同步异步创建的承诺

我正在开发一个小的nodejs程序，当程序的所有异步操作都完成时，我会遇到一些麻烦。

目前，该程序执行以下步骤：

1/生成具有一些参数的进程。此进程将在其stdout上打印数据。

2/听processstdout"data"事件，每次打印东西时，程序都会使用数据调用一个函数（我们称之为"process"）。

3/这个过程函数最终会将数据插入mongo数据库，并向amqp服务器发送消息。

3/当没有更多数据时，程序处于空闲状态，因为与amqp和mongo数据库的连接仍然有效，所以我需要知道何时完成所有工作才能关闭连接。

所以，我试着用when.js来利用承诺，但我无法让它实现我想要实现的目标。

我让"process"函数返回了一个promise，这个promise将在mongodb插入和amqp消息发送完成后得到解决。在我的程序中，我正在创建一个数组，它将收到所有的承诺，能够在when.all（）时调用，以知道它们何时都被解析。

但是，由于我在派生进程将数据打印到其stdout流时异步创建promise，所以对when.all（）的调用是用一个空数组进行的，该数组似乎可以立即解析。

下面是一个代码示例，它说明了我正在实现的目标：

var when = require('when')
  , _    = require('lodash')
  , cp   = require('child_process');
var promises = [];
function process(data) {
    var deferred = when.defer();
    setTimeout(function () {
        deferred.resolve(true);
    }, 3000); // Let's say we need 3 seconds to process and save data
    return deferred.promise;
}
var ls = cp.spawn('ls', ['-la', '/usr/bin']);
ls.stdout.on('data', function (data) {
    console.log('Received data, creating a promise to notify when this data is processed.');
    promises.push(process(data));
});
when.all(promises).then(function (values) {
    console.log('All promises are now resolved', values);
});

正如你可能已经猜到的，这个程序的输出是：

All promises are now resolved []
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.
Received data, creating a promise to notify when this data is processed.

有没有办法让这个代码按照预期的顺序（最后打印第一行）示例打印控制台消息？

谢谢。

ls.on('close',function(){
    when.all(promises).then(function (values) {
        console.log('All promises are now resolved', values);
    });
});