使用python的selectors模块时, 出现描述符过多的ValueError异常, 如何修改最大文件描述符上限？

Question

• 环境

  python version >= (3,4,0)
  win10系统

---

• 异常位置

    if sys.platform == 'win32':
        def _select(self, r, w, _, timeout=None):
            # 由于描述符过多，在下面抛出了ValueError异常
            r, w, x = select.select(r, w, w, timeout)
            return r, w + x, []

  ---

• 异常堆栈

  Traceback (most recent call last):
  File "multiio_client.py", line 70, in <module>
    result = client.run()
  File "multiio_client.py", line 50, in run
    events = self.select.select()
  File "E:\pythoninstall\lib\selectors.py", line 324, in select
    r, w, _ = self._select(self._readers, self._writers, [], timeout)
  File "E:\pythoninstall\lib\selectors.py", line 315, in _select
    r, w, x = select.select(r, w, w, timeout)
  ValueError: too many file descriptors in select()

  ---

• 猜测

  windows和linux的进程最大文件描述符分别是509, 1024,需要改变内核中的宏定义，或者通过一些类似的系统调用来改变

---

• 查看cpython select源码

  selectmodule.c

/* Windows #defines FD_SETSIZE to 64 if FD_SETSIZE isn't already defined.
   64 is too small (too many people have bumped into that limit).
   Here we boost it.
   Users who want even more than the boosted limit should #define
   FD_SETSIZE higher before this; e.g., via compiler /D switch.
*/
#if defined(MS_WINDOWS) && !defined(FD_SETSIZE)
#define FD_SETSIZE 512
#endif

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我没有问题了。。。发现自己都弄明白了