如何在Node.js中编写非阻塞代码？ [英] How do I write non-blocking code in Node.js?
问题描述
我可以在 I / O http://en.wikipedia.org/wiki/Node.jsrel =nofollow noreferrer> Node.js 非常容易。这就是整个库的设置。
I can write non-blocking I/O in Node.js very easily. It's what the entire library is set up for.
但是所做的任何计算都是阻塞的。任何通过事件发射器阻止的消息都会阻止。
But any computation done is blocking. Any message passing over event emitters are blocking.
例如，发射事件立即被解决，因此阻塞：
For example, emitting events are resolved immediately and are thus blocking:
var e = new process.EventEmitter;
e.on("foo", function() {
console.log("event");
});
process.nextTick(function() {
console.log("next tick");
});
setTimeout(function() {
console.log("timeout");
}, 0);
e.emit("foo");
> event
> next tick
> timeout
除了在 nextTick 中包装电话外，如何使代码无阻塞？
Apart from wrapping calls in nextTick, how do I make code non-blocking?
我想尽可能少地在事件循环的每个周期进行计算，这样我就可以同时为多个客户端服务可能。
I want to do as little computation per cycle of the event loop as possible, so that I can serve as many clients simultaneously as possible.
如何以非阻塞方式编写代码？
How do I write my code in a non-blocking fashion?
当我有非阻塞代码，如何在多个进程中扩展？
And when I have non-blocking code, how do I scale that across multiple processes?
一个选项是等待WebWorker子进程API完成。
One option is waiting for the WebWorker sub-process API to be finished.
推荐答案
JavaScript是单线程的。这意味着无论事件，超时或延迟使用nextTick，任何完成的计算都将阻止整个过程。
JavaScript is single-threaded. That means that regardless of events, timeouts, or delaying with nextTick, any computation done will block the whole process.
如果使用<$ c $分步处理c> process.nextTick ，就像它在客户端使用 setTimeout（fn，0）一样，以避免阻止UI，你可以传播你的工作量在较长的时间跨度内，为其他功能提供了一些空间。
If you split your processing in steps using process.nextTick, like it's done with setTimeout(fn, 0) on the client-side to avoid blocking the UI, you could spread your workload over a longer time span, giving some room for other functions to run.
但这是一个非常无用的解决方案 - 总工作量是相同的，分布在所有周期（使每个请求稍慢）。在实践中，任何预计需要花费超过几毫秒的计算都应该卸载到不同的进程中。为了最大化并发性，您应该始终尽快返回事件循环。
But that's a very innefective solution - the total amount of work is the same, distributed among all cycles (making each request a little slower). In practice, any kind of computation that is expected to take more than a few milliseconds should be offloaded to a different process. To maximize concurrency you should always return to the event loop as quickly as possible.
child_process.fork（）<几天前将/ code>添加到v0.5。它简化了子进程的创建和通信 - 不仅仅是Web worker API，而是关闭，请参阅 URL
https://github.com/joyent /node/blob/master/doc/api/child_process.markdown 。
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