node.js是否在内部使用线程/线程池?

问题描述

我决定使自己熟悉node.js，并阅读了有关该主题的几篇文章.我仍然不清楚的是，当您调用node.js函数时，node.js是否在线程池中创建新线程和/或在线程上调度任务.

I've decided to familiarize myself with node.js and have read a several articles on the subject. What remained unclear to me is if node.js creates new threads and/or schedules tasks on threads from a thread pool when you call node.js functions.

例如，如果我调用fs.readFile，它是否在其他线程上执行?

For example if I call fs.readFile is it executed on a different thread?

如果是，[如何]我可以编写自己的函数readFileCustomized或doLongOperation在不同的线程上运行?

If yes, [how] can I write my own function readFileCustomized or doLongOperation to run on a different thread?

推荐答案

没有用于文件操作的异步API，因此node.js为此使用了线程池.您可以在 libuv 的代码中看到它.

There is no async API for file operations so node.js uses a thread pool for that. You can see it in the code of libuv.

该池可以运行4个线程:

static uv_thread_t default_threads[4];

阻塞FS任务发布到 uv__work_submit .例如，这是实现 read的方式:

Blocking FS tasks are posted with uv__work_submit. For example, here's how read is implemented:

int uv_fs_read(uv_loop_t* loop, uv_fs_t* req,
               uv_file file,
               void* buf,
               size_t len,
               int64_t off,
               uv_fs_cb cb) {
  INIT(READ);
  req->file = file;
  req->buf = buf;
  req->len = len;
  req->off = off;
  POST;
}

...

#define POST                                                                  \
  do {                                                                        \
    if ((cb) != NULL) {                                                       \
      uv__work_submit((loop), &(req)->work_req, uv__fs_work, uv__fs_done);    \
      return 0;                                                               \
    }                                                                         \
    else {                                                                    \
      uv__fs_work(&(req)->work_req);                                          \
      uv__fs_done(&(req)->work_req, 0);                                       \
      return (req)->result;                                                   \
    }                                                                         \
  }                                                                           \
  while (0)

如果要实现自己的线程，可以查看详细介绍.

If you want to implement your own threads, you can check this great introduction.

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