process
+    workers[i].on('message', function (message) {
+      console.log(message);
+    });
+  }
+
+  // Process is clustered on a core and process id is assigned
+  cluster.on('online', function (worker) {
+    console.log(`Worker ${worker.process.pid} is listening`);
+  });
+
+  // If any of the worker process dies then start a new one by simply forking another one
+  cluster.on('exit', function (worker, code, signal) {
+    console.log(
+      `Worker ${worker.process.pid} died with code: ${code}, and signal: ${signal}`
+    );
+    console.log('Starting a new worker');
+    cluster.fork();
+    workers.push(cluster.fork());
+    // Receive messages from worker process
+    workers[workers.length - 1].on('message', function (message) {
+      console.log(message);
     });
-  })
-  .catch((error: Error) => {
-    logger.info(`Database connection failed with error ${error}`);
   });
+};
+
+// Setup an express server and define port to listen all incoming requests for this application
+const setUpExpress = () => {
+  createConnection()
+    .then(() => {
+      logger.info('database connection created');
+      app.listen(PORT, () => {
+        logger.info(`Server running at ${PORT}`);
+      });
+    })
+    .catch((error: Error) => {
+      logger.info(`Database connection failed with error ${error}`);
+    });
+
+  // In case of an error
+  app.on('error', (appErr, appCtx) => {
+    console.error('app error', appErr.stack);
+    console.error('on url', appCtx.req.url);
+    console.error('with headers', appCtx.req.headers);
+  });
+
+  // Handle unhandled promise rejections
+  process.on('unhandledRejection', (err) => {
+    console.log(chalk.bgRed('UNHANDLED REJECTION! 💥 Shutting down...'));
+    console.log(err.name, err.message);
+    // Close server & exit process
+    server.close(() => {
+      process.exit(1);
+    });
+  });
+
+  process.on('SIGTERM', () => {
+    console.log('👋 SIGTERM RECEIVED. Shutting down gracefully');
+    server.close(() => {
+      console.log('💥 Process terminated!');
+    });
+  });
+};
+
+// Setup server either with clustering or without it
+const setupServer = (isClusterRequired) => {
+  // If it is a master process then call setting up worker process
+  if (isClusterRequired && cluster.isMaster) {
+    setupWorkerProcesses();
+  } else {
+    // Setup server configurations and share port address for incoming requests
+    setUpExpress();
+  }
+};
+
+setupServer(true);