升级Node.JS web app而不重新启动

是否有一种方法可以在不重新启动Node.JS应用程序的情况下更改其代码

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例如，如果当时正在从服务器下载一个文件，是否有办法升级服务器而不中断文件传输？

是的，可以使用该模块

基本上，您将通过主进程启动应用程序的多个从实例，这些从实例共享同一端口。主设备将把传入连接分配给从设备

当您要重新启动时，主机将按顺序：

worker 5156 died
- starting slave with PID 5164
worker 5157 died
- starting slave with PID 5165
worker 5158 died
- starting slave with PID 5166
worker 5159 died
- starting slave with PID 5167

• 停止向从属服务器传递连接
• 轻轻地告诉它重新启动
• 等待它重生

这里有一些代码可以帮助您开始（您需要

npm安装异步下划线

）

注意：这只是为了让您开始。您应该准备好在实际设置中处理意外的从属设备故障和超时

var cluster = require('cluster');
var http = require('http');
var _ = require('underscore');
var async = require('async');
var numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  console.log('starting master with PID', process.pid);
  // Fork workers.
  var slaves = {};

  for (var i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

  cluster.on('fork', function (worker) {
    slaves[worker.id] = worker;
  });

  cluster.on('exit', function (worker, code, signal) {
    console.log('worker ' + worker.process.pid + ' died');
    delete slaves[worker.id];

    // restart the worker
    cluster.fork();
  });

  process.on('SIGHUP', function restartApp() {
    console.log('restarting all slaves');
    // important: force node.js to reload all js sources
    delete require.cache;

    var toRestart = _(slaves).values();

    async.eachSeries(toRestart, function (slave, done) {
      slave.kill('SIGTERM');

      // when the new worker starts, proceed to the next instance
      cluster.once('listening', function () {
        done();
      });
    });
  });
} else {
  console.log('- starting slave with PID', process.pid);
  // Workers can share any TCP connection
  // In this case its a HTTP server
  var server = http.createServer(function(req, res) {
    res.writeHead(200);
    res.end("hello world\n");
  });

  process.on('SIGTERM', function () {
    // finish all current connections, then stop
    server.close(function () {
      process.exit(0);
    });
  });

  server.listen(8000);
}

重新启动时，始终有3个正在运行的从属设备来处理传入连接

最后一件事：如果您尝试，

console.log

不会在从属SIGTERM处理程序中执行任何操作，因为它已与主处理器断开连接