添加守护进程，优化多核心系统性能

daemon.js

@@ -0,0 +1,28 @@
+var cluster = require('cluster');
+var numCPUs = require('os').cpus().length;
+
+if (cluster.isMaster) {
+    var worker;
+    //遍历CPU核心数
+    for (var i = 0; i < numCPUs; i++) {
+        //生成新的工作进程运行主模块
+        worker = cluster.fork();
+        console.log('worker：%d 正在运行...', worker.process.pid);
+    }
+} else {
+    //运行主模块
+    require('./bin/www');
+}
+
+//监听退出事件
+cluster.on('exit', function (worker, code, signal) {
+    if (code !== 0) {
+        console.error('worker：%d 异常退出（%s），30s后尝试重启...', worker.process.pid, signal || code);
+        setTimeout(function () {
+            var new_worker = cluster.fork();
+            console.log('worker：%d 正在运行...', new_worker.process.pid);
+        },30000);
+    } else {
+        console.log('worker：%d 正常退出！', worker.process.pid);
+    }
+});