python3通过gevent.pool限制协程并发数量

协程虽然是轻量级的线程，但到达一定数量后，仍然会造成服务器崩溃出错。最好的方法通过限制协程并发数量来解决此类问题。

server代码：

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Author        : Cain
# @Email         : 771535427@qq.com
# @Filename      : gevnt_sockserver.py
# @Last modified : 2017-11-24  16:31
# @Description   :

import sys
import socket
import time
import gevent
from gevent import socket,monkey,pool    #导入pool
monkey.patch_all()

def server(port, pool):
    s = socket.socket()
    s.bind(('0.0.0.0', port))
    s.listen()
    while True:
        cli, addr = s.accept()
        #print("Welcome %s to SocketServer" % str(addr[0]))
        pool.spawn(handle_request, cli)    #通过pool.spawn()运行协程

def handle_request(conn):
    try:
        data = conn.recv(1024)
        print("recv:", data)
        data = 'From SockeServer:192.168.88.118---%s' % data.decode("utf8")
        conn.sendall(bytes(data, encoding="utf8"))
        if not data:
            conn.shutdown(socket.SHUT_WR)
    except Exception as ex:
        print(ex)
    finally:
        conn.close()

if __name__ == '__main__':
    pool = pool.Pool(5)    #限制并发协程数量5
    server(8888, pool)

client(通过gevent模拟并发数量)：

import socket
import gevent
from gevent import socket, monkey
from gevent.pool import Pool
import time

monkey.patch_all()

HOST = '192.168.88.118'
PORT = 8888
def sockclient(i):
    #time.sleep(2)
    s = socket.socket()
    s.connect((HOST, PORT))
    #print(gevent.getcurrent())
    msg = bytes(("This is gevent: %s" % i),encoding="utf8")
    s.sendall(msg)
    data = s.recv(1024)
    print("Received", data.decode())

    s.close()

pool = Pool(5)
threads = [pool.spawn(sockclient, i) for i in range(2000)]
gevent.joinall(threads)

由于服务器限制连接并发数量；所以客户端同时并发连接数超过服务器端并发数量，就会引发连接错误信息：

Exception in thread Thread-849:
Traceback (most recent call last):
  File "C:\Users\admin\AppData\Local\Programs\Python\Python36\lib\threading.py", line 916, in _bootstrap_inner
    self.run()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python36\lib\threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "E:/chengd/python/python3/matp/die/geven_sockclient.py", line 26, in sockclient
    data = s.recv(1024)
ConnectionResetError: [WinError 10054] 远程主机强迫关闭了一个现有的连接。