190221协程与IO模型
2024-09-02 03:37:59
一、协程
- 又称微线程
- 协程是一种用户态的轻量级的线程
- 在单线程下实现的并发,例如:yield
优点: - 无需线程上下文切换的开销
- 无需原子操作锁定及同步的开销
- 方便切换控制流,简化编程模型
- 高并发,高扩展性,低成本:一个CPU可支持上万的协程
缺点: - 无法利用多核资源
- 进行阻塞操作会阻塞掉整个程序
import time,queue
def consumer(name):
print('--->starting eating bun...')
while True:
new_bun = yield
print("[%s] is eating bun %s" %(name,new_bun))
def producer():
r = con.__next__()
r = con2.__next__()
n = 0
while n < 5:
n += 1
con.send(n)
con2.send(n)
print("\033[32;1m[producer]\033[0m is making bun %s" %n)
if __name__ == '__main__':
con = consumer("c1")
con2 = consumer("c2")
p = producer()
二、greenlet 手动切换
# Author:Li Dongfei
from greenlet import greenlet
def test1():
print(12)
gr2.switch() #切换至gr2
print(34)
gr2.switch()
def test2():
print(56)
gr1.switch()
print(78)
gr1 = greenlet(test1) #启动一个协程
gr2 = greenlet(test2)
gr1.switch() #切换至gr1
三、genent 自动切换
- 遇到sleep自动切换
# Author:Li Dongfei
import gevent
def foo():
print("Running in foo")
gevent.sleep(2)
print("Explicit context switch to foo again")
def bar():
print("Explicit精确的 context to bar")
gevent.sleep(1)
print("Implicit context switch back to bar")
def func():
print("in the func")
gevent.sleep(0)
print("in the func again")
gevent.joinall([
gevent.spawn(foo),
gevent.spawn(bar),
gevent.spawn(func),
])
- 协程并发爬网页
# Author:Li Dongfei
from gevent import monkey; monkey.patch_all() #把当前程序所有的io操作单独做标记,让gevent识别
import gevent
from urllib.request import urlopen
def f(url):
print('GET: %s' %url)
resp = urlopen(url)
data = resp.read()
f = open("url.html", "wb")
f.write(data)
f.close()
print('%d bytes received from %s.' %(len(data), url))
gevent.joinall([
gevent.spawn(f, 'https://www.python.org'),
gevent.spawn(f, 'https://www.github.com'),
gevent.spawn(f, 'https://www.aliyun.com'),
])
- 通过gevent实现单线程的多socket并发
- server
# Author:Li Dongfei
import sys,socket,time,gevent
from gevent import socket,monkey
monkey.patch_all()
def server(port):
s = socket.socket()
s.bind(('localhost', port))
s.listen(500)
while True:
cli, addr = s.accept()
gevent.spawn(handle_request, cli)
def handle_request(conn):
try:
while True:
data = conn.recv(1024)
print("recv:", data)
conn.send(data)
if not data:
conn.shutdown(socket.SHUT_WR)
except Exception as ex:
print(ex)
finally:
conn.close()
if __name__ == '__main__':
server(8001)
- client
# Author:Li Dongfei
import socket
HOST = 'localhost'
PORT = 8001
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
while True:
msg = bytes(input(">>:"), encoding="utf-8")
s.sendall(msg)
data = s.recv(1024)
print('Received', data)
s.close()
四、I/O模型
- 阻塞
- 非阻塞
- I/O多路复用
- 信号驱动
- 异步
- Python select socket server代码示例
# Author:Li Dongfei
import select, socket, sys, queue
server = socket.socket()
server.bind(('localhost', 9000))
server.listen(1000)
server.setblocking(False) #设置为非阻塞
msg_dic = {}
inputs = [server,]
outputs = []
while True:
readable, writeable, exceptional = select.select(inputs, outputs, inputs)
print(readable,writeable,exceptional)
for r in readable:
if r is server:
conn, addr = server.accept()
print("new connect", addr)
inputs.append(conn)
msg_dic[conn] = queue.Queue()
else:
data = r.recv(1024)
print("recv data",data)
msg_dic[r].put(data)
outputs.append(r)
for w in writeable:
data_to_clinet =msg_dic[w].get()
w.send(data_to_clinet)
outputs.remove(w)
for e in exceptional:
if e in outputs:
outputs.remove(e)
inputs.remove(e)
del msg_dic[e]
五、selector模块
# Author:Li Dongfei
import selectors, socket
sel = selectors.DefaultSelector()
def accept(sock, mask):
conn, addr = sock.accept()
print('accepted', conn, 'from', addr)
conn.setblocking(False)
sel.register(conn, selectors.EVENT_READ, read)
def read(conn, mask):
data = conn.recv(1024)
if data:
print('echoing', repr(data), 'to', conn)
conn.send(data)
else:
print('closing', conn)
sel.unregister(conn)
conn.close()
sock = socket.socket()
sock.bind(('localhost', 9000))
sock.listen(1000)
sock.setblocking(False)
sel.register(sock, selectors.EVENT_READ, accept)
while True:
events = sel.select()
for key, mask in events:
callback = key.data
callback(key.fileobj, mask)
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